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KenWH
10-17-2007, 08:34 AM
Hi guys,

Maybe you guys can help me with bi-amping my front JBL 4675's & 4670.
Pre/pro=Denon 2807
HF amp= L/C/R channels of an Outlaw 7700
LF amp=Monster MPA-3250

Signal from Denon is unbalanced.

I've tried several different prosound x-overs including a behringer dcx2496 digital, an analog dbx, an analog behringer, and I currently have a bbe ds48 digital. All of them have caused too much hiss.

Thinking maybe the hiss is due to trying to run a balanced pro sound x-over with an unbalanced signal I even tried my old Audio Control caraudio x-over and it hissed badly also.

Everything I've tried results in WAY too much hiss coming from the horns.:banghead:

I tried various level settings such as boosting the input signal and cutting the hf outputs on the x-overs but it really didn't help. Basically with all trims on the x-over at their minimum I still hear a lot of hiss.

If i just run the signal straight from Denon right into the Outlaw(hf amp) then there's barely any hiss at all.

Both the Outlaw and the Monster have the balanced input option so would getting something like a rane balance buddy to get a balanced signal help hiss?

Thanks in advance for the help,
Ken

JBL 4645
10-17-2007, 08:40 AM
The cinema setting is usual 500Hz 24db down at the LF end that is you know at the top of the range, the HF horn is crossed off at 24db where it starts off at, if you what to cross off the LF at the lower end to prevent excursion with lower filter setting that’s up to you, personally the JBL 4675-A THX is bitching loudspeaker that kicks ass BIG TIME!

Add some EQ filtering to you know fitter out the hiss, that should compensate, and besides you don’t need the whole sonic range to rip you’re ears off in home, you’ve got those JBL 2360-A horns haven’t? those beasts are very sensitive, so set the microphone to the RTA if you have one and just set them for a lower level in the room they have a wonderful dynamic range handling that needs less in the home, so have ago with that idea if it helps.:)

85db in the cinema so try aiming for 75db rather than 85db set the levels up high on the Behringer DCX2496 and reduce the amplifier power keep going at it and don’t give up, I noticed this yesterday when I decided to boost the level outputs on the DCX2496 all I did was turned down the amplifier levels and besides I’m running far smaller JBL loudspeakers than you, only wished I had a set of JBL 4675-A three!

JBL 4645
10-17-2007, 09:06 AM
Look at the size of that thing! :D

http://gallery.avsforum.com/data/501/P1010424.JPG

I gather youíve add a third JBL 4675-A since last year then, yeah set the amplifier levels at a differently I was speaking to one of the UKís top cinema installers a last month and I canít remember what the guy said as I had a dozen questions about the THX set-up at the Empire, where different mixtures of crossover filters are used a combination of (Bessel and Linkwitz-Riley).

Amplifier levels as far as I can remember he said where set at different levels, I could chase this up for you in the morning UK time and get a little feedback.

KenWH
10-17-2007, 09:46 AM
Hi jbl 4645,

Yah that's an older pic of my front stage. I've since changed the center channel a bit where each woofers in their own cabinent and the horn is between them. I did this cause I'm running a larger 133" screen now and I needed to drop the horn down below the screen.

I've also sold the maggies.

I'm now running four 2242's for subs.

I want to keep the 500hz x-over point. The Outlaw and the Monster don't have adjustable level controls. I have been using QSC amps and I could run the gains down on them to get the hiss bareable but I was having to crank up the denon to the point where it started adding some unpleasantries. I would like to keep the "hifi" amps in the system for now if possible as the lack of fan noise is nice plus from what little I've run them I like the sound of them paired with the JBL's.

Now matter how I calibrate the hiss is present even at idle. It doesn't go up with volume...just a steady loud hiss.

I wonder what are the x-overs doing to the signal to add so much hiss?
I could understand if I had the x-over gains cranked wide open but even at their lowest settings the hiss is far too loud.

JBL 4645
10-17-2007, 09:51 AM
KenWH

I looked around and remembered thereís the JBL cinema handbook or cinema manual, it might come in handy with most of the pro JBL that youíre using there.
Donít leave home without it.;)

http://www.jblpro.com/pub/cinema/cinedsgn.pdf (http://www.jblpro.com/pub/cinema/cinedsgn.pdf)

JBL 4645
10-17-2007, 09:59 AM
How about then a simple routable voltage control volume pot that can brought from any electronics store and just apply several in-between the line outputs to the amplifiers, solder up the cables, starting to get the picture now! This should cost no more than $15.00 US dollars for six, with cable and a few RCA phone plugs to be attached on one end or it might cost over $15.00 if you amps have XLR, this is the easiest approach I can think of at the moment.

http://bothner.co.za/articles/hotrodpot.jpg
In fact I donít know why I didnít think of this before, I think Iíll use the same approach, Iíll need to pop down to (DJ electronics) the week after next. Iíll need a plastic box to fit the volume pots in, and attach the necessary RCA phone inputs and outputs on the back of the box, otherwise LOL it would be a load of dangling wires everywhere.:D

JBL 4645
10-17-2007, 10:29 AM
This got me thinking for a moment while I have this weeks top region 2 film playing, I muted all the channels turned up the volume on my Marantz 1050 which are driving the JBL control 1 as a mid and high end, I know that sounds confusing no matter, I then adjusted the crossover on the HF while reducing the high end from 20KHz down to 1KHz the hiss became lesser and lesser.

I notched the hiss is more on the right output channel with my DCX2496 and after a little toying around I activated an EQ filter and reduced the level and widened the Q and the hiss dropped down considerably. Have a go with that solution and see if this adds any remedy for the hiss issue. :)

JBL 4645
10-17-2007, 10:54 AM
This need some basic looking into so I powered up the Behringer MIC 100 hooked up the ECM8000 and placed it near to the JBL control 1 mid high end and looked at the RTA to see what range of the hiss was at, the Technics SH-8055 gave me a broad range from 8KHz to 16KHz! So it looks like the hiss covers from 8KHz though the high range up to 16KHz kind like wideband pink noise being filtered or something like that.

Here’s a little picture show of what I did within the last 15 minutes. I had to turn the CRT off because the ECM8000 picks up the high frequency transmission from the TV.

If you look close to where the RTA is, you can make out a display I know you can’t see it in greater detail, but that’s 8 and 16KHz being displayed on the RTA.

toddalin
10-17-2007, 03:39 PM
When I was running Yamaha 31 band eqs between my preamp and power amp sections, I was also really bothered by the hiss it added.

Rather than using pots, I simply soldered a series resistor right on the hot lead inside the 1/4" phone jack. Worked like a charm. I tried a couple until I found a value that substantially cut the hiss (a little over 10 dB), but left plenty of volume to play with.

pelly3s
10-17-2007, 07:20 PM
i tell my customers this all the time proper gain structure is everything. make sure if you have a -10db output the input it goes to is a -10db input. I would suggest trying a balancing box like the Rane you mentioned. if your gain structure is right then you will have no issues (well shouldnt)

JBL 4645
10-18-2007, 12:56 AM
When I was running Yamaha 31 band eqs between my preamp and power amp sections, I was also really bothered by the hiss it added.

Rather than using pots, I simply soldered a series resistor right on the hot lead inside the 1/4" phone jack. Worked like a charm. I tried a couple until I found a value that substantially cut the hiss (a little over 10 dB), but left plenty of volume to play with.

toddalin

Yes, yes someone mentioned that before. What value are the resistors that you used that might turn out to be an even more affordable solution, resistors don’t cost much.

But from what I noticed last night the hiss was on the right channel MORE and much lesser on the left and centre can anyone confirm this.

KenWH
10-18-2007, 06:37 AM
Thanks for the help guys.

I was hoping the consumer amps would have been easier to intergrate...I might just send the Outlaw back and reinstall my pro-amps. At least they had quality level/gain controls.

I am in contact with Marchand about their XM46 passive single ended line level x-over which is supposed to be very quiet so I'll see what he has to say before sending the Outlaw back.

I also suppose I could "Y" the l/c/r signal coming from my pre/pro. Then I could run one end of the "Y" directly to the HF amp then use my JBL speaker level x-overs as a high-pass filter and run the the other end of the "Y" through the active line-level x-over to get the lows...in theory that'd keep the noisy active x-over away from my horns.

-Ken





toddalin

Yes, yes someone mentioned that before. What value are the resistors that you used that might turn out to be an even more affordable solution, resistors don’t cost much.

But from what I noticed last night the hiss was on the right channel MORE and much lesser on the left and centre can anyone confirm this.

Last year when I tried the dcx2496 I ended having to send it back as one channel had a lot more noise on it than the others reguardless of how it was configured. I ended up with a BBE ds48...not as many features as the dcx but it's a decent unit none the less.

JBL 4645
10-18-2007, 06:45 AM
Thanks for the help guys.

Last year when I tried the dcx2496 I ended having to send it back as one channel had a lot more noise on it than the others reguardless of how it was configured. I ended up with a BBE ds48...not as many features as the dcx but it's a decent unit none the less.

Afternoon there, are you winning?

Well I can live with the issue that Iíve noticed Iíll just work around that problem, with resistors volume trimming pots even the kitchen sink if the situation called for it.

I wonder what the dbx 4800 sound like giving the cost £2000.00 I mean whoís got 2 grand for several of those, unless you win the lottery. :D

KenWH
10-18-2007, 07:12 AM
Afternoon there, are you winning?

I don't know exactly what your asking here but:
I'm not winning anything as this hiss is driving me nuts.:D
Not whinning (complaining) about the DCX either.;)

The sound mine was making was not something I don't think anyone should have to live with...it wasn't just a slight hiss. I recall many other DCX users back then having a similar issue and I believe it ended up being solder joints on the pc board were grounding out on the chassis. As it was a brand new unit I decided to send it back rather than voiding the warranty by attempting to fix it myself. I liked the DCX alot...it had a much better user interface than the BBE for sure.

If your DCX is an older unit and out of warranty you might open it up and put some kind of nonconductive material(electrical tape,etc.) on the chassis in the area's where it could come in contact with the board. You could search the web for more info as it was a fairly common problem with the DCX2496's back then.

I assume Behringer made some changes to correct the issue as I've not heard much about that problem in awhile.

-Ken

JBL 4645
10-18-2007, 08:23 AM
Well it canít be any worse then ďtinnitusĒ thatís, noise and half to depress me for days on end. Iím sure thereís an easy solution thatís eluding us, it just hasnít been found yet.

Iíve just got back and I need to rest for a few hours and then Iím going to patch the HF outputs of more rather test each output with each output plugged into my (Technics SH-8055) turn the levels up on the unit and on the DCX2496 and get another view of this (hiss issue), I find it most fascinating.

toddalin
10-18-2007, 10:44 AM
toddalin

Yes, yes someone mentioned that before. What value are the resistors that you used that might turn out to be an even more affordable solution, resistors donít cost much.

But from what I noticed last night the hiss was on the right channel MORE and much lesser on the left and centre can anyone confirm this.

I pulled the Yamahas out of the system some years back. Give me the weekend to try to go though my multitude of cords and find it.

JBL 4645
10-18-2007, 10:50 AM
LOL there’s a multitude of cables behind the equipment looks like "spaghetti junction" on Friday afternoon.:D

toddalin
10-18-2007, 06:51 PM
I found the cord. Resistors are 100K ohms (brn/blk/yel). (Actually measure about >~98K.) I think they are 1/8 watt (very small) to fit within the 1/4" phono plug.

Zilch
10-18-2007, 11:23 PM
I don't get what the problem is.

Compression drivers require very little power, like one watt, in home use.

If you have a 50W amp running them with no input attenuation, all of the noise of the crossover is being amplified, as you have to attenuate the signal ahead of the crossover, or use its inputs to do it.

You need a gain structure which allows the active crossover to operate with a decent signal to noise ratio, which means attenuation of the amp.

Making matters worse is the fact that you're driving consumer amps with pro level gear.

Sticking a high-value resistor in series with the input is neither a rational nor recommended approach to accomplishing what needs to be done; all you're doing is increasing the amplifier input impedance, a bad idea. You want to use a divider there.... :(

JBL 4645
10-19-2007, 01:41 AM
I don't get what the problem is.

Compression drivers require very little power, like one watt, in home use.

If you have a 50W amp running them with no input attenuation, all of the noise of the crossover is being amplified, as you have to attenuate the signal ahead of the crossover, or use its inputs to do it.

You need a gain structure which allows the active crossover to operate with a decent signal to noise ratio, which means attenuation of the amp.

Making matters worse is the fact that you're driving consumer amps with pro level gear.

Sticking a high-value resistor in series with the input is neither a rational nor recommended approach to accomplishing what needs to be done; all you're doing is increasing the amplifier input impedance, a bad idea. You want to use a divider there.... :(

Donít JBL 2360-A HF horns have a sensitivity of around 113db! So I agree less is more.

http://www.jblpro.com/pages/pub/components/23606566.pdf (http://www.jblpro.com/pages/pub/components/23606566.pdf)

Ian Mackenzie
10-19-2007, 04:19 AM
Ken,

I am not sure why you are biamping if its this much trouble?

The problem as I see it is you have very high sensitivity horns running from a source that is inherantly noisy ie the active crossovers. The S/n is badly degrade at the active crossover, with the unbalanced leads and with the horns.

If you insist on biamping use the JBL 5235 (bal in and out) and run it to dedicated amps with balanced inputs and attenuators. I would also have an L pad on the horn to -10 db to further enhance the final s/n.Otherwise it jsut wont work in the domestic scene. Not an issue in apub or a night club of course and they live with this issue all the time.

Robh3606
10-19-2007, 05:18 AM
Does the crossover have a selectable output level so you don't have to run at the Pro levels +10?? Can you put volume pots on the inputs to the amps or use a simple voltage divider to pad it down. I run 2 set-ups and both have a mix of balanced and unbalanced equipment. I have no issues with hiss. You just need to get the gain structure right.

Rob:)

Thom
10-19-2007, 06:20 AM
How about then a simple routable voltage control volume pot that can brought from any electronics store and just apply several in-between the line outputs to the amplifiers, solder up the cables, starting to get the picture now! This should cost no more than $15.00 US dollars for six, with cable and a few RCA phone plugs to be attached on one end or it might cost over $15.00 if you amps have XLR, this is the easiest approach I can think of at the moment.

http://bothner.co.za/articles/hotrodpot.jpg
In fact I don’t know why I didn’t think of this before, I think I’ll use the same approach, I’ll need to pop down to (DJ electronics) the week after next. I’ll need a plastic box to fit the volume pots in, and attach the necessary RCA phone inputs and outputs on the back of the box, otherwise LOL it would be a load of dangling wires everywhere.:D

I've been going to do the same with a couple of Haffler 200 but I was going to add a little series resistance as I'm not sure what happens if you turn it all the way down and apply a short to your preamp or crossover output. If someone knows for sure speak up please. Of course this may be different brand to brand. Also what is a reasonable value? I'm sure there is a broad range that would work but if someone could help keep my trial and error to a few less trials and a lot less errors it would be appreciated.

Also, any experience out there using those little 5 legged or 7 legged TO220 cased amps to run compression drivers? I know they have plenty of power for a living room setting, but I don't know about the quality.

grumpy
10-19-2007, 07:29 AM
all you're doing is increasing the amplifier input impedance, a bad idea. You want to use a divider there....

I believe what Todd did qualifies as a divider (would guess worth 10-15dB, depending
on the amp input impedance). No, it didn't preserve the input impedance as seen by
the preceding device, but that's not necessarily a big deal; it's just not a universal
solution. -grumpy

JBL 4645
10-19-2007, 09:02 AM
Ken,


I am not sure why you are biamping if its this much trouble?

The problem as I see it is you have very high sensitivity horns running from a source that is inherantly noisy ie the active crossovers. The S/n is badly degrade at the active crossover, with the unbalanced leads and with the horns.

If you insist on biamping use the JBL 5235 (bal in and out) and run it to dedicated amps with balanced inputs and attenuators. I would also have an L pad on the horn to -10 db to further enhance the final s/n.Otherwise it jsut wont work in the domestic scene. Not an issue in apub or a night club of course and they live with this issue all the time.

Excellent notion! L-pad there affordable and very easy to use.


I agree with what Zinc said. Perhaps he should pop on over and give Ken a little help. I keep the levels on the mid to high frequencies down at a low amplifier volume level and have no difficulties hearing the highs, some films tend to be a little bright so I hope Ken is running those JBL 4675-A at near to cinema levels because I was seating at least 20 feet away when listening to those at the Empire years ago and I tell you it was ďJust Bloody LoudĒ and powerful.

So Ken mate a little less get the SPL db metre out and start over again. Note set the fader volume level at 0db set the gain levels on the DCX2496 at +15 on outputs (1 2 3 4 5 and 6) Start off with the centre channel using (wideband pink noise) set the SPL db metre to C weighting and aim for a peak of 75dbc weighting, while adjusting the volume on the amplifier for that value.

Note: mute each channel on the DCX2496 while adjusting each of the LF and HF Iíve practiced this and have found it to be speedy and easy.

Once set move over to the HF and set the SPL db to A weighting and aim for 75dba while adjusting the amplifier volume.

Now move over to the left and right and repeat this over again, once done play the (automatic pink noise sequencer), if you hear anything that sounds like a peak or a jump in the tone then you need to set up a microphone to an RTA and conduct the wideband noise over again while looking at the individual left centre and right this takes a few hours at best.

Once done play the (automatic pink noise sequencer) to verify the timbre, is matching as close as possible.

I do hope the JBL 4675-A are all at the same height level including HF horns otherwise the sound will not match up, it will be going from left then dropping down or upwards as is the case that I noticed with one cinema where the HF horns left and right where placed on the floor behind the screen!

Once all is sounding well with pink noise play a few films that have dialogue panning a good choice is Indiana Jones and the Temple of Doom and the Last Crusade, when Donavon enters the drawing room, his voice is heard over to left and partly on the centre channel it takes a bit of skill to obtain a good clear openness with a little delay on the centre channel LF and HF.

JBL 4645
10-19-2007, 09:15 AM
Thom

I get wonderfully ideas but LOL I’m not a qualified electronics expert, I know how to use a soldering iron and so does the rest of the population, if someone said use these components and in this order, then I’ll do so to make it work.

Also I noticed the function of the DCX2496 becoming more active when adjusting the levels higher early this week, the audio limiter function was more active rather than sitting way below, the dynamic EQ was more alive and the overall barograph was lighting up like a Christmas tree a few peaks in the (amber) I’ll have to see how it goes with Lord of the Rings and a few dts laserdiscs last thing I want to see is consent clipping.

Zilch
10-19-2007, 01:28 PM
If you insist on biamping use the JBL 5235 (bal in and out)....5235 is UN-balanced out, potentially a trap, if one is unaware.


I've been going to do the same with a couple of Haffler 200 but I was going to add a little series resistance as I'm not sure what happens if you turn it all the way down and apply a short to your preamp or crossover output. If someone knows for sure speak up please.NO, man, the potentiometer is connected as a voltage divider, not as a variable resistor (rheostat); it's the amp input that gets shorted to common at max attenuation. :yes:

What value? What's the preamp or active crossover output impedance? :dont-know

toddalin
10-20-2007, 07:49 PM
I don't get what the problem is.

Sticking a high-value resistor in series with the input is neither a rational nor recommended approach to accomplishing what needs to be done; all you're doing is increasing the amplifier input impedance, a bad idea. You want to use a divider there.... :(


Maybe, but it certainly worked for me. I say for the $0.10 for a resistor, try it and let your ears decide. Ultimately, as long as it does no harm to the equipment (and it won't), shouldn't your ears the final judge?

Zilch
10-20-2007, 08:56 PM
....shouldn't your ears the final judge?Regarding arbitrarily adding 100k to the input impedance of an amp?

I don't THINK so.... :no:

JBL 4645
10-21-2007, 03:25 AM
Maybe, but it certainly worked for me. I say for the $0.10 for a resistor, try it and let your ears decide. Ultimately, as long as it does no harm to the equipment (and it won't), shouldn't your ears the final judge?

Well Iím going to try it. Iíll use my ears and SPL db RTA to see the differences, 100K thatís not to costly, thou I donít think Maplin, sale them separately so packet of assorted resistors, would be fine.

JBL 4645
10-24-2007, 03:35 AM
Just thought Iíd mention, this the DCX2496 does have slight humming sound emission when the output gain is raised to +15db. Also I noticed last night when selecting anyone of the buttons on the left hand side channel 1 2 or 3 youíll hear a sound that is in-sync with the flashing LEDís? Itís a very faint sound but it is there.

Baron030
10-24-2007, 10:36 AM
Hi Ken

I have been following this thread for a while. And I am not really sure that I can help you or not. Personally, I have never had any problems with hiss. In my own system, I run unbalanced lines from the preamp into an electronic crossover network. And then I use balanced line XLR cables between the crossover and an array of 5 amplifiers. So, I really donít think cables are the source of the hiss.

I know most people set all of the amplifiers input controls to their maximum gain setting and then adjust each of the output levels on the electronic crossover network to achieve a system balance. But, because the HF drivers are so much more efficient then LF drivers, I have found that it is better to first set the all of level controls on the electronic crossover network to a common neutral gain setting. And then adjust the input levels on each of the amplifiers to bring the system into a coarse level of balance. After, all of the amplifiers input levels have been adjusted, I then go back and make only fine adjustments to the crossover networkís output levels to finally bring the system into balance. I know this may contradict what others have said on the subject. But, I have found that this method has given me the quietest noise floor in my own system.

For example, I run my Crown D75a HF amplifiers with their input levels set all the way down to -26db for the 2446 drivers and -22db for the 2405 drivers. While, my Crown K series, LF amplifiers are set to their maximum (-0db) input setting.

Since, your Outlaw 7700 amplifiers do not have any input level controls, it might be possible add some attenuators between the electronic crossover and the HF amplifier inputs to help balance the gain levels and hopefully reduce the hiss. I would suggest trying a -20db T or H Pad. The T-Pad can be thought of as a symmetrical variation of the L-Pad and it is for use with unbalanced line inputs, while the H-Pad is for use with balanced line inputs.

Assuming that the Outlaw 7700 has about the same input impedance as a Crown D75a (20K balanced/10K unbalanced), a -20db T or H Pad could be made using 1/8 watt 1% metal film resistors following one of the schematics pictured below. Since, physically these resistors are really small, it might be possible to build the H-Pad directly inside the XLR connector's housing that plugs into the HF amplifierís input. This would put the attenuation right at the amplifier's input, which should reduce any noise to a minimum.

Here is a link to a T or H pad attenuator calculator program should you need to calculate different attenuator values: http://www.icycolors.com/nu9n/tpad-calculator.html

And here is a link to a good source for the resistors: http://www.mouser.com/xicon/

Well, I hope you find a solution to your hiss problem.

Best of luck,
Baron030 :)

Zilch
10-24-2007, 10:59 AM
I know this may contradict what others have said on the subject. But, I have found that this method has given me the quietest noise floor in my own system.Nope, no contradiction here. It's a major reason amps have input attenuators.

Amp doesn't have them, you add them as required for the desired system gain structuire.... :yes:

KenWH
10-24-2007, 03:16 PM
Wow...sorry for not posting lately...for some reason the site stopped emailing me new reply notices...I thought this thread was dead.

I've been in contact with Outlaw Audio and they seem to think the problem is the rca to xlr connections at the xover.

Since the xover only has balanced xlr in/out they suggested using a di box to get a signal the xover likes. So I've got an Aphex 228 rca to balanced xlr interface/converter box on the way. The 228 will be in tommorow and I'll install it asap and report back.

Btw...the Outlaw tech also advised me against using a diy level control at the amp as it could possibly increase noise potential.

edit:
As for using level controls on the amps...before the Outlaw/Monster combo I've been using pro-amps in my system for a few years and set them up pretty much just as Baron does. I ended up with the horn channels levels on the amps nearly turned completely off in order to get the hiss down to acceptable levels. Again though I was still trying to run the unbalanced signal thru the balanced xlr x-overs so hopefully the Aphex will help.

edit#2:

Thanks for the help/suggestions everyone!!!! :)

hjames
10-24-2007, 03:33 PM
Interesting - I run (preamp-level) RCA out from my Harman Kardon AVR-335 receiver over to the JBL M552 crossover, then run Balanced XLR out for Low and High to a terminal strip on a pair of JBL amps.
No problem like that with my gear. Opimax will vouch that it sounds ok ...


Wow...sorry for not posting lately...for some reason the site stopped emailing me new reply notices...I thought this thread was dead.

I've been in contact with Outlaw Audio and they seem to think the problem is the rca to xlr connections at the xover.

Since the xover only has balanced xlr in/out they suggested using a di box to get a signal the xover likes. So I've got an Aphex 228 rca to balanced xlr interface/converter box on the way. The 228 will be in tommorow and I'll install it asap and report back.

Btw...the Outlaw tech also advised me against using a diy level control at the amp as it could possibly increase noise potential.

edit:
As for using level controls on the amps...before the Outlaw/Monster combo I've been using pro-amps in my system for a few years and set them up pretty much just as Baron does. I ended up with the horn channels levels on the amps nearly turned completely off in order to get the hiss down to acceptable levels. Again though I was still trying to run the unbalanced signal thru the balanced xlr x-overs so hopefully the Aphex will help.

edit#2:

Thanks for the help/suggestions everyone!!!! :)

JBL 4645
10-25-2007, 03:57 AM
I agree with what timc said to me on MSN messenger the DCX2496 does inherit a ďnoisy ground floorĒ that is quite distracting for a professional product. He said all pro gear is noisy and I hope with his ďmodificationĒ he might turn up with a few easy solutions.

I hiss is more easy to detect and humming, well you might partly blame the amplifier. Well Iíve discounted the RCA phones that go to the amplifies from the DCX2496 and when raising the gain level output thereís a slow steady increase in noise.

It gets worse when the amplifiers are turned up to there fullness, hiss and humming, where does the fault lead to and how simple, for one to make alterations to the fault to improve on the function of the DCX2496.

I have second active crossover which Iíll check-out later to see if that model is noisy both in hiss or humming.

hjames
10-25-2007, 04:20 AM
imc said all pro gear is noisy and I hope with his “modification” he might turn up with a few easy solutions.
I hiss

I think Bo and a few others might chime in here about that line - I doubt that all Pro gear is noisy, i would think the correct phrase is Cheap pro gear is noisy. Did anyone ever confirm if the hiss was the problem we've already read about here in other threads with poor solder joints and grounds in that model of device?

Good troubleshooting technique would be to substitute it with another similar device and isolate the problem ... (You can get a used JBL 552 for about $120 on "the bay" for testing - you can always resell it later for the same price if you don't like it).

It also sounded like Zilch and a few other had a good idea - get the signal level down to a reasonable level and the crossover and Amps will no doubt play much better. Hit your device with too hot a signal and you are outside the point of linear behaviour and into distortions and noise.

For "4645" - One issue with hiss may be cascading device after device - extended strings of EQs, expanders, Active crossovers and such have a real potential for noising up the signal. Simplify the signal chain while troubleshooting and listen for improvements.

KenWH
10-25-2007, 06:02 AM
Interesting comments on the low quality=noise issue.

I've used several different pro crossovers in my system including the Behringer dcx2496(digital), DBX 224xl(analog), Behringer cx3400(analog), and now the BBE ds48(digital) and their use has caused similar levels of hiss. Again though I was not running them balanced so the Aphex unit will finally settle the signal issue one way or the other and I'll go from there.

KenWH
10-25-2007, 08:02 AM
Good news...got the Aphex in about 10min ago and now I can only hear a faint hiss if I'm within 2 or 3 feet of the horns. Even with all the xover levels set flat the hiss is not really noticeable.


So far so good...:applaud:

boputnam
10-25-2007, 05:37 PM
...would getting something like a rane balance buddy to get a balanced signal help hiss? Hi, Ken..

I need to read all this thread closely, but my grab is: "No" the Rane Balanced Buddy would do nothing for this - it is intended to avert ground loops )"GL", i.e., Pin1 problems). "Hiss", is not a Pin1 problem.

boputnam
10-25-2007, 05:51 PM
...I can only hear a faint hiss if I'm within 2 or 3 feet of the horns. Even with all the xover levels set flat the hiss is not really noticeable. Bullshit. There should be no hiss.

The hiss is only noticable (audible) in the HF, but my grab is there is noise throughout your signal path - you have a very high noise floor. You talk of trialing all manner of xovers and no change. My guess is the noise originates BEFORE the xover insertion point.

QSC's are not the problem. Stay with the pro amps.

Can you trial another player and preamp unit, like Heather suggested? I mean hell, I've used all manner of consumer gear but the thing that totally ruined me was a lame Onkyo consumer-grade preamp. That said, all it had was a poorly grounded (designed) power supply, but there was no hiss.

I'd start at the beginning of the signal path. I think your problem is rigth there, and not related to a GL (balanced vs unbalanced).

KenWH
10-26-2007, 07:37 AM
Bullshit. There should be no hiss.

The hiss is only noticable (audible) in the HF, but my grab is there is noise throughout your signal path - you have a very high noise floor. You talk of trialing all manner of xovers and no change. My guess is the noise originates BEFORE the xover insertion point.

QSC's are not the problem. Stay with the pro amps.

Can you trial another player and preamp unit, like Heather suggested? I mean hell, I've used all manner of consumer gear but the thing that totally ruined me was a lame Onkyo consumer-grade preamp. That said, all it had was a poorly grounded (designed) power supply, but there was no hiss.

I'd start at the beginning of the signal path. I think your problem is rigth there, and not related to a GL (balanced vs unbalanced).

Your right in that balancing didn't help hiss. The Aphex is going back. In my first post about the Aphex I didn't realize the tiny gain knobs where at full min when I hooked it up. I barely turned the gain knobs...HISS.:banghead:

The crossovers appear to be the problem as if I remove them the horns are dead silent. I've also been using passive speaker level crossovers and they are dead silent also...so active line level xovers=loud(hear from 20+feet away) hiss for me.

So at least I finally know it's not a really a signal balance/unbalance thing either. It appears that whatever the active x-overs do to the HF the process just adds a lot of noise/hiss.

I'm going back and staying with the passive speaker level JBL 3160 x-overs for now. Yes the bass section performance will suffer a bit but at least it's quiet. The only other thing I know to try would be a passive line level x-over like the Marchand xm46...but at $750 for a custom 3ch. unit, that's not something i want to do without some certainty it will work...quietly.

Thanks for the help guys,
Ken

Zilch
10-26-2007, 12:31 PM
Do what Baron030 suggested at #32.

This is virtually a no-brainer. Transistors hiss. IC and circuit designers work to minimize the impact and maximize the signal-to-noise ratio.

BUT, if you crank the signal down and then amplify it by 20+ dB, your S/N ratio has turned to crap. You're amplifying the hiss, mostly, is what, and despite what the amp rep says, you need attenuation at the amp input so that everything before it can be outputting SIGNAL, primarily, not noise.

THEN, if there's any hiss remaining, it's coming from the amp, which is too friggin' big to begin with....

Baron030
10-26-2007, 04:19 PM
Hi KenWH
I am still scratching my head on this one. :blink:
Last night, I played around with my own system, trying to make it HISS.
I turned up all 3 of my CrownD-75a to their maximum input levels (-0 db).
Thatís one Crown D-75A feeding a pair of 2405s with up to 40 watts per channel and two Bridged-Mono Crown D-75As feeding a pair of 2446H drivers with up to 110 watts per channel.

Itís definitely a system that Zilch would call, "too friggin' big to begin with".
But, I just happen to like it that way. Loud transients are reproduced so effortlessly. :thmbsup:

I performed a full system test with the CD player set on "pause", the pre-amp was set to a insanely loud dial setting of 6, and I then placed my ear just one inch way from each of the drivers.
And I could not hear any HISS at all.
I know if someone had pressed the "play" button, with my ear placed that close to a driver.
It would have blown out an ear drum. (>140db @ 1 inch).
So, I think it was a viable HISS test.

Ok, for the record, my system was not completely silent, there was very faint hum coming out of the 2226H drivers.
But, at normal listening distances this hum is not noticeable.

I have looked at your Outlaw 7700 amplifier specs and they appear to have a good signal to noise ratio.
So, I really donít think they are at fault. But, I then again, I could be wrong.

Since, you have tried several different crossover networks and they all hissed.
Then, maybe itís time to start looking at the pre-amp or the CD player as the source.

But, if you do find that the source of the HISS to be the crossover network, then try Ashly crossover.
I am really happy with my Ashly XR-4001.

But, I still think the source of the HISS is coming from somewhere before the crossover network.

Baron030

grumpy
10-26-2007, 05:08 PM
if you use a 100-600 ohm resistor as your "signal source" (nearly shorting the
input to the active crossover), does the hiss go away? or if the input really is
shorted, is there still hiss?

boputnam
10-29-2007, 04:34 PM
Do what Baron030 suggested at #32.

This is virtually a no-brainer. Maybe not so fast there, cowboy.

Way back in post #4, Ken described using QSC's, with gain control, and this did not remedy the symptom:
...I have been using QSC amps and I could run the gains down on them to get the hiss bareable but I was having to crank up the denon to the point where it started adding some unpleasantries. ... No matter how I calibrate the hiss is present even at idle. It doesn't go up with volume...just a steady loud hiss.


I think we remain guessing at this one... :hmm:

pelly3s
01-04-2008, 04:40 AM
this may sound stupid but how clean is the AC line power? Are you using any power conditioners? I cant really say I have heard RF in the power come through as a hiss but I have heard it cause other noises in the high frequency range. Its a wild guess, dont hold me to it. Also start at the beginning of the signal chain and unplug one piece of gear at a time and see what that does then if can help eliminate the main source of the noise.

KenWH
01-04-2008, 06:39 AM
I'm running everything behind Furman PS PROII's(20amp units). I've got 2 other small systems in other rooms and they both have line conditioners with ac meters on the front. They show my AC voltage at around 123-125v. Would the slightly above average voltage have any effect on noise...and hiss specifically?

Mr. Widget
01-04-2008, 07:50 AM
Would the slightly above average voltage have any effect on noise...and hiss specifically?No.

I read this thread months ago, but don't remember the details... I am sorry to hear you are still being frustrated by this. I would guess your problem is either gain structure, crappy electronics, or both. Realize that with a high efficiency system, the background noise of the electronics becomes much more noticeable, that said with the proper gain structure and good electronics you can have the hiss level down to where you need to be right on top of the tweeter or midrange to actually hear it.


Widget

KenWH
01-04-2008, 09:57 AM
As a last ditch effort I just installed an Ashly XR1001 in place of the digital BBE x-over...still hissing...though I really like the Ashly's sound. Very noticeable improvement in sound quality over any of the other x-overs I've used. I even ripped my whole system apart and rewired it to a 2ch bare minimum this morning:

cd player>preamp>x-over>pwr.amps>speakers= same loud hiss from horns!!!:banghead:


Mr. Widget:

Basically I had QSC pro-amps which I could dial their gain back to reduce the hiss to fairly tolerable levels.

In order to stream-line my system some (two power amps instead of 5) and reduce fan noise I decided to use an Outlaw 7700 and a Monster 3250 consumer amps. The consumer amps don't have gain controls so the hiss hits full bore. I've narrowed the hiss down to the active x-overs(I tried several different brand analog and digital units). They all seem to inject a same amount of hiss through the horns(easily audible from 20' away).

My only other recourse is maybe some attenuation at the power amps...I've stumbled across some attenuators from Rothwell which are plugged inline with the rca inputs on the amp. They give around 10db of attenuation at the input.

What do you guys think?

Thanks,
Ken

pelly3s
01-04-2008, 10:46 AM
take the crossover out of the picture and just plug your preamp directly into the amp and see what happens then. that will definately tell you if it is the crossover doing it. I had the same issue with a customer when he switched to an active crossover or a passive in his PA the components in the passive crossover are using up some of the energy that goes to the speaker so there was little to no hiss but once they were bi-amped you could hear a hissing. It was fixed by properly setting the gain structure through the system. There is always a solution to a problem

hjames
01-04-2008, 10:53 AM
bringing the original post up to the head of the pack ...

Are you having the same problem no matter what media/source you are using?

Do you get the same hiss if you run a CD player directly to your xover and skip any receiver/preamp?


Hi guys,

Maybe you guys can help me with bi-amping my front JBL 4675's & 4670.
Pre/pro=Denon 2807
HF amp= L/C/R channels of an Outlaw 7700
LF amp=Monster MPA-3250

Signal from Denon is unbalanced.

I've tried several different prosound x-overs including a behringer dcx2496 digital, an analog dbx, an analog behringer, and I currently have a bbe ds48 digital. All of them have caused too much hiss.

Thinking maybe the hiss is due to trying to run a balanced pro sound x-over with an unbalanced signal I even tried my old Audio Control caraudio x-over and it hissed badly also.

Everything I've tried results in WAY too much hiss coming from the horns.:banghead:

I tried various level settings such as boosting the input signal and cutting the hf outputs on the x-overs but it really didn't help. Basically with all trims on the x-over at their minimum I still hear a lot of hiss.

If i just run the signal straight from Denon right into the Outlaw(hf amp) then there's barely any hiss at all.

Both the Outlaw and the Monster have the balanced input option so would getting something like a rane balance buddy to get a balanced signal help hiss?

Thanks in advance for the help,
Ken

johnaec
01-04-2008, 11:12 AM
It sounds to me like you just don't have your gain structure adjusted correctly. Set the CD player for maximum output, then the preamp for max before overload, (if it doesn't have signal overload meters or lights, put the volume control at least halfway up), then, while being driven, be sure the amps are turned all the way down, then, adjust the signal lights to just below clipping on the inputs and outputs of the crossover, (it does have these indicators, I hope). Now, with all these signal sources running at max [optimization], bring the power amp levels up to the volume that bsuits you.

The procedures above should guarantee the least hiss in your system. The way you currently have the levels set, it's obvious that either the preamp or crossover has its levels set way below optimum, so the amp is having to be turned way up to compensate, resulting in overamplifying the hiss from the upstream components.

John

KenWH
01-04-2008, 12:13 PM
Thanks for the reply guys.:)

When the active crossover is out of the system so is the hiss.

As to gain structure...I've tried every possible gain adustment. My current amps do not have gain controls so yes that's not helping matters. BUT even when I had amps with gain controls and had the gains in the entire system properly set as suggested by many in this thread the hiss was still there...quieter yes but still there and noticeable during quiet moments in movies and music.

JBL 4645
01-04-2008, 01:46 PM
Happy new year Ken, :) I thought you had shot the DCX2496 by now! You know just like, Evils! Damn that hiss! BANG! :die::D

What is the gain settings on the outputs of the DCX2496 again please? And what is the level settings on the amplifier levels, hey about some pictures, of you tearing your hair out over this hiss issue?

Otherwise turn down the volume for each LCR amplifier that is driving the JBL 2360-A HF horns, use pink noise to make sure each one of them has the same SPL db level.

Oh one more thing is the DCX2496 clipping on the inputs or outputs, with program source material?

Earl K
01-04-2008, 02:49 PM
When the active crossover is out of the system so is the hiss.


- If the active crossover is truly the source of your hiss problem / then that hiss will continue to present itself / with just the following components connected to each other ( & turned on, of course ). *** Active Crossover > Amps > Speakers .***

- Make sure you don't utilyze any of the on-board EQ features that may be present ( this applies to any of the crossovers previously mentioned ) ie ; don't use any CD Horn Compensation EQ ( if present ) . These EQ circuit are all noise generators IME, & also sound quite lousy .


I also suppose I could "Y" the l/c/r signal coming from my pre/pro. Then I could run one end of the "Y" directly to the HF amp then use my JBL speaker level x-overs as a high-pass filter and run the the other end of the "Y" through the active line-level x-over to get the lows...in theory that'd keep the noisy active x-over away from my horns.

- I do this on my biamp setup. The active crossover feeds the woofer amp only / while the horns ( fed through a "Y" split ) have passive filtering applied after the amp. ( FWIW , I also limit lowbass going into the HF amp by inserting a simple inline cap that rolls-off frequencies below 250 hz .)

:)

Mr. Widget
01-04-2008, 03:42 PM
When the active crossover is out of the system so is the hiss.

As to gain structure...I've tried every possible gain adustment.Gain structure is definitely your problem... now you need to figure out a fix. I know when I was using the Ashly in my system I had it's input gain turned almost all the way off and the output was also below unity gain to reduce hiss to an acceptable level.


Widget

JBL 4645
01-04-2008, 05:40 PM
Gain structure is definitely your problem... now you need to figure out a fix. I know when I was using the Ashly in my system I had it's input gain turned almost all the way off and the output was also below unity gain to reduce hiss to an acceptable level.



Widget

Widget

How much will this decrease the ability of the DCX2496 factions like dynamic EQ or the audio limiter function, with the levels turned down to -15db on the DCX2496, not that I have investigated this issue as of yet. But how will this affect Ken’s situation will he be smiling or still banging his head against the wall?


Earl K

What you’re saying is if I where to playback each channel into an RTA with some pink noise and careful look at the display starting with channels 2 4 and 6 has that is how the HF outputs are assigned I would notice a peak difference with channel 6 as that is where the hiss is mostly noticeable.

Therefore its going to change the characteristics of sound? With a little boast between the 4 and 8Khz range because that’s where I plotted it when playing the channel into an RTA with no sound, I just turned the levels RIGHT UP! And noticed the noise moving on the RTA.

Tim Rinkerman
06-23-2008, 01:22 PM
I have used many Denon CD players, and they are not particularly quiet to begin with...you have yet to mention a crossover that I would say is audiophile quiet...Mr. Grumpy had the best attack...short the inputs and see if it is quiet..I would bet your hiss is originating from the Denon..by taking the active crossover out of the system, you are eliminating at least 2 gain stages,that will lower the overall noise floor.

boputnam
06-23-2008, 02:24 PM
..by taking the active crossover out of the system, you are eliminating at least 2 gain stages,that will lower the overall noise floor.Uh, I am going to look way moronic here, but in doing so, he won't be bi-amped.

:dont-know

Tim Rinkerman
06-23-2008, 04:25 PM
Sorry about that...I missed a page of attempts...
Your pre-amp is probably running at-10 db. ( consumer level) output, pro crossovers are usually set up to see a signal more like +4 db. I think what you are hearing is a -10 db source with 14 db or more of operating noise added to it....kind of like trying to amplify a microphone level signal with a line level pre-amp.

JBL 4645
08-31-2008, 02:05 PM
I was just thinking of KenWH where is he has he falling off the face of the planet?

I was wondering about the HF hiss issue as if I didn’t care, well I do! I was thinking what about wiring a passive crossover and use the woofer section to filter down the hiss.

Now this will change the characteristics of the tone when sending pink noise around so a little EQ might have to be applied to bring it back up.

This is hiss on that is mostly on the right HF is centred around 4 or 8 KHz I forget which, but I think its 4Khz.

hjames
08-31-2008, 07:03 PM
Ya know, its pretty pointless to troubleshoot someone else's problem if he hasn't been here since January to give any feedback on people's previous suggestions ...

Can't be much of a problem if he hasn't asked for more suggestions in 9 months since this started ...





I was just thinking of KenWH - where is he? Has he falling off the face of the planet?
I was wondering about the HF hiss issue as if ...

JBL 4645
10-09-2008, 02:43 PM
Ya know, its pretty pointless to troubleshoot someone else's problem if he hasn't been here since January to give any feedback on people's previous suggestions ...

Can't be much of a problem if he hasn't asked for more suggestions in 9 months since this started ...

Yeah maybe youíre right.:confused:

KenWH
02-05-2009, 07:09 AM
Hi guys and thanks again for all the help in this thread. Sorry for not posting...I didn't fall off the planet. :)

It seemed the thread kept running into the same brick wall...gain structure...and I basically exhausted all adjustments I have. I just decided to live with it. A couple months ago I did add HSL -12db line level attenuators on the horn amp inputs which did help a bit but I'm far from statisfied.

My next step will be replacing the Denon receiver with a new pre/pro with balanced outs. I'm looking at the new Outlaw that's on the way(if it ever gets released).

I figure the "hotter" balanced signal from the pre/pro can only help with noise.

My other thought was to go ahead and having Marchand build me a passive 3ch. line level x-over as to eliminate all the sources of noise(op amps etc) within typical active x-overs.

Anyway thanks again guys!!!

JBL 4645
02-05-2009, 07:15 AM
Hi guys and thanks again for all the help in this thread. Sorry for not posting...I didn't fall off the planet. :)


Well it was good simulation.:D

I see you Ken! Where in the blazes have you been in these past few months?

Have you solved he hiss issue?:D


Keep the level down on the output stages as it does produce a mild overload of sort at low frequencies.

Just amp up the level and test the LF and HF for a soft mild 75db use the amp to control the level, keep it soft you only need so much of it, too much and you’ll get that sodden his noise on the right channel 6 on the DCX2496.

Yeah get some amplifiers that you can adjust.

JBK
02-12-2009, 10:50 PM
hi!!:)
My hifi system is composed by two 4675A, wich horns (2360A) have been removed, and I have put two IWATA horn instead. compressions are two 2450j, and as tweeters, two fostex T925A.
My amp is a MC7300, my preamp a C220, and my cd/sacd is a MCD301...
I've choosen to built a passive crossover...
(loudspeakers in the 4648 box are the 2226H)
The cutoff frequency is 500Hz, and the slope I've choosen 12db:
For the bass:
3,3mH, 31ĶF
Med/High:
10ĶF, 10,1mH, (att: 8db:R1=2x4,7 ohms, R2=8,2+2,2 ohms)

I find that's great!!!
Sorry for my language, :o: I'm french!!:o:
Regards, JBK

KenWH
02-13-2009, 06:08 AM
Hi JBK

When I run the passive JBL 3160's the horns are very clean...barely any noise at all...the drawback I found was the woofers were crippled a bit. Running the speakers bi-amp'd gives me much better control over the levels. Now if only I can get the noise out of the horns when using active x-overs.:banghead:

Mr. Widget
02-13-2009, 11:07 AM
Hi guys and thanks again for all the help in this thread. Sorry for not posting...I didn't fall off the planet. :)What crossover(s) are you currently using?

I think you summed it up when you said the hiss goes away when the active crossover does... it is still likely a combination of the crossover and gain structure. Virtually every active biamped system I have owned or heard has had some background hiss... then to add insult to injury this is always exacerbated by using high efficiency horn systems in small to medium sized quiet listening rooms... acceptable hiss in a stadium just doesn't work at home. :)

That said, I have always been able to get the hiss level down to where it was not noticeable at the listening position. You need a quiet crossover and diligently set it up... I believe from your posts you have exhausted the set up, so it would appear you need a quieter crossover. I doubt a new pre-pro will solve your problem.


Widget

grumpy
02-13-2009, 11:21 AM
Maybe not the most efficient use of equipment, but why not use the passive
crossover for the horn and active crossover for the bass? (as was stated
earlier in the thread).

Mr. Widget
02-13-2009, 11:54 AM
Maybe not the most efficient use of equipment, but why not use the passive
crossover for the horn and active crossover for the bass? (as was stated
earlier in the thread).I'd give that a try... what's to lose? It should take care of the hiss and give you most of the control you want.


Widget

JBK
02-13-2009, 11:57 AM
You're absolutely right when you tell that bi-amp allows a better control of the woofer...
The only thing which hold me back is money!!!!:deal:

For this reason, I have to wait... And I hate it!!
When I will be able to buy it, I will put a mac MC275 for the high and the mids, and my MC7300 will control the 2226 with strenght and ease!!!

The question I'm asking you is: What will sound louder in the horns? Active crossover, or tubes from the MC275?
One way or another, it will be better than tubes+active XO!!

A friend try to dismantle a passive crossover from an old JBL speaker... But it was full of resin!!! Impossible to see which values were used!! If you broke resin with a screwdriver, you will pulverize the components!!
When you've worked two years to build the ultimate XO, you don't want everyone to be able to make the same!! Clever idea!!

You're lucky to live in USA, there are a lot of cheap tubes amps to buy!! But in France, 230 volts forced us to buy it in Europe... Price is more more and more expensive, snif!!!!:(

Regards, JBK

Egil
02-27-2010, 03:36 AM
Bringing up an old thread..

But here goes; Just like the op, I want to bi-amp some Waveguide speakers im currently working on, Im using a Behringer DCX 2496 as an active crossover.



CD: BMS 4550 (driven by an Emotiva XPA-3: http://www.emotiva.com/xpa3.shtm )
LF: JBL 2226H (driven by a Behringer EP2500)


There is a 33uf capacitator on the CD.

Here is a picture of how everything is set up:

http://img692.imageshack.us/img692/8552/setupvq.jpg

I just bought the Samson S Converter, hoping it would take care of the hiss problem.. it didn't..


- When I turn off the DCX 2496, the noise is basically gone (you can hear some really low hiss. If I then turn off the Emotiva XPA-3, the noise is completely gone, naturally. So I assume that LOW-lvl hiss is caused by the Emotiva? If it was like that I would be more than satisified)

- There is noise regardless of where my AVR level is (maxed or off), and the noise doesn't get louder/lower when playing with the AVR level

- I tried plugging the DCX2496 and Emotiva XPA-3 in a plug with ground wiring - same noise

- I have even tried another DCX2496 (my brothers), same noise !

- I connected the CDs to the same speaker outputs on the EP2500, driving the JBLs, using banana plugs.. - I did this just to see if there was noise coming from the CDs with a PRO-amp as well.. I didn't play any music of course. The noise was still there..

- If I MUTE the CD on the DCX2496, the noise is still there !

- Btw, the noise is A N N O Y I N G ! You can hear it so loud & clear when im sitting at the LP 5m away.. im still able to enjoy music if I just crank it up a bit.. but I don't think I can live with that hiss.



After reading this thread, I can say that I haven't tried any attenuation (L-pad) of some sort, on the XPA-3. The Samson S-converter I bought seems to be a waste of money, - unless - I need to hook it up in a different way (Im going to try and hook it up from the Emotiva -> Samson Converter -> DCX2496).


EDIT: Problem solved!
I hooked up the Samson S-converter from the Emotiva-> DCX2496, and the hiss is pretty much gone!!!
I guess I was a bit too hasty :)

lgvenable
03-12-2010, 04:37 PM
ground loop hum, use balanced connectors,
or
Behringer hd400 hum destroyers...they work.

Guy in WNY
07-15-2010, 10:05 PM
Hi,
I use 3 Furman tx3 tuneable crossovers. The first is stereo 2 way and splits off the sub woofer from the rest. The rest goes to the other pair ,one for each channel, configured as a mono 3-way (LF 2x12", Mids 2350/2482, HF 2402). Very little hiss, but all equipment is in the 7' rack so I have the ground loop problems that cause hum. I used insulated washers to mount the amps, that helped a lot. Using Crown PSA-2 for subs, DC-300a Series II for LF, DC-300a Series II for Mids, and Marantz amp section for the 2402's.
Very little hiss, but the hum bothers me at times.
FYI
Guy in WNY

boputnam
07-15-2010, 10:15 PM
I used insulated washers to mount the amps, that helped a lot. ...but the hum bothers me at times.Hi, Guy...

The washers are fine, but that is not your biggest source of the GL. You will need to unplug everything and work backward from the amps (upstream) toward your sources, plugging one source's signal in at a time, until you find the culprit. That signal will need to be isolated from the system using some isolation transformers. There is a thread here somewhere that discusses this. Radio Shack has a cheap and very effective cable for this - works great.

glen101
07-16-2010, 07:59 AM
have not read the complete thread in detail, but feel I have been there with the x-over hiss.
There is a forum that covers the Behringer and describes a passive output stage, the mod is easy and makes a huge difference to the hiss. It will also drop the output by about 15dB.
I also found unless you are driving the x-over properly it will sound real compressed at low volumes, the only way out of this is to have a 6 channel attenuator after the x-over, the same forum covers this. In the ned I gave up and went back to my L96 3 ways and added a sub.
Best of luck.

ellisr63
10-15-2015, 10:18 AM
I switched out my MiniDSP balanced crossovers with a Xilica XP4080, and the hiss is gone.

audiomagnate
10-15-2015, 11:11 AM
have not read the complete thread in detail, but feel I have been there with the x-over hiss.
There is a forum that covers the Behringer and describes a passive output stage, the mod is easy and makes a huge difference to the hiss. It will also drop the output by about 15dB.
I also found unless you are driving the x-over properly it will sound real compressed at low volumes, the only way out of this is to have a 6 channel attenuator after the x-over, the same forum covers this. In the ned I gave up and went back to my L96 3 ways and added a sub.
Best of luck.

One of the reason I like my BGW 620B's so much...Alps attenuators.

loach71
10-15-2015, 03:01 PM
have not read the complete thread in detail, but feel I have been there with the x-over hiss.
There is a forum that covers the Behringer and describes a passive output stage, the mod is easy and makes a huge difference to the hiss. It will also drop the output by about 15dB.
I also found unless you are driving the x-over properly it will sound real compressed at low volumes, the only way out of this is to have a 6 channel attenuator after the x-over, the same forum covers this. In the ned I gave up and went back to my L96 3 ways and added a sub.
Best of luck.

What is that forum's URL?

Ed Zeppeli
10-15-2015, 05:50 PM
I switched out my MiniDSP balanced crossovers with a Xilica XP4080, and the hiss is gone.


Nice. How do you like the Xilica overall? Nice interface etc....?

Thanks,

Warren

allen mueller
10-17-2015, 01:12 PM
I've got an xilica crossover that I'm very happy with. I do the programming via the USB on the front and the program is easy to use.

ivica
10-18-2015, 07:11 AM
I switched out my MiniDSP balanced crossovers with a Xilica XP4080, and the hiss is gone.

Hi ellisr63,

What model of MiniDSP You have been used before using Xilica XP4080 ?

regards
ivica

ellisr63
10-19-2015, 05:00 PM
Nice. How do you like the Xilica overall? Nice interface etc....?

Thanks,

Warren

I like it very much. It has a little learning curve, but not much. Once you learn it it is very easy to use. I prefer doing most of my adjustments with the web interface which is very nice IMO.

ellisr63
10-19-2015, 05:03 PM
Hi ellisr63,

What model of MiniDSP You have been used before using Xilica XP4080 ?

regards
ivica
I had the balanced 2x4 in a box version (not the kit). I originally had the unbalanced and loved it, but when I went to the balanced version I had a hiss problem. I am not sure if most people would hear it, but in my setup it was hearable from over 12' away. With less efficient speakers it might be fine.