trying to bi-amp...crossover adding too much hiss

[boputnam]

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...

[pelly3s]

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]

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]

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]

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!!!


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]

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]

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.

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]

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]

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]

Happy new year Ken, I thought you had shot the DCX2496 by now! You know just like, Evils! Damn that hiss! BANG!

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]

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]

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]

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]

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]

..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