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trekman
12-03-2005, 07:49 PM
Anyone have any favorite amps large and small for running high efficiency speakers including compression drivers with respect to background noise (hiss/hum) in a multiway active crossover system? My old Biamp,QSC,Phase Linear, and Crown PS-400 all seem too loud unless the gains are turned way down. Thanks.

bbrown
12-03-2005, 08:02 PM
If you can build anything yourself, I would suggest some of the gainclone amps. They can be very quiet and clean. You could easily make a multi-channel amp with them without spending much money. There is almost nothing to them. At least for the mids and tweets.

Bruce

Ian Mackenzie
12-03-2005, 10:47 PM
Trekman ,

This is always an issue.

Not only your amps but also preamp and active crossover will contribute to noise.

Why swamp your system with noise and distortion?

Unless you are running a PA and want to squeeze every last drop of power one solution is to pad back the horns to a sensible sensitivity like say 97-100 dba.

Why you ask?

The benefit is in picking up 10 db on your S/N ratio and you also get improvements from pushing the signal chain 10 db harder.

This is important when you are sitting 15 feet from the mouth of those horns!

You amps will also sound cleaner running above of the sub 1 watt range where they tend to be most non linear....Another reason why horns sound subjectively better with passive crossovers to some audiophile purists!

Ian

Ken Pachkowsky
12-04-2005, 12:57 AM
Anyone have any favorite amps large and small for running high efficiency speakers including compression drivers with respect to background noise (hiss/hum) in a multiway active crossover system? My old Biamp,QSC,Phase Linear, and Crown PS-400 all seem too loud unless the gains are turned way down. Thanks.

This is a can of worms that I had opened and dealt with for almost a year before completely solving it. Have all your equipment using the same electical circuit. DO not use cheater plugs to solve the problem.



My Westlake’s use an active 4 way crossover with balanced in's and out's. "The best piece of advice I ever got relating to hum problems was from Bo". He suggested dropping pin 1 at every input on evry piece of electronics. Some techs call this telescoping balanced interconnects.



Being that my monitors require 3-4 guys to move I dabbled with changing some cables to the above and eliminated most of the problem. It's when I hired 4 guys to move the monitors and painted the living room that I got the opportunity to reconnect everything. I built all new cables using Canare Star Quad cable and Neutrik Gold XLR's with all pin 1's dropped per Bo's instructions. Dead silence was the end result, even running up to 8 separate amps. You literally have to put your ear up to the mouth of the large horns to hear even a slight hiss. The hum in the 2235's is non existent. I also built new RCA connectors using the same cable.

The point is, hum is not normal if your equipment is wired properly and in good working order. I waisted a ton of time and money buying isolation transformers and screwing around when the answer had been given to me 8 months before. I wish I had painted sooner:banghead:

Ken

trekman
12-04-2005, 10:38 PM
This is a can of worms that I had opened and dealt with for almost a year before completely solving it. Have all your equipment using the same electical circuit. DO not use cheater plugs to solve the problem......He suggested dropping pin 1 at every input on evry piece of electronics. Some techs call this telescoping balanced interconnects..............
Ken

My equipment chain is this: Preamp to a KT DN410 EQ (which has the balanced box checked off on it) with a RCA to XLR adaptor cable, to a XR4001 crossover with XLR-XLR cable. (I don't know if the KT has been modified for polarity, I plugged it in and it worked) Then some amps xlr and some rca or 1/4 phono. My cables are all under 10 feet, so I assume balanced operation won't save much noise. I did notice removing ground from those pro amps that had 3 pin power plugs reduced noise about 1/2. Home amps seem to have 2 pin power plugs. Do balanced inputs really make any difference with short cable runs?

Pin 1 is the ground pin. So break the ground path between units? This can't be done with the RCA or 1/4" non TRS cables, right? Can the chassis or something else be grounded between units, even though the theory seems to be eliminating grounds?

One really can't use the 2 pin AC adaptor? Doesn't drop noise totally either. I checked amps with a shorted or open input and they seem quite quiet on their own. Thanks.

Ian Mackenzie
12-05-2005, 02:17 AM
Bo is Dab hand at this stuff, zip him a pm.

Incidentially you should never lift or remove the amp ground from the mains, it tends to reduce life expectancy statistically!

Ian

boputnam
12-05-2005, 08:10 AM
So break the ground path between units? This can't be done with the RCA or 1/4" non TRS cables, right? Can the chassis or something else be grounded between units, even though the theory seems to be eliminating grounds?trekman...

Sorry - missed this.

You haven't mentioned your problem/symptom, except that the described signal path and interconnects is fraught with opportunity for ground loops... :spin:

But, the first trouble-shooting step is actually upstream from where you started.

1) Disconnect all device inputs to the pre-amp, but leave the pre-amp connected to the EQ, etc.
- No noise? Then, your problem lies between the preamp and the devices (a "common" location).
- Noise? Then, your problem lies from your preamp onward.

Come back with a report, and we'll work on that decision tree.

Oh, and please do not use an AC plug adaptor to lift the AC ground. Really a bad idea. You might have lessened the symptom (hum), but have not fixed the problem and have now voided gods warranty on you... :scold:

Mike Caldwell
12-05-2005, 08:28 AM
Hello
I would look over the gain structure of your system, adding a lot of gain at one point only to turn it down at another or adding a lot of gain to make up for a low level some where else.
I know the Phase Linear and the Crown will have unbalanced inputs, most likely RCA on the Phase and 1/4 tip sleeve on the Crown. The PSA 400 is basicly a DC 300 dressed up a little for home use. Depending ont he age and model of the QSC and Biamp they could be either way. The Older QSC MX series of amps had 1/4 inch balanced inputs that are wired with the tip (-) and the ring (+) backwards from most 1/4 tip ring sleeve balanced inputs. You mentioned using RCA to XLR adaptors. Short of using a active or transformer unit to do a balanced/unbalanced conversion you can adapt an unbalanced output to a balanced input or a balanced output to a unbalanced input you need to tie pin 3 (-) to pin 1 (ground). In the case of you Klark Teknik EQ that most likely is wired with pin 3 (+) you would tie Pin 2 to Pin 1, however if you would use pin 2 input to output you would not hear the difference. The adaptor you have should be able to be opened up to check the wiring by removing the XLR pins by turning the screw that on that end in to allow the pin body to slide out. Unless your adaptor had the RCA connector insulated from the rest of the XLR connector body it will connect the signal ground to the chassie ground on the XLR equipment that you plug it in to. Most pro audio equipment has the chassie ground isolated from the audio signal ground and or has a switch or a jumper to remove to help in ground hum isolation. Pin 1 lifting between equipment is a effective way to reduce or eliminate hum. An easy thing to do is make up a few short cables or buy adaptors with pin 1 dissconnected and try connecting them in at different places to see where you need them before cutting the connections on you perminate cables, just unplug one end and add your pin 1 life cable to the line. Also having everything powered from the same power source can help.

Mike Caldwell

toddalin
12-05-2005, 11:09 AM
While it is a receiver, my Yamaha RX-Z9 is dead quiet through my very efficient 130A/LE175/075 system. If their high end amps are as good...

For the Yamaha, you have to put your ear right up to the speakers to hear any residual noise. On the other hand, my dBx subwoofer amp through a 130A is easily heard in my quiet room in the seating position 13 feet away. Ambient levels in the room are on the order of 30 dBC.

trekman
12-05-2005, 04:56 PM
Thanks for all the helpful responses. I have eliminated sources before the preamp as noise source. When preamp is directly hooked to 1/4" non TRS Phase A60 amp, the noise is the least. Also inserting AC adaptor makes no difference. I suspect, because the Ashley crossover has TRS ins and outs, and the Phase doesn't, I need to make up a cable from XLR to 1/4, what would the pin connections be to the tip and sleeve? Is this the correct way or can it still be done using non trs 1/4" cable? Also, some mention lifting pin one, while others mention connecting pin three to pin one. Later I will tackle the Klark, right now that is out of the loop.

Thanks, Malcolm

boputnam
12-05-2005, 06:21 PM
Hey, Malcom...

Still need to know, with only preamp and Phase amp you still get a GL?

And, the preamp has balanced outs? If so, I worry about the balanced -> RCA adaptor, but you can try making one. Drop Pin1, and only connect the signal (+) and (-). But, I expect this will howl. Maybe not. Never can be sure.

If so, or otherwise, get an isolation transformer between the two components. We covered this in another thread recently. There's a number of ways to go. Let me search for that thread for you. HERE: http://audioheritage.csdco.com/vbulletin/showthread.php?p=75586#post75586 (http://audioheritage.csdco.com/vbulletin/showthread.php?p=75586#post75586)

If the preamp has balanced outs, and so does the KT, these interconnects are likely not the source of the GL.

I think the problem arises from that Phase amp. Since it is the last thing in the signal path, once it is connected it could be causing a host of problems upstream that otherwise appear/sound good.

trekman
12-05-2005, 09:53 PM
...

Still need to know, with only preamp and Phase amp you still get a GL?

I think the problem arises from that Phase amp. Since it is the last thing in the signal path, once it is connected it could be causing a host of problems upstream that otherwise appear/sound good.


The preamp (DB-1A) is standard RCA affair, and the Phase runs very quite when directly connected. I don't think the Phase causes upstream damage. I noticed my Biamp 2400 makes all the other amps hum, thats why I went to the Phase. I would prefer not to get any transformer couplers, and try the wiring route first.

boputnam
12-06-2005, 09:15 AM
OK, well, in the meantime, maybe some clarity would come from you doing the following:

1) How did you determine there is not GL coming from devices plugged into the preamp? The preamp having only RCA outs (not what I first understood...) makes me wonder about it.

More importantly:
2) Please list all the component names, models and bal or unbal.

It's confusing without more detail...

boputnam
12-06-2005, 09:20 AM
When preamp is directly hooked to 1/4" non TRS Phase A60 amp, the noise is the least. OK, this is making more sense.

You are going:

DB-1A preamp -> (RCA-1/4 unbalanced interconnect) -> Phase amp

Correct? And that has "the least" noise? But, it is not noise free?

So, we need to work from the speakers, backwards:
1) Phase amp -> Speakers, only. No Noise? Go to #2
2) DB-1A preamp -> Phase amp -> Speakers. No noise? Go to #3
3) post your findings. Then the riddle continues... ;)

trekman
12-06-2005, 09:49 AM
DB-1A preamp -> (RCA-1/4 unbalanced interconnect) -> Phase ampCorrect this is the hookup.

Phase amp only - no hum. very very low noise.

Add the preamp directly connected to Phase -- tiny bit more noise, but only noise increase comes from turning the volume way up on the preamp, not by merely connecting it.

Add the Ashly xr4001 xover, in between, more noise right away, just from hooking it up.


1) Phase amp -> Speakers, only. No Noise? Go to #2
2) DB-1A preamp -> Phase amp -> Speakers. No noise? Go to #3
3) post your findings. Then the riddle continues... ;)
1) No noise.
2) No noise.

boputnam
12-06-2005, 10:12 AM
Interesting...

1) Are all the components into the same AC outlet (same AC ground path)? Guessing they are.

2) The XR4001 is the only balanced component, correct? If so, all other components are finding an additional AC ground through the XR4001.

My grab is you are going to need an isolation transformer before the XR4001, between the DB-1A and the XR4001. Try that Radio Shack thingy first, before spending a lot of money - it should show if the diagnosis is on-track.

trekman
12-06-2005, 10:17 AM
There is no other way besides a transformer? I would rather not get involved with those in the signal path. Nothing can be done using xlr to 1/4 and wiring it a certain way?

boputnam
12-06-2005, 10:30 AM
Not that I'm aware of.
I - at one time... - tried all the possible wiring configurations myself. Futile, and I solder good! :p

The isolation transformer worked excellent for me on my unbalanced preamp. You will notice almost no signal loss, nor decrease in S/N ratio.

One day I realized I had something like three of them dangling off the preamp, between almost every component! :spin: That's when I finally admitted to myself that the preamp really was the issue, for me, since everything else downstream (and some components upstream...) were balanced.

Out went that preamp and in came the Adcom GFP-750, and Dixie Bell!! problem solved. :banghead:

Now I have quite a cache of unused isolation transformers!

trekman
12-06-2005, 10:44 AM
Will the balanced preamp need balanced sources such as Tuner, cassette, etc.? Thanks.

JuniorJBL
12-06-2005, 10:51 AM
Unplug EVERYTHING from that circuit. Make sure you are not on a GFI circuit as well. Then plug only your stereo equipment in. It is also best to make sure that your circuit that you are using does not have any lights on it. You want to have only one point of ground to eliminate ground loops. If you have some bad outlets you can also get ground loops.

If you plug all your equipment in and you still have noise then you have a problem with your equipment (if you have determined your circuit is good). Then you need to do Bo's troubleshooting tip's (BTT).


I have a mix of balanced and single-ended equipment and there is no noise in my system. alot of times I have found the circuit that people use has their fridge on it and that just creates havoc with audio equipment. A light will always feedback to the neutral from the hot side as well. I hope this helps ;)

boputnam
12-06-2005, 10:53 AM
Will the balanced preamp need balanced sources such as Tuner, cassette, etc.? Thanks.:no:

Mike Caldwell
12-06-2005, 02:56 PM
Hello
When you refer to "noise" with the Ashly hooked up is it in the form
of hum or hiss, static, white nosie ect. The type of noise can point to
different problems.

Mike Caldwell

Ken Pachkowsky
12-06-2005, 04:15 PM
Now I have quite a cache of unused isolation transformers!

%^%$, I thought maybe I could sell you some...

Ken

trekman
12-06-2005, 04:29 PM
Hello
When you refer to "noise" with the Ashly hooked up is it in the form
of hum or hiss, static, white nosie ect. The type of noise can point to
different problems.

Mike Caldwell

Hi Mike.
A little hiss, which seems normal for compression drivers.
The woofers have a grainy hum, perhaps centered at 240hz or lower, but not bassey sounding. Thanks, Malcolm

trekman
12-06-2005, 11:38 PM
..... Unless your adaptor had the RCA connector insulated from the rest of the XLR connector body it will connect the signal ground to the chassie ground on the XLR equipment that you plug it in to. Most pro audio equipment has the chassie ground isolated from the audio signal ground and or has a switch or a jumper to remove to help in ground hum isolation........
Mike Caldwell

Progress so far is leaning towards Bo's isolation transformer. The Klark doesn't seem to be the problem. Unbalanced preamp seems to be the source. With a balanced amp and the preamp disconnected noise is very low. With unbalanced amp noise is higher, ac adaptor inplace reduces it.

I thought perhaps using the +- on TRS plug (and no ground), too standard 1/4 on other end might do something, but much worse, and made the fault lights come on on the Phase A60 when ac adaptor used.

So last attempt before radioshack transformers...

My RCA to XLR does connect rca sleeve to the xlr sleeve. But I can pull the guts out and resolder. That leaves the 3 pin holder with or with out sleeve on one end, and rca female on other. How do I wire for the Klark? Thanks, Malcolm

johnaec
12-07-2005, 07:09 AM
Trekman - you may find this link informative: http://www.rane.com/note110.html

John

boputnam
12-07-2005, 08:40 AM
Progress so far is leaning towards Bo's isolation transformer. At least we know that will work.


ac adaptor inplace reduces it.:shock: :spchless: :flamed: :scold:


My RCA to XLR does connect rca sleeve to the xlr sleeve. But I can pull the guts out and resolder. That leaves the 3 pin holder with or with out sleeve on one end, and rca female on other. How do I wire for the Klark?If I understand ("3 pin holder"...? = XLR male), you should disconnect Pin1 (shield) at the Klark end of the interconnect. But, I expect this might howl, too.

Thanks for the updates. Now, get that "ac adaptor" into the trash...

trekman
12-07-2005, 10:47 PM
Thanks everyone for the good advice. In the end I probably should have done more online research and could have spare you guys the effort.... I wasn't expecting the balanced verse consumer interface to be such a problem. Lifting pin one on the rca/xlr adaptor did nothing by the way. The balancing transformer seems to help a little more. Thanks again, Malcolm

Charlie4350
12-07-2005, 11:12 PM
Trekman, I used to run a thin wire from the chassis of my crossover to chassis of the preamp before my system was fully balanced. It reduced hum/noise significantly. I had the crossove sitting on the preamp and if they weren't making contact just right, major hum. Finally I figured out to run a wire and no more problems. At the time it was Hafler 110 preamp (unbalanced) 5234, and my brandy new QSC EX amps (balanced).

boputnam
12-08-2005, 12:15 AM
....I wasn't expecting the balanced verse consumer interface to be such a problem. You are only the most recent to admit to falling into this snake pit. It is very difficult to overcome.

In the end, a balanced preamp may be your most satifsying solution - and in my case, revealed an enormous (read: stunning) improvement in audio quality. I was quite ignorant of what I was missing.