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Ken Pachkowsky
02-05-2005, 12:37 AM
Hi all

As a few of you know I have been struggling with ground loop hum and buzz since going to a multiple amplifier system. The problem is mild but never the less quite disturbing between tracks on a quiet evening.

I purchased a Xentek 2.5Kva 8 output single phase extreme power isolator transformer/conditioner.

I don't know a damned thing about these but have noticed several studio's use this brand so figured "what the hell".

Here is a link to the purchase. Does anyone have any experience with these units? Any thoughts would be welcome.

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&rd=1&item=3870456557&ssPageName=STRK:MEWN:IT

Ken

jtgyn
02-05-2005, 01:34 AM
G'Day Ken,
I have never even seen one of these actual units before but from the units I have used for computer systems this looks like a "ultra isolation transformer".

The "8 output" is probably "8 outlet", my guess is that all the outputs are commoned.

A good unit will have an electrostatic shield around the primary and secondary windings of the transformer (and possibly two earth points).

This unit will reduce EMI from the mains coupling to your amps.

Regards Scott

JBLGUY
02-05-2005, 07:29 AM
I have had great sucess in my multi amp system by using Ebtech Hum Eliminators. Try a music shop for these. Musicans use them and they even sell a unit that is rack mountable for doing several leads in one unit. I think the rack mount unit has eight eliminators in one box.

Mine solved many hum and ground loop noise with these units. I found they had no adverse effects on sound qaulity at all.

They are for isolating ground loops and getting rid of it from your signals

Worked for me and I tried many solutions before finding these units

I couldn't find Ebtechs site directly but here is some info for you anyway

http://www.sweetwater.com/store/manufacturer/Ebtech

Flodstroem
02-05-2005, 08:25 AM
Hi Ken

Read about your problems with groud loops. Im not an expert in this field but I know some basics.

At the very first, I dont know anything about your own system and there is why Im asking this:

Is your equipment a balanced system or is it unbalanced (or a combination)?

Generaly, ground loops (hum and noise) show up when systems are "double grounded" or even worse "multi grounded". which will be the case when you use grounded power mains outlets/cables to your amplifiers in combination with shielded, grounded signal cables (maybe also you have a rack system installation?).

When going to try to find out of the fault/problem, there is a good rule to NOT to use your main speakers, but only use "krap-speakers" (to detect hum/buzz etc..). Instead of speakers you could also use stereo headphones. This will sawe your main speakers to not to "burn up" if a realy "ful power" ground loop occures when working with different solutions.
----------------------------------------

1)
The first thing to do is to try to detect which amp is double earthed (mains earthed + signal earthed). If this is the case, then you must cut the earth wire from the mains cable to that amp. But, be aware of this: there must be at least one amp that must be properly mains grounded to avoide power/mains shock if something does a failure.

2)
Another possibillity to a double ground loop connection could be if you have your equipment mounted in a rack cabinet system (if 19" rack system made of metal is in use).

In this case you could try to cut both the mains grounding and the signal grounding (grounding is stil ashived by the cabinets metal-case inter connections to the amplifiers ( but remember, at least one amp must be properly grounded to the mains earth.

3)
You could have a cable who is not properly internerly connected eg. the signal and signal ground is not connected in the right way (only if using a balanced coupled system)

4)
Maybe you have a big power amp placed at the top of / or at the bottom of your control console/ line amp ore CD/ DVD player. In this case the power transformer in the power amp can produce a magnetic field iduced hum and noise in the conrol console.

6)
Is it possible that you use a common (-) kable to your speaker (eg. drivers)
This is generaly the case if ther is a separat lodspeaker switch connected between the power amp and different types of loudspeaker in the signal/speaker leads (a switched distribution system). Solution: keep all the loudspeaker kable pairs separated. If a bad switch: change it to one which have all the (-) kables separated.

5)
If it is an RFi distortion induced case, then you could try to connect RFi filters at the inputs of your control amps (also to your power amp.). It could also help if you cut your inter signal ground connection (in control/line amp) right there where it is connected to the shassis (often at the sides in the near by of the input connectors) and place a 1-10 ohms (2-4 Watts) resistor between the ground and the shassis.
----------------------------------------

When there is an environment which containes a many different types of grounded and ungrounded electrical products, and there is a possibillity to an human electrical shock, then it is very common to use an isolation transformer to eliminate that risk.

Ok I stop here,
the few hints presented here could be a solution for you, Ken, but you have certainly checked all this?

Best Regards :dont-know

stevem
02-05-2005, 08:45 AM
I was plagued by ground loop hum for years. I finally got rid of it by plugging everything into a dedicated 30 amp line, which gave the whole system a single ground point.

Ken Pachkowsky
02-05-2005, 09:27 AM
Hi Guys

I appreciate all the reply's. Yes, I have tried switching all components to balanced lines. I run my whole system off 1 15 amp circuit.

I may go the dedicated 30 amp route if this Isolation Transformer does not solve the problem. I can't help but think 15 amps is not enough anyway?

Bo has spent a fair bit of time helping me get the system to this point which is far better than it was.

Funny, when it was a simple bi-amp system it was dead quiet.

With eight amps, I have created a nightmare.

Still interested if anyone is familiar with this Isolation unit?

Ken

Ken Pachkowsky
02-05-2005, 09:31 AM
I have had great sucess in my multi amp system by using Ebtech Hum Eliminators.

Thanks JBLGUY

I have contemplated this route but will only do it as a last resort. I have heard great things about Radial Engineering Products (JD6). They use passive Jensen transformers which are highly regarded as the best. It retails for 800.00 bucks.

Ken

Ken Pachkowsky
02-05-2005, 09:38 AM
Hi Ken

Read about your problems with groud loops. Im not an expert in this field but I know some basics.



Flodstroem, you put a great deal of time into this post and I appreciate it very much. This is one of the reason's this is a great site with great members.

The short answer to your reply is "yes". I found your comments re placing a large Power Amp near a CD Player most interesting. I had exactly this problem when racking (Wood Rack) my Sony CDP-D11 above a AB 980A amp.

Its a complicated system at best and without spending thousands of dollars I may never completely eliminate the problem.

Thanks again for a great reply to my post.

Ken

Ian Mackenzie
02-05-2005, 02:38 PM
Ken,

Continue to persist, don't let the Hum Bugger you (sorry could not resist..LOL).

So here is your Hum Bugger Recipe..

1. If its a faint hum it could EMI induced from a hi level component near a transformer or a hi level lead close to a mains cable.

2.You mention no hum with a two way. Were you using the same crossover unit and pre amp. Are all your amps the same kind or brand?

3. As a means of process of elimination does in fact the hum come from both channels?

4. Does the hum come from one driver..low, or mid, or high or tweeter or all the drivers? If the former is the case check the signal and mains wiring for this unit.

5. If not try this. Unplug one amp at a time from the mains (breaking the mains earth connection from common earth and try and determine of the total hum from the system is eliminated. By process of elimination you will fine the offending amp.

6. If this does not reveal the problem the hum or potential ground loop is further up stream in the signal chain. Carefully check the shield of all signal cables that the shield is terminated to both ends of all cables.

Another source is the crossover itself, carefully disconnect one crossover band at a time to determine if the hum is eliminated. If not disconnect the signal input from the crossover and check again.

7. It should be pointed out that multi amping a hi sensitivity system is going to make any source of noise an issue for the user, particularly in a small room.

Why? If the horn has a rated sensitivity of 107db for example, the noise floor
and dynamic range will be stretched whereas if the sensitivity were for example 93 db, there woulde be a 14 db reduction in noise.

With this information a reasonable solution is to use passive attention at the power amplifier output to the horn (or other drivers with exception of the woofer) to pad back the driver sensitivity.

If you have attempted the above steps try this approach to noise reduction, not as a last resort but will improve the signal to noise ratio of the system.
This approach should not in anyway hinder the sound quality of the system but some adjustment of the power amp input levels will be required. As only small amounts of power are required for hi sensitivity drivers , the power losses when multi amping ae not a major issue, use suitable power resisters however.


Good luck

Ian:blink:

Zilch
02-05-2005, 04:29 PM
A brief hum sleuthing story I haven't figured out yet. Generally, I have no problem running unbalanced consumer sources into balanced pro gear.

M552 crossover was sitting on top of the 6230 amp. I could move it around and eliminate the hum. Good. I'll just re-arrange things and put some separation between them. Transformer in amp is likely inducing hum in the crossover.

Nope. Turns out it was the unbalanced cables from the source into the M552 picking up from somewhere. When I held the cables in my hands, the hum diminished. Tying the cables to each other with cable ties reduced it to below the irritation level.

More investigation yet to do on this one, obviously. It makes NO sense thus far. Sounds like shield is not connected on one or both of them, maybe, or the source is floating....

Ian Mackenzie
02-05-2005, 05:29 PM
Now that is odd.

As a rule of thumb the -ve input of the balanced unit should be shorted with a link to ground at the input of the balanced unit.The inner or signal lead of your unabalanced RCA lead should go the the +ve of the balanced input and the sheild to ground.

Check your wiring.

Ian

JBLGUY
02-05-2005, 09:03 PM
Ian's suggestion is valid and worth trying. I did all of that and more and finally narrowed it down to a home made unit I was using for creating a true mono centre output from the pre out.

But the Hum Eliminators also did a lot as well. Without them I'm not sure I could have done it with huge cost and massive trouble. I really don't have the space to lay everything the way I would like.

There must be a least 70 set of cables and speakers wires.

I have 13 channels of amps and over 21 differant pieces connected and there is no Hum or buzz at all.

Just some hiss that is a result of using Ultra effecient speakers.

Tim Rinkerman
02-08-2005, 07:49 AM
You have a hum...no doubt a 60cycle hum..usually transmitted from one a.c powered device to another a.c.powered device through a wire that should only be carrying precious audio information.
Have you tried dis-connecting the shield from one end of your interconnects? Hum is a ground loop...even though you ground all your devices to a common ground and only use one supply circut, you have two devices with a different ground potential talking to (arguing with?) each other.
There as many ways to hook up a system as there are ways to do your taxes,but these are a few fixes that have worked for me and many others in the past,with great success....
Are all of your components mechanically racked together? Screwed into the same metal rack rail? Some components tie the chassis to the audio ground,not always good. Measure for potential voltage between the pin 1(shield) of your balanced connectors. It sounds to me like your are carrying current down your shields. Solution? disconnect the shield on one end. It will still act like a shield,but won't conduct between components. I have fixed many ground problems between two pieces that hated talking to each other simply by cutting the shield on the RCA interconnects!
If you have 3 wire plugs on your gear(I hear OSHA coming..)use grounding adapters to un-ground one or more components and see if the hum changes..
When you split a signal many ways, its potential for picking up interference multiplies every time it goes to a new component.
I would try these before going to more drastic($) methods. I have used Xentek's before, they will give a very good isolation between neutral and ground, and that's about it. They don't fix "bad" power..the fact that your bi-amped system was clean, tells me that there is nothing wrong with your A.C. source.
Could you list your components,or do a block diagram as to how your equipment is connected? I have NEVER been beaten by a buzz or hum, I'd love to help.. Tim

Ken Pachkowsky
02-08-2005, 08:38 AM
Could you list your components,or do a block diagram as to how your equipment is connected? I have NEVER been beaten by a buzz or hum, I'd love to help.. Tim

Tim

Thanks for the reply. I will do up a block diagram and post it here. I will try and have it posted today.

Ken

Ken Pachkowsky
02-08-2005, 01:41 PM
Here is a BD. I forgot to note the PIN 1 connections are NOT lifted between the white 4400's in and outs with the preamp. But as I recall I tried it with no better results.

Tim Rinkerman
02-08-2005, 03:21 PM
OK, first, a couple of questions...is the system quiet with nothing plugged into the crossover? I'm getting at finding out if you have interaction between your amps and crossover, or if you are inducing a problem in the Adcom,and passing it along and amplifying it. You basically have a mixing section and an amplification section...from the Whites to the AB's, you should be able to achieve nothing but hiss, or operating noise through a combination of pin 1 lifting and ground lifting at the AC plugs. Make your amplification section quiet and work backwards.
Do you know what kind of amplifiers the Westlake was originally meant to drive? Do you know the input sensitivity of your amps? A low output crossover with a high input sensivity amp will magnify noise problems.Do all of your devices have the same pin polarity? Pin 1 is always ground, but many manufacturers differ on pins 2 and 3,3 being positive sometimes, or negative sometimes. In a truly balanced situation it's not supposed to matter, but if the negative side is tied to ground some where, or referenced to shield, it matters alot,fast.
So, Mr. Phelps, your mission, should you choose to accept it, is to determine which section of your system is causing your hum...you find it, I'll help you kill it. As always, if any of your IM force is caught or killed, the secretary will disavow any knowledge of sending me your monitors....:D Tim

boputnam
02-11-2005, 03:37 AM
1)
The first thing to do is to try to detect which amp is double earthed (mains earthed + signal earthed). If this is the case, then you must cut the earth wire from the mains cable to that amp. I would not do this.

Ken, we've gone 'round on this, I know! Were you successful trying to find the source of the hum as we talked some weeks back? This is the advice you also got from Ian, and some others, here.

Isolation devices can work (and I have in the past used them, too), but you are merely covering-up the symptom without knowing the problem. You can trace the hum using your Westlakes without risk - just keep the gain low. Try one speaker at a time (that is, only one way of your four way so all other transducer sets are disconnected), one amp at a time (all others disconnected), after unplugging EVERYTHING into the preamp. If a hum, bypass the White. Bypass the crossover.

Hell, start with just the nekked preamp going full-range to one amp to one transducer (LF), and see if she hums. Not a slight buzzing (from a nekked preamp) but hums. If not, add the crossover. Then if not, add another amp. Then, if not, add another amp. Then, if not, add another amp. Then, if not, add the CD player to the preamp. Then, if not, add the whatever to the preamp... Build it up, man. The source(s) can and will be found.

Yours with love from South Africa,

Ian Mackenzie
02-11-2005, 04:20 AM
Hey you,

Where's the Post Card??:D

Ian

boputnam
02-11-2005, 04:26 AM
It's not in the Project May budget!!

:hmm: Neither is my return airfare. Uh-oh!! Now I gotta real problem! :rotfl:

Ken Pachkowsky
02-11-2005, 05:55 AM
I will be doing a complete dismantle and rewiring of the system this coming week. I have finaly recieved info from Westlake re ground lifting the HRX.

I will keep you all posted. By doing a complete rewiring it makes it much easier to be methodical in the approach to isolating the problem(s).

Thanks for all the help.

Ken

Alex Lancaster
02-11-2005, 07:27 AM
;) Bo: If You cannot get returnplane fare, You could:

Plan A: Get a job on a cargo ship that eventually ends up in the US.

Plan B: Watch out for sharks.

Best wishes, Alex.

johnaec
02-11-2005, 07:43 AM
Plan C: Prospect for diamonds!

John

Ken Pachkowsky
02-11-2005, 01:10 PM
Well, you guys were right. The isolation transformer did not do a damned thing to remove the GL. I did notice an improvement on my Pasma however. More detailed and absolutely no faint lines running through on any channel. They say I should get better detail on the sound system as well. We will see.

AS in my previous post. I am going to completely strip the system on Monday and follow your suggestions to the letter. One channel and amp at a time till I find the culprit.

The only reason I have not done this is the weight of these $%^& ing things. It takes 2 guys to move em (even on casters).

Will keep you all posted.

Ken

Ian Mackenzie
02-11-2005, 05:18 PM
Ken,

In an attempt to save some effort, can you unplugg the drivers systematically at the amp outputs? (or ar the amps under the speakers)

Ian

Tim Rinkerman
02-11-2005, 05:21 PM
Atta Boy....the Westlake crossover was the only piece I was not familiar with but seeing as how it is primarily a studio type piece that is meant to be tweaked to its surroundings, I'm not surprised if you have to adjust it to your set up. My thing is is that if you break the path between the pre-amp and the E.Q.'s you can1. see if the amp system is generating its own hum..2.see if the hum is an interaction between the pre section and the amp section, or, 3. if the inputs being ganged together in the pre amp are creating a hum that is being induced into the rest of the system..looking for interaction between different input devices. Good Luck,Tim