[Davey]

As far as I know, which is limited, any tube amplifier with an output transformer has to be hooked up to a load (dummy or speaker), or the transformer itself will be damaged.

I am sure some amp manufacturers can do something to the circuit to circumvent this issue, but my Manley Neo Classic 250s have to be hooked up to a load at all times, as per the manual.

I wouldn't consider them poorly designed, or not quality amplifiers, just the nature of the beast.

He was talking about the amplifier inputs, not the outputs.  (At least that's what he said.) 

Dave.

[Big Red Machine]

BRM,

Did you try putting cheaters on the speaker servo amplifiers? Just a thought. 

Yes, and a very bad result.

[jtwrace]

Something like this might be useful to look at - http://www.avahifi.com/index.php?option=com_content&view=article&id=270:ava-humdinger&catid=41:special-functions&Itemid=256

This is for transformer mechanical hum (DC on the line) though. 

[pjnad]

I had an issue with hum that could not be pinpointed or resolved despite many good suggestions from this forum and the manufacturers (Modwright,Krell)...someone suggetsed connecting a small gauge wire from the preamp to the amp ( I loosened a screw on the amp casing and attached it there) and lo and behold the hum was completely gone. It wasn't pretty but it worked. At some time later I had been changing cabling, although now I don't recall if it was ic's or power cords, and decided to disconnect the wire...no hum. Don't know if this helps but it's a easy solution to try.

[jea48]

I have tried quite a few things on my own to try and find the origin of a slight flutter, flutter, flutter coming from the tweeters.  At this point it is either the amps or the preamp.  It is not audible from my chair but the fact that it is there is making me angry.

If I disconnect inputs to the preamp the buzz is still there.

If I turn off the music server the buzz is still there with inputs connected.

If I add a cheater plug to the amps the buzz is way worse - sounds like a grounding issue.

For background the amps are balanced inputs only.  The preamp has only psuedo balanced connections and the preamp itself is NOT grounded to the AC.  It only has hot and neutral inputs connected off the IEC.  So the balanced connectors have the shield and return tied together at each connector.  Not sure this is relevant but mentioning it.

I am using balanced cables between the pre and amps right now.  I don't recall that SE cables were less noisy with an adapter at the amp end.  If it were the case I'd be there in the set-up.

If I move the amps to a different outlet on the same circuit the noise is the same.

If I move the entire front end power strip to a separate circuit, the noise is the same.

This tells me that the amps or preamp are causing the noise.

Any suggestions?

 "slight flutter, flutter, flutter coming from the tweeters."

JMHO, that is not AC 60Hz hum. If you said you have a tube preamp or tube power amp I would say you may have dirty small signal tube/socket pin connections.   

[sfox7076]

What happened when you put the cheater on the sub amp?  Odd that that would create a bad result.  Ground shouldn't operate to good effect really. 

[Big Red Machine]

What happened when you put the cheater on the sub amp?  Odd that that would create a bad result.  Ground shouldn't operate to good effect really.

Don't own a sub amp.  Main amps are the culprits.

[jhrlrd]

The Humdinger works like a hot damn for eliminating toroid buzz in my experience.
It is not intended to eliminate anything coming from the speakers however.

[jostber]

Did you find a solution to this problem? Have had a similar issue myself with one of my tube power amps with a large transformer. Have you tried to disconnect all components from the power except the power amp and then add them one by one to check if one of the components is causing a ground loop?

[tube-vds]

i had the same problem.

MY solutions were:

1. costs nothing: i had the turntable left and the tube amp right with about 20 cm distance (i thought that was enough - it was NOT); the turntable is now right and the tube amp left -> at least 60cm distance from tonearm to tube amp (output transformers)
2. costs 400$: i use this device for clean power (never believed in that stuff) of the phonoamp ->audioplan powerplant

the noise has gone now. good luck.

[werd]

Is it on both left and right tweeters, same amount of hum?

[Devil Doc]

J. Gordon Holt once wrote that if you can't hear it from the listening position, you shouldn't worry about it. I followed his advice and saved myself a whole lot of aggravation and anxiety.

Doc

[werd]

J. Gordon Holt once wrote that if you can't hear it from the listening position, you shouldn't worry about it. I followed his advice and saved myself a whole lot of aggravation and anxiety.

Doc

Depends on how the flutter manifests itself.  If it gets louder as you turn up the volume with nothing playing than that is a problem.  If the volume isn't a factor and its the same as you move the volume control then I probably would not worry about it.

[gregcss]

Jensen Iso-Max worked for me.

http://www.jensen-transformers.com/home-theater/audiophile/

[gregfisk]

J. Gordon Holt once wrote that if you can't hear it from the listening position, you shouldn't worry about it. I followed his advice and saved myself a whole lot of aggravation and anxiety.

Doc

I'm with Doc on this one, I have a very slight hum on my speakers and can only hear it with my ear to the tweeter. It doesn't change with the volume so I could never here it from my chair even at low volumes. I don't believe it somehow effects the sound of the music unless you think the only thing that matters is measurements...

[tube-vds]

60 hz from a tweeter is just a strange thing...my hum came from the woofers.

[sfox7076]

That is what I was going to say.  60Hz hum comes out from the woofer/midrange, not the tweeter.  And I doubt it is the amp design.  It's more likely than not EMI or RFI.  I recently ran into this issue. A person was coming over to demo my speakers and a Wells Amp and he asked me to switch to using the LampizatOr as a preamp instead of my concert fidelity.  Anyway, I hooked it all up that way, turned it on, and it hummed like crazy.  I mean I could hear it across the room and it was coming from each driver.  I was perplexed.  I unhooked it all.  Turned on the amp with no interconnect hooked up.  Hum got louder.  l and rehooked up my Concert Fidelity and the hum was gone.  The ground lift on the concert fidelity did not matter for that.  So when the Wells arrived, Vinh brought shielded RCA cables (DanaCable Diamond Reference that are shielded).  I hooked that up between the Lampizator and my amps and the hum was gone.  Just vanished.  I could have my head next to the tweeter and there was not even the slightest hint of tube rush from my 1625 tube amps.  So I would do what was suggested before and remove the shield connection from one side of the XLR and see what happens.  My guess is that the hum vanishes. 

Shawn

[gregfisk]

That is what I was going to say.  60Hz hum comes out from the woofer/midrange, not the tweeter.  And I doubt it is the amp design.  It's more likely than not EMI or RFI.  I recently ran into this issue. A person was coming over to demo my speakers and a Wells Amp and he asked me to switch to using the LampizatOr as a preamp instead of my concert fidelity.  Anyway, I hooked it all up that way, turned it on, and it hummed like crazy.  I mean I could hear it across the room and it was coming from each driver.  I was perplexed.  I unhooked it all.  Turned on the amp with no interconnect hooked up.  Hum got louder.  l and rehooked up my Concert Fidelity and the hum was gone.  The ground lift on the concert fidelity did not matter for that.  So when the Wells arrived, Vinh brought shielded RCA cables (DanaCable Diamond Reference that are shielded).  I hooked that up between the Lampizator and my amps and the hum was gone.  Just vanished.  I could have my head next to the tweeter and there was not even the slightest hint of tube rush from my 1625 tube amps.  So I would do what was suggested before and remove the shield connection from one side of the XLR and see what happens.  My guess is that the hum vanishes. 

Shawn

On my system it sounds like a ground hum to me and all of my wiring is shielded. In fact all of my wiring is dual shielded so I don't know what it is. I can't hear it in the midrange or the woofers but it might not be loud enough for me to here as it is very faint?

[G Georgopoulos]

You cant eliminate hum in a power conditioner...

[jostber]

What about a ground loop isolator to check if that helps?

http://hallresearch.com/page/GLI-RCA