[OBF]

A question so I have an idea of where to investigate:  I recently noticed after shutting off all my gear while my 100N+ was still on, there was a pretty loud hum coming from just the left channel.  First off, would a ground loop only affect 1 channel, and secondly, can you have a loop when everything is shut off besides the amp?

At the time I don't have cable tv hooked to the system as I know this can cause a problem, and my pre is passive.  My DAC and DVD player are both fed through a power conditioner and this is plugged into the same wall socket as the AKSA.  

I just noticed it this morning while leaving home so I suppose the first thing would be to disconnect the interconnect wires and if it still is humming from one channel?  For all I know this may be new, or it may have been doing it for some time because the conditioner hums quite loudly itself and may or may not have masked the noise from the speaker.

TIA for any suggestions,
Mark.

[andyr]

... I recently noticed after shutting off all my gear while my 100N+ was still on, there was a pretty loud hum coming from just the left channel.  ...

Hi, Mark,

Hum can be a real bugger to get rid of - when I first put my GK-1 (line stage pre-amp) into circuit I had a terrible (unlistenable to!) hum only when I selected one particular source ... my external phono stage.  I had to experiment, using an earthing wire with an alligator clip at each end in the phono stage, before I found what took the hum away.  What I've ended up with is not logical ... but it IS quiet!!  

I have noticed when I switch off my GK-1 but have my AKSAs on, that I get some hum ... I don't consider this to be anything to worry about, simply a strange effect when my system is in an "intermediate" state (really, it should either all be on or all be off ... but, as the GK-1 has tubes, I turn it off to save tube life).  Everything else stays on permanently ... unless I go away for a few days!!  I know you have a passive pre but maybe the sources which are plugged it, which are switched off, are making your pre act like my GK-1??

My guess is, if you took your pre out of circuit and simply plugged your DAC into the AKSA - with the DAC switched off - you would get the same hum you are experiencing now, when you turned your AKSA on??

I then recently had a different hum problem when I plugged my new TV into my GK-1.  This was solved by plugging the TV and all associated components (DVD player, VHS deck, set-top box) into a mains isolating transformer ... yet with my previous TV and the same units, plugged into the same mains circuit, I did not have a hum problem!

Why your hum should only appear on one channel, though, IS a mystery.   Are you sure both channels of your AKSA are identical?

Regards,

Andy

[Rom]

Hi Mark,

I don't experienced these kind of problem but if I do. these is what I will do.

Change or swap the left and right signal cable, left to right and right to left

if the hum stay on the same channel then your problem is coming from that particular channel ( amp in this case), if the Hum changes then your problem is not coming from the amp but from your source.

these is only to determined exactly where the hum is coming from.

I hope these help

Cheers
Rom

[AKSA]

Mark,

Hum can be infuriating.  It is definitely the final frontier on any audio installation, no question.  Rom and Andy have both explained techniques here which work.  This is anyone's guess;  it's a black art.  It is doubly difficult to give advice on this issue without having the system there.  I have spent months, two hours every day, chasing hum.  A systematic approach is required, but difficult to adopt.

When preamps switch off, sometimes their earthing regime goes west.  This would create an unterminated, unshielded input which the amp would amplify as hum.

Cheers,

Hugh

[OBF]

Hum can be infuriating.  It is definitely the final frontier on any audio installation, no question.  Rom and Andy have both explained techniques here which work.

Would it be normal to have it in only one channel under any situation?

Well, at any rate I finally got back home and did some experimenting from the suggestions and perhaps the problem is solved but I still find the symptoms rather odd.

So.....the amp had been off for a couple days and when I switched it back on with NO interconnects attached, it still had the loud hum in the left channel.  This of course worried me as one of the downsides to buying a completed DIY project is that if something goes wrong......

This particular 100N+, which I bought from an AC member, has a polarity switch on the mains power.  I tried shutting it down and then reversing the switch (don't know which is which) and it popped and then hummed and then made a cracking static noise and then the hum mostly went away.  So.....then since it seemed to be power related somehow I checked the AC cord and it's a fairly typical J.R. type with a Wattgate IEC.  The IEC doesn't get a very good grip on the inlet and so the cable sags.  When I pushed it up the crackle was obviously responding to the movement.  I switched cables to a different one with a Shurter IEC (which I thought some people consider lower quality) and the cracking and hum is gone.

So.....I guess there's nothing wrong with the amp and that's a relief but the whole episode is a head scratcher for me.  I'll monitor to make sure it doesn't return  

Any logical explanation for a poor contact causing hum in one channel, depending on which was the switch was set and crackle on the other setting?

Thanks,
--Mark.

[Carlman]

Since I'm the previous owner, I'll chime in and say I'm relieved.  I was waiting to see what you did to get a better idea of the problem before commenting.

The only reason I can figure that you had crackling and the hum removed when changing the switch is just a simple matter of better contact via one path than another.  Changing the switch position allowed a different path from the IEC to the transformers... simple as that.... And when there's not a good connection, results are a little unpredictable... I guess there could be an outside chance that there's something wrong with the switch itself as well.

However, it sounds like you may have a problem with the power cord's IEC.  Could the connections inside come loose a little?  

Feel free to PM me with your phone no. if you'd like to talk more.  I'd be willing to help resolve this if it happens again.

Thanks,
Carl

[OBF]

Hey Carl, how's it going?  I was wondering if you'd notice the thread.  Thanks for commenting.  

I'm not sure there's anything "wrong" with the cord, except it's not getting a good grip on the IEC inlet and is sagging.  But I do intent to open up the connector and see if anything is loose.

[Occam]

My cheap SOB fix for loose IEC plugs is to wrap some white teflon plumbers tape around the plug, sufficient to make it nice and snug & then Bob's yer uncle....

Just because the Wattgates are more expensive than the Shurter doesn't means its better. After all, subjective opinions are quite subjective, and you really must consider the context. I guess it also depends on who is rendering the opinions (mine are allways correct   ).

[Carlman]

Similarly to Occam, I use electrical tape wrapped around the male IEC to tighten the physical connection.

I'm still around, Mark... just let me know if I can help.  I hope you're still enjoying that amp otherwise... I haven't found anything truly better yet for under 3-4,k.

-Carl