[ogygia]

Quote:

Originally Posted by arie123 /img/forum/go_quote.gif I replaced all wires indicated by the yellow arrows in Ogygia's picture of the amp by copper/silver teflon coated flexible wire. Unfortunately: no effect. Moving around the wires at various places does nothing to the hum level. It was worth the try, but it must arise somewhere else.

Can you post more pic inside the amp in the left part of the amp?

The fact till now is the noise come from power since it is at 100hz. And it come after potentiometer, since the hum doesn't affect by vol control.

let try 2 more wires since they seems just stick to power....If no effect after this, I have no idea~

White arrows....they are after potentiometer, but the tube circuit seems after the potentometer as well....so my analysis about the problem on no effect of changing vol was not compeleted. The problem part should consider the whole part after potentimeter. This part is the tubes and cap.

 

[Audict123]

Ogygia: I was wrong to tell you the hum does not change with volume control. There is hum at zero volume, but it increases 2 to 4 fold (on ear) when I put it on full volume. So maybe there is hum introduced before the volume control? It is NOT the wires that connect the cinch plugs to the little print on which the pots are (I even desoldered that cable at the print, no difference in hum)

>> Edit! The above is not correct after all. The above increase is only present with the DAC connected. Stand alone, the hum is almost constant.

I did not yet change the wires you indicated with white arrows in the picture above. Changing these is a lot harder, there is very little space near the socket.

 

[BigTony]

Update:
I recieved some new tubes for Yuking yesterday, some new Chinese tubes and some NOS Russian tubes.
I dropped the Chinese tubes in, and out of the box there was a hum present, not very loud, noticeable. After 10 hours this hum has subsided, its not totally silent, but its in the 'niggling' category, i.e. you notice it every now and then. Going to burn them in some more and see what happens.
Might also burn the Mullards in some more, seems this amp like tubes 'well done' for best results

One thing about the Chinese tubes though, more gain that any other tube I'd used. Minimum db level from the amp into my HD650's is 85db, which is too loud for my sensitive ears Even with RAC attenuators in there it hurts my ears after an hour or so. The Mullards I'd removed gave a more pleasing 75 db at minimum level (i.e. when the sound is nicely balanced - its about 2-3 mm of movement on the pot.)

Tony

 

[deltaspirit]

I too got some tubes from yuking yesterday, I set of stock chinese tubes and some western ones. I had the amp going for about a minute and did not notice the problem I had before with the loud cracking in the left channel so it looks like that is solved. I too have some slight hum that is not effected by volume. TBH the hum is very slight and almost impossible to hear with music playing.

 

[gbacic]

The hum will probably die down, mine did and now it's very faint even when there isn't music playing.
Will replacing the headphone out on my DV332 improve the quality at all? I'd think so, I need to replace it anyways because the right channel sometimes cuts out but it comes back if I jiggle the plug.
Any suggestions for plugs to use? Can I put a locking Neutrik or would that be too hard (aluminum face plate)?

 

[gordonshowers]

Quote:

Originally Posted by gbacic /img/forum/go_quote.gif ...I need to replace it anyways because the right channel sometimes cuts out but it comes back if I jiggle the plug.

Try spraying switch cleaner (contact cleaner) on the headphone jack, and plugging it in and out of the socket several times. It is probably just a dirty contact in the headphone socket.

 

[gbacic]

Never thought of that. If that is the case that will save me a lot of trouble.
Thanks!

 

[gbacic]

[sorry for double post]
I used isopropyl alcohol to clean the headphone out and it worked! That's a load off my chest

Thanks, gordonshowers

 

[BigTony]

Well I've burned in the new tubes for a week, and the hum is still present (plus some other grumbles from the tubes) If anything my NOS Mullards are quieter. So I'm back to square 1, no tube combination resulting in a hum free background.
Anyone hum free?

 

[Audict123]

I also received two sets of supposedly hum-free tubes from Yuking, but unfortunately that didn't cure the hum in my 332s either. I informed Yuking on this. He expressed he very much regrets this issue and kindly offered to take back the amp and give a full refund. I think I'll take the offer, even though I hate to let it go given the other sound qualities and stunning appearance. I really was ready to put serious effort in to make it hum free, but ran out of tricks.

Please note: the hum my amp has is really siginificant. In soft music, e.g. with solo vocals, soft guitar solo etc, you can hear the hum. Like you're sitting too close to the fans of a (regular, not silenced) pc. It's not in the nitpicking category, although I realise audiophiles are nitpickers by nature. If I plug in low-impedance phone, the hum is so loud it gets through in any music but really loud music. If any of you has an amp with hum 'you have to look for', stay happy and ignore it.

 

[deltaspirit]

Quote:

Originally Posted by arie123 /img/forum/go_quote.gif I also received two sets of supposedly hum-free tubes from Yuking, but unfortunately that didn't cure the hum in my 332s either. I informed Yuking on this. He expressed he very much regrets this issue and kindly offered to take back the amp and give a full refund. I think I'll take the offer, even though I hate to let it go given the other sound qualities and stunning appearance. I really was ready to put serious effort in to make it hum free, but ran out of tricks. Please note: the hum my amp has is really siginificant. In soft music, e.g. with solo vocals, soft guitar solo etc, you can hear the hum. Like you're sitting too close to the fans of a (regular, not silenced) pc. It's not in the nitpicking category, although I realise audiophiles are nitpickers by nature. If I plug in low-impedance phone, the hum is so loud it gets through in any music but really loud music. If any of you has an amp with hum 'you have to look for', stay happy and ignore it.

Yeah, that hum sounds serious. I cannot hear any hum with any sort of music playing. So what amp are getting now?

 

[laobrasuca]

Hi all, I'm willing to buy an amp for my hphone and the 332S seems a nice one. But 3 questions:

Quote:

Originally Posted by yuking09 /img/forum/go_quote.gif We are working to change the Potentiometer.Because Chinese New Year ,Express companies do not work. When Chinese New Year is over,I'll give your issued with a new potentiometer.

Any news on it?

Wouldn't it be a nice thing to build a little/simple internal mechanical thing to control both volume pots buy turning only one of them? Something that could be switched on or off by a mechanical bottom or switch.

Another question: whats the swing volt of this amp ? x Vrms (y.yy Vp-p)

thx for your time,

lao

 

[gbacic]

How noticeable is it if tubes aren't matched? My 6ak5's seem to be pretty unbalanced throughout the frequency spectrum (bass hits lean towards one side a bit, different voices lean towards one side or the other). Maybe it's just me but I don't know.
I'll experiment with my huge array of CK5654's.

 

[Mullet]

Someone correct me if I'm wrong, but I feel like I've read that matched signal tubes aren't necessary with these amps. The idea I took away is that you should have your power tubes matched or have the same bias. I have several tubes that aren't matched or even from the same year that seem fine to my ears. But I'd say my ears suck. I can barely tell the difference between the variety of 6AK5 variants out there.

 

[gbacic]

Maybe it is my power tubes. I'll rotate them, too.