HUM

[maheeinfy]

My question is not about a BH amp, but I am posting here looking for some help. Pls bear with me, I m new to this forum and tube amps.

I recently got a Wooaudio WA2 amp, new from wooaudio, and i am using it with Beyer T1 and few other cans.

It does hum through the headphones when volume is at 11' clock and hum only becomes louder from there.

 i did some testing to isolate the device in the chain that is causing this problem. I found that when nothing is connected to amp(except power), there is no hum.

However when i connect a DAC, there is hum thru headphones. Even with DAC turned off, there is hum(i tried output of Schiit Modi, Emotiva DC1, line out of Fiio X3ii  - each of them powered off and not even connected to my laptop). RCA cables i am using are from Schiit and Emotiva, so i think they are good quality.

I tried different power cable, wall sockets, even took the amp to friend's apartment for testing, and the result has been same.

I have been using Schiit Magni, JDS O2, few speaker amps from Emotiva for more than a year - none of them have any hum issues.

 I contacted Wooaudio and was told to upgrade cables, dac to resolve the hum problem. But I think the cables, dac are not the reason.

On other note, one of the 6080 tubes i received, i think is faulty. It gives out hiss on one of the cups on headphone, even at zero volume. When i switch 6080 tubes on the amp from left to right, hiss also switches on headphones

 My question - What could be the reason for this dreaded hum? i'd appreciate any help in resolving this. This is my first tube amp, and i havn't been able to enjoy it due to all these problems.

[JamieMcC]

No idea about Woo amps but you could try wrapping/twisting your rca input cables round each other and see if it  has any effect on the hum.

[maheeinfy]

No idea about Woo amps but you could try wrapping/twisting your rca input cables round each other and see if it  has any effect on the hum.

Thanks i will try that.
I just tried this...I removed all the input RCA connections from the amp. Then connected the left and right input of the amp with a single RCA cable(i think the apt word is 'shorted'). With this, there is no hum.

I don't know what that means, but thought i ll put it out there

[Paul Birkeland]

It does hum through the headphones when volume is at 11' clock and hum only becomes louder from there.

What's 11 o'clock?  Is that all the way up? 1/8 of the way up?

i did some testing to isolate the device in the chain that is causing this problem. I found that when nothing is connected to amp(except power), there is no hum.

Then the amp is working fine.

However when i connect a DAC, there is hum thru headphones. Even with DAC turned off, there is hum(i tried output of Schiit Modi, Emotiva DC1, line out of Fiio X3ii  - each of them powered off and not even connected to my laptop). RCA cables i am using are from Schiit and Emotiva, so i think they are good quality.

This sounds like a grounding issue.  Woo should be able to help you with this.

On other note, one of the 6080 tubes i received, i think is faulty. It gives out hiss on one of the cups on headphone, even at zero volume. When i switch 6080 tubes on the amp from left to right, hiss also switches on headphones

If this isn't intrusive with music playing, I wouldn't worry about it.

[Doc B.]

Sounds like you have a ground loop. I would contact the manufacturer and ask them specifically if they have any suggestions for resolving ground loop issues. You might get a little more info from them on how to deal with the issue if you present them with that additional info.

This kind of thing puts us in a difficult position. We do our best to help our own customers. Presumably because of that people will tend to come to us to ask for help about non-Bottlehead products. The problem is that if we answer we will be viewed by some as denigrating the competition's product, though that is not our intention.