How to resolve persistent hum

[atul.mehta6]

Hello All,

I get a slight hum across both my Bottlehead amps. I *think* this is because of RFI/dirty power. Can someone recommend a _cheap_ power conditioner which can fix this. Are there any other tweaks which I can do to weed out the hum (maybe some diodes or something).

Thanks in advance!

 

[Larpy]

It's unlikely a power conditioner will fix the problem.

The first question usually asked is whether the hum is 60 Hz or 120 Hz.  How to fix the hum will depend on the answer.

Does the hum stay the same if you move the amps a few inches away from their current position?

 

[atul.mehta6]

Thanks for the note... I have tried moving it around and it is not changed much.. it is coming from both my C2A and S3X 3.0. I am not sure how to figure out whether it is 60 or 120 Hz..

 

[Paul Birkeland]

You can listen to a 60Hz and 120Hz tone on your computer to see if that mimics the noise you hear.  Is this noise from the amps themselves or your speakers?

 

[atul.mehta6]

The noise is only from the amps when I listen via Headphones.. the S3X powers my overnight sensations but that is dead quiet.. I will check on the 60/120 Hz later tonight and update you all..

thanks a lot for all your help so far..

 

[Paul Birkeland]

If it's just your SEX amps and some super sensitive low impedance headphones (especially IEMs), the output of the amp can be padded down a bit to make it even quieter.

 

[atul.mehta6]

No I hear a low hum with my C2A also. But it is apparent only when I use a 6SN7 and not a 12AU7..

 

[Mucker]

That's a normal experience for me. I've never experienced hum with a 12AU7, E80CC, or 12BH7A, but I have with 6SN7, some more than others. I have used 2 different adapters with 6SN7 ( a Chinese one and a Garage one) and they both performed identically. It's just low level hum and doesn't prevent me from using the 6SN7. However, I am pretty stuck on the E80CC now and don't want to use another tube to be honest (other than the 12BH7A).

 

[atul.mehta6]

Hmm.. the E80CC looks interesting. From the little reading I did last night, I understand that it is NOT a drop-in replacement for the Crack at least. Does the same hold for the C2A? Would love to do more tube rolling

 

[Paul Birkeland]

The same adjustments would be required for the C2A if using the E80CC.

 

[Doc B]

The 6SN7 does not have a center tapped heater like the rest of the tubes mentioned. Thus it will have less symmetrical leakage of the heater current to ground than the other tubes. This could possibly be why it hums more. Or there could just be a less than optimal situation created by using the nine pin to octal adapter (the wiring inside somehow causing the hum).

 

[Thermioniclife]

I just sent you a message.

 

[Mucker]

Good info Doc, interesting!