[EagleKent]

I had noise issue in the past too but I did two things that made the tube amp completely silent now.
(1) Move the tube amp one shelf down (further away from my gaming PC) - in hindsight, now that my knowledge about audio noise etc is better, it wasn't a smart thing to do to put a tube amp near noise sources like power transformers etc.
(2) Changed the cable of my ZMF VC to another cable from ZMF. Previously I was picking up RF noise (Indian music) and moving the HP cable got rid of it so got me thinking about upgrading my cable. Happy to report that helps. I bought another no brand handmade cable to try recently and with it the intermittent buzzing came back so it was pretty annoying. I think I will stick with branded well know good quality cables from now on. Definitely no cheap Chinese stuff from AliExpress etc (I've got a drawer full of them that I don't use as they were hopeless - complete waste of money and time).
YMMV but best of luck. Having gone through it myself I know how much of a pain it is to try to fix. Preservance and patience will see you through

 

[Alenotta]

Does the hum change at all if you touch the unit, specifically anywhere metal? Odds are you've got DC floating on your power lines. You'll want a DC line blocker. Something like THIS.

No the hum doesn't seem to change when I touch the metal. I bought this emotiva power strip that has DC offset. That hasn't helped.

 

[Erwinatm]

No the hum doesn't seem to change when I touch the metal. I bought this emotiva power strip that has DC offset. That hasn't helped.

I used to have hum with dynamic hp , PS1000e, Atrium and VC. Dead quiet with Susvara and Empy.

I did this to eliminate it:
1. Put Finite Elemente - Ceraball underneath the feet. I also slip a sorbothane gel between ceraball and feet. First it acts like extra suspension and also makes it not slippery between 2 metals.
2. Connect all digital sources, computer, DAC to Isotek conditioner, incl the LPSU if you have one. Separate HA300 power source , i plug it directly to wall socket.
3. Use USB cables with shielding one. I2S is better.
4. I also use Synergetic power cable with active shielding for HA300.

All above interact as a system, but putting ceraball underneath the amp has more significant effect.

 

[jamato8]

You might have a ground loop. If you have more than one device plugged into the AC I would float it with no ground and you have grounds with the RCA cables etc., and just ground the amp.

 

[ColSaulTigh]

No the hum doesn't seem to change when I touch the metal. I bought this emotiva power strip that has DC offset. That hasn't helped.

I use the Emotiva as well. I may have missed this one - but have you disconnected everything and see if the hum remains?

 

[Alenotta]

I use the Emotiva as well. I may have missed this one - but have you disconnected everything and see if the hum remains?

Yeah last night I went crazy and disconnected everything. Still getting a constant hum and my VU meters aren't resting at 0.

 

[Erwinatm]

Yeah last night I went crazy and disconnected everything. Still getting a constant hum and my VU meters aren't resting at 0.

I don't read all the posts, if you have replaced all the tubes, disconnect every cables and the hum still there. You better try it in the dealer. If it is still there I suspect there is a blown resistor or other parts malfunctioning.

 

[Alenotta]

I don't read all the posts, if you have replaced all the tubes, disconnect every cables and the hum still there. You better try it in the dealer. If it is still there I suspect there is a blown resistor or other parts malfunctioning.

Would it be worth trying to swap the fuses by the tubes? I haven’t messed with those.

 

[Erwinatm]

Would it be worth trying to swap the fuses by the tubes? I haven’t messed with those.

Nope. Fuses don't make noises.

1. Replace tubes - eliminates bad tube problem.
2. Disconnect cables - ) ground loop.
3. Test in dealer -) bad power lines, radio interference.

What you haven't tested left only with transformer and internal parts.

My 2 cents

 

[Alenotta]

Nope. Fuses don't make noises.

1. Replace tubes - eliminates bad tube problem.
2. Disconnect cables - ) ground loop.
3. Test in dealer -) bad power lines, radio interference.

What you haven't tested left only with transformer and internal parts.

My 2 cents

Well, I haven’t swapped the 300s yet. I don’t have another pair to test. Waiting on Elrogs to become available again…

 

[ColSaulTigh]

Can you feel a physical vibration?

 

[Erwinatm]

Well, I haven’t swapped the 300s yet. I don’t have another pair to test. Waiting on Elrogs to become available again…

Is it also hum with planar hp?

You can also try these :
1. Use coax/toslink/AES EBU instead of usb to DAC.
2. Reduce voltage out from DAC to 2V.
3. Use preamp (preferably solid state) instead of direct from DAC

 

[Erwinatm]

And weirdly today when I turned it on the VU meter is maxed out at 100 again.

@Andykong any idea why this would be happening? Is it a tube thing?

@Alenotta reading this, I am almost certain your amp is not normal. Could be the 300B or something else inside.

I beleive you should bring it to the dealer

 

[Alenotta]

Is it also hum with planar hp?

You can also try these :
1. Use coax/toslink/AES EBU instead of usb to DAC.
2. Reduce voltage out from DAC to 2V.
3. Use preamp (preferably solid state) instead of direct from DAC

The buzzing continues when the DAC is off so I don't think it is cables, a voltage thing or input. I don't hear it much on my planars even on H. When I put Grados on the L it is still pretty noticeable when the music is off.

 

[Alenotta]

Can you feel a physical vibration?

Nah no vibrations. Thanks everyone for trying to help me.