I can tell its definitely a 60hz hum, actually not that dissimilar from a street lamp but ive heard this type of hum from other tube amps.
Im not sure what to tell “Mike” from quicksilver but I think what I put on the previous post may be a good start.
Remember that the right preamp tube socket has some sort of false? When the tube is at a certain position it will flash its light as if trying to turn on but fail and stay off.
Does it make more sense now that theres some wiring damage related to that? I do suspect RF based on the hum; wheter related to the “damaged socket?” Or not.
Also I purchased some tubes with as little microphonics as possible, for phono that I could test with. Theyll take a while to arrive tho.
This is distinct from Microphonics, every piece of wire in a device is an aerial, transmitting and receiving, that includes the filaments in the tubes, if something happens to be just the right length, it’ll pick up noise, everything from AM radio to mains hum.
Assuming you’ve tested without a source connected, this is critical, you can’t rule out a ground loop if you have a source connected at all.
It could be damage to the socket or the wiring to it, but without knowing what normal is for the amp, it’s hard to say if quicksilver would even consider it a problem, which is why I suggested contacting them before sending it back for repairs.
I went through this with A&S, talked to Justin sent the amp back for testing and all they did was test it, say it was normal and send it back with the same hum. ZMF and A&S payed for the round trip but it was still annoying.
Is there a distinct sound to a ground noise to that of RF?
This noise ive heard before when my yamamoto ha02 was broken, that one had a broken metal rod that connected the pot to the handle
The BHC also hummed as the screws on the transformer got loose by the vibrations.
I call all these 3 transformer hum but they had a distinct sound, the yamamoto I would describe as “feedbacky” like in noise music it was manipulated by even getting the hand close to the amp
The one on the BHC would stay the same no matter what changed (source, tubes, etc) much like the one im having on the Quicksilver, until I tighten the screws.
Thanks for the suggestion. Ill see what mike suggests and only send him if he requests, I would think he would want to fix the malfunction on the socket, although that could be an easy fix he should have the first say on that. Also I dont think its meant for users to open as you point out its danger is overstated.
Thats quite annoying. I hope you could fix it or find a good use for it.
No it’s mostly just a mains hum.
A ground loop is caused when there are multiple paths to ground, we’re taught to think of ground as an absolute 0V potential, but that’s not how it works, in fact every ground in a device will be at a slightly different potential, and as a result current will c\flow between them.
If at any point one of those currents flows through signal ground you hear it.
There are at least 2 grounds in pretty much every device in an audio chain with a 3 pin plug, depending on how the device is grounded. Signal ground may or may not be connected to power ground and if it is, it could be ac or dc coupled.
Your Amp has grounds at the Inputs and the power connector which is why you need to disconnect one of those to test and you can’t test it without power, There can be ground loops inside a device but those are the designers problem.
If it is a ground loop there are solutions, but you need to establish if it is.
Hello again, just wanted to follow up on my last post.
Its been some time but I actually sent Quicksilver’s Mike an Email the day I made the previous post and he replied within hours, very politely and helpful.
Obviously the amp couldn’t be properly diagnosed without taking it apart but based on the information we had Mike told me that I have one of the earliest units of the QSHA which would have this exact hum that I get on higher sensitivity headphones.
After the initial run of these amps Mike redesigned the amp to lower the Hum as much as possible on the newer units by Improving the shielding on the output transformers and some circuitry changes.
My unit can be redone with these changes with a cost of around $300, but since im in south Mexico sending the unit on a round trip to California would cost around $400 all and all.
The amp is really good and I can still use it with my planars and higher impedance cans with 0 noise. I even got some nice Amperex and Telefunken for it, I can take it to Mike’s for way less by crossing the border myself, but im not really sure if I should invest those $300 (maybe more with the tariffs) or save that money for the Trafomatic Head 2 that Id like to get.
The other issue was the that one of the sockets had a malfunction, it probably got loose by having too many different tubes plugged in and out; which Mike told me how to fix by myself, leaving the amp off overnight and wedging a needle in between each tube socket pin and the edge of the socket as to close the pins down and make a nice tight fit for the tube which worked like a charm.
Props to Mike for making such a nice amp, Im not sure if ill get it upgraded but im definitely enjoying it with many headphones still.