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Sounds like induction into ground loops created by power cords and interconnects. Try moving cables around / away from power transformers and other sources of magnetic fields. Could just be a placement or orientation issue.jh
Is buzz or hum mechanical from phonostage? Or via output signal into your amplifier?jh
Have you tried changing the tubes?
I'd try to disconnect all inputs and short out the active (selected) input. This eliminates any "device through" noise from any combination of sources and power amplifiers.Second try (if the previous experiment reveals nothing) - not just switch off the device, but pull out the mains cable (from the mains outlet or from the device). If the noise is persisted - then it is not from the Clarinet definitely. Disconnect the output interconnects in this case - and you'll hear the same noise. If the noise in this experiment is off - then IMHO it is a ground loop through the shielding of the output interconnects to the ground wire of the mains cable or the ground in your mains is noisy/improperly connected. Then you may try the ground breaker of some sort, but first - detect the source of the noise.
First of all, I'd not touch any part when the device is on, especially with the second hand grounded through the case. The high voltage here is dangerous!!!C101 itself is unlikely to buzz. It seems the mechanical force goes to the part of circuit from the transformer which is straight above the place. In normal situation there should be no problem about it, but if you use "microphonical" tubes it can be the source of faint noise.The experiment with unplugging the mains is very interesting. If the device is on and you unplug the cord - the capacitors charge should support the power of the device for several seconds. I mean -after unplugging - the noise stops abruptly or gradually fainting? IF it is possible - could you (with GREAT precautions!!!) connect the device only to line and neutral, without ground connection and listen to the noise? By the way... The book is cool!
Those huge Soncap capacitors certainly are not what the PC card was designed for!I wonder if these or other so called good sounding parts are not the source of your bad sound (hum).Frank Van Alstine
Yeah I had read in one or two other hum themed posts here that it is "somewhat" safe to touch the components themselves as long as you are not touching the leads or traces on the board.
I don't think it was C101 itself, it seems to catching the buzz from whatever source it may be coming from. I did listen to the transformer withe the power amp off, I thought I maybe heard something but not like a regular transformer buzz, which I have heard on other stereo equipment before.
So the buzz/hum cuts off as soon as I pull the power cord out of the clarinet, and the preamp abruptly shuts off, the LED almost instantly turns off. I did try to disconnect the internal wire which is connected to the power plugs ground and runs to the ground on the chassis, this had no effect.
1. turn it off and listen if the noise is off (immediately cuts off) or fainting gradually;2. unplug the power cord from the mains and listen the same.
Use your DMM, set to frequency, and with the inputs shorted, measure the frequency at the outputs. 60Hz is ground, 120Hz is transformer, other is other. If 60Hz, try a cheater plug, no ground prong, at the outlet. Also, since you didn't build the unit, I would reflow the solder joints. But first, measure the frequency of the noise and report back.Cheers,Geary
Geary,I am not exactly sure how to measure this. My DMM does have a frequency function but am not sure how to use it, can you help me out here with step by step directions? I really appreciate it! When you guys say short the inputs you mean put for example use a single rca connecter with one end connected to left and the other to right for that input channel, correct?