I just acquired my first tube amp, a used Jolida integrated JD-102b and it sounds beautiful driving my newly acquired and re-panelled Quad 988..........but the amp is emitting a hard edged noise. Not through the speakers and not a 60hz hum. The speakers are silent when the amp is powered on.
The noise may be 120hz, I’m not sure and has higher harmonics and can be heard when seated 7’ away in my smallish music room. Cupping hands behind my ears really accentuates the harmonics.
I have a dedicated single circuit from the breaker panel to the four receptacles feeding the amp, cd, tt etc.
I have built or bought a dozen amps that have all worked without issue on the same circuit.
I have tried removing all the inputs which results in no change in the noise.
The noise does not interfere with music until quiet passages and speech.
When I power the amp on, there is a soft bump when the tubes illuminate and no noise for about 5 seconds. Then the noise starts quietly and increases to a constant volume after about 5 more seconds and remains constant bzzzzz.
Volume pot does not affect the intensity.
Anyone had a similar experience and can hopefully tell me where to start looking?
Thanks and Merry Christmas to all.
Peter
The noise may be 120hz, I’m not sure and has higher harmonics and can be heard when seated 7’ away in my smallish music room. Cupping hands behind my ears really accentuates the harmonics.
I have a dedicated single circuit from the breaker panel to the four receptacles feeding the amp, cd, tt etc.
I have built or bought a dozen amps that have all worked without issue on the same circuit.
I have tried removing all the inputs which results in no change in the noise.
The noise does not interfere with music until quiet passages and speech.
When I power the amp on, there is a soft bump when the tubes illuminate and no noise for about 5 seconds. Then the noise starts quietly and increases to a constant volume after about 5 more seconds and remains constant bzzzzz.
Volume pot does not affect the intensity.
Anyone had a similar experience and can hopefully tell me where to start looking?
Thanks and Merry Christmas to all.
Peter
If the buzz is twice your mains then it is a bridge rectifier issue, as each half cycle is rectified there is current flowing.
I would get a wooden spoon, place the spoon shape against your ear and the pointy bit at the transformer, parts of the chassis, capacitor etc listening to pin point the noise source.
We can then deal with that issue.
I would get a wooden spoon, place the spoon shape against your ear and the pointy bit at the transformer, parts of the chassis, capacitor etc listening to pin point the noise source.
We can then deal with that issue.
The loudest noise, using the wooden spoon, seems to be coming from the sheet metal transformer cover, possibly a little louder on the right channel side, but not by much. Much lower noise level on the chassis close to the tubes and underneath on the bottom plate. These are all external surfaces, I haven’t ventured inside yet.