Thread: GZ34
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Big Bad Bob Big Bad Bob is offline
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Default GZ34

On 07/27/17 18:16, wrote:
The PS transformer is wound serially so that the two sides of the winding are not the same resistance.


I'm not sure how having a tube rectifier there, vs solid state, would in
any way improve the hum factor.

As for the PS transformer, they were obviously being cheap if that happens.


one appeal of tube vs solid state rectifiers is the 'punch' effect you
get with a guitar amp. At high load you get an 'attack/decay' amplitude
effect because the capacitors discharge for a short time, giving you
slightly higher power levels than the power supply can deliver with a
sustained signal. This is due to internal resistance of the rectifier
tube. But if the behavior is non-linear, having a series resistor on a
diode won't give you the same effect...

Anyway, they should be using LC filters after the diode to minimize hum,
and a properly balanced power transformer secondary winding. That's how
the old Hi Fi systems were done. Just boost secondary voltage a bit to
compensate...

/me would consider adding a series voltage regulator using a transistor
and zeners and solid state rectifiers and a current limiting circuit, to
give you a nice clean primary power supply that doesn't 'surge' the
capacitors when it starts up. A 25-50V drop would be sufficient, not
unlike what you get with a tube rectifier anyway.

but yeah, that's not very 'purist' of me. I just think the pre-amp and
output tubes are what matters for hifi tube audio, or guitar amp audio
for that matter. The power supply [other than the 'punch' effect] is
less important, but could be simulated if needed, using a derivative of
a current limiter circuit.