Standby switch question

[catalin gramada]

Hello. Built the exact replica of stacked power supply as Hiwatt did (less stb indicator). The standby switch makes the amp thud as hell quake when switch on. The switch supply directly voltages to the plates and grids. Any ideea to suppress the thud with the stb switch in those position please ? Thanks.

[xtian]

Omit the standby switch.

[Leo_Gnardo]

You might try having your standby switch work only on the screen grids. Some high power amps do this, Ampeg SVT Classic is one IIRC. Worth a try, it will be a fast & easy experiment.

[catalin gramada]

I tied the OT in UL configuration for a test. Same standby switch configuration after the bank caps linked directly to OT. The only noise I heard is mechanical click of the switch. No pops or thud at all. Think the thud is a function of how the pentode is supplied. If cannot be suppressed maybe the first power on transient can be canceled by a perfect balanced stage ....?

[catalin gramada]

You might try having your standby switch work only on the screen grids. Some high power amps do this, Ampeg SVT Classic is one IIRC. Worth a try, it will be a fast & easy experiment.

Thanks. Allready did. Makes no difference,

[vintagekiki]

Connect the standby switch as done on the Stramp 2100 amp.
The standby switch is located between the preamp and the power amp, it connects the audio signal to the gnd in the standby position.
Standby switch is noiseless because no any voltage passes through the switch (there are no transients).

[Helmholtz]

I tied the OT in UL configuration for a test. Same standby switch configuration after the bank caps linked directly to OT. The only noise I heard is mechanical click of the switch. No pops or thud at all. Think the thud is a function of how the pentode is supplied. If cannot be suppressed maybe the first power on transient can be canceled by a perfect balanced stage ....?

Yes, I think there must be some output stage imbalance involved.
Maybe the screen section of the switch tends to chatter?

Or the screen voltage switching produces an oscillation burst?

Do you know if the Hiwatt 200 also suffers from this problem?