Standby Switch question

[tonelab2]

Which is better and why?
Standby switch before the totem caps as per hybrid A or
after these caps as per 70's schematic?
What's the pros and cons of each, anybody know?
thanks

[Bob-I]

Which is better and why?
Standby switch before the totem caps as per hybrid A or
after these caps as per 70's schematic?
What's the pros and cons of each, anybody know?
thanks

I'm not a guru on this, but I like the to charge the caps before applying power. All my amps have the SB after the first filter stages but before the choke/load resistor.

[tonelab2]

Thanks for the reply Bob.
I've always hooked the SB switch pre 1st caps typical Fender style but liked the thought of having those caps charge up first since it usually take 8-10 seconds before fully charged. Looks as though HAD changed to the pre 1st filter cap setup as the 70's morphed into the 80's model. I wondered if there was a reason or if anything negative in doing it this way.
thanks

[Pete]

I've always hooked the SB switch pre 1st caps typical Fender style

I thought typical Fender style was AFTER the first caps (i.e. after the 2 large series ones) and Dumble style was before any/all caps. (I'm also curious about any negative effect of D style)

[tonelab2]

Pete you are 100% correct with the Fender post 1st filter cap SB switch.
I installed a couple of SB switchs in champs a few years ago for friends
who wanted to try plugin SS rectifiers ( didn't have schematic) and presumed the SB went pre caps ( worked O.K then presumed all F amps
were done this way ). Would still like to know the pros and cons of each.

[Pete]

Would still like to know the pros and cons of each.

Me too ... I don't have the electrical background to apply much theory but I kinda thought that with the SB switch before any caps it would take a little time to charge up the caps. That way nothing gets hit hard with sudden B+, a sort of "soft" start up (i.e. the voltage comes up slowly). This could be easier on many components.
Just my $0.02.

[tonelab2]

You know I think you could be right, sometimes I can't see the trees for wood. My wife wants me to enroll in this evening course.

[d95err]

My theory is this:

With a tube rectifier, you want the SB switch after the first filter cap. That way, the rectifier charges the caps slowly and there is no big current rush that will wear out the rectifier tube (since it will be conducting slowly while heating up).

With a solid state rectifier, the initial current rush is no problem for the rectifier. So, you might as well have the switch before the caps, in order to let B+ come up a bit slower when you turn the Standby switch to On.

[jaysg]

With a tube rectifier, you want the SB switch after the first filter cap. That way, the rectifier charges the caps slowly and there is no big current rush that will wear out the rectifier tube (since it will be conducting slowly while heating up).

With a solid state rectifier, the initial current rush is no problem for the rectifier. So, you might as well have the switch before the caps, in order to let B+ come up a bit slower when you turn the Standby switch to On.

That seems correct. You can add a B+ inrush limiter like the Ametherm SL15 22102. You'll see about a 2 second rise time. I believe that the inrush on filaments is harder on the tubes than B+. Unfortunately, inrush limiters on filaments leave a fixed drop and optimally, you'd start with about 8Vac, not 6.3Vac.