Power supply ripple - how much is too much?

[jhstewart9]

RC filtering in a power amp not a great idea. A choke can make a huge difference, worth the expense. But see the attached, something else to think of in an SE amp.

 

[kylej1050]

the FET in the cct will need a gate protect zener.

The only time I can think of that a gate protection diode will be needed is if the tubes are either cold or missing when turned off and the bulk electrolytic is discharged while the downstream caps are still charged.

I tend to be a boots and suspenders kind of guy and would add the protection anyways but it should be said that the protection diode isn't necessarily needed under pretty much all normal operation.

 

[jhstewart9]

The attachment describes a proven SE amp, complete with performance results. It has built-in tone controls & phono preamp as well.

In service since December 1964, it still runs every day here in the workshop. Sources are Eico AM & FM Tuners & a CD player.

 

[kylej1050]

I run this in my 6sn7 push pull, change that preceding resistor to a smaller value, and may be increase the 12k resistance to a 18~22k for more headroom. Easy build, parts are cheap. Dead silent, even with 97dB/w speakers. Much more cost effective than a choke, and no stray magnetic fields to fool with. Nice little soft start feature too.

Digging this guy up again!

Any particular reason you don't use a CCS and a Zener to set your gate voltage? Is it just that it's quiet enough without it or have you tried it and didn't care for it(for example, parts cost added for little to no benefit)?

I'm looking at using this as a regulated supply in an amp that doesn't really deserve it and in playing with sims I've found the CCS/Zener combo to have the stiffest regulation where I'm seeing 10mV ripple on the resistor network.