My F5T V3 build

[AndrewT]

What is the current draw of the ClassA amplifier?
Now at the instant you pull the mains plug from the mains supply socket, what is the current draw of the ClassA amplifier.
Now take a guess at how slowly, or how quickly the smoothing capacitors will discharge.

Why do you need to add extra resistors to draw more current from the PSU?
Put your thinking cap on.

[flg]

Bleeders are still a good safety measure. let's say the amp needs trouble shooting? You are not garunteed the supply will discharge it's caps and could get burnt, blinded, etc. It's only a few mA extra draw vs. Amps for the output section.

[AndrewT]

Originally Posted by flg

Bleeders are still a good safety measure.

so good? I have never seen the need for them and despite my reputation for safety have never used them.

I have looked at relay connected discharge resistors that ONLY connect AFTER power down. That is a quite different topology.

[Odysseas]

"I have looked at relay connected discharge resistors that ONLY connect AFTER power down. That is a quite different topology."


Like?

[AndrewT]

They don't conduct while the amp is operational.
They don't get warm/hot.
They don't increase current draw.

They do conduct when required.
They do discharge high voltage capacitors in a controlled way.

I even bought lots of 24V tungsten bulbs to gain some advantage in non linear resistance characteristic as the capacitor voltage drops.

[Odysseas]

No, I meant do you have an example of a circuit. I haven't seen something like that so far.

[Russellc]

Originally Posted by AndrewT

What is the current draw of the ClassA amplifier?
Now at the instant you pull the mains plug from the mains supply socket, what is the current draw of the ClassA amplifier.
Now take a guess at how slowly, or how quickly the smoothing capacitors will discharge.

Why do you need to add extra resistors to draw more current from the PSU?
Put your thinking cap on.

I never thought of it that way but it explains a lot. On my Tube amps with large power supplies or various Class A/B amps, I would always wait a period of time after switching off the power amp before switching off the pre amp. As they would continue to play after switch off otherwise, I always thought this was a good idea for bleeder resistors. With the F-5, I always noted it was "Dead" immediately with switching it off, and immediate switching off of the preamp caused not a sound.

I would imagine it bleeds off almost immediately. I have noted several have noted in F-5 builds these bleeders werent necessary, now I know why.

Russellc

[Boscoe]

Originally Posted by Odysseas

No, I meant do you have an example of a circuit. I haven't seen something like that so far.

I wouldn't have said it was exactly hard...

Drive the relay with the secondaries of the transformer which switch the caps power to the amp or through the bleed resistors. This gives a much more controlled power down of the amps too and eliminates the possibilities of one rail draining faster than the other.

[Odysseas]

"Oh really?"
Well have you done it?

[Boscoe]

Originally Posted by Odysseas

"Oh really?"
Well have you done it?

What's your problem I'm trying to help!?