audio-talk

I'm back on the case with this 811a in A2.

I sat looking at my previous efforts to make this +/- 80v power supply, but re-reading this topic has put me back on track.

I can't decide, even after reading the Vishay data sheet, does the IRF820APBF mosfet need an insulating washer ? It's a T0-220ab package.

https://www.vishay.com/docs/91059/91059.pdf

Assume yes

Nick wrote: ↑Sun Apr 26, 2020 9:39 pmAssume yes

Thanks Nick.

Out of interest Phil I was looking at 811 curves other day. Once you’re using power drive you can bias it quite positive for equidistant cut off’s to maximise power. That’s what I would do, but I’m just dusting off a plan for a 10y power driven, with sufficient voltage gain and ac swing to drive 801a to full power. Though the initial project power supply won’t be dual capable. I should get 2.2 watts from 10Y. If it’s not powerful enough at home an upgraded power supply and more voltage gain both required (the additional voltage gain required would entail compromise; why I’m stopping at 10Y in the first skirmish.) which I estimate 7.78 Watts, and not a 300b in sight.

Hi Paul, good to see you are back in action with a project.

Thanks for the info, but I'm not totally sure I understand.

According to my circuit, the bias supply is +24v to achieve 90ma current through the 811a. To be on the safe side I'm aiming to get the bias adjustable from +20v to +33v to achieve 90ma.

That’s where my thoughts were, you should get a good result. You have the advantage that you don’t require much gain.

I know from experimenting how 811a sounds. Worthy of you’re project.