Dual rail +/- 80v power supply.

[pre65]

On the new 811A amp I need a +/- 80v power supply for the mosfet follower part.

I'm not sure where to start.

If I use PSU designer to design a 160v power supply can I then use the transformer secondary centre tap to create an 0v rail and connect to the other two with capacitors ?

I have a transformer with two 120v secondarys, what sort of current will the circuit take ?

[ed]

whatever load you put on it until it smokes

the diodes will be specced for the load or use heavy duty bridge depending on load..like this plus as much smoothing as you need

[pre65]

Thanks Ed.

I was more thinking of the mosfet follower likely current draw.

[Nick]

Thanks Ed.

I was more thinking of the mosfet follower likely current draw.

Ohms law gives you that. 20ma I think I remember, 104v across 5k

[pre65]

Thanks Nick, although I can't see from the circuit where those numbers came from ?

Regarding the PSU I found these PCBs on Ebay, and as space is a consideration I'll get a couple to try.

https://www.ebay.co.uk/itm/Dual-Polarit ... 0009.m1982

[Nick]

Thanks Nick, although I can't see from the circuit where those numbers came from ?

Not claiming equivilance:

At the question period after a Dirac lecture at the University of Toronto, somebody in the audience remarked: "Professor Dirac, I do not understand how you derived the formula on the top left side of the blackboard."
"This is not a question," snapped Dirac, "it is a statement. Next question, please."

[Paul Barker]

At the question period after a Dirac lecture at the University of Toronto, somebody in the audience remarked: "Professor Dirac, I do not understand how you derived the formula on the top left side of the blackboard."
"This is not a question," snapped Dirac, "it is a statement. Next question, please."

Like!

[ed]

Thanks Ed.

I was more thinking of the mosfet follower likely current draw.

my apologies Philip, I was trying to be funny, then facetious, then I lost it by not referring to the circuit post....

it is a valve, put a voltage across it and bias it through the grid(gate) and current will flow through it...you have supplied most of the figures

[ed]

I thought something was familiar...I believe it's George Anderson's power-drive. I used to follow him on diyaudio back in the day when he'd test big valves to find the limit..and then push them over the edge...most amusing...and he also used to play his guitar whilst semi naked..not as much fun to watch...

anyway, I digress, this may be of some use if you're scratching your head:

http://tubelab.com/articles/circuits/po ... /cookbook/

[pre65]

Semi naked in front of an 833a amp no less.

Yes, Powerdrive it is, and I've wanted to try it for a while.

[pre65]

The split rail PCBs came today.

I've populated them as much as I can from stock parts, the rest are ordered.

The board has provision for four (4) 2200uf caps @ 25v, but as I'm using a higher voltage than intended I can't fit them on the PCB.

Anyway, I've soldered PCB pins in the mounting holes, and the caps will be off board.

[Mike H]

Semi naked in front of an 833a amp no less.

Yes, Powerdrive it is, and I've wanted to try it for a while.

I remember him! Did he have videos on YouTube? Can't find any now. Or was it not YouTube?

[pre65]

More progress.

I'm running these dual supply boards with a 240v - 9v transformer into a 12v - 240v transformer.

Output (unloaded) was 120v, but loading both + and - outputs with 390R resistors has given me +/- 80v, which was the target.

When in situ the mosfet load may drag the voltage down a bit but I can adjust on test.

I was surprised how hot an Arcol 50W 390R resistor gets when passing 102ma, which is 4.1W. I know the 50W rating is halved when not on a heatsink but even so.

The 390R value was selected part by calculation and part by whats in my resistor box.

This supply (one of two) is on a breadboard and far too big to go in the amp case, so will have to go offboard.

[pre65]

I remember him! Did he have videos on YouTube? Can't find any now. Or was it not YouTube?

It was on here.

http://tubelab.com/prototypes/833-se/

[Mike H]

Ah thanks.

I was surprised how hot an Arcol 50W 390R resistor gets when passing 102ma, which is 4.1W. I know the 50W rating is halved when not on a heatsink but even so.

Oh yes!


I'm always surprised how hot 1 or 2 Watts is.


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