PSUD2 for S.E.X. 2.1

[ZacharyP]

I was wondering if someone could give me some pointers on how to model the S.E.X. 2.1 power supply.  It would be greatly appreciated.  Going for a CLCLC filter and trying to figure out ideal capacitance values given the C7X choke.

Thanks for reading and any possible help!

[Paul Birkeland]

For PSUD, start with the values present in the schematic (use 75mA constant current load).

The extra choke and capacitor will take up a lot of space, and are going to take power supply ripple down further than we would say you need to given the demands of high efficiency speakers and headphones.  Assuming that you're going to keep the power supply split for each channel, this would mean 4 chokes and 2 extra caps.

You could, however, use a pair of Hammond 154G chokes in place of each power supply resistor without too much trouble.

[ZacharyP]

For PSUD, start with the values present in the schematic (use 75mA constant current load).

The extra choke and capacitor will take up a lot of space, and are going to take power supply ripple down further than we would say you need to given the demands of high efficiency speakers and headphones.  Assuming that you're going to keep the power supply split for each channel, this would mean 4 chokes and 2 extra caps.

You could, however, use a pair of Hammond 154G chokes in place of each power supply resistor without too much trouble.

Thank you.  With regards to space, I had a wooden case made that is twice as tall and quite a bit wider.

 I'll look into the Hammond chokes, they're reasonably priced.  The rated resistance of 700 ohms is quite a bit higher than the 270 ohm triad filter chokes.  Would it not ultimately be preferable to get the lower DCR filter choke?


Also is there any headroom with the PT-7 transformer?  I've been intrigued with the possibility of implementing a solid state shunt regulator.

It is the experimenters kit, after all!

[Paul Birkeland]

I'll look into the Hammond chokes, they're reasonably priced.  The rated resistance of 700 ohms is quite a bit higher than the 270 ohm triad filter chokes.  Would it not ultimately be preferable to get the lower DCR filter choke?

The design calls for voltage drop from a 680 Ohm resistor.  700 Ohms is much closer to 680 Ohms than 270 Ohms.

Also is there any headroom with the PT-7 transformer?  I've been intrigued with the possibility of implementing a solid state shunt regulator.

Undoubtedly there is a bit of headroom, but you'd want to dump a fair amount of current through such a regulator. 

[Paul Joppa]

You talked of four chokes; notice the second resistor in each channel's supply is 8200 ohms, and the current is very low, 2-3mA. Hammond has a nice, tiny 60henry/8ma2750ohm choke. It seems a likely choice but I have not engineered, much less tried, this. It will pick up magnetic hum and inject it into the power section grid, so watch out for that.

High voltage headroom is very small in the PT-7 in the SEX amp, maybe 10mA tops, less with the C4S kit.