Experience is that BJT's are less likely to introduce oscillation into the circuit.
While your waiting for an update, and as the thread is still called 'JamJar: an HPA-1-inspired power amp', here's a couple of terrible pics and a bad screen shot. I updated Alice/Frank and gave it a new name after using some of the suggestions in this thread. Just waiting for some zenners to be delivered before I can start testing.
Any recommendations - even if it's 'get a spade, go into the garden...!'
Any recommendations - even if it's 'get a spade, go into the garden...!'
Attachments
Thank you Jam. Ditto on the THAT, I bought the lowest gain group for the NPN to match the PNP; I suppose everything is a compromise, at least the N's & P's are matched and thermally coupled; the data sheet advocates the use as current mirrors, the emitter resistors are 0.1% so hopefully it will work reasonably well; if not, I can pull them from the socket and patch in some BC550/60 or something underneath.
Super tidy and neat as always Jeff 
What diodes are you using these days? I see TO-220 2-pin creatures. Any preferences or good experiences in particular?
I don't remember which thread it was in but I saw someone trying out FERD diodes but the only ones I can find are rated at 100V or lower. Isn't that too low for mains AC even in North America?
STMicro FERD20H100SFP is one example. The price is good and I like full packs because I'm cheap and lazy but doesn't the diode need to be rated higher than your input voltage?
What diodes are you using these days? I see TO-220 2-pin creatures. Any preferences or good experiences in particular?
I don't remember which thread it was in but I saw someone trying out FERD diodes but the only ones I can find are rated at 100V or lower. Isn't that too low for mains AC even in North America?
STMicro FERD20H100SFP is one example. The price is good and I like full packs because I'm cheap and lazy but doesn't the diode need to be rated higher than your input voltage?
I'm using FRED Pt's: https://www.mouser.ie/datasheet/2/427/vs-etu3006fpm3-1147833.pdf
Much larger Vf than the FERDs (so more heat), but then this amp was never going to run cool anyway.
I would think your bridge diodes would only need a hefty margin above your secondary voltage. If you transformer fails and passes primary voltage through to the secondaries, your diodes aren't going to be the only thing popping.
Much larger Vf than the FERDs (so more heat), but then this amp was never going to run cool anyway.
I would think your bridge diodes would only need a hefty margin above your secondary voltage. If you transformer fails and passes primary voltage through to the secondaries, your diodes aren't going to be the only thing popping.
The old tired FREDs with their high Vf and their 30 year old semiconductor device+process design, were middle-of-the-pack performers compared to the other diodes tested in The Shootout.
Fortunately you can bring old tired FREDs up to state of the art performance, at a piddling cost of $1.00 worth of parts plus €2,99 worth of article download
Fortunately you can bring old tired FREDs up to state of the art performance, at a piddling cost of $1.00 worth of parts plus €2,99 worth of article download