16-03-2017, 07:02 AM
(This post was last modified: 16-03-2017, 07:03 AM by Diabolical Artificer.)
Slowly plugging away with this amp. I've been looking into the power supply side of things which will mean winding my own tfmr. I've wound my own before but this one being about 400VA is taking some research. I found this article - http://ludens.cl/Electron/trafos/trafos.html - that has a spread sheet that has helped.
I also have to decide whether to make a seperate PSU for two monoblocks, this means a massive tfmr, or use separate tfmr's. I also have to decide whether to use smoothing chokes or just lot's a capacitance. I'd appreciate some guidance here, what are your thought's?
As it stands one monoblock tfmr would need a 320v HT winding at around 1A, a 6.3v htr wdng @ 6A if I use 807's or 6.3v @ around 10A if using EL34's. There is a lot to be said for running the OP stage htr's in series, it keeps the heater wiring neater. Front end htr's could also be run in series @ 12.6v DC @600mA. then there's the fixed neg bias and CCS supply - 80v @ 50mA. There is also the supply to any protection circuit's and other add on's. See attached screenshot of a similar PSU.
I've also been tweaking the OP stage as I found I had an asymetrical OP so needed to pop in a couple of pot's to be able to balance the two "sides". Have also matched the OP valves to within 5%. all these tweak's resulted in less THD and more OP power, not much, but an improvement non the less.
I also have to decide whether to make a seperate PSU for two monoblocks, this means a massive tfmr, or use separate tfmr's. I also have to decide whether to use smoothing chokes or just lot's a capacitance. I'd appreciate some guidance here, what are your thought's?
As it stands one monoblock tfmr would need a 320v HT winding at around 1A, a 6.3v htr wdng @ 6A if I use 807's or 6.3v @ around 10A if using EL34's. There is a lot to be said for running the OP stage htr's in series, it keeps the heater wiring neater. Front end htr's could also be run in series @ 12.6v DC @600mA. then there's the fixed neg bias and CCS supply - 80v @ 50mA. There is also the supply to any protection circuit's and other add on's. See attached screenshot of a similar PSU.
I've also been tweaking the OP stage as I found I had an asymetrical OP so needed to pop in a couple of pot's to be able to balance the two "sides". Have also matched the OP valves to within 5%. all these tweak's resulted in less THD and more OP power, not much, but an improvement non the less.
