I have managed to procure both the 2sk170 and the 2sk1058, I'm not sure whether I will try the MCA or the ZCA first.
In the meantime I have been working on my own minimal component class a amp, it now has a thread:
http://www.diyaudio.com/forums/solid-state/270539-hot-stuff-2w-bipolar-class-amplifier-newbies-first-effort.html
In the meantime I have been working on my own minimal component class a amp, it now has a thread:
http://www.diyaudio.com/forums/solid-state/270539-hot-stuff-2w-bipolar-class-amplifier-newbies-first-effort.html
I believe that I have found another legitimate source for the 2sk170's:
Cricklewood Electronics
They are based in London and they have long been known to source rare semiconductors, particularly the Japanese numbered parts, the 2sa,2sb,2sc, etc. They also sell the 2sk1058's that are used in the ZCA. Not sure how quick they'd be to locations outside the UK, but I ordered my parts on Friday afternoon and got them on Saturday morning!😀
Thanks Mark, that was my inclination anyway. Do you think it would sound even better with a 2sc5200? I have one on the way.
Mark: I have decided that the MCA is perhaps not the best choice for me just now as my speakers have only 88 db sensitivity and the MCA if I remember correctly only puts out 1.2 W RMS. I am wondering perhaps if it could be adapted for headphone use, with a much lower standing current.
I want to thank Mark for inspiring me to get into audio electronics again. If I get a hold of more sensitive speakers in the future I may well return to building the MCA.
I want to thank Mark for inspiring me to get into audio electronics again. If I get a hold of more sensitive speakers in the future I may well return to building the MCA.
Thanks for the nice comment. You need at least 90db efficient speakers for any low power amps. After saying that I have 807 and 300B SE power amps which play quite we'll though 88db efficient speakers. Both amps develop about 4 to 6W.
Feniks, interesting looking build. Did you build a ZCA also? How do you rate the sound I thought it better than the ZCA?
Sound is beautiful, didn't make ZCA, i prefer MCA .Thank you, great amp design. I listen it every day, great sound stage.
I like this amp becouse it dosent need preamp, plays nicely from cd player. i just needed volume pot.
I like this amp becouse it dosent need preamp, plays nicely from cd player. i just needed volume pot.
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Might not this circuit work better with the Drain terminal of the fet tied to the 28V supply? The FET doesn't significantly contribute to the output power, and having its Drain swinging with the output will contribute miller effect HF loss and magnification of the FET's nonlinear D-G capacitance effect. The FET is acting as a Source follower, there isn't a benefit to having its Drain ac hot, is there?
Or am I not seeing something correctly?
Or am I not seeing something correctly?
A couple of thoughts about this circuit.
1. I think it might be interesting as a guitar amp. I know that some guitar speakers and cabs can put out a fair bit of volume with low output powers, going by the surprising number of lm386 based diy guitar amps, also in this context it would be interesting to see how it sounds when deliberately overdriven.
2. As a HiFi amp, might be worth giving it a try with a 2sc5200 instead of a 2n3055, I'd expect the distortion could be lower.
Gordon.
1. I think it might be interesting as a guitar amp. I know that some guitar speakers and cabs can put out a fair bit of volume with low output powers, going by the surprising number of lm386 based diy guitar amps, also in this context it would be interesting to see how it sounds when deliberately overdriven.
2. As a HiFi amp, might be worth giving it a try with a 2sc5200 instead of a 2n3055, I'd expect the distortion could be lower.
Gordon.
I have 12" Beyma speakers with my 6W 300B. The other night it played loud to a large room with over 80 people listening to the music. The Beymas are 98db efficient.
I think 2SC5200 would definitly be an improvement.
It has higher gain than 3055.
This means less currents for the JFET to deliver.
My own thinking is using a power MOSFET, like 2SK1058, is better for this kind of circuit.
Or why not try IRFP240.
There is a reason why Nelson Pass uses these in some of his designs.
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perhaps a little source degeneration on the power FET would tame gain and aid thermal stability ?
