Always fascinated by this Elektor amp from late 80s, but never had access to the parts etc to build it. Recently found this schematic again on the web. Idea looks simple, drive the NMOS with a differential pair. Since it uses same transistor types, NPN/PNP, finding the matched devices can be easy. But this one uses a complex bias stabilization and temperature protection schemes. Don't have any idea about the sound quality etc? Has anyone build this amp? what is the experience?
This uses NMOS devices, BUZ23. I am not sure if they are still available, may be they can be replaced by IRFP devices.
This uses NMOS devices, BUZ23. I am not sure if they are still available, may be they can be replaced by IRFP devices.
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I made those amps for sale,both for hifi and PA.Very reliable amp, sounds good.Stabilization is simple in fact,an NTC thermistor is inserted in second diferential pair's current source to decrease bias for output mosfets.I used irfp250,irfp240,irf540,irf640,everything works.
I made those amps for sale,both for hifi and PA.Very reliable amp, sounds good.Stabilization is simple in fact,an NTC thermistor is inserted in second diferential pair's current source to decrease bias for output mosfets.I used irfp250,irfp240,irf540,irf640,everything works.
I've build this on a vero board, used as a sub amp 5 years ago..now retired used IRF540 --2 nos drve 4 OHMS comfortably, can we increase power output if we use IRF240 and increasing voltage ?
the PCB on top is the said power amp on vero board, power by an half bridge SMPS (IRF2155 & 2x IRF840) below is the sub filter board
Hi, I have build this amp, it was a kit from velleman K2587, it is verry god amp I have use it for 20+ years 🙂
Yesterday I got to actually listen to the amp
I would say stereo image was quite good and also had good depth after it warmed up.
I did not notice that power would be groundshaking but then again it was very pleasant to listen to.
I would say that hitachis J50/K135 application note amp is better and so are e.g. all designs from Pass.
But then again this is much better than, say, the 399 chepo amps from your local TV dealer. (at least the ones in Finland)
First impression was slightly worsened by the fact that amp was humming a little even with like 88dB/W speakers. Might be due to the terrible wiring 😉
I need to remove all junk from the box and redo the wiring.
I will also add DC protection, this one only has delay on the speaker relay.
I would say stereo image was quite good and also had good depth after it warmed up.
I did not notice that power would be groundshaking but then again it was very pleasant to listen to.
I would say that hitachis J50/K135 application note amp is better and so are e.g. all designs from Pass.
But then again this is much better than, say, the 399 chepo amps from your local TV dealer. (at least the ones in Finland)
First impression was slightly worsened by the fact that amp was humming a little even with like 88dB/W speakers. Might be due to the terrible wiring 😉
I need to remove all junk from the box and redo the wiring.
I will also add DC protection, this one only has delay on the speaker relay.
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