Hi there all
Howdy all, I have just registered to this Forum as an ex-crescendo builder and user. I built this amp as a project in 1984-5 and it worked great, nice to see that the ME integrated most of the protections I had built into it as a result of experience and trials. The very first power up worked well, then it went down hill. It oscillated on one side and a plate over two of the Mosfet got rid of it, i can't remember which ones though, anyhow, I have only the transformer (toroidal) and the two heat sinks left as a souvenir, thinking of rebuild it one day. This day is coming back now.
after reading about it and it's oscillation problems, I think I might go for another kit. Still using what I got, so my homework starts here.
As an electronician by trade, I made a complete dossier of the kit, I will try to put it on line when I get the time and willingness to do it. Unfortunately I haven't got any photos (AFAIK) of the thing. I am still working ona another project at the moment which is not Audio related (web cam system)
So that's all for the long winded post and I hope that I will be able to contribute/get advice from this Forum.
All the best for 2012!
G.
Howdy all, I have just registered to this Forum as an ex-crescendo builder and user. I built this amp as a project in 1984-5 and it worked great, nice to see that the ME integrated most of the protections I had built into it as a result of experience and trials. The very first power up worked well, then it went down hill. It oscillated on one side and a plate over two of the Mosfet got rid of it, i can't remember which ones though, anyhow, I have only the transformer (toroidal) and the two heat sinks left as a souvenir, thinking of rebuild it one day. This day is coming back now.
after reading about it and it's oscillation problems, I think I might go for another kit. Still using what I got, so my homework starts here.
As an electronician by trade, I made a complete dossier of the kit, I will try to put it on line when I get the time and willingness to do it. Unfortunately I haven't got any photos (AFAIK) of the thing. I am still working ona another project at the moment which is not Audio related (web cam system)
So that's all for the long winded post and I hope that I will be able to contribute/get advice from this Forum.
All the best for 2012!
G.
200W Class A Power Amp
Hi im newbie here...
need to ask the expert, is this audio circuit worth to be build?
http://www.tasel.net/images/200W-MOSFET-Audio-Amplifier-circuit-with-K1058-diagram.jpg
are there any suggestion from you guys...
some said this is a pure class A and better than crescendo, what do you think.?
Hi im newbie here...
need to ask the expert, is this audio circuit worth to be build?
http://www.tasel.net/images/200W-MOSFET-Audio-Amplifier-circuit-with-K1058-diagram.jpg
are there any suggestion from you guys...
some said this is a pure class A and better than crescendo, what do you think.?
"some said this is a pure class A and better than crescendo, what do you think.? "
Looking at R18 /820Ohm, it looks like it's high biased yes.
The schematic:
Cascade complementairy input with beta enhanced VAS. For Drivers I would select other parts. I would run the VAS at minimum 20mA, the BF469/470 would not handle the dissipation.
It's a Non Feedback amp, I personaly have no experience in non feedback amps.
It doesn't look like an expensive design, build it, and let us know your opinion. The BF469/470 will be very hard to get these days, you can use 2SA1209/2SC2911 as replacement for example.
Looking at R18 /820Ohm, it looks like it's high biased yes.
The schematic:
Cascade complementairy input with beta enhanced VAS. For Drivers I would select other parts. I would run the VAS at minimum 20mA, the BF469/470 would not handle the dissipation.
It's a Non Feedback amp, I personaly have no experience in non feedback amps.
It doesn't look like an expensive design, build it, and let us know your opinion. The BF469/470 will be very hard to get these days, you can use 2SA1209/2SC2911 as replacement for example.
thanks for responses...
btw this is the pcb layout:
http://www.tasel.net/images/200W-MOSFET-Audio-Amplifier-circuit-component-layer.jpg
and i think there are lots of improvement at the layout (diff from the schematic)
i also never build a NFB power amp, but when i saw the pcb layout
i am interesting to build one.
so now, by looking at pcb layout, are there any possible error from this design?
or are there any improvement i should make...?
from the schematic it use electrolite capacitor for the input, as i know this should be better to use a non polar rather than polar cap... is it?
the layout and schematic basically match, there are only a few addition of 1 set mosfet (2sets at schematic, but 3sets at pcb) and also increasing the power supply capacitors (2 100uF/63v at the schematic, but 12pcs 470uF/63v at the pcb)
thats all no else.
The Elector Crescendo was my first DIY amp that wasn't a kit.
I borrowed the Elector magasins at our local library and had some 'amateur' make the PCBs, which turned out having lanes that didn't connect properly.
I am far from being an expert in electronics, but I think maybe ocsillation was never a problem in my project because I put some very small caps close the the FETs. I think this was recommended because I had to move the FETs away from the PCB on to a cooling tunnel. And then all the old tricks like, one ground in the cabinet. No hum at all.
It had dual Toroids with 'cumputer graded' Caps that was speeded up with some small poly caps? Wow.. It's all coming back to me know. It was good fun to build and the amp proved to be stable and lived for some years being mistreated in a Disco -often driving speaker configurations in 2 ohms. Then I sold it for good money. This was back when DIY could actually save you or make you some money.
What is not good about this design? - except for the tendency to oscillate?
/ Andy
I borrowed the Elector magasins at our local library and had some 'amateur' make the PCBs, which turned out having lanes that didn't connect properly.
I am far from being an expert in electronics, but I think maybe ocsillation was never a problem in my project because I put some very small caps close the the FETs. I think this was recommended because I had to move the FETs away from the PCB on to a cooling tunnel. And then all the old tricks like, one ground in the cabinet. No hum at all.
It had dual Toroids with 'cumputer graded' Caps that was speeded up with some small poly caps? Wow.. It's all coming back to me know. It was good fun to build and the amp proved to be stable and lived for some years being mistreated in a Disco -often driving speaker configurations in 2 ohms. Then I sold it for good money. This was back when DIY could actually save you or make you some money.
What is not good about this design? - except for the tendency to oscillate?
/ Andy
I was referring to the circuit linked by wengtech some post above.
Drawing errors in the schematic and a mismatch between schematic and layout...enough reasons to avoid it!
This is not a non-feedback (NFB) design. The feedback goes to the input in an normal inverting amplifier mode.
This is not a class A amp. Ordinary class AB output stage.
There are some capital flaws in the schematic.
The "miller" capacitors C6, C7 are in phase in the loop that will oscillate the VAS.
Also the circuit board contans the same fault as the schematic, wich guaranteed will burn the driver transistors & the output FET´s (ie the whole amp) if the ouput is shorted to ground.
F.ex. diodes D5, D6 & D7, D8 should be connectet to the VAS output, not the emitter follower drivers. The VAS transistors must then also have some current limiting.
Otherwise the VAS transistors will still go into unsafe operating area and burn (etc), if theirs collectors are shorted to the output......
When there are so sewere faults in a design, you should know that the designer has never built it to funktion. He has probably just borrowed some schematics and modified, without knowing much of amp design or actually building it.
I really advise NOT TO BUILD this amp.
Johan
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I have had 20 years and 3 months cressedno as the used preamp tube amplifier and the result was incredible and I found the atmosphere and warmth of the sound produced. Currently I'm stringing SK135 and J50 mosfet in the circuit that uses a buffer of LME 49830 from National Semiconductor, does anyone of you have tried it? and what were the results?
it is better then crescendo
It is better than crescendo,but without reversing transistor polarity or some other catastrofic mistakes.I put this amp in another thread named AXL.
It is better than crescendo,but without reversing transistor polarity or some other catastrofic mistakes.I put this amp in another thread named AXL.
it is better then crescendo
It is better than crescendo,but without reversing transistor polarity or some other catastrofic mistakes.I put this amp in another thread named AXL.
It is better than crescendo,but without reversing transistor polarity or some other catastrofic mistakes.I put this amp in another thread named AXL.
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