Hi,
If I use 2SJ201/2SK1530 instead of 2SJ162/SK1058 (different pin out) what other changes sould I do to the circuit?
Has anyone thought about having a professional etched pcb and organizing a group buy?
Thanks.
OK, I now can answer my own question. The 2SJ201/SK1530 are vertical mosfets and not lateral as I first thought. Therefore they can't be used without some changes to the circuit like a VBE multiplier. As I have some around I added 3 more diodes for more bias and because the 2SJ201/SK1530 don't suffer from thermal runway (however they are vertical) it worked. I could then taste the SSA sound and it really sounds very very good! The cymbals, the piano notes, sound impressively natural without any hint of harshness and in a sweet presentation. Curiously, the SSA sound signature is very similar to the SYMEF, the same lively and sweet presentation, very very similar.
Hi PauloPT
Glad you like it, enjoy.
Thank you Lazy Cat for designing this wonderful amp!
I'm going to order some 2SK1058/2SJ162 to make a proper build. I have some questions about it:
1) Is it completely stable, no worries about?
2) The input filter cap is only 22pF, shouldn't it be about 10 times higher?
3) Can I use it with 4 ohms speakers? How much power would I get safely?
4) Has anyone mesured THD, just curious I'd like to know TDH at 20KHz.
5) My home made pcb's always look like something out of an horror movie. I would much prefer to have a nice professional etched pcb, is a group buy for pcb's out of the question?
Sorry for so many questions...
May-i recommend-you to set the input filter with a FC of 200Khz ?
Or to do-it listening: More you filter EMI and residual distortions from previous stages, better it is. The limit is to keep the phase right at 20KHz.
OK, I now can answer my own question. The 2SJ201/SK1530 are vertical mosfets and not lateral as I first thought. Therefore they can't be used without some changes to the circuit like a VBE multiplier. As I have some around I added 3 more diodes for more bias and because the 2SJ201/SK1530 don't suffer from thermal runway (however they are vertical) it worked. I could then taste the SSA sound and it really sounds very very good! The cymbals, the piano notes, sound impressively natural without any hint of harshness and in a sweet presentation. Curiously, the SSA sound signature is very similar to the SYMEF, the same lively and sweet presentation, very very similar.
Hi paulo.
Congratulation.
So the SSA, with less parts, less poles, less lyricals and no formula sounds same as the "world's best amplifier"?
Bravo. 
Btw, which schematic are you using?
Well maybe there is a formula; which is "emitter feedback injection" and is no magic or secret and speaks for itself.
Hi shaan,
Both the SSA and the SYMEF are very good sounding amplifiers.
What impresses me most with the SSA is the treble - it's beautifully sweet and extended!
The SSA proves we don't need to go class A to have high end sound. The highs on the SSA are class A quality, best of the best! And I checked the bias - 125mA only.
I'm using your circuit, except with the 2SJ201/2SK1530 instead of the laterals. I'm going to order the proper fets, they simulate less distortion in LTSpice.
I only have one criticism - the lows seem too light. I suspect the electrolytic caps in the board - I'm only using 330uF for the caps across the zeners, Panasonic FM's. Do you have a sugestion for specific brand/type of caps that sound best? I read some posts ago the FM's weren't too good with the SSA.
Both the SSA and the SYMEF are very good sounding amplifiers.
What impresses me most with the SSA is the treble - it's beautifully sweet and extended!
The SSA proves we don't need to go class A to have high end sound. The highs on the SSA are class A quality, best of the best! And I checked the bias - 125mA only.
I'm using your circuit, except with the 2SJ201/2SK1530 instead of the laterals. I'm going to order the proper fets, they simulate less distortion in LTSpice.
I only have one criticism - the lows seem too light. I suspect the electrolytic caps in the board - I'm only using 330uF for the caps across the zeners, Panasonic FM's. Do you have a sugestion for specific brand/type of caps that sound best? I read some posts ago the FM's weren't too good with the SSA.
Verify the bandwidth. Good slew-rate and high dumping factor make often the basses to sound faster... and, so, lighter. There is no reason (other than insuficient caps values), for the ***** to loss anything: that the easiest audio part to be reproduced by electronic.
What impresses me most with the SSA is the treble - it's beautifully sweet and extended!
The SSA proves we don't need to go class A to have high end sound. The highs on the SSA are class A quality, best of the best! And I checked the bias - 125mA only.
Of course. That's what happens when one successfully builds an SSA.
Please note the following points.
1. Zener caps should be 1000uF or bigger.
2. VAS bias should be greater than 10mA for better driving of FETs.
3. Input cap should be large enough(10uF) for good bass response.
4. Laterals will perform better here in all respects.
5. PS reservoire caps should be 10000uF minimum for deep bass production.
Personally I use Punsumi 15000uF 50V caps at the PS and Keltron caps in all my diy amps, and IMO they are the best(and expensive). But both of them are Indian products, so may not be available where you live.
Happy listening.
Shaan
Will it be safe with 30V rails and 4 Ohms speakers?
Here I don't have acess to those brands of capacitors. I can buy Nichichon, Elna, Panasonic, and those industrial brands like Lelon, Yageo, Jamicon, etc.
You published a schematic and pcb layout with a DC servo. Should I go for it?
Thanks.
It should, as long as there is good heatsinking for the FETs.
Why not? I've built the schematic and it runs okay. The PCB hasn't been tested by me as a printed version, however it seems to be free of layout errors.
All the best.
Shaan
I was wondering how much power can I have from a single pair os fets and what would be highest safe rail voltage for 4 ohms use. Rod Elliot in his mofet P101 amp claims 150W but I see in the fets datasheet they rated only 100W.
Can you share the schematics? Do you find the servo doesn't impact negatively the sound? And why 45V rails?
Thanks.
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