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Old 1st February 2013, 05:03 AM   #3871
shaan is offline shaan  India
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Originally Posted by PauloPT View Post
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.
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Old 1st February 2013, 10:05 AM   #3872
PauloPT is offline PauloPT  Portugal
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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.
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Old 1st February 2013, 10:29 AM   #3873
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I only have one criticism - the lows seem too light.
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.
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Old 1st February 2013, 10:47 AM   #3874
PauloPT is offline PauloPT  Portugal
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I had a bad 1000uF cap. Replaced and now the bass is fine

How much power can I get with 4 Ohms speakers with the laterals? They are only rated 100W so 80W should be safe?
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Old 1st February 2013, 11:11 AM   #3875
shaan is offline shaan  India
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Originally Posted by PauloPT View Post
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.

Quote:
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.
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
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Old 1st February 2013, 11:18 AM   #3876
shaan is offline shaan  India
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Ya 80watt does sound safe.
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Old 1st February 2013, 12:20 PM   #3877
PauloPT is offline PauloPT  Portugal
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Originally Posted by shaan View Post
Ya 80watt does sound safe.
Will it be safe with 30V rails and 4 Ohms speakers?


Quote:
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.
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.
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Old 3rd February 2013, 07:48 AM   #3878
shaan is offline shaan  India
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Will it be safe with 30V rails and 4 Ohms speakers?
It should, as long as there is good heatsinking for the FETs.

Quote:
You published a schematic and pcb layout with a DC servo. Should I go for it?
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
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Old 3rd February 2013, 09:54 AM   #3879
PauloPT is offline PauloPT  Portugal
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Quote:
It should, as long as there is good heatsinking for the FETs.
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.

Quote:
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.
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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Old 3rd February 2013, 12:36 PM   #3880
PauloPT is offline PauloPT  Portugal
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Quote:
And why 45V rails?
I have 2 transformers - one with 25-0-25Vac (about 35V dc rails) and other with 35-0-35Vac (about 50V dc rails). Can I use any of these for the servo version?

Thanks.
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