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Old 21st August 2011, 11:17 AM   #321
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Quote:
Originally Posted by Nico Ras View Post
I added the 3.3 pF FB capacitors only to band limit the amp in case of spurious pick-up from the speaker cables. Some FM tuners 10.7MHz can radiate IF and the amp can still operate at that frequency.
Yes I agree, SSA could be a very good RF transmitter amp up to 10MHz bandpass.
On mine PCB there will also be a space for these two caps, to have exact -3dB bandwidth limit. Also I will limit the input signal bandwidth with low-pass filter set to -3dB at 1MHz.

Quote:
Originally Posted by Nico Ras View Post
Comparing subjectively between MOSFET and switching to BJT version I cannot detect any difference in sound character.
So the input CF diff-amp and unique feedback loop determine the sound character in general.
This is very important info Nico, thanks, cause I only experimented with BIGBT's and for my home amp I have intent to do a little more sophisticated version, hopefully the sound will stay the same.

Quote:
Originally Posted by Nico Ras View Post
I used On Semi MJ15001 and MJ15002 for BJT and Rensas 2SK1058 and 2SJ162 for MOSFET. I do not have IGBTs so I wont bother. I personally choose the MOSFETs because the circuit is simpler.

Regards

Nico
Yes, IGBT and MOSFET output versions are the simplest.

Regards, Andrej
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File Type: jpg SSA IGBT.jpg (288.7 KB, 1118 views)

Last edited by Lazy Cat; 21st August 2011 at 11:38 AM.
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Old 21st August 2011, 05:55 PM   #322
Sheldon is offline Sheldon  United States
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Quote:
Originally Posted by Nico Ras View Post
Comparing subjectively between MOSFET and switching to BJT version I cannot detect any difference in sound character.
If so, then I'd like to build this version: http://www.diyaudio.com/forums/attac...ier-ssa-tt.jpg

I have some Thermaltraks. PCB file anyone? Are two diodes enough compensation for thermal drift?


Sheldon
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Old 21st August 2011, 06:33 PM   #323
Bigun is online now Bigun  Canada
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Sheldon, I'd love to hear how you find the all-bjt version as this is the one I'm most likely to build if I give it a try.

Seems to me that thermaltracks would be fine re: thermal comp of the output stage.
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Old 21st August 2011, 06:44 PM   #324
radio is offline radio  Macedonia
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Quote:
Originally Posted by Nico Ras View Post
I added the 3.3 pF FB capacitors only to band limit the amp in case of spurious pick-up from the speaker cables. Some FM tuners 10.7MHz can radiate IF and the amp can still operate at that frequency.

Comparing subjectively between MOSFET and switching to BJT version I cannot detect any difference in sound character.

I used On Semi MJ15001 and MJ15002 for BJT and Rensas 2SK1058 and 2SJ162 for MOSFET. I do not have IGBTs so I wont bother. I personally choose the MOSFETs because the circuit is simpler.

Regards

Nico
Hi !
Where is the version with MJ15001/MJ15002 ?
thanks
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Old 21st August 2011, 07:37 PM   #325
radio is offline radio  Macedonia
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Alex mm you do not have a version of this amplifier with bipolar output transistors (PCB and schematic) ?
thanks
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Old 21st August 2011, 09:13 PM   #326
Sheldon is offline Sheldon  United States
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Quote:
Originally Posted by Bigun View Post
Sheldon, I'd love to hear how you find the all-bjt version as this is the one I'm most likely to build if I give it a try.
I plan to repurpose an amp with this. Was considering the Fetzilla, but this is more intrigues me a little more. I'll wait until the design settles in a bit.

Quote:
Originally Posted by Bigun View Post
Seems to me that thermaltracks would be fine re: thermal comp of the output stage.
I was thinking of Mihai's FC100, that I built. It uses 5 diodes in the bias string. But, looking at the respective output buffer sections, it now makes sense to me that this one would only require two. Elegant little amp.

Sheldon
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Old 21st August 2011, 10:27 PM   #327
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Quote:
Originally Posted by radio View Post
Alex mm you do not have a version of this amplifier with bipolar output transistors (PCB and schematic) ?
thanks
It was posted by Michael (MiiB) a few posts earlier go have a look four or five pages back.

Last edited by Nico Ras; 21st August 2011 at 10:29 PM. Reason: It is POST #301
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Old 22nd August 2011, 12:19 AM   #328
Bigun is online now Bigun  Canada
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Quote:
Originally Posted by Sheldon View Post
I was thinking of Mihai's FC100, that I built. It uses 5 diodes in the bias string. But, looking at the respective output buffer sections, it now makes sense to me that this one would only require two. Elegant little amp. Sheldon

If I can indulge in a quick off-topic: how did you find the FC100 ? I used the output stage with one pair of power devices in my TGM3 and found it very good.
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Old 22nd August 2011, 12:52 AM   #329
Sheldon is offline Sheldon  United States
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Originally Posted by Bigun View Post
If I can indulge in a quick off-topic: how did you find the FC100 ? I used the output stage with one pair of power devices in my TGM3 and found it very good.
I like it. Very solid and smooth. It's going to be a permanent part of my main system. Also, no noise at all, and not turn on/of transients. I'm using it on the mids and lower. Might be overkill in terms of sophistication for that, but plenty of current capacity to drive my 15" mids. I'm thinking of the SSC amp for the upper mids and tweeter.

Sheldon
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Old 22nd August 2011, 02:25 AM   #330
Bigun is online now Bigun  Canada
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Quote:
Originally Posted by AKSA View Post
I doodled a single ended version of your amp, with PP output stage using lat fets.
I kept moving along, reducing and refining - and I virtually ended up with a bipolar version of the FetZilla!!
sounds interesting - let's have a gander then ?
fyi - the nearest to a SE version of the SSA that I know of is here: Renardson-Audio, Hi-Fi Audio Amplifier Designs.

However, despite my penchance for SE designs, this SSA has me quite excited (with option for CFP driver and BJT power device)

Do we have an OLG estimate for the SSA ?
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Last edited by Bigun; 22nd August 2011 at 02:38 AM.
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