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Old 22nd August 2011, 03:36 PM   #341
Sheldon is offline Sheldon  United States
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Quote:
Originally Posted by AKSA View Post
LC,

You nailed it expertly..... that's exactly how Roender does his driver, but I think he uses 18R, not 16R - so essentially, your solution is identical.

Hugh
Original was 16R @ 77mA, but 12R, and 100mA as the latest version. I don't want 3 output pairs - only one. With the cfp, I think you need more than the two diodes for biasing/thermal comp..

Sheldon
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Old 22nd August 2011, 04:28 PM   #342
Bigun is offline Bigun  Canada
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I also don't want 3 output pairs, one is enough.

The CFP doesn't add more Vbe's into the mix for thermal comp because the slave device is under the control of the master device before it. Keeping in Class A is important but this seems to require the use of a quadruple output stage - not sure if that's wise ?
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Old 22nd August 2011, 04:53 PM   #343
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Quote:
Originally Posted by AKSA View Post
LC,

You nailed it expertly..... that's exactly how Roender does his driver, but I think he uses 18R, not 16R - so essentially, your solution is identical.

Hugh
Yeah it is simple as that.

I just combined SSA front-end with Roender's output stage to show how simple is to play within certain topology and it is just a matter of our imagination what the limits are.
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Old 22nd August 2011, 05:25 PM   #344
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Can this amp be done with 2SK1530/J201?
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Old 22nd August 2011, 05:51 PM   #345
Sheldon is offline Sheldon  United States
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Quote:
Originally Posted by Bigun View Post
I also don't want 3 output pairs, one is enough.

The CFP doesn't add more Vbe's into the mix for thermal comp because the slave device is under the control of the master device before it. Keeping in Class A is important but this seems to require the use of a quadruple output stage - not sure if that's wise ?
Believe me, my understanding of this is very shallow. But connected as LazyCat has shown, requires two pair for the 4 diodes, as there is an extra diode drop over the sc3788/sa1478. However, with the same output buffer, Roender used 5 diodes (4 are under compensated), which means 3 pair of outputs are required. Could use other diodes, but that defeats the purpose of the Thermaltrak.

Is there another way to do this? Otherwise, I'd just go with LazyCat's original thermaltrak version.

Sheldon

Last edited by Sheldon; 22nd August 2011 at 05:54 PM.
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Old 22nd August 2011, 09:32 PM   #346
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Has anybody made a PCB for a single pair BJT version?
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Old 23rd August 2011, 10:40 AM   #347
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Exclamation SSA High Performance

If someone would like to make high performance SSA, here is my proposal. Of course I could make it even more complex but I think this one would have enough zeroes for minimal THD lovers.
Attached Images
File Type: jpg SSA TTC.jpg (539.1 KB, 1152 views)

Last edited by Lazy Cat; 23rd August 2011 at 11:05 AM.
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Old 23rd August 2011, 12:03 PM   #348
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Quote:
Originally Posted by Sheldon View Post
Is there another way to do this? Otherwise, I'd just go with LazyCat's original thermaltrak version.

Sheldon
Normally with thermal track BJT's, integrated diodes are used to compensate the thermal drift, how many diodes will be in the bias loop depends on two factors:

- correct DC voltage to set the output stage quiescent current
- thermal drift cancellation

So if Roender used five TT diodes in this output stage than you could do the same. For the DC bias voltage purposes four of them plus 500 ohm trimmer are enough.

If someone would like to use regular BJT's as output devices, than Vbe multiplier should be implemented instead of serial TT diodes. This solution also requires some fine adjustments to cancel thermal drift to minimum.

Last edited by Lazy Cat; 23rd August 2011 at 12:31 PM.
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Old 23rd August 2011, 12:16 PM   #349
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Quote:
Originally Posted by odysseybmx414 View Post
Has anybody made a PCB for a single pair BJT version?
Not yet.

Until now three PCB's were made:

- post #224 dual mono PCB, Nico's version according to Nico sch, one pair 2SJ162/2SK1058 laterals

- post #227 single mono PCB, Alex's version according to Nico sch, one pair 2SJ162/2SK1058 laterals

- post #301 single mono PCB, Alex's version according to Miib sch, three pairs 2SJ162/2SK1058 laterals

There are quite a lot sch proposals and for an "all BJT's" version we have to make a consensus for the one Alex could possibly design as a thread request.

Please put down your suggestions which sch we should pick to make another PCB. My would be for the last one ...

Last edited by Lazy Cat; 23rd August 2011 at 12:35 PM.
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Old 23rd August 2011, 12:24 PM   #350
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Quote:
Originally Posted by Josip_Del View Post
Can this amp be done with 2SK1530/J201?
Any thought or doubt against why not to use them?
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