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Old 4th June 2012, 03:58 PM   #21
Bonsai is offline Bonsai  Taiwan
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Luckily there are many ways to solve this problem ;-)
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Old 4th June 2012, 04:11 PM   #22
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Very well done. Now we need listening test vs SYMEF
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Old 4th June 2012, 11:29 PM   #23
Bonsai is offline Bonsai  Taiwan
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Yes, I can only do listening tests on my other amp and a low fi Marantz right now. Some comparative listening tests would be great.
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Old 5th June 2012, 08:28 AM   #24
wahab is offline wahab  Algeria
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Originally Posted by Bonsai View Post
Is the file opening on your side?
It works , it was just my version of Adobe Reader (7.0)
that was outdated...


Nice work Bonsai , but you surely know that i m fond
for this kind of topology...

Will give it a try in the simulator , anyway.
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Old 5th June 2012, 08:42 AM   #25
Bonsai is offline Bonsai  Taiwan
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Good to hear you got it sorted out.

Let me know your results! We should start a balanced symmetrical club here!
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Old 5th June 2012, 02:22 PM   #26
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Interesting read especially the part about cascode stability, nice work. I never thought that it could be a problem in a amp design although there is literature warning about this. Your solution is right on target with what you find in books.

Another problem Im recently exploring is the peaking in current mirrors. These suffer the same fate as the cascodes. Here the solution is not as straight forward. I have to wonder if there is any correlation to people stating that current mirrors sound cold and like the cascodes can cause a little oscilation at some high frequency. Again there is not much literature on this.
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Old 5th June 2012, 10:36 PM   #27
Bonsai is offline Bonsai  Taiwan
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Interesting Homemodder. I never heard much about mirrors peaking as well (do you have link or can you point me in the right direction?). I am certainly now much more attuned to the possibility of these kinds of problems following mt experience with the cascode.

I would never have caught the cascode oscillation without my wideband scope BTW. Invaluable for audio
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Old 6th June 2012, 10:58 AM   #28
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Originally Posted by Bonsai View Post
Ian,
basically what I found is that EF3's are quite hard to thermally compensate. You can get them stable over a narrow temperature range, but once the heatsink heats up, you get errors - in my case, the Iq increased significantly.
Very impressive work and very professional in every respect, not least the PDF. A pleasure to read a balanced and considered analysis in an audio publication
Did you consider a triple with CFP + EF? Self shows this and says it looks to have promise. Seems to me that it would be easier to thermally compensate than a triple EF. And I think the distortion should be even a little lower. I note Roender used one with success but I am surprised it is not more common.
Of course I haven't tried to stabilize one yet so I may learn.
My respect for your work and thanks for an informative analysis.

Best wishes
David

Last edited by Dave Zan; 6th June 2012 at 11:01 AM.
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Old 6th June 2012, 11:27 AM   #29
Bonsai is offline Bonsai  Taiwan
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THanks Dave, appreciate the comments.

I have not tried the CFP+EF - so many circuits, so little time!

This might be one for me to look at in the future. I will do more high power amplifiers but have to decide whether I refine the e-Amp and build on that, or try something very different. The time consuming challenge is that very topology has a learning curve, and here I refer to the process of going from the sim to a finished, well performing amp. On the e-Amp it was cascode issues, thermal comp (I think I have it nailed now) and output EF3 stability.
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Old 6th June 2012, 12:37 PM   #30
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Originally Posted by Bonsai View Post

I have not tried the CFP+EF - so many circuits, so little time!

This might be one for me to look at in the future. I will do more high power amplifiers but have to decide whether I refine the e-Amp and build on that, or try something very different. The time consuming challenge is that very topology has a learning curve, and here I refer to the process of going from the sim to a finished, well performing amp. On the e-Amp it was cascode issues, thermal comp (I think I have it nailed now) and output EF3 stability.
I am reassured that you haven't actually rejected it. Here's my idea for why you should try it.
Self shows an example to indicate that one overall feedback loop lowers distortion more than two separate ones, so it seems that a CFP loop should be lower in distortion than 2 EFs where each EF is effectively a separate 100% local -ve feedback loop.
The circuit becomes a superEF + EF and the superEF does not have the crossover problems that trouble a CFP output.
And the driver is practically out of the thermal compensation so there is just a little TO-126 pre-driver where a bias spreader transistor can conveniently be bolted.
Then ThermalTrak outputs. Easy!
Similar to Dadod's TTrak scheme but perhaps even a little nicer.
So no major curve to learn.
Any idea why it's not more popular?

Best wishes
David

Last edited by Dave Zan; 6th June 2012 at 12:43 PM.
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