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Old 22nd March 2012, 06:15 PM   #3921
bcarso is offline bcarso  United States
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Quote:
Originally Posted by janneman View Post
Brad, doesn't this ring of two have poor neg supply PSRR?

jan
And as one contemplates it, the ring of two is a lot better for PSR than it might appear at first. The sensitivity of the effective reference voltage, Vbe of the error amp transistor Q1, to changes in the power supply via R1, is reciprocal to the transconductance of that device. And the input impedance at the base of Q2 is low, again due to feedback. So if we wiggle the power supply voltage, the major effect is reference voltage modulation, and that is about (delta V)/(R1*gm), and the effect on output current is calculated as the ratio of that to the emitter resistor R3.

If R1 is replaced by a higher-impedance source of current things get a lot better still. But for two transistors the performance is pretty nice.
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Old 22nd March 2012, 06:24 PM   #3922
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Hi,

Quote:
Originally Posted by dvv View Post
Eh? Come again?

T., I think a small diagram would make things comprehensible again.
Okay. Monkeywrench:

Click the image to open in full size.

Ciao T
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Old 22nd March 2012, 06:40 PM   #3923
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Bootstrapped current source. Like oiled butter.
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Old 22nd March 2012, 07:33 PM   #3924
bcarso is offline bcarso  United States
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Quote:
Originally Posted by ThorstenL View Post
Hi,

Okay. Monkeywrench:

Ciao T
I guess I like everything about that except the propensity to bottom out for sagging negative rail voltages, which I gather in the case of the Hafler is a real concern. With good rail regulation it should work great.
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Old 22nd March 2012, 07:49 PM   #3925
a.wayne is offline a.wayne  United States
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The circuit or the monkey wrench ...?
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Old 22nd March 2012, 09:11 PM   #3926
dvv is offline dvv  Serbia
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Quote:
Originally Posted by ThorstenL View Post
Hi,



Okay. Monkeywrench:

Click the image to open in full size.

Ciao T
Duh ... d red ting up dere, anoder immortal Loesch family invention?

I get it now, thank you Thorsten. You already know I'm a bit thick. I get it in the first pass at the same rate wisdom teeth come out.
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Old 22nd March 2012, 09:14 PM   #3927
dvv is offline dvv  Serbia
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Originally Posted by Wavebourn View Post
Bootstrapped current source. Like oiled butter.
Perhaps with you, my Polish cousin. But with Thorsten, things are always nuclear.
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Old 22nd March 2012, 10:00 PM   #3928
tvrgeek is offline tvrgeek  United States
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Quote:
Originally Posted by bcarso View Post
I guess I like everything about that except the propensity to bottom out for sagging negative rail voltages, which I gather in the case of the Hafler is a real concern. With good rail regulation it should work great.
Yes and no. Yes the 54 volt rails collapse like any mutual fund I ever bought, but for the moderate level loads this amp is intended for, it can probably hold up to rated output needing about 36 or so volts. I also have twice the main bank as original. I'll model the above suggestions. A volt or two would be worth it if it could pass the hearing test. All learning, circuits and sim. I could always call it a DH-60, increase feedback a bit, and claim 3dB overhead! Or in the way of modern advertising, 120W of dynamic music power.

There is a lot to take in in the last few posts. I am working on being able to visualize the current flow. I can get about half way there. Maybe if I draw a picture with more of the secondary features, like all the caps. This may sound strange, but I am very good at visualizing things that others can't. Stress in a structure, waves, what things will look like. I should be able to internalize a two transistor circuit fully. Trying to picture Early and temperature at the same time is hard on my beer budget of one per day. I guess in the 60's at some well known West coast universities, other , shall I say methods?, were taken advantage of. With all due respect to Timothy. I remember them because I was too young not too.
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Old 22nd March 2012, 10:11 PM   #3929
tvrgeek is offline tvrgeek  United States
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And to think, I never replaced my Beta version of A Clockwork Orange. Now there is an altered state for you. Not as far out as some of the cartoons that came out of Eastern Block countries "in the day". I remember "The Man Who Had To Sing" .This was about the time of the immortal short, Bambi vs. Godzilla. It was a good time to be a cartoon fan. No modern CGI can match what a Tex Avery could do.
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Old 22nd March 2012, 11:26 PM   #3930
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Quote:
Originally Posted by tvrgeek View Post
Not as far out as some of the cartoons that came out of Eastern Block countries "in the day". I remember "The Man Who Had To Sing" .This was about the time of the immortal short, Bambi vs. Godzilla. It was a good time to be a cartoon fan. No modern CGI can match what a Tex Avery could do.
How about Jan Lenica, or Trinka's "The Hand". On this subject I could go on forever, Zagreb studios had many great shorts.
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