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Old 24th August 2012, 01:09 AM   #141
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Quote:
Originally Posted by dirkwright View Post
He says right in the article that a version of it was first used in the LH0002 buffer, which I assume was a chip.
I have about 20 of them on PCBs. Do they have any ebay value?

I used discrete version of diamond buffer in phaser pedal for keyboard, in 1970'th. It was all discrete, with LDRs around a light bulb, using pnp+npn "concertinas" for APFs. Such a way I kept almost zero level shift.
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Old 24th August 2012, 01:14 AM   #142
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Quote:
Originally Posted by RNMarsh View Post
can you tell us in which ways this is different from an IC packaged circuit? What parameters can be bettered with discrete (besides output current)? Thx RNM
No claims made other than output current, bias, etc. diy'ers feel good about doing it themselves i.e. fun.
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Old 24th August 2012, 01:23 AM   #143
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Quote:
Originally Posted by dirkwright View Post
He says right in the article that a version of it was first used in the LH0002 buffer, which I assume was a chip.
The H in LH was for hybrid (IIRC)
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Old 24th August 2012, 01:23 AM   #144
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Quote:
Originally Posted by scott wurcer View Post
No claims made other than output current, bias, etc. diy'ers feel good about doing it themselves i.e. fun.
Please explain in more detail the rising thd with frequency cause. Thx - RNM

Last edited by RNMarsh; 24th August 2012 at 01:27 AM.
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Old 24th August 2012, 04:13 AM   #145
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Quote:
Originally Posted by bear View Post
Yes, this is the usual method of bringing the opposing collectors of the input to the rail... Was Walt Jung first or?? But, the variation of bringing them to the output stage, between the emitter resistor and the output device is an improvement. Incremental. But incremental counts?
I believe HP used the diamond buffer pretty early on, according to Rich May, who then did some discrete buffers for a crossover he did at Harman for Greg Timbers. But who knows --- as Scott pointed out in connection with Jensen's input inductor(s), these things often are proprietary within a company for a while, and thus the USPTO doesn't necessarily know about them when they review claims.

Rich also bootstrapped the collectors of the input devices for his circuit, but did so with big caps and resistors to the rail, rather than running them from the output device emitters. This has advantages (smaller Ccb to begin with), but requires some bulky caps.

Both bootstrapping approaches help reduce the effects of the voltage-variable collector-base capacitances, as well as Early effects on beta and Vbe. The capacitance variation is a distortion mechanism that is proportional to the source impedance and the frequency. Another advantage is reduction in dissipation shifts with voltage.
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Old 24th August 2012, 05:45 AM   #146
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Scott, I thought the challenge was for 8 transistors? ;-)
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Old 24th August 2012, 11:56 AM   #147
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What about moving biasing of output devices to the 2nd gain stage?
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Old 24th August 2012, 12:50 PM   #148
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Let me offer an example of a simple, elegant, balanced circuit that can be made into the highest quality amplifier, preamplifier, or whatever, with a minimum number of parts.
This is NOT my circuit, and it is at least 40 years old, but Constellation makes world class amps with it, today. I give the credit to Bascom King, but it might go back earlier, I don't know.
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Old 24th August 2012, 01:23 PM   #149
Hentai is offline Hentai  Romania
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The biggest advantage that i see in discrete opamps would be higher power supply voltage capability and thus higher output voltage swing.
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Old 24th August 2012, 01:25 PM   #150
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Quote:
Originally Posted by john curl View Post
Let me offer an example of a simple, elegant, balanced circuit that can be made into the highest quality amplifier, preamplifier, or whatever, with a minimum number of parts.
This is NOT my circuit, and it is at least 40 years old, but Constellation makes world class amps with it, today. I give the credit to Bascom King, but it might go back earlier, I don't know.
I thought P Channel JFET's were out for this exercise. I can also see why you worry about clean supplies.
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