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SemperFi 27th November 2012 10:06 PM

Tube/SS opamp
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So I decided I need an opamp for large voltage swings. I mean, why not? It's not really ideal as an opamp should, too low open loop gain, but it seems to work.
(I know, 200v too high for 6922s...well, I've got a whole bunch, besides, I'll probably settle for +-175v rails).


SemperFi 27th November 2012 10:07 PM

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FFTs at 180Vpp, 240Vpp, and 300Vpp.

SemperFi 29th November 2012 09:37 AM

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Using a resistor as load Gives bigger output swing if needed. Placing a mirror on second half of diff-pair gives differential output. Swings 300Vpp with -60dB second harmonic!

SemperFi 29th November 2012 09:43 AM

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Second is -62 and third -37dB. Not bad for +-150Vp.

SemperFi 29th November 2012 09:44 AM

Enough desktop engineering...Need to start building.

SemperFi 29th November 2012 09:55 AM

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I can play around all day..Here several outputs. Can be referenced to gnd or anywhere else. Can add more, but for each stage the dist goes a little up. Helping base currents with an additional PNP should help.

SemperFi 29th November 2012 09:57 AM

Sorry guys. I've posted my mirror loaded tubes before and should know by now they are not very interesting. But I cannot quite understand why, they really do sound good. Does the mirror have some kind of 'bad rep' in the audio society?

Anyways, if you need large output swings, referenced to gnd or some other fixed voltage, these are pretty good.

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