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Valve Itch phono
Valve Itch phono
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Old 20th January 2019, 05:43 AM   #3231
zz1969 is offline zz1969  Russian Federation
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Can C4 and C6 be replaced by transformers? Can anyone explain, please?

I see C4 cannot since it is part of RIAA, but what about C6?
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Old 20th January 2019, 11:09 AM   #3232
Salas is online now Salas  Greece
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Valve Itch phono
C6 possibly, even with an SE to BAL Tx if a genuine XLR output is needed. But it should be able to handle DC in its primary.
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Old 20th January 2019, 11:45 AM   #3233
zz1969 is offline zz1969  Russian Federation
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Thank you , Salas! I have the following trans at hand, do you think it is OK to use in your pre-amp?

Click the image to open in full size.
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Old 20th January 2019, 03:21 PM   #3234
Salas is online now Salas  Greece
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Valve Itch phono
That's an interstage transformer to employ as plate load and output AC coupling for tubes of (optimally) 3kΩ rp. It would take some substantial redesign to usefully employ it in this circuit. Must replace the second stage mu follower with just common cathode of similar gain when loaded with that transformer. In other words save it for somewhere already designed for interstage and build the standard Valve Itch schematic.
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Old 20th January 2019, 03:49 PM   #3235
zz1969 is offline zz1969  Russian Federation
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I will.
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Old 20th January 2019, 03:56 PM   #3236
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Valve Itch phono
Quote:
Originally Posted by stocktrader200 View Post
I tried the LED as the bias on a 6922 instead of a resistor and bypass cap, oddly the waveform on the scope was terrible but the sound was ok. The led is a current variable resistor.
In a mu follower there is constant current bias coming from the bootstrapped top so the cathode LED shows steadier resistance especially around small signal swing. The less mA bias though, the more resistance in all types of diodes.
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