One choke for Two V72 s

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saint gillis

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Nov 4, 2012
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Hello, I found in an old tube psu a big choke, 150H, 1K6 DCR, the size look like it can handle a good amount of current.

I was minding if I could use this choke in a dual V72 preamp, for the last tubes of two different preamps, completing it with resistors in series to get the correct plate voltages.

Here's the V72 schematic : https://groupdiy.com/index.php?action=dlattach;topic=45156.0;attach=72957

Attached is what i have in mind. Mayby it is stupid.. open question! thanks
 

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abbey road d enfer

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No. It just won't work correctly.
The choke in this arrangement (parafeed) not only helps filtering out B+ ripple, it also increases the output capability by a factor 4 (twice the voltage). For that, it is essential for the choke to be submitted to the full AC swing, which obviously precludes it from being connected to another circuit that would superimpose antagonistic signals..
 

Tubetec

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Nov 18, 2015
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Also a choke for power supply smoothing and a plate choke like in the V72 are wound very differently . Typically the V series plate chokes are wound with three indentical coils side by side on the bobbin, this helps give good high frequency response . A PSU type choke while it may have the required Henries wont have the bobbin construction so you'd expect the HF to start to drop away well before the limits of the audio range . You can check CJ's teardowns  for more details on the V series plate chokes .
 
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