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Old 9th December 2007, 06:06 PM   #1
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Default TVA-1 cathode resistor value

I just simulated Michaelson & Auatin TVA-1 driver stage. The value of 2nd stage (12AT7) cathode resistor as shown (33K) cannot be correct.

I used 3k3 instead. Is the schematic in error?

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Old 9th December 2007, 06:43 PM   #2
ichiban is offline ichiban  United States
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Location: Tonawanda, N.Y.
Default 12AT7 cathode resistor

The schematic I have, which is from an owner of a TVA-1,
shows the resistor value at 2k2R. At the bottom is a note
stating that the "Latest TVA-1 has 47R in cathode". I don't
know which cathode the note refers to!? Possibly the output
tubes, in place of the 100R's.
The owner of the TVA-1 used it to power the base panels
of a Magnapan Tympani D-1 crossed over, with a Waldron
tube 3rd order xvr at 1000 cycles for the lowpass and a
simple 6dB cap filter to a Marantz 8B for the highpass.
The bass of the TVA-1 was awsome with GoldLion KT-88s.
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Old 9th December 2007, 07:04 PM   #3
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On my schematic the cathode resistor has the value 2k2.
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Old 9th December 2007, 07:15 PM   #4
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Location: Los Angeles, California
The schematic I used is available on line. Thanks for the response though, 33K is defintely wrong value, 3k3 cathode resistor results in 3.2 mA of tail current , 2k2 is around 4 mA.

The step network (4.7Meg in shunt with 0.022, in series with 470k) is pretty much useless, since the plate voltage of 12AX7 is only 25V.

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