• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Should my TVC x formers be input or output

euro21

Member
Paid Member
2004-09-17 12:16 pm
Budapest
Preamp output has definite output impedance, thus drives TVC (every 100H of TVC inductance represents about 12k5 impedance at 20Hz) -in the working frequency domain- with mostly constant driving capacity, independently of the input source device.

If you use TVC in the input side, the unknown source might cause problems at low frequencies.
 

euro21

Member
Paid Member
2004-09-17 12:16 pm
Budapest
If you use amp with average sensitivity (about 1-2V RMS for full power), the preamp gain must be about 6dB over it (2-4V). It must be below the TVC max. voltage.

Most of the -good- magnetic volume control manufacturers defined measuring/operating conditions: usually 600R source impedance, 5-8V RMS max. voltage.


See Dave Slagle's forum for more information:
intact audio
:: View Forum - Attenuators

p.s. For some years I use S&B TX-102 (400Hy) as the parafeed TVC of my CCS loaded #26 preamp.
The lover -3dB point is about 12Hz.

The other critical factor is the output interconnect capacitance. Use the possible less capacitance IC (50-200pF overall), or you have HF falling.
 
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