Since I had a pair of Hammond 124B transformers in hand, I thought of giving it a try. So, I quickly built a single channel to see if it was any good. Tube used was 6E6P, with a constant current anode source and a 4 μF coupling capacitor to the 124B. Doing a frequency response test, I interestingly found that there was a resonance at ca. 34 kHz. In particular, amplitude begun to rise from 8 kHz upwards, reaching a huge +25 dB at 34 kHz. I didn't bother to listen to it.
Andy, I wonder if you have checked the frequency response of your implementation with the parafeed 124B. I yes, what were your findings?
Cheers,
Evangelos
Andy, I wonder if you have checked the frequency response of your implementation with the parafeed 124B. I yes, what were your findings?
Cheers,
Evangelos
Hi. I have used the 124B on the input of a SET amp. It sounded OK. I haven't checked FR. I couldn't hear that high anyway at my age.
I thought you had tried it in a parafeed configuration as depicted in your #167 post...
Probably, in my case, there is a resonance circuit with the parafeed coupling capacitor.
The parafeed resonant is usually at about 5-10Hz (depends of capacitor and primary inductance values).
p.s.
sample simulation
p.s.
sample simulation
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Not parafeed. Looks like I tried it as a stepdown after a 26 stage. Didn't remember that.
I recently built this one using the Russian 6P43P-E (6CW5 / EL86). Mu is supposedly ~7 or 8 and output impedance is under 1k. Build cost was just under $100.
Details here: https://audiokarma.org/forums/index.php?threads/the-flow-pre4d-a-diy-tube-preamp.1084409/
Details here: https://audiokarma.org/forums/index.php?threads/the-flow-pre4d-a-diy-tube-preamp.1084409/
