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In Reply to: RE: Difference between an AVC and a TVC posted by Tre' on March 16, 2015 at 11:58:18
I use the Bent Audio slagleformer modules (silver wound) on the output of my 26 preamp, in parafeed (4.3uF PF cap) and they work great! The slagleformers have about 150H inductance, which is plenty when fed from the mu output of the 26 tube plate CCS (Z of approx 1500R). Bass is deep and powerful, and flat to below 10Hz (lowest my RTA reads).
By the way, the laminations of the slagelformers can be restacked to have up to 190H inductance, but 150H works fine for me.
Follow Ups:
Yes, 150Hy has a reactance at 20Hz of almost 19k ohms and the mu output of a CCS has a low output impedance.
I do the same with a CCS loaded 5687 as the last stage of my phono pre through a 7.8uf cap. That and my CD player drive my AVC well.
Paul didn't state the step down ratio of his output transformer nor the value of the plate resistor, operating point, etc... so It's hard to know/calculate exactly what impedance he has to drive a AVC.
I guess my point was....an AVC is not a "one size fits all" deal.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
The thing to watch out for on the single winding autoformers is that the load impedance that the source sees changes with every tap... so you will actually have say 23 different impedances that the tube (or cd player, etc) will be looking into.
so you might say that the "primary impedance" is not stable nor constant.
An avc will behave similarly to shunt type attenuator.
MSL
Builder of MagneQuest & Peerless transformers since 1989
As attenuation is applied the load impedance goes up. As long as it's not part of an EQ, isn't that a good thing as far as harmonic distortion is concerned?
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
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