Who is using passive preamps and why?

Agreed, in that case it is. I was looking at the bigger picture. I'm not sure where that falls into the equation but according to ears I trust they say best is

.....autoformer at 1:1 or less

.....then autoformer with a small amount of voltage gain

.....then true transformer at 1:1 or less

It is wild conjecture on my part but logically following that sequence a step up followed by a pot would seem to be the next lower desired configuration.

I'll probably never try it but it would be an interesting experiment.

.

Al is correct, not a TVC but a slightly different animal. Considering I have spent a lot of time with Jack Elliano the last few weekends (we are Las Vegans) I can say the guy knows his stuff and his SET amps sound great (with which he uses a PVA with 1:8 ratio). However, I think in this case Al and I are in agreement. I've fiddled around with this and a 1:1 or 1:2 ratio would be best. My main problem right now is I can't get the volume control past 9 o'clock, which supports the case for a lower ratio IMO.

Question: Jack tells me the transformers are wound for 100 ohm impedance, meaning the source must have an output impedance of 100 ohms or less. Any of this make sense?

For comparison, the S&B 102 has a Zin 0f 10.4k and Zout of 1.4k @ 1kHz at it's worst case of zero attenuation. Zin halves for within each of the next few -3dB steps and Zout doubles. My setup never approaches the end of the dial.

http://www.stevens-billington.co.uk/page102.htm

Why does the I/C from the source to passive pre have to be as short as possible while from the passive pre to power amp can be longer?

Cdc: Why does the I/C from the source to passive pre have to be as short as possible while from the passive pre to power amp can be longer?

Actually, the reverse is true. The high output impedance of a passive preamp will form an RC low pass filter in conjunction with the capacitance of the cable that is connected to its output. The longer that cable is, and the higher the capacitance per unit length of the cable, the more likely it is that significant upper treble rolloff will occur.

The relatively low input impedance of a passive preamp will produce a minor increase in the amount of current flowing through the cable between source and preamp, thereby perhaps increasing some subtle cable effects if the cable is long, but those effects will be minor in comparison to the effects of excessive capacitance in the cable connecting passive to power amp.

Clio09:Question: Jack tells me the transformers are wound for 100 ohm impedance, meaning the source must have an output impedance of 100 ohms or less. Any of this make sense?

Transformer impedance ratings, as distinguished from the reflected impedances corresponding to the connected source and load impedances and the turns ratio, have always been something of a mystery to me. Perhaps someone else will comment more knowledgeably. But I believe that the rated impedance of the transformer itself corresponds to how lossy the tranformer is in terms of flux leakage and dc resistance, and represents the amount of current limiting that would occur in the primary with the secondary short circuited (and a voltage source with near-zero output impedance connected to the primary). The higher the output impedance of the source component, the greater the losses that would result from that transformer impedance.

Best regards,
-- Al