2. amps-preamps
  3. 1268737214

Who is using passive preamps and why?

Seldom has there been any discussions on passive preamps in the forums and although my experience with them has been limited I have found them so far to be very enjoyable and refreshingly different. They seem to fall into their own category, somewhere between solid state and tube. Finding a preamp that is satisfing has been difficult. Some active solid state preamps can be very good but they seem to inject grain to some degree in the upper registers and some tube preamps are not too far behind. So far I think they should at least be matched up with an amp that has sufficient gain which is often overlooked. Which passives are you using and with what amp? Why do you like them?
phd
almarg's avatar
Ag insider logo xs@2x
almarg
9,670 posts
 
Herman -- As I understand it, it's not a TVC. It's a step-up transformer followed by a resistive attenuator.

Best regards,
-- Al
herman
2,273 posts
 
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.

.
clio09
3,360 posts
 
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?
ngjockey
1,042 posts
 
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
cdc
1,845 posts
 
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?
More to discover