Are passive preamps better?

Albertporter...You criticize a lack of "enhancement from the original signal." Wouldn't that be *distortion* of the original signal? Pleasant perhaps, but not "transparent".

Albertporter...First of all, I do agree with you that an active preamp usually works best. I guess I would agree with your original comment if it said "lack of signal degradation" rather than "signal enhancement".

I don't know when passive preamps became commercially available, but several decades ago I made one to suit my particular (rather unique) matrix multichannel system. I had plenty of gain, and my solid state source components had the low output impedance to drive tube amps having high input impedance.

By the way, an integrated amp or a receiver essentially has a passive preamp in it (without the external interconnects).

Albertporter...Just as tube circuits are known to modify the incomming signal by generating harmonics which some think are pleasant, I am suggesting that the extra circuitry of an active preamp may be doing the same thing. I think this is an idea to consider: not just semantics.

Of course "great gain, improved dynamics, vivid contrast and improved bandwidth" is not distortion. But these do not "enhance" (add to) the input signal. They preserve it. Anything added is distortion.

The Placette "Active" approach of following passive switching and volume control functions with a unity gain buffer seems ideal to me. In practice most preamps are operated at less than unity gain overall although within the unit there may be many dB of gain. Most of it is discarded in the volume control. Most disc players, for example, have a nominal output of 2 volts rms, and 2 volts would drive most power amps into clipping.

When I built my home brew "passive preamp" several decades ago I also built what I called a "line driver" which was a unity gain buffer amp with high input impedance and low output impedance. This was necessary when I changed power amps from tube units with 250K input impedance (high even for a tube amp) to SS amps more like 20K. I was very aware of output impedance requirements from my work as an aerospace systems engineer where it was necessary to transmit both analog and digital signals through as much as 300 feet of 20-year-old wires. There was always a circuit dedicated to this "line driver" job.

Arnettpartners...Just curious...in what way did it "not work"?

A 600 ohm LOAD is tough! A 600 ohm OUTPUT impedance used to be normal for tube preamps, but then the tube power amp input impedance used to run 100K and up, so it was probably OK.

Solid state preamps have output impedance of 50 ohms or less, which would be OK even for a 600 ohm load.

Unsound...No problem. I also made a mistake once. I thought I had made an error, but was wrong about that :-)

Unsound...You got that backwards. Low sensitivity means that, to be heard, a signal needs to be strong. Noise pickup is a weak signal.