Oomph or pressure?

And yet there are guys out there who don’t care for the result. “It sucks the life out of the music”, is a commonly heard refrain (really - I’m being serious here!). Maybe they are reacting psychologically to the need to turn the volume control up compared to an active preamp.

Precisely the complaint of this thread. Nelson goes on to say:

I suppose if I had to floor the accelerator to drive 55 mph, maybe I’d think the life was being sucked out of my driving. Then again, maybe I like 55. Nice and safe, good gas mileage…

Is impedance matching an issue? Passive volume controls do have to make a trade-off between input impedance and output impedance. If the input impedance is high, making the input to the volume control easy for the source to drive, then the output impedance is also high, possibly creating difficulty with the input impedance of the power amplifier. And vice versa: If your amplifier prefers low source impedance, then your signal source might have to look at low impedance in the volume control.

This suggests the possibility of using a high quality buffer in conjunction with a volume control. A buffer is still an active circuit using tubes or transistors, but it has no voltage gain – it only interposes itself to make a low impedance into a high impedance, or vice versa.

- essentially pointing out the same problems I did earlier in this thread.

Since all digital sources make way too much voltage to clip any amp made, a buffered control is a good idea, as it isolates the volume control from the output, and the buffer circuit helps to control the interconnect cable. Note that Nelson is careful to point out that this is an active circuit. We build similar circuits for customers that don't need the gain (but using tubes with a direct-coupled output).

Yes he does, for amps with low input impedance (<20khoms) that aren’t passive friendly, you need a unity gain buffer (no gain as he infers) and those amps thankfully are very not common place, and are around 5% of the market share. some Class-D and some First Watt, Pass Labs

Any amp that is 33kohm or "industry standard input of >47kohm" or higher is fine for any passive pre without the need for a unity gain buffer.

As for active preamps with gain they are not needed in this world any more, and are a left over from phono days when a preamp needed gain.

Even Pass Labs now has lowered the gain of many of their amps from the common 28-34db, down to the low 20’s, just so his and other high gain preamps can be used with most of the volume range they have, instead of being at 9 o’clock for loud!!

Since all digital sources make way too much voltage to clip any amp made

Not just digital even analogue sources, tuners, phono stages etc etc. Have more than enough voltage to clip just about any poweramp.

Cheers George

Sal,
Autospell got me again! I surely meant appropriately named in referring to the Emotive Audio Epifania. I believe that my post however made it clear that I’m complementing the Epifania and its heightened level of involvement you cited.
Charles 

Hello Ralph, 
I've heard your MP-1 preamplifier with several different amplifiers including my own and find it to be an excellent component.  Could one be ordered by a customer with either no gain or say low gain (10db and less) ?  Just curious. 
Charles 

@charles1dad ,
Are you a manufacturer/designer?
Bob