High end stereo preamps? Worth it?

Glad to hear Pass agrees with me. Now if I could only afford any of his equipment....

@georgehifi 
You forgot to post the rest of Pass' thoughts on the subject:

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.

If you put a buffer in front of a volume control, the control’s low impedance looks like high impedance. If you put a buffer after a volume control, it makes the output impedance much lower. You can put buffers before and after a volume control if you want.

The thing here is to try to make a buffer that is very neutral. Given the simple task, it’s pretty easy to construct simple buffers with very low distortion and noise and very wide bandwidth, all without negative feedback.

There are reasons many like what they hear through a preamp (or a unity gain buffer) better than through no preamp or through a passive.

There are reasons many like what they hear through a preamp (or a unity gain buffer) better than through no preamp or through a passive.

Let’s hear your technical reasons Mitch on this.

If you quote someone you need to put before it
Quote:Nelson Pass
you still have quite a few minutes to correct your post.

And you don’t understand, today there is 99% of the time NO impedance issues, unless you have one of those stupid power amps that are 10kohm or less input impedance, then not even tube preamps will drive them no matter how expensive they are.

Cheers George

Glad to hear Pass agrees with me. Now if I could only afford any of his equipment....

Yes well he is a "business man", and does make preamps, there’s money to be made there also, that’s just what you pay for knowledge and you’ve got to say if your a "glitz queen" they do look the part.

I preferred his older Threshold poweramp circuit designs, when he used bi-polar output devices. Mosfets are good if you only use N channel top and bottom (but he doesn’t and it’s difficult), because then both top and bottom N Mosfets can give current, but the problem is the P channel doesn’t it’s always weaker, so a conventional push/pull complimentary l N and P channel Mosfet amp can’t give the current into low impedances like a NPN/PNP bi-polar can.

Cheers George