Preamp Noise with High-Efficiency Speakers

Neat post, German B. And that guide book is pretty clearly written. Nice contribution!

George, you can't count on a preamp having a 47K input impedance- that is for phono, not a line section, which might often be more like 100k.

Amplifiers frequently have 100K input impedances too. When you run impedances that high and then introduce a high impedance (passive volume control) between the source and the amplifier, the result will be that the system is going to be extremely sensitive to cable colorations. There will also be a loss of bandwidth as capacitance in the cables take their toll. In addition, if there is any input capacitance in the amplifier it will not matter if the source is direct coupled- you will loose bass impact.

There is no 'blasphemy'. As much as I respect him (I think of him as one of the top ten designers worldwide) Neslon Pass is simply wrong about this although I agree that it makes no sense to have a lot of gain and then burn it off. There are more elegant ways to do it than passive controls though.

A simple solution is a buffered volume control. This offers proper volume control performance with it acting as a mild tone control or hindering dynamic impact.

Atmasphere,

Did you mean to say "without" instead of "with"? If not, then I am confused by the statement.

"A simple solution is a buffered volume control. This offers proper volume control performance with it acting as a mild tone control or hindering dynamic impact."

Wow, I did not know my thread can attract so many responses in days! It looks like noise is more attractive than music.

Georgelofi, I currently do exactly what you say: set the input impedance at max (57k Ohm on RCA) and run DP-777 directly. I normally listen at -30 dB on my DP-777, so you are right, modern electronics have too much gain and we are throwing the signal away. And I have to either throw it away at DP-777's internal volume control, or at an external preamp. I don't know which way is better because the noise issue doesn't allow me to evaluate preamps.

I appreciate your (and Nelson Pass's) belief on the preamp-less approach, but I am not convinced that the volume control inside the DP-777 is a world beater; and I am not sure the DP-777's output impedance (at more than 100 Ohm) and the FL-100's input impedance (57k Ohm) is a match made in heaven.

When I use conventional speakers (85-92 dB), having a good preamp is a clear winner. Audia's own Flight Pre actually worked much better than Cary SLP-05 due to impedance matching, and running AMR DP-777 direct sits somewhere between these two preamps. With a Cary V-12R power amp the results is totally reversed in favor of the Cary SLP-05.

I don't want to turn this thread into another arguement over preamp/preamp-less comparison, but we all know system matching is key and there's no way better than all others. At one point I bought an all Audia system (CD/Pre/Pwr), and an all Cary system to reduce the hassle of system matching. But at the end of the day it is still not simple. Now I am thinking about buying a Devialet D-Premier and sell everything else.

Cheers!

just read this quote from Nelson Pass, I think we could all aggree that we all here with our combind wisdom pale into insignificance compared to him.

Given the fact that Ralph from Atmasphere is among the contributors to this thread I certainly do not agree with the above. :)

Regarding the preamp vs. no preamp issue my experience is that it also depends (very much in fact) on the component used (maybe on how transparent these components are). I have recently upgraded my power amp from the Accuphase A-45 to Accuphase A-65. Except for the power ratings and price the two amps are almost identical on paper, in fact, the cheaper amp has better specs in some cases (though maybe those are typos in the manual). In reality, A-65 + cd player sounds better than the A-45 + pre-amp + cd player. Putting the pre-amp between the A-65 and cd player has brought some improvements. Whether or not these improvements justify the price of my pre-amp is debatable.

I too have very efficient speakers, i.e. Avantgarde UNO G2, and luckily I had no "noise" problems.

Paul