What causes more disagreement? Religion? Politics? Passive preamps?

[franjy]

There are so many disparate "rules" about passive preamps on this and every other audiophile site, it's mind boggling. The 10 times rule. The 100 times rule. The over exaggerated loss of dynamics and frequency loss warnings, etc, etc, etc, that accompany many posts, stopping many from trying them. I started experimenting with potentiometers 25 years ago, before I knew what I was doing. Since then, I have used quite a few quality pots passively and although some sounded better than others, none sounded less clear to me than my active (not state of the art but good) preamp. However, after reading all the archives on the subject, on this and many other sites, I can confidently say, I now know, I think I know what I'm doing.

Ric Shultz of EVS sells the popular Ultimate Attenuator, about which, I have never read anything but praise from its customers.
Here are his simple guidelines.

1. How do I know if I am passive compatible?

Passive preamps (attenuator/volume control) do not work in every system. Here is a very general rule: If you have a 2 volt CD source (player or DAC), an amp with at least 26 db of gain (20 times), speakers at least 88db sensitive and don't listen screamingly load and don't have a huge room, then you are probably passive compatible. Any one perimeter not met and it may not work.

2. Why do you have two different impedance models and how do I know which one I need?

The low impedance version works best with solid state amps and can be used for tube amps as well. It has a 1K input impedance at low volumes and has a somewhat higher input impedance at higher volume settings. The output impedance is always below 1K and usually in the 100 ohm range in normal use.

If you have a tube amp with at least 100K input impedance than the 10K attenuator would be the best choice. Its input and output impedance are 10 times higher than the low impedance version at the same volume settings. Because it has at least a 10K input impedance it is easier for the source (CD player, phone stage,etc.) to drive and the low input capacitance of a tube amp insure that there is no high frequency rolloff. Neither the low or high impedance attenuators can be driven by tube electronics
unless they have a low output impedance follower (at least 500 ohms or less).

I coudn't use the Ultimate Attenuator as it rquires installation on the back of the amp, which wasn't covenient in my case but I did follow this advice. I used a 1K stepped attenuator between my Sony 555es and my SS Mac (10K input impedence) and now have the best preamp, active or passive, that I've ever owned.

[Peter Daniel]

Some interesting thoughts on that subject can be found here: http://www.high-endaudio.com/RC-Linestages.html

[jleaman]

AS a few friends and also the person that taught me lots Dave and my dad. I am currently running all passive stuff. With a single pot and a Gain clone. I was so surprised to hear a difference in the pre-amp being removed and a simple volume pot. After that i did do some adventuring and tried a new cd player a old cd-rom that i build a external psu for and took it out of it's case. after switching back and forth i would also have to say that my cd-rom based cd-player sounds best to my ear's and more clear. It might not go as loud as the other one but it sure sounds better. If i want it to go louder ill build a simple Buffer.