Active vs Passive Pre amps

in reality it's very simple math instead of science:

passive volume control will vary resistance from valueA to valueZ where we can assume Z will be the the highest so to control the output voltage.

active volume control(active preamp) will have stable or fixed output impedance to supply variable input voltage to your amp.

by all possible and impossible means it means that supplied stable output impedance is preferable for best amplifier performance.

than you can do the rest of science to decide.

I have been on both sides of the active/passive debate over the years. I love the purity of passives and have never felt the need for more gain, or an expanded soundstage. On the other hand, I appreciate the added body, weight and drive an active can supply.

A year ago, I tried a Music First Baby Reference, the most expensive preamp I had ever had in my system. I felt, as Sam Tellig apparently did, that this was at last the preamp I'd been searching for, so I bought it. It was and is considerably better in my system than a number of other excellent passives I'd tried, including various Placettes, TVC and autoformer units from Bent, and the Lightspeed Attenuator, not to mention going direct from DAC to amp (for digital).

I think I might be able to do as well as the MF (perhaps better, I really don't know) with a truly great active, but I think I'd need to spend well north of $10K to get there without giving up what the MF does so well.

"in reality it's very simple math instead of science:"

That's what I used to tell my professors in college. Unfortunately, they never saw it that way.

" I know you are supposed to lose dynamics with a passive pre."

That's not always the case. A lot of it depends on how good the output is on your source.

Zd, It's all regardless and nevertheless at the same time.

regardless of your output source, input sensitivity and impedance of your amp, it will benefit from stable output impedance of active preamplification.

nevertheless, there are benefits of passive with transparency, but with lower dynamic headroom and volume ranges.

David12: The passive seemed more neutral and detailed, the ARC a little rich and lush. I know you are supposed to lose dynamics with a passive pre.

Hi David, first off your system as you have found just by listening, is a perfect impedance match for passive preamps as are most others out there.

Your ARC Ref 75 has a great 300kohm input impedance, 1.5v input sensitivity for full output and your Resolution Audio Resolution Audio Opus 21 has 2.5v output at 100ohms absolutely perfect for any passive.
And your speaker are 96db, efficient no need for extra active preamp amplification.

As for passive and dynamics, if I can explain, this belief is a total "furphy". If a passive preamp is a good impedance match as you have, they are more neutral have better detail and more dynamics than any active preamp.

The only way an active preamp can have better dynamics than a properly implemented passive as you have, is if the active preamp has a "dynamic range enhancer" (DBX) built into it, which sound like rubbish.

An active preamp cannot make better dynamics than what the source is giving, if anything they can only diminish dynamics, as all active components have losses when compared to source to amp direct in, like a well implemented passive can mirror.

Read Nelson Pass's quote on passive preamps.
" Nelson Pass,
We’ve got lots of gain in our electronics. More gain than some of us need or want. At least 10 db more.
Think of it this way: If you are running your volume control down around 9 o’clock, you are actually throwing away signal level so that a subsequent gain stage can make it back up.
Routinely DIYers opt to make themselves a “passive preamp” - just an input selector and a volume control.
What could be better? Hardly any noise or distortion added by these simple passive parts. No feedback, no worrying about what type of capacitors – just musical perfection.
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."

Cheers George