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