Passive preamp

CD standard output via RCA is 2 Volts and the HDCD standard output via RCA is 2.2 Volts, many don’t play be the rules. Some are over and some are under.

Yes that was the Redbook standard way back in early 80’s when it was first stated by Philips.

For the last 10-20 years I’ve found "the majority" are way over, more like 2.5v even to up to 6v on some dacs I've seen is the output these days.
Only few tube output and "boutique" ones I’ve seen are under 2v
And as far as the amps input sensitivity the majority only need 0.5 to 1.5v input for to be driven to full output

Cheers George

smodtactical
How come passives are not more popular? Everyone seems to use active and seems more commonly made as well.

They are, and now going direct because so many sources now have volume controls are taking over from them now. But if you don’t have source volume control passives are the next most transparent/dynamic/uncoloured way of having a volume contrpol.

A Quote from 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

@georgehifi 
I have sent you an email asking for pricing info for the Lightspeed Attenuator. A friend and I will test it seeing as though the reviews have been rave. Excellent work, George. Incredibly excellent work. However, when I am having a party (I have them quite often) and would like to change among sources, it would be great to have a passive tube preamp that can accomplish this.

Sent with mandatory propaganda attachments.  And yes as Wolf points out the Freya is a great universal unit, I have recommended it many a time here on Audiogon.
As for a passive though the transparency/dynamics of the Lightspeed has no equal, as there are no contacts  in the signal path in the circuit.
 https://ibb.co/XbCsn2B

Cheers George

If you have the gain,a passive is the next best thing to straight wire.

Hit the nail on the head, it’s the most transparent/dynamic/uncolored way of getting the sources signal to the poweramp/s

Quote from Nelson Pass

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

How does one avoid impedance mismatches?

Using the accepted impedance matching ratio of 1:10 or higher.
A 10khom series/shunt passive preamp is the best most versatile value to go for as it has:
10kohm input impedance
2.5kohm max output impedance.

The source (dac ect) should have an output impedance
10 x lower than the input of 10kohm passive pre (which most are) so sources with 1kohm or lower output impedance are a match.

The power amp/s should have an input impedance 10 x higher than the output impedance of the passive pre 2.5kohm (which most are) so amps that are 25kohm or higher are a match.

The above is good for "nearly" 100% of systems out there

Good practice also is to use low capacitance interconnects (100pf per ft or lower), which most good quality ones are.

Tube sources should be questioned as they have output coupling caps that "may" not be large enough value, and easy fix though.

So your Classe with 27kohm input will be fine for a 10kohm passive preamp like mine.
https://forum.audiogon.com/discussions/lightspeed-attenuator-best-preamp-ever

Cheers George

bluetosman
What is passive preamp and how to connect them

A passive preamp controls the volume of the source just like an active preamp, except there’s no added gain, which means no added noise or coloration’s or distortions, they use all the gain that the source has to offer instead of throwing most of it away away.
They replace an active preamp and go in the same position, between the source and the power amp.

Quote from 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