I used to think passive preamps were superior to active preamps given right the setup, but

The bass problems cited don’t just exist with passive preamps.

Yes there are some sources that have output coupling caps, and if they lose bass into a 10kohm passive, they will also lose the same bass into many class D amps some linear amps some of Pass Labs Amps and also may active speakers, as these are also 10kohm input impedance.

Ralph is right about this, but the problem is the output coupling cap of the source is too small.

EG: with a source output coupling cap of 2uf into any of the 10kohm loads above, you will have a -3db at 7hz point. If it were 1uf it would be -3db at 15hz. If .5uf -3db at 30hz.

As you can see a sources output coupling cap of at least 1uf or bigger is needed not to hear any bass roll off with any of the above 10kohm loads.

Saying that I hate caps in the signal path, give me direct coupling any day over it, as all caps have their own sound as well.

Cheers George

All the above 5 post have valid statements, the best preamp is no preamp, this is closest to a straight piece of wire sound.

Source direct or through a simple direct coupled passive is the most transparent/dynamic way of hearing the source. 

You may not like the sound this way because your hearing the source for what it is, does this mean you add an active preamp to colour that sound hopefully in the right areas or get a source that doesn't need to be coloured?

Cheers George     

Mitch you say "controlling the interconnects".

There are two parameters interconnects have that could influence the sound with a passive, resistance and capacitance. And they would have to be very high to have any effect.

Resistance is nothing to worry about as it would be so low it’s not even worth considering,, even in 5mts of interconnect.

Capacitance: A 10kohm passive has at worst output impedance of 2.7kohm, with a bad case cheap interconnect of 100pf per ft, if you had 2mts that equates to 600pf cable capacitance. This would have a HF roll of effectively at -3db at 98khz!!!

There is no having to controll the interconnects full stop with a 10kohm passive!!

That’s why you should always use a 10kohm passive, as a 20kohm passive with the above interconnects would be -3db at 49khz. A 50kohm passive would be -3db at 20khz as you can see that does cause a HF cut in the audio band.

Let me remind you what Nelson Pass said.

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

Not really, like I said over 90% of systems are a perfect match for a 10kohm passive, it's the few oddball high impedance tube output sources that are the trouble.

eg: like the well know "cottage industry" dac with a 12AX7 output tubes at 3kohms!!!, the 12AX7 was never meant to be an output tube buffer. High gain input tube for phono/preamp/poweramp stages yes but an output tube?? Really?? 

Cheers George 

1.6Kohm could also sound fine so long as the amp is still over 33kohm, because the 1.6kohm has to drive the combined load of passive + the amp.

If you have say 33kohm amp and 10kohm passive that's a combined impedance the source sees of just under 8kohm, a 1.6Kohm source will drive this no problem as the ratio is still 1:5, but a ratio of 1:10 is the really the minimmum one should aim for, and then it could sound even better instead of fine.

Cheers George

dracule1 System matching with passive pre is critical indeed. It can make or break the sound

You are right dracule, but lets get the "critical matching" in perspective

We (most of passive users) are after nirvana, that’s why we persist with passives and get the impedance matching right "makes the sound". Which by the way in 99% of systems is a great impedance match.

Except for some tube output sources which have ridiculous high output impedance (more than >1kohm). Or some ClassD amp that are very low input impedance (less than <10kohms). These users usually find something wrong with the sound of passives, and say active preamps are better, oblivious to the fact that they had an impedance mismatch with the passive they used.

Cheers George

You’ve got all the voltage gain and current you need in the sources today, as they all have the ability to overdrive all amps, any more and your just turning it down with the VC. Look at the input sensitivity of amps then look at the output of sources there is way more than you need. Cheers George

A Quote from the master 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.

+1 jmcgrogan2

Cheers George

Sounds cynical I know, but he is selling his latest BHK Preamplifier design through P.S. Audio. Why wouldn't he say this now, and not back then when he probably heard much better as well. This clip doesn't convince me one iota.

For the ultimate transparency and source signal transfer to the amp: Direct (source to amp) is best, if you don't "bit strip" with the digital domain VC, if it does, then 10kohm passive comes in a close second, so long as the impedance are matched, which 90% of system are matched. 

But if your system is not quite right and needs to be coloured in some way, then a preamp with the "right" colouration can be fix for that, but good luck finding the "right" one. As none I know of, sound like a "straight wire with gain", they all sound different to each other.

Cheers George