Preamps can color sound considerably. Surprising?

@atmasphere 

If the active line stage is good at controlling the interconnect cable it stands a very good chance of being more neutral than a passive device and possibly also lower distortion, depending on the passive device to which its compared.

So its a mixed bag, which is why this conversation persists.

Such a keen point. 
I n theory and on paper, the passive approach should be more invisible/transparent, more out of the way. Yet in practice, a high quality active will often yield the better or more realistic sound quality. It is indeed a “mixed bag.”

Charles 

@charles1dad it has been some of covered in a few places…

In theory and on paper, the passive approach should be more invisible/transparent, more out of the way.

In theory it starts to barf when the passive is doing more control.
Running “wide open” the passive is essentially a wire.

Remember that the passive pre is attenuating both voltage as well as impedance.

The pros and cons from my list:

• A high output impedance source = con
• Low output impedance source = pro
• High input impedance amp = pro
• Low input impedance amp = con
• High listening levels = pro
• Low listening levels = con
• Low sensitivity speakers = pro
• High sensitivity speakers = con
• High gain amp = con
• Low gain amp = pro

So the worst situation is driving some highly seniors give horns, at low volume through an amp with high gain from a high impedance source.

The volume is then cranked around anticlockwise, and the passive is attenuating the already high output impedance of the source to become tens of hundreds of kohms. 
 

If it is less sensitive speakers listen to at higher volume then the passive does not attenuate nearly as much.

If we add in ICs with high capacitance or inductance then we get a filter.
At that point it is often better to have a preamp than a passive, when the passive is trying to go very low… and it’s better to run a passive if it is doing very little attenuation.

@atmasphere,

many thanks for answering, a really helpful contribution. Am I right in saying that most digital devices are designed to have low output impedance?

@antigrunge2 Can you find it for your specific DAC?

In the example I gave above, one would likely be better off to adjust the DAC’s output level much lower, and then a passive pre would be cranked around louder.

I suppose those with a passive pre and a DAC with adjustable output level, could do this at home and tell us if there is a difference or not?

A DAC without the output level adjustment should not be as good (if all else was equal)…

@holmz 

my Dac is an Antelope Zodiac Platinum with a relay based attenuator and an output impedance of 56 Ohms unbalanced into my Wavac EC 300b power amplifier with an input impedance of 100kOhms. Hard to see where the problem might be with a 200x span. I’d love to try Ralph Carstens ClassD monos on balanced; this raises the Zodiac’s output impedance to 112 Ohms for his 100kOhms input impedance. Most problems discussed around attenuators deal with marginal situations, which on modern designs to my knowledge are rare. Your last sentence only applies to digital attenuation, which is lossy.