Is no preamp the best preamp of all?

I found going direct from my DAC to my amps and using my Squeezebox volume control to be a huge improvement in frequency extension and transparency. I can even do the highpass filtering needed by my Quatros in the digital domain on the Squeezebox server, which is also a huge improvement.

I do need to figure out how to eventually integrate analog back into the system (probably with a switchbox of some kind).

I've seen several several people state that more than about 10 dB of digital attenuation is "bad". In the evening I'm typically using 20-25 dB of attenuation or more. I haven't noticed any evil effects. I tried some Rothwell inline attenuators (XLR version), but prefer the sound without them.

The Vandersteen highpass filter is actually not very accurate for my amps. The closest I can get is with the dipswitches at the 100kOhm setting, which gives a drop of about -2.25dB @ 100Hz, and the slope is steeper than it should be. Disappointing for such expensive little boxes. The digital filter is very accurate, but there is the danger with software of it screwing up that's not there with a passive device. I sometimes wish I hadn't bought such fussy speakers.

@Trebejo

I just don't hear it. I've done a lot of listening at various levels of digital attenuation with a wide variety of lossless files, and I don't hear any ill effects. Can you be specific about what I should listen for or give some technical details?

What does 75-85% translate to in terms of dB?

I'm aware that I'm losing information when I use digital attenuation, but how does this translate into what one hears that is different that what one hears when an analog volume is lowered. Saying that one "loses resolution" is not really telling me anything as I don't know how a "loss of resolution" sounds different from just a lower volume.

Well, let's say my analog volume is cranked up so that peaks are at 90dB above the threshold of hearing, 0 dB, on my dB meter. I can hear 90dB of signal above my threshold of hearing (for simplicity I'll ignore the high noise floor of the typical domestic listening room). Now I lower my analog volume so that peaks are at 60 dB. Details that were at 30 dB and under are now below my threshold of hearing. How is that not a "loss of resolution"?

@Atmasphere

I don't follow. Why doesn't it work like that? I'm not trying to be obtuse, I just don't see what you're trying to get at. We agree that detail that was at 30dB before the volumen was turned down is at the very threshold of hearing afterwards, and that the detail that was between 0 and 30 dB is no longer audible, right?

@Georgelofi: Thanks for that subjective description of the effect. Do you mean "bit stripping"? Googling "bit striping" only gives me a bunch of pages on RAID. I'm aware that as you lower the digital volume you are losing some of the least significant bits.

I'm sorry, but this analogy is even less illuminating than the last one. I'm not afraid of a bit of technical language if you want to use it.

"those least significant bits contain detail."

Of course, I never disputed that, though it is disputable how much detail can be heard at -80 or -90 dB down. What I'm am disputing is the idea that turning down an analog volume control does not also lead to a loss of information in the signal that reaches one's ears.

OK, after a bit of thought I think I see what you are trying to say with the analogy. It helps me to think of it in terms of arithmetic. If you start out with 16-bit audio you have 2**16 different peak-to-peak voltages available. If you reduce the volume by 12 dB you then only have about 2**14 available voltage steps, which is perhaps where the don't-go-below 75% maxim comes from (75% being about a 12.5 dB cut in .5 dB steps.) So don't go below 75% or you playback sounds like an old 14-bit CD player!

But most digital volume controls these days are 24-bit or 32-bit. The Squeezebox outputs 24-bit words, and shifts 16-bit audio to the most-significant bits of each word. This doesn't magically give you 24-bit resolution, but it does mean that with a 24-bit DAC you retain at least 16-bit resolution even with a quite large attenuation (theoretically 8 bits or about 48 dB; but that's nearly the full range of the volume control). Even with 24-bit files, I wouldn't worry until the attenuation was more than 24 dB (or about 4 bits) since you can't really expect to get more than about 20 bits of resolution anyway.

I agree that many issues with passives are probably impedance issues. Inline attenuators will also reduce your effective input impedance.

It would help if more amps had adjustable sensitivity so that less attenuation was needed for the high output voltage of most DACs and CDPs (which is one reason why I got the original Neko DAC with the 1V output).