If you think about the output of the DAC being as good as it gets, then the sound only gets worse from there.
Rather than thinking about things improving the sound, what is really of concern is what degrades sound the least.
So on first thought it would seem that adding a preamp would increase distortion
Somehow the preamp and amp together must create less distortion than a volume control and amp.
Hi Jeff,
This is a thought-provoking post... thank you. I think there are at least two ways to look at it
:
1) Exactly what you stated above... the analog output of the source is as good as pure as it gets and the sound can only get worse from there from increased distortion from passing to the next stage, and the stage after that, etc.
2) Adding an active preamp to the signal path will "flavor the sound" in certain ways. With tubes, you can get tube distortion, which is not necessarily clipping or nasty sounding. I'm talking about even-order harmonics that some like as they like how the sound gains more richness, more body, fullness, dimensionality, etc. Even if tubes are not used, some prefer putting an active preamp (solid state) in the signal path because it boosts the voltage and/or current of the signal from the source and allows an amplifier to see a signal from a lower output impedance (not always the case, but it is usually the case).
In general, I think some say the a preamp adds more life to the music. Others say that a preamp will take away from the purity of the signal and thus cause more harm than good.
I say there is no correct answer... it depends on the rest of your system (what source, what amp, what speakers, what room, what kind of music) and it depends on you, the listener who likes the music to sound a certain way and that might be different than the next person.
And then there is another case that I like to believe it kind of separate from the two above. This is the case where you need an active preamp in your system no matter if you like it or not:
3) Your source + passive volume control + amp does not have enough gain. In other words, even at max volume on the passive volume control, the speakers do not get loud enough. The amp is not clipping, the speakers are not being driven to max, but you simply cannot go louder unless the input signal into the amp is larger. If you love your source, amp and speakers but you want to be able to go louder, in this case a can provide the voltage gain required to allow your amp deliver max RMS power.
However, it seems that under many circumstances the impedances involved would seem to work perfectly well with passive preamps. In the case of the Clari-t (minus volume control) that I own, Vinnie stated that its input impedance is 120KOhm. This would seem ideal for working with a passive preamp.
This is a good point. There are plenty of circumstances where the matching of a source + passive "preamp" and power amp will work very well. I'm sure there are also plenty of circumstances where a good quality preamp can add to the listening experience... that "flavor" that I described above.
Again, there is no correct way. YOU need to find what is the best for you.
I have been really tempted to get a Panasonic receiver to run the whole chain digitally, so that I can forget about all this impedance/drive stuff. However, the Panasonic that I have heard hooked up to the cheap surround speakers never impressed me. Perhaps it is the cheap speakers. However, many mention a forward sound to them and I hear this on the cheap speakers and it is part of what I object to.
Well, I'm sure you know that just because you are keeping everything in the digital domain does not mean it is going to sound better. Forgetting about "impedance stuff" does not mean the road to simplicity and sonic nirvana.
Perhaps on the outside it seems like a simple thing... send digital output of source into amp and then connect amp to speakers... but on the INSIDE, there are many things going on that WILL have a big effect on the sound!
Great discussion!
Vinnie
