Preamps. Why?

[bigthinker]

I know i'm not the first to wonder this.... Do preamplifiers have a purpose other than to control the gain and select inputs? Do they make any sonic difference or even still, should they make a sonic difference? I've been told the fewer components the better, which makes me think a DAC with volume control may be enough.

thoughts?

[FerdinandII]

They also act an impedance converter, providing a low impedance drive to the Power amp and the cables between the two. If your power amps are some distance away from the preamp, like monoblocks located near each speaker, there is a real need for this. For many systems, the modern DAC may have a healthy, low impedance output stage, and it can drive the power amp OK. many have had very real experiences where the "line level" (2V RMS) output of a source component was too weak to properly drive the power amp + cables.

IMHO, a preamp should not contribute anything to the sound, except fidelity. To the extent that it allows the system to perform like a bunch of ideal components (see above) it does increase the fidelity of the system.

Disclaimer - I haven't used an analog preamp for > 10 years....

[Guy]

I think you're right, BigThinker - each component can color the sound, increase noise, and damage the image, so the fewer, the better. If you're a dedicated listener of CDs, then all you need is a volume control, a power amplifier, and speakers. CD players or DACs are sufficient to drive most power amplifiers (or impedance converter, as FerdinandII said.)

If you want to listen to low-output devices like magnetic tape or vinyl, then you need to boost their outputs dramatically to drive a power amp. most people do that by adding another amplifier (the pre-power amplifier) to goose the source signal up to drive a power amp. If done well, this can produce rewarding sound.

So it's all down to what you want to do. I currently have a "passive preamp," which is not a preamp at all but a selector switch followed by a volume control. Either feature can be bypassed to prevent them from affecting the sound but I'm satisfied with their combined performance so I don't bother - I have bigger issues with my power amplifiers! I have borrowed a phono preamp from Charlie (bless you, please let me know when you want it back!) and am building my own because vinyl can be exciting.

These are my opinions, and are subject to experiment.

[charliewphelps@gmail.com]

I have just used a passive preamp (Selector switch and P&G fader) for years. My phono stage is built on purpose to have a low enough output impedance that it can drive my amps directly. Also I design my amps to have enough gain that I don't need a preamp for gain. I think that an extra device just adds more coloration to the sound. Something that I'm trying to avoid. I do believe in keeping things as simple as possible.

Guy, feel free to keep the phono stage as long as you like. I've got to many lying around here (failed experiments) and to make it worse I'm thinking of making a version of Ciuffoli's Phono End to see if it's better than what I came up with.

Charlie

[rock4016]

Speaking of keeping Charlie's phono preamps, I still have the Pearl in case you need it for anything.