what's 'Active preamp' vs 'Passive preamp'?

Thanks for the responses.

The main reason I asked this question is because I was wondering about not using preamp at all. That question led to this question.

I actully posted another question on that subject, but no response yet.

I'll kind of repeat what I said on that posting.

I'm looking at some of the newest high performance DACS such as Benchmark DAC1, Bel Canto DAC3, Slim Devices Transporter, etc, and I noticed most of those DACs have built in volume control with remote.

So, I was thinking that I can connect these DACs directly to my Power Amp eliminating preamp entirely.

I was wondering what's the implication on that approach?
What'll be the pros and cons?

Is it better because I'm skipping additional device that I don't need? or A good preamp somehow does some good thing to improve the sound quality?

There is just something to be said for a good active preamp IMO. I have tried passive ones and they did not float my boat. I have used CDP directly into amp and it was missing something. Over a period of time it sounded lifeless or sterile as did the passive.

Eandylee

"Is it better because I'm skipping additional device that I don't need? or A good preamp somehow does some good thing to improve the sound quality?"

I'm of the opinion that the simpler the signal path, the better the sound MUST be, in theory. HOWEVER, practically, that doesn't always result. There are techical reasons having to do with characteristics measured by input sensitivity, impedance, etc. I can't fully understand that stuff so, I resort to trying it out and listening. It's pretty inexpensive to try...Give it a shot!

Eandylee, most volume controls that are in DACs are not of the best quality- particularly if they are digital. Digital volume controls essentially subtract bits to lower the volume; the result is audible loss of resolution as you turn the volume down. If you want to do it right, an active preamp (especially one *without* remote) will have a better chance of doing the job right- you would run it and have your DAC turned all the way up for maximum resolution.

One other task of active preamps is to control the interconnect cable. If set up properly, the line section of the preamp will minimize or eliminate the effects of the interconnect cable. Be careful though- many preamps may do their other jobs well but fall flat on their face in this department, introducing coloration due to the cable. BTW, this is a serious weakness in 'passive preamps' which in fact are not preamps at all.

Only a brief comment about passive pre-amps and gain. Although passive, if they use transformers (TVC) they can add gain too. Typically +6 dB. And that is sufficiant in most applications.