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AdamZuf 14th September 2004 05:51 PM

Soundcard as a pre-amp ? (and more)
Hello friends, I would like to have your advice.

I'm building my first decent speakers setup and I will get an Israeli DIY'er to make the Seal Electronic's OPTI-MOS monoblocks amplifier. However, I need a pre-amplifier, or to say, a volume control for the amp. I've always loved the convenience of using my computer as a source. My computer is an IBM T23 laptop.

My optional sources for now are:
A. the soundcard of my IBM laptop. Many people have bashed me for this but I A/B'ed it with a Mensa DI/O with an upgraded PS on my PPA headphones amplifier, Etymotic ER-4P and Grado RS-1 headphones, and found the soundcard to edge the Mensa a bit. With the ER-4P, I have to really get it to high output to hear any hiss - my listening volume levels are far below that.
Please, no "all soundcards are crap" remarks, because for me these remarks are just as crappy.
B. I have a DI/O which I'll mod in a few days for my Sony CD3000 headphones. I love the sound of the modded DI/O and I had one before (which turned into a Mensa, which I sold because I liked the previous DI/O better for the CD3000). The DI/O outputs 7V, vs. the 800mv of the amp:

The input sensitivity of all of our designs is standardized at approximately 800 millivolts RMS for 0 dBm into 8-ohm speaker loads
So if I wanted the setup to be: USB coaxial output->DI/O->amp, I assume that volume would have to be really lowered by the computer, and this whole deal seems quite wrong and totally risky for my speakers. (setup #3 below)
Since I want to keep the DI/O especially for the CD3000, maybe I can use it in setup #4 below.
I have the Xitel Pro-Hi-Fi Link USB coaxial output to use, BTW.

The optional setups, as I see it now:
1. IBM SC->amp setup, in which volume is controlled digitally, and might be lowered (which highers the noise floor, as far as I understand).
please take into consideration that I'm still deciding on 200/400W. the 200W will be enough for my setup, but maybe I'll go for the 400W, which will blow my speakers away in full volume (It's a bit of a risk with that setup)
2. IBM SC in full volume->pre-amp->amp setup, which adds lots of stuff to the signal, not mentioning money.
3. a USB coaxial output-> modded DI/O -> amplifier.
4. a USB coaxial output-> modded DI/O -> preamp -> amplifier
This one will require the pre-amp to be able to accept 7V without clipping. My question is if most preamps can, unlike many power amps and headphones amps. If I go the pre-amplifier route, I prefer to be able to use the DI/O as well.
5. a USB soundcard with analog volume control to use as a pre-amp -> amp.

My preference is to know that setup 1 is sonicly good and safe to use, assuming that the soundcard is good, and get away without paying anything.
I have a DIY'er in Israel; so if you suggest anything, I prefer cost effective DIY projects.

1. Not to risk my speakers
2. Stay as low as possible with the budget
3. Get as much quality as possible, of coarse.
4. Having the W400 as a bonus to cover other options in the future - nice!

Please advice, and thank you for your time and effort to help another guy that just wants his music to sound decent, as it's supposed to be..

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