[sdiy] Tube weirdness

[Dave Krooshof]

>Okay, maybe it's just me, but I think this might be carrying the "tube
>sound" thing a little too far...
>
>http://www.aopen.com/products/mb/ax4b-533tube.htm
>
link was posted here before.


Putting tubes behind your DAC is a reealy good idea!
It's like this:
a dac converts from digital code to _current_.
converting that to voltage could theoratically done with a resistor.
But practically, if that resitor is to big, the voltage gets to high,
so it confuses the dac, as diodes will be opened that shouldn't have been.

So you convert to a small voltage and crank it up over an opamp,
or worse (soundwise) in a current to voltage IC.
The sh!t comes in here. Those IC's tend to sound harsh.
Amplifying a low voltage over a tube, however, works beautifully.

Often the lowpass filter is left out as well. 8 times oversampling
gives a samplerate-tone thats way out of the range of your
amplifier/speakers anyways, so they figure.

Several friends of mine have trown tubes in their cd-player.
Lot's of fine details were revealed.
Downsides:
- most cd's sound quite dark. As if distorion was calculated in.
- Bjork sounds very depressed on her lasts album. Is joy captured
in high freqs?
Upsides:
- Top freqs are spotlessly clean and transperant.
- Noise disappears, even from my recordings!
I wonder where all my noise went, and why it is present on my system.
Spectrometers show no high cut, so the effect is psycho-acoustic.
We compared with the same but non-tubed cdplayer. What a difference.

BTW have you seen my old cdplayer?
http://www.xs4all.nl/~krooshof/tech/cdspeler.html


Dave

-- 
fruitpower movie (with huge partly tube synth):
http://pages.vpro.nl/3voor12/journalism/index.shtml?2534202+2584688+2584508+7333367