[LAU] "discovery" on db50xg clones (NEC XR385); example/demos w/ analog modification

[Niels Mayer]

On Sat, Jul 3, 2010 at 12:24 PM, Josh Lawrence <hardbop200 at gmail.com> wrote:
> ok, now you've got me curious...
>
> so if I were to purchase one of these cards, how do you go about using
> it in a computer or via MIDI?  is some additional hardware required?

The simplest way is with an ALSA-compatible soundcard containing a 26
pin wavetable header. Per
https://vsr.informatik.tu-chemnitz.de/twiki/bin/view/Sonstiges/WaveTableSoundCards
the two soundcards I've determined as being of recent design, and
still available are: "Terratec	 DMX 6fire 24/96	 PCI	 inside the
breakout box, Good as of 2005!" and the Dynex dx-sc51 (which is a POS
with an recent soundchip but a throwback AC97 codec that imposes a 48k
sample rate).

Note that the "original" files from my examples are recorded on the
Terratec, and the better sounding files, whose filenames contain
"on-analog-modded-dynex", are recorded at 48k on the Dynex... but
"better sounding" is due IMHO to my modification helping get rid of a
bunch of analog coloration that I felt was going on, mostly due to
eliminating three 10uF coupling capacitors and a low-quality op-amp
out of the signal path from D/A and into A/D. The terratec adding a
slow opamp and another too-small coupling capacitor to the signal
path. All those caps and op-amps in the signal path was IMHO
responsible for eliminating a lot of "thump" and fundamental bass
frequencies (listen to "Intelligent Summer" example for a D&B track
that emphasizes this aspect of the sound).  Unfortunately, the next
step, getting rid of the D/A -> A/D costs $75.00 and involves tapping
directly into the i2s-format digital stream feeding the NEC's AK4510's
DAC... which is sort of absurd for a $13.00 synthesizer:
http://www.twistedpearaudio.com/digital/wm8804.aspx  [[overall, I
recommend the Terratec because it has a better soundchip with digital
mixer, excellent digital I/O capabilities, and external MIDI courtesy
of via vt1712 chip, well-supported by alsa's snd-ice1712 and
envy24control...  once you get it running, you can always figure out
something to improve the sound of the db50xg ... see also
http://old.nabble.com/turning-a-consumer-soundcard-into-%22prosumer%22-w--quasi-balanced-outs-ts28791831i20.html
&& http://old.nabble.com/digital-upgrade-of-older-equipment-via-I2S-with-jitter-attenuating-S-PDIF-receiver-evaluation-board----ts28997419.html
]]

FYI, recently, the entire package was available on
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=170501815638
(which sold overpriced, given that you can get the db50xg clone for
about $15 with shipping and DMX6fires are available all the time in
Europe:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=230491593275 ...
Note that many of the terratecs prior to 2003 have waveblaster
headers, not just the DMX6Fire.)

The $1.00 card I modified, Dynex dx-sc51 is the US name (sold by Best
Buy). In Asia, it's more appropriately called "mediatek 1723" because
the card uses Via 1723 (
http://www.via.com.tw/en/products/audio/controllers/tremor/ ). Note
unlike the Terratec's superior soundchip, this one doesn't have a
digital mixer -- use alsamixer -- nor an extra external midi port, and
really only has one thing going for it other than the wavetable header
-- a toslink digital output  and alsa support via snd-ice1724
driver...
http://www.9final.com/computer/mediatek-1723-sound-51-channel-with-wavetable-connector-p-2084.html
http://www.pcresource.co.th/html/product/karaoke/images/mediatek_1723/1723_gal_800_2.jpg
http://www.pcresource.co.th/html/product/karaoke/images/mediatek_1723/1723_gal_800_4.jpg
(pictures of the original card whose top analog CD input I modified,
removing series resistors and increasing the 10uF coupling cap to
100uF.)

Or if you really want to go back in time there's the all-AC97 solution
of the Turtle-Beach Santa Cruz...
which is certainly supported by Linux, although I have no experience
with them. I can't imagine they'd sound very good -- I'd imagine even
the dynex has a better and more modern codec (
http://www.via.com.tw/en/products/audio/codecs/vt1616/ ) than the
Santa Cruz.

-- Niels
http://nielsmayer.com