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CVX USB Parallel Port experiments

Posted on 2017-01-19, 22:00

Here's a spinoff from my CVX experiments : try to add a 'real' parallel port over usb (or pci-express if USB really isnt feasible), it could serve several purposes : 1/ try to play music \ run demos through a real CVX resistor DAC from dosbox on windows 7 / windows 10, on usb parallel port --> I …

Re: CVX-2 : covox adapter

Posted on 2017-01-15, 14:30

As far as I can tell, the only difference in design between the FTL and the CVX-1 is the coupling cap on the CVX-1 that is missing on the FTL (and possibly on the real Covox as well, assuming it is not inside the resistor ladder pack). Yeah, the real covox is probably just a resistor pack, without …

Re: CVX-2 : covox adapter

Posted on 2017-01-14, 18:15

the CVX-3 'VOGON EXPERIMENTS EDITION' PCB's arrived 😀 this will allow easier experiments with different values / combinations (using jumpers). Filename CVX3.png File size 26.73 KiB Views 1135 views Filename CVX3_photo1.jpg File size 358.88 KiB Views 1135 views Filename CVX3_photo2.jpg File size 108 …

Re: CVX-2 : covox adapter

Posted on 2017-01-11, 23:32

yes i think this is the last piece of the puzzle with 100k this makes an RC low pass filter that can fall in the audio range so yes this could well be the reason for the more muffled sound please replace that resistor with a 0 ohm resistor or just bridge it. i think it will sound good then !

Re: CVX-2 : covox adapter

Posted on 2017-01-11, 22:48

yes i compared again and noticed it differs in 1 resistor : CVX has 1 additional resistor R19, we should test by shorting this resistor --> see illustration Filename resistorpack_VSCVX.png File size 60.12 KiB Views 1467 views

Re: CVX-2 : covox adapter

Posted on 2017-01-11, 22:32

of course not, I think CVX misses a lot of bass, it sounds thin, but clear I compared the FTL ladder with CVX ladder, it is almost identical, FTL ladder misses one resistor : on CVX-2 if we short R19, we should get it identical. you can try by bridging R19 ? (or replace it by a 0 ohm resistor)

Re: CVX-2 : covox adapter

Posted on 2017-01-11, 19:53

thanks for the recordings. test corpus is excellent for comparison. All sound very clean, yes the covox sounds brighter, not much bass the cvx sound a bit muffled, with much more bass (for example at 0:40s in test corpus) ideally we should get the CVX sound bright, but still have plenty of bass :-) …

Re: CVX-2 : covox adapter

Posted on 2017-01-05, 19:37

Here's my Pentium Pro streaming an old track of mine at 44.1 kHz via the CVX-2: https://soundcloud.com/scali/cvx-2-alive-441-khz Original version is here: https://soundcloud.com/scali/mdb-scali-alive-master-128kbps The original is 16 bit 44.1Khz, direct digital, and the CVX-2 is 8 bit 44.1kHz, …

Re: CVX-2 : covox adapter

Posted on 2017-01-05, 18:03

Hi Scali, THANKS! the recordings are quite close, after a few listens, I'd now really say the 286 (at 36Khz) is less noisy than the 486 (at 36kHz, and even at 44kHz)! Have a listen : compare this part (286) https://soundcloud.com/scali/286-36khz#t=11:52 with this (486-36Khz) https://soundcloud.com/ …

Re: CVX-2 : covox adapter

Posted on 2017-01-02, 09:37

I ordered some SMD resistors too; those pads look like they will accommodate 0805 parts too, right? :) (got a whole bunch in both 0603 and 0805 ranging from 5k to 200k) Yes, these are actually 1206 footprints, by hand it is easiest to solder 0805 onto it. 0603 also works, (I did that for the 100k …

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