Sun 28 Jun 2009
Well recently I made an Alien Dac kit purchased from Glass Jar Audio. This was to free up my Behringer USB sound cards for use in my laptop with MIXXX.
In short: the kit works and sounds amazing!.. Though the purity of it’s signal path (no output op amp to buffer) means it’s a lot quiter than my other sound cards. Interesting that playing my wife one of her favourite tracks she was asking about an instrument (snare drum brush) she hadn’t heard in the mix before.
It is the first kit I have ever soldered up using surface mount components, which was incredibly fiddly and you can see my soldering is messy - though after some initial debugging and removing excess solder with a desoldering braid I got a functional DAC.
The PCB as it came. Yes, I was a lightweight and ordered the PCM2702 chip presoldered.
Assembled and working kit, before I cleaned off the flux and with some temp RCAs quickly tacked on for testing.
It shows up in Linux as just another USB sound card, with the chip identified:
aplay -l **** List of PLAYBACK Hardware Devices **** card 1: PCM2702 [Burr-Brown Japan PCM2702], device 0: USB Audio [USB Audio] Subdevices: 1/1 Subdevice #0: subdevice #0
Detail of the front, with my short, hand made (and unshielded) solid copper RCA leads .. made to give a very short signal path from the DAC to the passive “preamp”.
The passive preamp is another simple bit of kit gear I ordered more than a year ago from Ebay, then took ages to get around to building it due to other distractions. It’s just a simple input switcher with a 20 position switching volume control made from pairs of matched resistors, essentially HIFI via the KISS principle.
All of this was soldered together using high grade solid copper wire and silver solder from http://www.diyaudiostore.com/ - looking at the site interesing to see they are closing down.
The stepped resistor volume control with the back removed before I soldered it up..
The Wanfai passive kit kit when it arrived.
June 29th, 2009 at 8:57 pm
looks cool. Is there any option for a output buffer? Perhaps a discrete one, like the Burson buffer.
June 30th, 2009 at 12:20 am
The circuit has an extra unused IC socket but it’s for something to do with if the unit is being powered from the amp.
Maybe I can adapt some simple op amp based circuit ala the CMOY headphone amp down the track… but right now just running the master volume on my amp higher is OK.. only thing is we need to be aware of the difference when switching to another source.
February 3rd, 2010 at 4:11 am
You may be right. Is the cable a shielded cable? You may be getting interference from two way radios or even power lines.
February 3rd, 2010 at 11:07 am
“oke tell me how to do it and what i do need.
note: i have a famicom console with mono output.
there,re 5 instruments/sounchannels inside the famicom, for wich 2 instruments are far to quit that i even can,t hear it.
my goal is to increase the volume from those 2instruments till it match eachother.
thank you very much.”