Glacial Communications

A few posts back, I mumbled something about starting to build things more along the lines of Hi-Fi gear (but don’t worry, there’s plenty more synth gear to build- I just need to be able to listen to it and record it better…). My original plan was to build something like a gainclone/chipamp amplifier (yes, sneer at me tube fans!). That may still happen, but my first piece of audio gear is going to be an implementation of this USB ADC/DAC.

For a while now, I’ve been desiring an external audio interface for my computer(s). Unfortunately, price on the high end, and other reasons I don’t want to get into on the low end have been preventing this.  After enough frustration with this and some helpful Google searches, I’ve decided to go ahead and build my own.  Mine will be a little different from the one at that link – it will have Neutrik XLR-1/4″ combo inputs and 1/4″ outputs, as well as S/PDIF input and output. It won’t have built-in preamps, but that’s OK, because they’re coming later, via an INA217-based design on that’s still forming in my head.

Will it be the best USB audio interface ever? Probably not, but it’s the best reasonably simple DIY one I’ve found thus far, and it will be the best one I’ve ever built

Now I need to go practice surface-mount soldering, since the PCM2902 is SSOP-only. Good thing I’ve accidentally ordered  SOIC ICs several times, and got some little adapters, so I can get my skills honed now.

A couple of weeks ago, I picked up one of these on a whim – it’s got an LCD display, a little keyboard, a card reader, and other crazy things – why not? I wasn’t terribly interested in having to deal with 8051/8031 series programming, however.

A couple of Google searches later, I’m happy to discover that none other than the Atmel ATMega32 (as well as a bunch of other Atmel microcontrollers) is more-or-less pin-compatible with the 8051.

And hey, various and sundry Atmel microcontrollers like the ATMega32 have some compatibility with the Arduino environment I’m familiar with.

Now, obviously, this is all still a bit of a thought experiment at this point – I would need to get an ATMega32 (I’ve had AVRSyn on my to-do list for a while now, so I was going to get one eventually) and some sort of programmer to go further, but it seems like this crazy plan will work with some hacking involved (i.e. the clock crystal would likely have to be replaced too – I’ll have to look at the schematics).

That SN76477 noisemaker I talked about last time? It’s done.

Take a look:

Is it done? There might still be a bug or two to deal with, and there is tons of room for expansion- both on the panel and on the protoboard that the circuit lives on. Filter? Bitcrusher? LM567 modulator? Crazy banana plug patching scheme amongst these things? Who knows?

• SN-Voice: Primered the front panel (not sure how well that’s going to work. I’m using spray primer and it’s 17 degrees F outside. It may get a coat of white latex paint if it doesn’t). Figured out an easier way to do pcb->panel connections instead of making my own cable rigs. Still need tempco, but going to work around it at first (putting in headers, and just using a regular 2k resistor for now)
• MPS: Most of the way there. Still need a couple of caps (the polystyrene ones) and panel components.
• Tried to build Rene Schmitz’s 4069 VCO. Thus far not successful. Not sure where the problem lies.
• The new rack chassis: Figured out the existing panels will need widening if they are to accomodate 1/8″ jacks. Given the material is some kind of reasonably study metal (steel? aluminum?), this could be a challenge)
• New thing: It’s a re-implementation of the 1970s/1980s Remco Sound FX Machine. The schematic is somewhat based on the Saratronics SARA-002, but with some improvements (specifically: added a switch for one-off or constant operation, and fixed some things that looked weird in the schematic). Working great in prototype so far. Working on a fancy enclosure (ok, a cigar box, as usual, but it’s going to be painted up all fancy-like, so it’s fancy, dammit!)
• I must really like the SN76477 – in addition to the two projects using it above, I’m also planning to build a Thomas Henry SN76477 SuperController. I may build a second Sound FX Machine box as well.
• Also trying to figure out a way to mount the power supply without electrocuting myself – I think it’s going to get its own enclosure, and hook into the cabinet(s) via XLR connectors.
• Even though I’m not a major Atari Punk Console fan (you get twice as much fun out of a CD4093), I went ahead and got a pack of GetLoFi’s APC 2.0 PCBs. If nothing else I may make a couple of little kits for friends who want to get into SDIY.
• I’ve got some other PCBs enroute. Looking forward to getting them.
• Debating some Hi-Fi type projects (chipamp, maybe speakers). Maybe when some of this other stuff is actually done.

Second hour started with Raymond Scott's Soothing Sounds for Baby (all three volumes at once), and finished with a little Merzbow.