Semi-Customized DAC Part VI: Ribbons, Mesh, and Teensy, Tiny Screws (Finale for Now)
by, 05-16-2014 at 06:09 PM (2557 Views)
"Ken, we're gonna have to take those screws out."
We both started laughing helplessly, in that punch-drunk kind of way you do when you've got to release the stress somehow. "Both" being me and Ken Burton, the master woodworker who not only designed and built the beautiful DAC chassis you'll see more of below, but also had spent an hour or more a couple of nights earlier inserting four tiny screws through tiny washers and 300 micro-inch copper ribbons into thin-walled brass RCA jacks, just to connect the outputs for my DAC. (Ribbons, washers, screws, all from Omega Mikro. Thanks, Ron! - Bauman, one of Omega Mikro's principals.)
Did I say tiny? I think they got these screws and washers from the assembly line where they fasten the flagella on bacteria.
Not only that, but though he'd followed my advice and done the work on a large workbench in case of dropping the screws and washers (the screws had to be pre-inserted in the washers, picked up with tweezers, carefully held in position over the hole in the ribbon and the matching threaded hole in the RCA jack, then tightened - but not too much - with the second-smallest jeweler's screwdriver I could find), no less than three times the screws and washers had popped out of the tweezers, bounced off the work surface and onto the pitted, shadowed, concrete workshop floor below. It was concrete with stone that had mica flecks in it, which just happened to glint exactly like a teensy screw or washer. So we had spent ten or fifteen minutes each time with our hearts in our mouths (no spare screws and washers, we'd have to pay to get more shipped if we couldn't find these) on hands and knees, our faces almost touching the floor, me in a MacGyver moment quickly installing a flashlight app on my iPhone to light up all the nooks and crannies in the rough concrete surface. Miraculously, we'd found both screw and washer all three times, and Ken had finally gotten all four ribbons fastened to the ground and hot connections of the two output jacks. He'd also sleeved each of the two ground ribbons with their insulation, "socks" crocheted - yes, crocheted - of a single strand of #42 gauge, 50 micro-inch insulated, copper wire. Trust me, this is not easy. (Mesh insulation from - yep, you guessed it - Omega Mikro.)
Ken of Windy Ridge
Master of the Tiny Screws
So I was telling him this had all been a waste - except, as Ken said, desperately searching for something kind, for the fact that it was great practice for next time. And it was all my fault.
I'm right handed, and have a slight hereditary tremor in my right hand. Doh! Couldn't be the left.... This is ordinarily not much of a problem, except for teacups filled to the brim with piping hot tea, or, hmm, just thinking of any random thing here, fine electrical soldering work. In an attack of hubris, I'd tried to de-solder the old Radio Shack wire I'd used for the output connectors in preparation for the ribbons. This was the result:
I'd taken this shonda (Yiddish for "shame") to Gary Leiby of Electronic Hardware Repair, and he'd patched it to the point where there was once again electrical contact. He'd then soldered the 300 micro-inch ribbons to the board outputs. (Not directly to the outputs, but by using short lengths of very thin - sensing a theme here? - silver-coated copper wire, provided by Ron Bauman of Omega Mikro, soldered to the outputs and then to the ribbons.) It was those ribbons Ken had just spent an hour screwing to the output jacks. But when I took the rig home and hooked it up, though the signal through the mangled output was present, it was lower in level and distorted. I'd need the rig taken apart again, and another board shipped from halfway around the world. Fortunately, my board supplier Albert, who's really responsible for the guts of this DAC, came through like he always does and got me a replacement in just a couple of days.
With the replacement board I returned to Gary with boards, ribbon, mesh, silver wire, and later emailed about a page worth of typed instructions. You see, not only are these ribbons, mesh and wire barrels of fun to work with from a manual dexterity standpoint, the ribbons and mesh are both directional. Also, Ron had told me that although the crocheted mesh was the next best thing to plain air as insulation, it was only the next best thing. If I could get away without it, even better. So I was using the mesh only on one ribbon per pair. Along with the page of directions, I'd cut points onto the ends of the ribbons to show direction, and taped little masking tape arrows onto the mesh. I was glad I wasn't there to see the eye-rolling that I'm sure accompanied Gary reading the instructions and seeing all the little directional arrows on everything. But he was a true professional, calling me only to ask which one of the ribbons connecting the power supply board (these are Omega Mikro's version of heavy duty - thicker, though still quite thin, and a bit wider) should have the mesh on it. I told him it didn't matter, and was once again glad I couldn't see the face that must have accompanied him thinking "I have to be careful of directions with little wire socks, and solder ribbons thinner than aluminum foil, but this doesn't matter?"
Gary of Electronic Hardware Repair,
Electronics Builder and Repairman
Extraordinaire, Solderer of
What I'd given Gary was a PITA full of fiddly bits; what I picked up from him looked like the insides of a real electronic component. The one bit of advice he gave me was to point out that the power supply ribbons ran right past a couple of brass board standoffs, and if they came in contact, "That would not be good."
Back to Ken's for The Reattachment of the Tiny Screws. First though, mindful of what Gary had said, I asked Ken to wrap a single thickness of extremely thin packaging tape (a suggestion of Ron Bauman's for insulating places where mesh won't do) around each of the board standoffs in the path of the power supply ribbons. Then, finally, the tiny screws and washers. Ken laid a towel over the workbench so this time the screws and washers wouldn't bounce. (He did drop a screw and washer just once, and I'm happy to report the towel worked!) I drove home with my heart in my mouth, hoping the result this time would be different. I inserted the analog output interconnects, USB and SPDIF cables, turned on the computer and fired up Audirvana Plus, and finally, plugged in the power cord. Nothing snapped, crackled, popped, or went up in smoke - but it hadn't the last time. Audirvana Plus recognized the unit - but it had the last time. I turned on the amp, flipped off the mute switch on the preamp, turned up the volume, started a track playing, and...
It does subjectively sound better to me than it did when it was a bunch of boards lying on a piece of plywood outputting through Radio Shack wires and jacks. Now the electronics are mounted on a 1" thick maple board, which sits on heavy brass feet, which sits on a 2" thick maple block, which sits on cork-and-rubber sandwich feet. The internal power supply connection to the USB/SPDIF input board, the connections for the USB/SPDIF input switch, and the analog output connections are all Omega Mikro ribbons. The four transformer secondaries all have John Swenson's "snubber" circuits wired across them (elegantly soldered by Gary). There is still a bunch of wiring that's, erm, wires - which demonstrates, I suppose, that there's a limit to my craziness.
It's been breaking in for the past week or so (not 24/7, but pretty consistently). Yesterday it had reached the point where everything was very, very clear, and was starting to sound sweeter and more musical: "Hunh, didn't realize that track was so beautifully played." Some music is just breathtaking at this point ("Tigers" and "Stewart's Coat" on the Acoustic Sounds DSD download of Rickie Lee Jones' "Traffic from Paradise" left me with a smile that wouldn't go away). And each track sounds so different from all the others. So it's been worth it.
Here's how it looks: