gepardcv

Happy birthday, Birgir!

Can confirm. The Neutrik RCA to XLR plugs work really well.

Sweet. Thanks for the explanation about the voltage jump, guys! Pictures attached to this post. This was my first time working with external heatsinks. I underestimated the difficulty, and ruined one sink trying to hand-drill it. Total fail. Luckily, I discovered that a colleague owns a Tormach PCNC 1100, and he was kind enough to invite me to his workshop and let me use the machine. A gorgeous device, let me tell you. It made short work of all the drilling. Then I hand-tapped all the holes (I think the Tormach machine can tap holes, but I wasn't sure how to keep the oil flowing and the taps clear of gunk for this operation). The heatsinks themselves took some finding. They are Fischers, 10mm high by 300mm long, with 40mm fins, part SK 56 100 SA. High quality, and hard to find in the US. With 10mm standoffs, the entire amp fits nicely into an enclosure just slightly larger than 2.5U. (I also tried sinks with identical dimensions from HS Marston, and they sucked: all extrusions I received were crooked, and there was no way I could have bolted angle brackets to them.) The rest of the chassis was done by FPE. In retrospect, I wish I extended the top and bottom panels to overlap the sharp edges of the heatsink fins, with large rectangular cutouts so air could still circulate. Still, I'm happy with how the case turned out. If anyone cares, I'm happy to share the .fpd files. Because FPE does not do anodizing, I had to have the panels made in two steps: one run before getting the pieces to an anodizer, and one run after. The circuit itself was easy to assemble and adjust. No trouble from the Toroidy transformer. Overall, the amp runs a little warm to the touch (at 20mA output): cooler than either my KGST or mini-KGSSHV, though we'll see how it fares after more than an hour (all I've listened so far). Many thanks to @mwl168 for the group buys and build notes, @sorenb and @jdineshk for the capacitor group buy and help, @vilts for making the spectacular titanium knob, everyone else who answered questions and provided inspiration, and many many thanks to Birgir and Kevin for making all this possible in the first place.

Thanks, Kevin. In light of this, any concerns with keeping headphones plugged in while turning the amp off?

I have music! Pretty obvious this is something special. It was pretty easy to adjust, and the circuit seems fairly stable so far. Still, something strange is going on: when I turn the amp off, all offsets jump to >250V, and then slowly down to 0. It's looks like the HV rails short to the output. I don't think this happens with my KGST and KGSSHV builds. Is this expected, or did I fuck something up while wiring the amp?

Thanks, John! So it's the current across the 50ohm resistor?

Finally made good progress with my build. PSU works, +403V and -406V on the rails (I guess I didn't match the resistors closely enough to get it perfect), and 560V bias (and climbing slightly as the 5% tolerance zeners warm up), all of which I believe should be fine. The 4 LEDs on the amp boards all light up. What is the procedure for adjusting the Carbon output current? Does it need a test tone playing? I put multimeter probes on the current adjust test points, but my DMM shows ~0.30mA, which quickly drops to ~0.06mA. Turning the trimpots doesn't do anything. I do not have the Stax jacks or pot connected yet.

I think goldenreference6.zip (single board) and the goldenreference7plus.zip and goldenreference7minus.zip pair (split board) are the latest available GRLV versions. They use different parts from the original goldenreference.zip (in particular, the MJW21193 should either be attached to a heatsink, or for a compact Dynalo, use the chassis as a heatsink; you may need to use an aluminum oxide pad and shoulder washers if the tab is not insulated). Disclaimer: I haven't gotten around to building any of the above yet. The other Gerbers in your post look like the right versions. You may also want to ask Birgir for XLR jack mount PCBs.

That looks sweet. I'm stuck on casework with mine. Drilling and tapping heatsinks for the first time. Turns out it sucks without a drill press.

4180G is the insulating pad, which I know about. I thought you were using a special shoulder washer..? Do you use PEEK bolts, then? Do you hand-tighten them, or use a specific torque?

What is the part number for the aluminum oxide insulating washer you use?

What about the SiC devices? Any special considerations for those, or just mount with a metal screw? (The tabs look insulated, so it doesn't seem like they need PEEK, anything exotic, or unusual washers...)

Sorry: are your impressions of the Ether, Ether C, or both?

I use this: http://www.amazon.com/MG-Chemicals-Isopropyl-Alcohol-Cleaner/dp/B004SPJP5O Still takes several cycles to get a PCB clean enough. Not looking forward to doing this with T2 boards.

Excellent choice! I made it to the last three Nightwish concerts in the Bay Area.

Stellardrone: On a Beam of Light — https://stellardrone.bandcamp.com/album/on-a-beam-of-light

I found this one, official Molex but much cheaper than the $300 specialty "premium grade" tool. Still worried about the 250V rating, though.

I've been thinking about replacing Phoenix Contact terminal blocks on future builds with Molex connectors. The SPOX line with a 5.08mm pitch seems like it would be a drop-in replacement on all Mafia PCBs. I am worried about the voltage ratings, though: Molex datasheets say 250V, whereas Phoenix datasheets for the terminals I've been buying say 400V. Judging by photos I saw posted, some people here use Molex. What's your take on this?

By far the easiest approach. I use Neutrik XLR-to-RCA adapters and they work well.

Incredible work. Any chance you might release Gerbers for these T2 boards?

Payment for shipping sent.

I don't suppose there's a way to shrink the split GRHV (fat version, kgsshvpssicfetsinglenewrightfatsw and kgsshvpssicfetsinglenewleftfatsw) so the boards match the footprint of the Carbon V6? It would allow me to just mount all boards on a 100mm heatsink without the use of angle brackets. I don't need the row of holes to do that, which I hope could save some space. Figured it can't hurt to ask.

Received my boards. @sorenb — do I owe you (or anyone else) for shipping? The USPS package has a $7.85 stamp on it, happy to reimburse as needed. Thanks, as always!

Just received a titanium knob from @vilts for an RK50. Looks and feels pretty fantastic!

I was just logged out of Safari on my laptop, also. Don't think I added any extra devices, and I've just been logged into HC from mobile Safari on my phone. There might be a cookie or local storage expiration issue..? I have "remember me" turned on whenever I re-log in.