gepardcv

Is this a different Arctic Silver from the one about which

For the power supply, I see that the silkscreen is not marked with extra space for a thermal pad for the FQPF8N80C transistors. Does that mean that I don't need an aluminum oxide ceramic pad for them? I can just use the Aavid TO220 4880SG kit with a metal screw and not worry about it?

The KGSSHV stereo mini board has four medium-sized heatsinks, each attached to two transistors (two 2SC4686A pairs and two IXTP01N100D pairs). Any tips or warnings for attaching transistors to both sides of the heatsink? Is there a recommended part number for the sink?

What kind of thermal paste does everyone use for heatsink mounting? I was thinking of using Aavid Thermalcote, but not sure it doesn't have

Was the error that some of the SMT parts were backwards in the pre 2015-05-17 version?

Don't know what you'd do about the ground sleeve contact on TRS when connected to 4-pin XLR. I just added two Neutrik hybrid jacks (http://www.neutrik.com/en/xlr/combo-i-series/ncj6fi-s), and their TRS outputs work.

I can hear a slight hum in a quiet room, assuming there isn't much noise coming in from open windows, nearby refrigerators, fans, or other noisemakers. Can't hear it with music playing, of course. It might bother other people less, but it bothers me just enough that if I build another one of these, I will definitely not use a Power-One unit. They are nice enough, but probably not intended for audio. I was thinking of making a Dynalo for a friend (I certainly like the amp enough to want to share), and would not feel comfortable with the result if it buzzes. Thanks for the comments and advice, everyone. I'll look into the sigma22.

I was reading some threads on diyAudio, and found this power supply: http://www.diyinhk.com/shop/audio-kits/50-17uv-ultralow-noise-dac-power-supply-regulator-1215v-1a.html In +/-15V mode, it seems like it should power the Dynalo well enough. It should also be quite a bit smaller than the power one haa15 units, even factoring in the size of the transformer. (And this gives the option of using a nicer transformer that doesn't hum.) Has anyone heard anything about diyinhk? Any thoughts on whether this PSU is any good?

I use a 750mA slow-blow, as recommended for 115V use in the haa15 power supply documentation (fuse is Mouser part 576-0239.750TXP). Works well.

@nopants: Yup, thanks, I saw that page — I'm trying to use the much smaller BH power supply and just push it harder. @spritzer: Then it looks like I just need to bump the two 450V caps to 500V, leave the zener strings alone, and that will give me 400V rails? For the transformer, would 2x 330VAC @150mA plus 1x32VCT (16-0-16) secondaries do the trick?

Interesting, thanks! I read earlier on this thread (or the KGST thread) that the zener string should be set 50V above the target output voltage. The stock zener string values on the two rails add up to 400V on a board that's supposed to put out +/-350V. I figured that to put out +/-400V, I should have the two zener strings each add up to 450V. Is that wrong?

Is there a circuit diagram of the kgbhultraminipsv4 somewhere? I couldn't figure out its file name based on the file listing on Kevin's site. I'm trying to figure out how to change the zeners for 400V: the board has two strings of 100V+150V+150V. Do they both need to change to 150V+150V+150V? (Was hoping the circuit diagram would shed some light on this.) For changing the 450V caps to 500V: I assume the resistors attached to them should also change to 430k (up from 330k)?

The transformer is just held in place with four bolts, should be easy enough. The board might be trickier. The Mouser picture shows the bottom accurately, and I'm not sure how to remove and replace the two metal pieces on the bottom. Not sure what they are, actually.

Thanks! Do you recommend using larger heatsinks on the transistors along with the 500V capacitors?

I just received a batch of KGSSHV mini stereo boards. Looking good. I've been thinking about the build, and it looks like my original plan to use a KGSSHV mini power supply with the stereo board in a Galaxy 388 chassis won't work, it's about 10mm too narrow, unfortunately. A larger chassis would certainly work, but the 388 fits really well on my desk. The question now becomes: do I have any alternatives for a smaller power supply board? The mini BH power supply is just the right size, but it's 350V, and I'd like 400V (though I'm also wondering if it would make significant audible difference if I tried running the KGSSHV mini stereo circuit at the lower voltage). I remember reading that the kgbhultraminipsv4 can be cranked to 400V — will I have heat issues? What are the drawbacks to using this power supply with the KGSSHV?

Apologies since I obviously missed this earlier: what is the advantage of the Carbon relative to the original ("classic"?) KGSSHV?

I see two 0.1uF caps with traces to the servo. Which of the two did you remove (or both)?

For the Antec transformer, I assume you (mwl165) used this one? Any downsides to it — like buzzing? This price is pretty tempting compared to a custom, but I'm a bit leery of noise.

Perfect. Thank you Kevin and mwl165!

I've been eyeing the stereo board version of the KGSSHV, and debating between building it next, or a KGST. Decisions, decisions. For the lower-voltage versions of the KGSSHV (like the 400V stereo), a couple of things I never quite understood (and would appreciate a link back upthread, since I seem to have missed this info previously): 1. What transformer specs do I need for a 400V version? 2. What parts need to change on the PSU board (I'm looking at kgsshvpsminifinal)?

This is really cool!

A few tweaks later, I made it better. Still not dead-silent with the JH13fp, but that might be too much to ask (28 Ohm, 116dB@1mW), but much less obnoxious than before. I wonder if the headphones pick up noise from the transformer? I tightened the screws on it as GrindingThud suggested, but it didn't help much. That's a little disappointing. I'll follow Kevin's advice about isolating the audio ground from the chassis ground next time I build something like this. I'd like to emphasize that the HD600 sounds great from both 4-pin XLR and SE outputs (I don't have a dual 3-pin XLR cable handy to test right now). Perhaps it just doesn't have the sensitivity to pick up the noise. The amplifier itself rocks. I'm listening to Janos Straker playing Bach's cello suites right now, and loving it. Many, many thanks to Kevin for making and sharing this design. Also thank you to everyone who answered my questions while I put this together.

All right, I finished my first Dynalo Mk2 build. Photos: http://imgur.com/a/GSxFt. Have now listened to a few tracks, so far so good with the HD600, completely silent. However, when I connect a sensitive headphone, like a JH13 to it (which yes, I know, doesn't need this kind of amplification), it has a pretty loud hum. Grounding problem somewhere? Could it be isolated to the SE output? I don't have balanced cables for any sensitive equipment I have. I grounded the TRS sleeve to the chassis, is that wrong?

Turns out I soldered the 7812 backwards. /facepalm It works now. Thanks for helping debug this thing!

Something is weird with the resistors. The 11k and 1k look fine, but the 100k and the 500k show something crazy, multiple M, then drop and fluctuate. I think I'll just order some more parts and rebuild it. Plenty of boards, luckily.