Pars

^ Yes, as far as joining two wires from a dual secondary transformer to form a center tap. Pay attention to the phase markings. For example, look at amb's instructions for the sigma22. The schematic shows two of the secondaries connected together. http://www.amb.org/audio/sigma22/

Happy Birthday Craig!

I usually crimp with something similar to what UFN posted, shape with needle nose pliers, check the fit, then solder them. Once done, with the keyed housings, it is impossible to fuck up when plugging in. Of course if you use 3 pin for both power and signal or something else, you need to watch that or mark them somehow.

Not to mention that the sand in a lot of these amps is getting very difficult and expensive to find. No sense in saving a couple of $ in hardware when it could cost you big $$$ if something catastrophic occurs, not to mention the probably huge amount of time finding the replacements and verifying that they are genuine.

I've never built a Stax or electrostat amp, but I'll take a swing at a couple of things you bring up: HV resistors: I think some people had problems with leakage in particularly the battery section of the T2. They found that the xicon 273 series, raised off the board alleviated that. From what I recall, PRPs exhibited this problem as well as the seemingly beloved Dales. Raising them above the board would seem to indicate symptoms of breakdown to the ever present ground plane below them. They are cheap (the xicons), so if that is what works, it's not like a Black Gate mantra... Thick traces: not sure where the now std. 2 oz copper came from. Back when I was more involved in board group buys, usually from Imagineering, 1 oz. was standard. Insulating pads and fasteners (PEEK screws) seems to have come about from a what works perspective. Realize that people like Kevin Gilmore, Craig Sawyers, etc. that are instrumental in these threads are also engineers.

One reason I never use those terminal blocks, much preferring these

Good 1st post diyampli

Yeah, you might get a couple of good pairs outta that

You make a good point as always I was planning on running @ 16V or so. I'll see what happens, but will probably stay around 16-18mA. I don't really want to use OPA445s for the servos, so need to stay below 18V.

Anyone have the latest DynaFET schematic, preferably showing the feedback options? The only one I am finding is the .png one that j4cbo had... Nevermind... I found the balanced DynaFet schematic so can discern what I might be looking for from that.

Kevin, After looking at the datasheets for the BJTs, 16mA seems rather low for these devices. Even the 18mA you noted on the previous page seems low. These seem pretty linear all the way out to 70-100mA. Any reason not to go higher than 18mA on these? I am currently measuring hFE on the PNPs (from Avnet). Still waiting for the NPNs from Mouser. At ~16mA, using this circuit, with 100K Rb and my Fluke in series on the base in uA mode, I am not experiencing the transistors even getting warm after 2-3 minutes. Current parameters I am planning on using for matching: V = 7.5Vdc Rb = 100K Ib = ~70uA Ic = ~16-17mA The original 2SA1015 / 2SC1815 in the Dynalo are considerably lower power handling. Looking at the datasheet, I can see where 16mA was a good operating point for these. Thanks. BTW, anyone still looking for thru hole devices: Avnet has the MPSW56s (around 1500 still left). Mouser still has the MPSW06.

Happy Birthday Naaman!

Don't you need to ground the - inputs to the board when using the RCAs?

Chinese trimpots? Has anyone tried these Bourns "clones" on ebay, such as this one? Funny, they use "Burans" but same font more or less as Bourns uses. I have a few of these and haven't noticed anything peculiar about them as compared to an actual Bourns, but wondered if there are any hidden gotchas, such as abnormal drift, etc.? EDIT: I see some posts on diyaudio about these, one in particular stating that the fakes are carbon vs. the cermet of the actual bourns. I'll buy the bourns...

How is the toggle switch on the back wired? It only affects input selection?

Too small is definitely worse. I normally ride the large end of the scale according to the numbers I got from Competitive Cyclists fitting tool.

Wow, that is really nicely done, with great attention to detail!

Happy Birthday!

Thanks Kevin. That is what I figured.

Happy Birthday!

I don't know if you would parallel the device to limit it to 270V or put it in series with the collector or emitter?

Happy Birthday Colin! Hope you have a great one!

You might check with Jim McShane... good guy and seems to know his shit http://www.mcshanedesign.net/tubes.htm

Happy Birthday Steve!!! and glad to see you back

Happy Birthday!