JoaMat

I'm sorry for your trouble. Transformers are not always nice things. When temperature rises - copper resistance goes up – power increase – transformer temperature goes up - copper resistance goes up more, as temp … und so weiter …

Nice progress Kevin. Did this test board today. I’ve an idea (have to many ideas) to replace top el34 with CCS. Save you lots of wires. Here a CCS of 10M90S/DN2540 and +/-400V applied. Current set to 22 mA gave 400V cross tube and cathode resistor.

So, another quarter has elapsed. Raised the current through output stage from 11 mA to 17 mA ...and, it all sounded shitty bitty. Fired up the desoldering gun. Removed FJPF2145 and replaced them with 2SC4686. Wow, what an upgrade and I’m happy again.

It’s a troublesome, difficult time – all shortages of components. KSC5026 might be replaced by STN0214 in a KGSSHV style PSU. Solder it in standing, bend outer “pins” slightly outwards if necessary.

Have you seen this, BCV61? To be used as current mirror. You get a hundred pieces for 22 USD, less than one 2SC3381.

Which ones do you have in mind?

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From above picture it looks like there are 12ax7 anode current sources and 330K anode resistors. You shouldn’t have both, should you?

I use/have used those CCS. Good for +/-500V. I’ve replaced 2SA79/2SK216 with KSA1220/KSC2690. Looks like KSA1220 is ended, but TTA004/TTC004 should be fine.

Bohuslan Big Band plays Blue Note Available from Swedish public service company SVT, worldwide until 15. Dec. 2021. https://www.svtplay.se/video/31377250/jazzsommar-bohuslan-big-band-spelar-blue-note

Send me gerbers and I’ll take a look into it.

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Yesterday I Had The Blues - The Music of Billie Holiday José James

I think you are right. I’ve used 2SK879 in one T2 battery since several years without any issues. From datasheet 2SK208 and 2SK879 look quite similar.

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Me too like schematics. I believe this goldenreference.pdf reflects goldenreference6.zip version.

Here are the connectors disassembled. Pins are from Neutrik NC3FD-L-B-1. Take a metal saw and make a cut so you can bend up the outer metal housing. Then pins can be removed from inner housing. I would have prefer Teflon over 3D printed. I haven’t figured out how to mill it out though, but I managed to 3D print something usable.

Thanks for dielectric values of PLA and PETG. Them in picture above are PETG but I’ve also used ABS which also works. I assume you can use PLA as well, but both PETG and ABS melting temperature are a bit higher than for PLA which might be an advantage when soldering wires to contacts.

As most other DIYers I use Teflon Stax connectors with a small PCB. But on below amplifier I use 3D printed connectors with female golden contacts from Neutrik 3 pole XLR. And they seem to work really well. On heat sinks are 4 groups of c4686/a1968/c4686.

Thanks guys. Yes, external PSU (T2 PSU with some addons). Maybe one can’t call it a Carbon since output stage is formed by NPN BJT - but else it’s similar. I think current is like 10mA. 300R emitter resistor and two LEDs in series. With +/-400V the heatsinks are “hand warm” and you can probably double the current.

Has been in service for a few months now. Sounds alright.

https://www.svtplay.se/video/31776463/jazzsommar-karl-olandersson-kvartett?id=KyE3oPV Should be available worldwide for the next 24 hours. From Sweden but Jazz is universal.

Nice, Kerry! Now I get it - and the three pins (-, +, o) and all vias visible on the other side make sense even to me.