MLA

Haven't tested these particular boards but my CFA3 runs fine and fully adjustable from no to full volume with a 10K pot, so I would say something's off...

I've sucessfully used stn0214 as replacement for ksc5026M as per JoaMat's recommendation in several other builds. Don't know the heat dissipation requirement for the position where they are used in KGSSHV, but someone more knowledgeable than me might chime in here.

I think you've done all you can and done it well, so next step is examining the circuitry closer and possibly start replacing parts, or plug in a new left channel (which actually might be the faster and more straightforward option, but requires some soldering skills). Or sell, of course. If sending to an expert, it's probably enough to send the circuitboard package rather than the whole amp; looks like you can take the whole thing out using a screwdriver if you loosen the headphone jack from the chassis; no need to desolder anything (unless I missed something in the pics).

A question on the CFA3; I just built one using 50k feedback resistors for SS and 4.2k ZF resistors, also excluding the C9/C10 caps as per mirkos final edit earlier in this thread. Builder error: was using the wrong LEDs (too much forward current I believe). Swapped those and now it's all well balanced with 10k at R1.

You can do both but do it in two steps; first, swap the output wires from the volume control so L+ and L- go to R+ and R- on the circuit board (and vice versa). If static moves to the other channel, the pot is the culprit. If no change, swap the XLR input wires on the pot so the one previously going to left channel now goes to right (and vice versa). If static moves to other channel, it's the XLR input wire or input jack causing trouble. Not likely, but worth ruling out.

Great! Having some boards made; have some current drive friendly speakers as well a 3 way active system that both will be great matches I think. Thanks!!!

So, the split cfp3 pre-board goes in front, right?

Where are you located?

You have to think Joachim style, i.e., smd-small and vertical . I believe the board is stereo and it mounts flat (vertical if seen from above) to a 2U heatsink. In the pic four posts above you can see how the previous edition boards are mounted through the grille.

Since there is bias on the inputs of the CFA3 but it's also a balanced amp, an additional thing to try is disconnecting pot ground altogether. It should in practice be happy with a differential input, as long as dac and amp chassis have a good grounds connection.

I would suggest go full dual mono as you've started above, with separate pot ground for left and right channels. Also, I would suggest not to connect the grounds as in the schematic above. With everything tied to one point, all current between amp and psu boards has to flow through that point, to which the pot grounds also happen to be connected. Not optimal, and not really what is meant with a star ground designed to avoid hum. Instead, try connecting the left amp board ground directly to the left GRLV ground and the right amp board ground directly to right GRLV ground, and then reference only the GRLV grounds and pot grounds (not amp grounds) to chassi ground, either directly or through 10R.

Just different pinout; no passive swaps so far. Will do some measurements in the coming weeks to check that all current sources have the right outputs, etc, but I don't expect any big surprises. JoaMat has run 1220/2690 replacement editions of his T2:s for a long time without issue as far as I know, and the tra/ttc004 pair seems quite on par with that combo. Measured breakdown voltage in the units I have is around 210V (rated 160V), compared to about 230V for 79/216 (rated 200V) if I remember correctly from somewhere in this thread, so not quite the same but close.

It's Joamat who is the brains behind the substitutions, not me. They seem to work fine though. I don't have a scope at hand so can't verify performance on any detailed level, but I'm listening to a T2 with tta/ttc004 replacements right now (no other modifications) and it does sound very good. Have some problems with a buzzing HV trafo that needs sorting, but the amp boards themselves seem stable so far.

LV supplies for front end (input jfets).

Is DynaMat having an impedance fight with mini T2 DHT edition ?

I suggest you get a kit from Spritzer if he still has these left: https://mjolnir-audio.com/diy-supplies/ That is about the only way to ensure real rather than fake parts.

Probably not what you need, but they are 6mm: https://www.mcmaster.com/panel-bearings/

This guy seems happy, though a bit principled on staying with the datasheet circuits https://www.audio-perfect.de/muses_72320.en.html

What could possibly go wrong ? Seriously; great idea though! Things could potentially get toasty on a 2U heatsink, so being able to choose current would be welcome flexibility.

Check the GRHV thread and files (James listed all flavours some time ago).

The C2M1000170D are in stock again at DigiKey. Grab 'em while they're hot. https://www.digikey.se/sv/products/detail/wolfspeed-inc/C2M1000170D/4399776

For Europe and for the 489/689, I was referred by Linear to: Ingenieur-Buero-Fluck Country:Germany Phone:+ 49-7533-949-8760 Fax:+ 49-7533-949-8762 Email:[email protected] Website:http://www.ib-fluck.de which turned out to be very close to a one man operation However, they didn't sell the 689 to private customers at the time (two years ago), so I had to use a company address to get those.

Had a batch of boards made on the above posted file a month or so ago and won't be using them all. You're most welcome to a pair if you want.

Arrow also has stock. Get 'em while you can

Works fine for me.