MLA

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.

Forgot to post; my boards came in last week. Thanks!

Mine just cleared customs...

With Blueman2 on this; not an issue for me.

Definitely not the case with the one I built, so something is off. Could be many things though Aside from out of phase driven cancellation, I wonder if this is unique to your HD800 or does the same thing happen with lower ohm headphones?

Sent. Thanks!!!

Please increase my grlv78/79 to 6 each instead of 3 each. Thanks!!!

I would like to go with bare GRHVxxx pcbs!

Very nice!!! I'm all for a batch of non-assembled boards (I actually enjoy SMD soldering), but happy to go with pre-assembled also.

So, about sizes. It will be hard to get any of the KG designs that live here really small. I happen to have a ADI2 home at the moment, so took a couple of shots. This is the ADI2 on top of a eCFA (in a repurposed case that actually used to hold a KGSS clone). Note that this eCFA runs a lot lower than max current, otherwise the case gets way too hot. All boards inside are on good heatsinks but there's simply not enough circulation to run full power. External heatsinks is I think a must if you want to run this one full out. Same thing with a KGDT (solid state input, tube output, lives in a thread somewhere here), in a highly utalitarian Modushop case: Both of these are shoehorn builds as far as my skills go; Birgir could probably fit it all a little tighter, but not me .