MLA

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 .

Very small does not mix too well with high voltage + significant wattage. See Spritzer’s page for a good overview of what the amp size limitations are: https://mjolnir-audio.com/

They are mil spec and thus derated, so can actually handle higher loads. If you look at Vishay’s CMF line, it’’s the same resistors as RN60D but with about twice as high ratings.

Could you please update my table numbers to 6, 3, 3, 3, 0 ? (i.e. one more complete PSU setup) ?

Source must be balanced (or made balanced as per Pars suggestion above). Then, for one balanced channel, one board amplifies the positive signal and another board amplifies the negative signal. In this context, it might help to think of a balanced source as a four channel device.

Hands raised , two full sets.

+1; JoeMat suggested a separate PSU for the +220V in a previous post somewhere. I'm planning on using the PSU Kevin created for the tube input board for the +220V (have to check it works first though :)).

Yes, just slightly bigger than the squarewave. I logged in to check prices and PCBWAY would send me a pack of 10 for about 20 USD if I repeat my order. Good times for DIYers :)

Not its forte. Really shines with planars though.

Have a couple of these since last GB (psu for the tube ubal to bal board). Guess they would do the trick (possibly with some component updates to handle +220V) ?

To ask away on top of the above What’s your grounding scheme? Inputs look floating, is pot floating too? Amp board and psu? A small diagram would be very helpful in troubleshooting. Also, do you have some form of virtual ground or elevated reference for the heater voltage?

Trafo depends somewhat on the psu also: if you’re using GRHV you only have 20-30V or so in dropout voltage (or even less if I remember correctly). 360V secondaries puts you at about 510V DC unregulated, so that leaves quite a bit to be turned into heat by the psu pass transistors if you’re aiming for 400V output.

I've used a bunch of MKDSN 5.08 spaced from Mouser, they exist (for example 651-1729131). Also, note that the 400V is its CAT III rating (see data sheet). The CAT II rating, which is more relevant for an amplifier for home use, (think broadly home appliances connected to a wall outlet) is 630V.

According to their web, they’ve taken over distributorship for Denmark and in the process renegotiated lower prices with Stax. Stax lists them as official distributor on their international pages.

+1 on Kawai. I have both a Yamaha and a Kawai at home; the lighter Kawai action is preferable.