seeking input on build concept

[centervolume]

Good morning

I have been sizing up one of those "looks small but packs a punch" design ideas.

Template is Harvard using 5F2(a) box and chassis with extra tube sockets as needed.

For speakers I'll want to compare 10 v 12 (latter like the Vicky Ivy league design); will attempt to dial amp in for harmonica and guitar.

The design twist is to outfit with next level power (i.e., 5881 PP, 5V4 rectifier).

Questions:

First: I am looking at the modern beefed up PTs with 2" x 2.5" mounting footprint but delivering target of 400VDC to plates. Leaning toward the first one but do either of these make more or less sense ? or am I missing a good option?

Heyboer 13240 : 325-0-325, 100mA, heaters at 3A each (this is also advertised as 315-0-315)
Hammond 291MZ: 350-0-350, 75mA (seems limited for intended application), similar heater specs
others?

Second, I have a 90's OT that has been servicing a 5C5 Pro but pulled working (047269, EIA 606--340). I am looking at the 5C5 power section as a reference point for voltages. Other than PT and rectifier, the power supply design appears to be in same general ballpark as the Harvard. Is this a decent reference point for managing the power boost?

Lastly, I have a general idea of the 6AT6/AV6 tonal fingerprint (clarity, transparent highs, not terrible distortion) but I'm frankly less interested in managing the smaller E7-1 base from an install and parts perspective. I know this is likely a crucial tonal decision as V1 casts the die as it were in terms of what sound is being amplified. But I'll ask anyhow, are there any recommendations for a 9-pin or even octal rough equivalent? I'll be aiming for local B+ at V1 to be lower than the 5F10 published 160VDC, (5C5 has 125VDC for example) as I have enjoyed builds with less than 100VDC there to increase harmonic content for amplifying harmonica in particular. Could this is good spot for an octal equivalent to 6AT6 like 6SQ7 wired as a single triode?

Apologies for the long message, any thoughts appreciated as I am at the drawing board as it were.

[bmccowan]

A couple thoughts on the V1 tube:
Octal - 6SL7 using one of the triodes or wiring the two triodes in parallel (that's what I would try)
           6F5 is a single triode that would work but there is no current production and you'd have a top cap

Noval - 12AY7 - as with the 6SL7, using half the tube or wiring parallel. An advantage is that you could plug and play the other 12_7 tubes.

Note - if you decided to go 6SL7, you could also use a 6SL7 in the V2 phase inverter. I built a 5E3 Deluxe type amp with 6SL7s - nice.

[pdf64]

If you're using a 6k OT with 6L6 in cathode bias with a 400V HT, I suspect the mains transformer will need to be rated far higher than 100mA, eg I guess at least 250mA, the Hammond suggested transformer is 300mA https://www.hammfg.com/files/parts/pdf/290D2X.pdf?v=1697661948

[printer2]

To fit in the chassis I would forgo the tube rectifier and go solid state diodes. You could go octal by opening up the 12AX7 hole and putting another one to the right of it. A 6SQ7 would give a single triode with a gain of 100 (same as a 12AX7), a 6SF5 but without the diodes. A 6SR7 gives a gain of 16, quite a bit lower though. You could go 9 pin and have the wider range of suspects to throw in. You could double up the dual triodes for the first stage.

[centervolume]

If you're using a 6k OT with 6L6 in cathode bias with a 400V HT, I suspect the mains transformer will need to be rated far higher than 100mA, eg I guess at least 250mA, the Hammond suggested transformer is 300mA https://www.hammfg.com/files/parts/pdf/290D2X.pdf?v=1697661948

Point well taken, thank you. I am looking at a fixed bias setup; hopefully that should run a little cooler; question is by how much.

Time for some maths... I'm at or over 100mA with the 5881 bias at idle and screens alone. Thanks for the recommendation on the Hammond 290D2X.