Transformers for SSS/Dumbleland build?

[Roe]

I'm planning a SSS/Dumbleand build, considering the following Toroid PTs [wall voltage here is 230v]:
1) 273VA: Pri: 230 V
Sec 1: 330 V @ 0,5 A
Sec 2: 15 V @ 1,5 A
Sec 3: 15 V @ 1,5 A
Sec 4: 3,4 V @ 9 A
Sec 5: 3,4 V @ 9 A
Sec 6: 100 V @ 0,01 A

2) 340VA: Pri: 0 - 220 - 230 - 240V
Sec 1: 350 V @ 0,4 A
Sec 2: 350 V @ 0,4 A
Sec 3: 50 V @ 0,1 A
Sec 4: 50 V @ 0,1 A
Sec 5: 6,3 V @ 4,0 A
Sec 6: 6,3 V @ 4,0 A

3) 500VA: primary 230V
Sec-1: 0-350-400-450V @ 0,84A [unloaded voltages are 372-425-478v]
Sec-2: 0-75Volt @ 0,1A(Bias)
sec-3+4: 2x 6,3V @ 8,0A
sec-5: 0-6,3V-12,6V @ 1A (https://btb-elektronik.de/wp-content/th ... 0_Spec.pdf)

I am considering the following OTs:
I) Twin-Style Outputtransformer
Pri.: 2200 Ohm C.T.
Sec.: 0-2-4-8-16 Ohm
Power: 140 Watt (25 Hz -3dB) (https://media.tubetown.net/info/datenbl ... 100-ot.pdf)

II) HiWatt Style Outputtransformer
Primary: 2.25 kOhm
Secondary: 4, 8 and 16 Ohm
Power: 250 Watt (https://www.tubetown.net/ttstore/en/tt- ... ormer.html)

The following combination of transformers seem to work: I) Twin OT (140w) w. either 1) 273va or 2) 340va PT for a 100-120+w amp.
Alternatively: Hiwatt dr 201 OT (250w) with 500va for a 150-200w beast, if the screen voltage can be lowered.

The tubes I have (8xJan 7581a), speaker cabs, and the chassis (59x19cm] favor the former, low-power alternative (used for guitar and light bass). But I am unsure about whether to go with the 273va or 340va PT then. Any suggestions here?

My experience with a similar toroid PT from tube town is that the voltage at idle is very close to the nominal voltages (330vac gives ca 465vdc).

[Roe]

with the 273VA PT, the first 3 primaries could be added in series for 330+15+15v=360v, something that should give ca 500vdc rectified. (Higher voltages would require a voltage doubler or tripler for the 15v secondaries).

with the 340VA PT, the rectified voltage would only be 490vdc, unless I use the 220v primary for 510+v. But this transformer should deliever more current than the 273VA one

[Roe]

I found two hammond 1650TAs for a good price. the 1k9 Z is a bit low but these should handle more bass and power than the 140w twin output transformer probably.

I guess the 1650TA would work with the 340VA PT, giving roughly 500v at the plates (and the option of UL)

[Roe]

More options:

- 120w 2k (20-40khz), UL taps: https://shop.piemme-elektra.it/Products/8166
- 150w 2k2 (interleaved), Sunn, UL taps: https://shop.piemme-elektra.it/Products/8339

The 120w and 150w Piemme Elektra OTs have similar weight and size but the more expensive 150w one has more interleaved windings, which adds cost and improves frequency response.

The Sunn OT should be the correct type for a 150w dumble

[Roe]

Piemme Elektra has a november sale, so I'm considering the Sunn OT, which seems like the right type of OT for a SSS

[didit]

Piemme Elektra has a november sale, so I'm considering the Sunn OT, which seems like the right type of OT for a SSS

I will endorse that.

..