Shoog, the IT has 65H primary induction; using it as 1:3 step up (so the other way around) the induction will be too low (65 / 3²).
If the IT has a small natural gap that's good because it can cope with some grid current in the output stage.
I would use an input phase splitter ( active or step-up transformer if the preamp can drive 600R) and then a "modest" triode strapped 6V6 PP stage to drive the transformer. The current production and vintage Russian 6V6's can surely take up to 420V plate voltage. Despite 3:1 overall step down it can still provide some 200V peak-to-peak in class A with very low distortion without using high supply voltage or accepting other compromises.
I would use an input phase splitter ( active or step-up transformer if the preamp can drive 600R) and then a "modest" triode strapped 6V6 PP stage to drive the transformer. The current production and vintage Russian 6V6's can surely take up to 420V plate voltage. Despite 3:1 overall step down it can still provide some 200V peak-to-peak in class A with very low distortion without using high supply voltage or accepting other compromises.
Sure I am weighing my options. I would like to do pure SE throughout - because I like things to be simple as possible.
I am thinking of input tubes (basically what I have):
- 6h6 (6h30's all died)
- d3a
- 6n1p
- 6sn7
- 6sl7
- ecc88
- ecc81
- ecc83
Output tubes:
- el84 or russian equivalent
- Maybe an alternative but I would need to buy those, so prefer el84
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You are coming from driving the loudspeakers with a real power beast (UCD class D), so important is what tube amp you would need unless your speakers are efficient enough.
Part of the reason why I stopped the Hypex trouble shooting is that I do not need the watts (PHY-HP 8 inch drivers). I guess only some watts will do.
Also the drivers are supported by 2 active subwoofers ~ to about 80hz.
Also the drivers are supported by 2 active subwoofers ~ to about 80hz.
If you wish to do open loop (which is the simplest) you're going to need a decent real triode, or then consider something more complicated like Schade.
If you want to use EL84 (nothing wrong with it) and use some iron with a simple circuit, a nice option might be input transformer / splitter - ECC99 - IT - 2 x EL84 triode PP. Great sound.
ECC83 and 6SL7 are surely ruled out unless you use more complicated stages like hybrid mu-stage with para-feed. The low plate resistance types (less than 2K) are those that will work best being the transformer made to work with 6H30.
PP class A driver stage is really the simpler option. If the power tubes are 2xEL84's in parallel for 8-9W you can use Schade feedback (plate to grid) with 6N6 or 6H30 as class A PP driver. No high voltage power supply and simpler audio circuit.
Not too many options if you want to keep it as simple as possible.....
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