Shaka Tube power supply

[Mick Bailey]

Anyone know why the resistors in the Shaka Tube power supply are different? (1k and 470R)?

[Pushtone]

Anyone know why the resistors in the Shaka Tube power supply are different? (1k and 470R)?

Yes I was wondering that too!

I meter the same pos and neg voltage BEFORE the resistors,
and offset voltage after.

I think I'm getting +13VDC and -9VDC out with a bias voltage of 6VDC.

I'll meter it again and confirm after work.


The PSU does seem to be working fine and stable.
However, my Shaka Tube is not.

[Mick Bailey]

My readings are;

Supply voltage 12.7 Vac

V- 11.83v
V+ 14.33v
Bias (measured on wiper of bias pot) -11.9v

All with respect to ground

My pedal sounds best with the bias set to the most extreme negative voltage and I'd like to get a little more negative to better explore my tube's sweet spot. It just starts getting interesting, then there's no more travel in the bias pot, so I'm thinking a little more negative range here might do the trick. Plenty of range in the other direction, though. I suppose the logical thing to try for me would be to lower the 1k resistor to 470R, but I'm missing the reason why it was designed this way originally.

[aron]

>but I'm missing the reason why it was designed this way originally.

I'm missing it too. The simple answer is ask Doug?

[Mick Bailey]

I've just put a switch in to toggle between 1k and 470R. Whilst it makes quite a difference to the -v (takes it up to 14.2), I couldn't tell any difference in sound. The bias pot also didn't behave any differently.

I tried biasing right on the edge of losing output signal to see if the lower value resistor would increase volume - it didn't (maybe on a scope something might have altered).

Perhaps some tubes behave differently. I suppose changing to a pair of 470R resistors would give a little more headroom for cleaner sounds, as the effective B+ would rise by a few percent.