How to bias 6SL7?

[needtubes]

I have a pair of Welborne Labs Laurel monoblocks (see attached schematic) and am considering some modifications. I've read that replacing R3 and C1 by a 1.2V AA-size NiMH rechargeable battery in series with a 220-ohm resistor improves bass response, dynamics, etc. I've also read the bias should be 2V cathode-to-ground.

So, I wonder if this is an ideal bias scheme, or is there a better alternative? Maybe LED bias?

Thanks all

[Alastair E]

Well, The scheme as it is, is pretty good.

Personally IME, having used the 6SL7 in a not completely different layout, I saw no benefit when I tried different cathode devices.

Ive tried a series of LED's and even direct with battery-bias to the grid, as well as a rechargeable in place of the cathode-resistor.

The battery bias seemed to lose something--not sure what, just didn't sound half as good...

I cant see how the current scheme would be lacking in LF response from the first-stage.
You could if you want try increasing the by-pass cap to say, 220uF, but doubt you'll get 'more bass'

You could however, try increasing the value of C4 driving the Grid of the 300B, say to 0.47uF, but take care there's no LF instability......