06-05-2012, 10:54 PM
Lawrence: you wrote: " . . . ideally though I would prefer a B9A or B7G valve for it if I can find one with similar characteristics as the 6J5".
Then you might care to consider the EC90 (6C4; L77); B7G base. Its Ra and gm figures are very similar, whereas the inter-electrode capacitances are substantially lower. However I'd be surprised if these differences caused a problem, since if all else fails, you can add on a bit of external capacitance to compensate! And as you and I know, a common problem with doing a 'sub' for a different valve (that is operating at R.F.) is usually having too much inter-electrode capacitance with the 'sub'
You're making good progress; I'm watching with interest; keep at it.
Al.
Then you might care to consider the EC90 (6C4; L77); B7G base. Its Ra and gm figures are very similar, whereas the inter-electrode capacitances are substantially lower. However I'd be surprised if these differences caused a problem, since if all else fails, you can add on a bit of external capacitance to compensate! And as you and I know, a common problem with doing a 'sub' for a different valve (that is operating at R.F.) is usually having too much inter-electrode capacitance with the 'sub'
You're making good progress; I'm watching with interest; keep at it.
Al.
