Improved tube stage

[zamaudio]

• Add resistor in series Ra = d(Vp)/d(Ip)
• Add Ranode tables for looking up the plate resistance
• Missing 6V6 tube specs so new table is wrong for this tube
• Converted tube_transfer.py to python3

Signed-off-by: Damien Zammit damien@zamaudio.com

[brummer10]

Hi Finlay found the time to checkout your PR. Thanks for that. While the changes sound nice so far, I've a issue with the produced dc-offset.
So this implementation requires a final dcblocker. I've implement : fi.dcblockerat(1.0) to remove the offset.

To the 6V6 tube tables, unfortunately we can't rebuild them, as we've lost the specs for it, and, it required a slightly change in tube_transfer.py (which we've also lost. So I reimplement the old tubestageF as tubestage6V6F definition for use it with the 6V6 tubes only.

regards hermann

[zamaudio]

@brummer10 i think tb is an integer that selects which tube model, I don't think its the input signal (?) If I am right, then it makes very little sense to use tb*

[zamaudio]

I think i fixed the DC offset problem in the commits that you merged already, I don't think you need the dc blocker, but I could be wrong.

[brummer10]

@zamaudio Ups, yes. it is the tube selector. Makes no sense to use it here. Just the DC offset is still there.

[brummer10]

so this one will use the input tube(x) = x:(+ : (tubeVp)) ~ (x*(Rk/(Rp + Ranode(tb)))) : /(divider);