So, what am I using CCS-es for? Voltage references. With Ohm's Law, and a stable resistance I am creating variable voltages( by varying the R, or stable voltages by *NOT* varying either R or 'i'. In the tail load of the Schmitt inverter, an infinite R( and V for it to work across ) makes the AC balance nearly perfect.

The heater-cathode capacitance provides a substantial bypass and likely is the contributing factor in the AC imbalance at HF. This can be transferred to primary-secondary coupling for the case of DH valves. There will always be a leakage path. Make it small compared to the stuff which does matter and the imbalance will be hard to measure.

Building a CCS which does not oscillate is fairly easy, and a building-block CCS which does not cause trouble has been built by a few of you with Guinevere.

The dual CCS and upper element parts of the cascode layout may take a bit. I'll draw it by hand and see if somebody can masage it to a point where it can be done on a proper Cu/TFE PCB( complete with thru-holes for mounting the bits! ).

I may decide to act as consultant to somebody who wishes to start a business. That is the sort of thing I wind up doing anyway, no sense trying to get paid for it...:) I like sharing the audio magic I happen to discover. Not that the Ferengi Rules of Acquisition would prohibit a bit of Profit.

http://www.dmwright.com/html/ferengi.htm

I especially like 11, 12 and 27. 57 is eternal.

The CCS-based circuitry for Merlin ought to be done with a PCB. Upon further investigation, there are two folks who are in on the current OPTx buy who have experience with PCB printing. I will investigate and see if we can get a run made, or if the artwork can be made public. Let me make a call or two and see what I can turn up. I would like a few of them myself for that matter. Plan on 5W Mills WW plate loads and one more thing can be incorporated into a simple board...:)
cheers,
Douglas