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In the Forum: Melquiades Amplifier
In the Thread: To drive the 6C33C...

Post Subject: Drifting and loadingPosted by N-set on: 11/6/2010

Romy, I'm of course familar with your MF design and Jim's 6E5P curves is what
I base my considerations on at this moment (along with the corresponding Spice model).
Your DHT MF is quite self-balancing due to the large cathode resistor. What
I have in mind is a deifferent topology (derived from Chimera's Axiom
http://www.chimeralabs.com/images/axiom.sch.jpg), which looks like much more sensitive
to the drifts. I post my lamentable approach here (feel free to (re)move it)

(I have problems with uploading the gif to the gallery so I attach it).

Most of the output's biasing is due to a voltage drop
on a big, 1.2k, DCR of 6E5P's chokes. Then follows a small selfbias with 150R,
which will not be efficient in correcting driver's drifts.
But what you say is encouraging:

"What is good about those tube is that if you get one that operate as you want then it will most
like to maintain this operation mode very stable."

As for the loading: thinking as a capacitor, voltage is what drives me, so I need
a constant current source. Paul, I'd have less problems accepting a huge choke
than e.g. a transistor CCS. I do in fact have in mind a choke on a huge amorphous core,
but heavily sectioned (and interlayed), so in reality a collection of small coils on a common core.
As for active tube loading in SRPP, I have no experience with
it, but IIRC in a more standard application of an input stage, it had some sonic problems,
which some people tried to link to a specific harmonic spectrum of SRPP. No idea if that
would apply to the current context though.

Best,
N-set

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