Posted by PakProtector [ 64.12.116.65 ] on October 06, 2005 at 05:12:00:
In Reply to: Re: simplifying the Guinevere posted by manualblock on October 05, 2005 at 20:06:37:
yes, I approve of any and all experimentation or use of that circuit for research.
I do wish to have an answer from the starter of this thread on the output impedance change. Maybe he didn't realize how the CCS works.
I would like to see some good plate load choke circuits. Unfortunately for a reasonable output Z, there is another stage required, or one takes the hit on drive capability.
Also, a more general Question: has anybody actually looked at the actual impedance provided by an anode choke? The capacitances from the winding-winding interaction usually give a self-resonance that is too low for my taste. There is no further increase in realized impedance after self resonance, so the choke does not really behave as an infinite load anymore.
With chokes, I have found that sonics improve with linearizing the inductive response. The easiest way to do this is with a gap in the stack. A non-linear load provided by a choke at LF, where its reactive and nearly round loadline is nearly equal to plate Z just does not make any reasonable sense to me. Yet!
I suspect this is a large part of what bugs me about a lot of SE amps I've heard. Take a 2A3 working into a 2k5 load. Textbook no? Primary L? let's say 10H. Omega*L at 20 cps is 1256 Ohms. That's going to be a squiggly mess at LF. Not to mention being more than a bit down on power delivery ability. It's -3dB point won't even come until 40 cps, where the reflected impedance equals the reactive one, and then we'll still be presenting the 2A3 with a load of 1k2( two 2k5 in parallel ). This sort of thing isn't going to start looking OK( let alone good ) until a few more octaves have passed under the bridge.
Absolutely room for some experimentation with inductive loads I always say. Just realize how they are working and figure a way to keep the less-than-ideal perfomance from becoming visible. But that's how we work anyway, no?
If there was such a thing as my hypothetical SE2A3 OpTx, I'd really like to know how to keep its shortcommings out of sight....
cheers,
Douglas
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