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In Reply to: RE: Owww! posted by cpotl on June 14, 2021 at 03:08:39
Well, I believe the confusion in Crowhurst's paper lies in a certain difficulty he may have experienced in translating what he knew and formulated into a plain English explanation. His text must be read very carefully in order not to misinterpret his meaning. That's not what I see when reading the hypothesis by Broskie or Rozenblit. Their descriptions of the circuit seem flawed by a fundamental conceptual error. No matter how many times I review, it simply isn't possible to reconcile what they're saying with my understanding of the circuit, which includes results obtained in SPICE. :(
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Buy Chinese. Bury freedom.
Follow Ups:
Crowhurst's schematics leave a little bit to be desired. In his first schematic, Fig. 624, I was assuming that the connection to the grid of V2 should be understood to be at ground potential, and that the "non-cathode end" of Rk is connected to the supply written as something not quite readable, but looks like maybe -B0, which is presumably indicating some negative voltage (relative to ground). This would be a standard type of LTP. (It would have been nice if a ground symbol had been attached to that line coming from the grid of V2, though!)But then he says he is going to redraw the schematic in the form of Fig. 626. But now, in Fig. 626, the "non-cathode end" of Rk is connected to ground, which is also where the grid of V2 is connected, of course.
So it appears that his Fig. 626 is not merely a redrawing of Fig. 624; he has done away with the negative supply for the bottom end of the tail of the LTP.
Unless, of course, the line from the "non-cathode end" of Rk in Fig. 624 is actually supposed to have a blob at the point where it crosses the line from the grid of V2. In which case the slightly unreadable voltage that could be -B0 is actually just denoting the negative end of the B+ supply, and is intended to be synonymous with ground.
I don't think that is a very likely scenario, though. I think the whole essence of a long-tailed pair, in its traditional form, is that the "non-cathode end" of Rk should be connected to a negative voltage (i.e. negative with respect to ground)? As an LTP, it would really work very poorly indeed if Rk were connected to ground at its bottom end.
But then, what is going on with Fig. 626? It is clearly then not simply a redrawing of Fig. 624.
Edits: 06/14/21
just for giggles...-
separate the two tube halves, using a CCS for each one and couple the cathodes together with a cap.
"just for giggles...- separate the two tube halves, using a CCS for each one and couple the cathodes together with a cap."
There shouldn't be any difference, other than the LF rolloff of the cap. I took a quick look at this in SPICE, and it agrees.
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Buy Chinese. Bury freedom.
can you spice circuit in fig. 626 and split up v1 and v2, cap couple them, adjust Rk for singles. use same RL value for each. no CCS.
What are we looking for?
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Buy Chinese. Bury freedom.
balance or lack thereof. cap should be ~8uf for Fc decade below 20hz, right?
How big shall we make this cap????
:)
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
my random number generator chose 5. so 5uf.
'f'-FIX-1, and *MY random number generator took about 7 tries to hit 5( .5 actually ).
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
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