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Old 2nd February 2004, 05:41 PM   #11
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Join Date: Jan 2004
Location: greece
Default 2a3 dir.coupled

Thanks Steve , i`ll try to do this , and i hope [??] for good results..3-4 hours every day i am working for this..[ i have sufficient quantity from 2a3 tube ]
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Old 2nd February 2004, 07:19 PM   #12
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Join Date: Sep 2003
Location: Texas
I agree with much of what was said here. I think there is also some misunderstanding of what the signal path is an any given audio circuit.

For example, many consider eliminating plate-to-grid coupling capacitors as removing capacitors from the signal path, but then are quite happy with large electrolytic bypass capacitors. Yet, the bypass caps are also in the signal path. After all, the AC current flowing through the tube and causing changes in the plate voltage is affected by the characteristics of this cap.

As someone else pointed out the PS caps are also part of the signal path. In other words, the current that is flowing into and out of the various components in the circuit, including the load, is colored by the characteristics of the caps in the PS and its characteristic impedance.

Most of those Loftin-White circuits had capacitors somewhere, even if there were no plate-grid coupling caps.

Furthermore, when you look at the transfer function of the circuit, which really defines its basic audio behavior, you cannot really eliminate the PS from this analysis and any bypass caps are inherently part of the analysis and create characteristic poles and zeroes whether you like it or not.

So, it's really a matter of trade-offs, not absolutes. And, it's almost impossible to not use an capacitors at all in an audio circuit when you include all of the circuit. It's only a matter of where you want them to be.
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