Can a plate choke and CCS be combined as plate load?

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Deke609

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I have in mind a combo loading of output tubes. I suspect the answer is no, and that the two devices, both being current regulators, would fight each each other. [Edit: or more specifically, that the CCS, by pinning down the current, would deprive the choke of the current variations it needs to store energy]. But I don't know enough to be sure or even relatively confident.

I ask b/c my understanding is that the devices have opposite strengths and weaknesses: a CCS as a plate load gives huge and comparatively even impedance across frequencies, but it can't swing voltage above B+; whereas a plate choke can swing voltage above B+, but provides less, and less even, impedance across frequencies.

So I'm wondering whether the two could be combined so that the CCS sources needed voltage to swing above B+ from the choke. That way, B+ could stay relatively low -- e.g., 400-500V for the Kaiju instead of 800-1K V.

cheers and MTIA, Derek
« Last Edit: June 14, 2020, 10:21:06 AM by Deke609 »



Offline Paul Birkeland

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Reply #1 on: June 14, 2020, 10:48:14 AM
When we consider the advantages of a CCS over a choke, the CCS will provide a high AC impedance with little regard to the frequency in question (at least for audio we can make this statement).

If you have a choke loaded tube and the choke doesn't have a ton of inductance and you don't have a ton of compliance voltage (as you've suggested in your scenario), then the impedance of the CCS isn't going to mean squat.  As the choke impedance falls, there won't be any voltage margin for the CCS to use effectively.  If you have sufficient compliance voltage, then your CCS is going to get super hot and you wouldn't need the choke in the first place. 

Paul "PB" Birkeland

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Deke609

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Reply #2 on: June 15, 2020, 04:04:51 AM
Thanks PB.

Yeah, I figured something like that would be the case.  I was just hoping for a way around needing high B+ with a choked CCS loaded output stage.

cheers and thanks, Derek
« Last Edit: June 15, 2020, 08:31:09 AM by Deke609 »