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Author Topic: Chokes As Plate Loads In FP 2 & Seduction  (Read 3633 times)

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Offline Grainger49

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Chokes As Plate Loads In FP 2 & Seduction
« on: October 21, 2009, 04:39:57 AM »
I asked this question in a Quickie thread.  I wanted to move this to the correct folder so...

I asked, "would plate chokes be good in the FP 2 or Seduction (already has C4S)?  This because I am an admitted imaging freak!"

Len replied, "I think Gary Pimm went into this in one of his iterations. IIRC, his opinion was that for a small frequency range the choke helped get rid of a little graininess of his CCS, but otherwise did not do much. The question became where to put the choke, and I think his answer was after the CCS.

When I was looking into it, I couldn't get many replies about it. But the fact that the choke would allow storage of current whereas the CCS keeps it constant seems, to me, to show that the two effects would be fighting one another.

I'm interested (academically) in what other people have found, too."

And now my response:


Thanks!  My FP 2 has no C4S but I was considering removing the C4S in the Seduction in favor of the chokes.  Of course I don't know what to use there anyway.

I guess I'm looking to burn some birthday money.  
« Last Edit: December 07, 2009, 05:08:32 AM by Grainger49 »

Offline Paul Joppa

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Re: Chokes As Plate Loads In FP 2 & Seduction
« Reply #1 on: October 21, 2009, 06:40:39 AM »
A current source provides superior performance to a choke, both higher impedance (especially at low frequencies) and immunity from hum fields. Current sources need enough compliance voltage to accommodate the peak output voltage plus an operational margin, which chokes do not - that's why a choke is good in the Quickie where there is little voltage to spare.

In Foreplay, the compliance voltage is used to to set the direct-coupled operating point, so a choke would be difficult to implement, perhaps requiring a new center-tapped power supply. In the Seduction, the compliance issue means the power supply voltage would have to be reduced to about half, and of course the hum sensitivity would be a real problem in a high-gain amplifier.
Paul Joppa

Offline Grainger49

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Re: Chokes As Plate Loads In FP 2 & Seduction
« Reply #2 on: October 21, 2009, 06:49:40 AM »

I am taking your answer to say that relative stock iron for both Seduction and FP 2 would not benefit from a plate choke.

In my case I built both my Seduction (first Bottlehead kit) and FP 2 (second) with outboard power supplies.  (More to come on the Seduction Monster Power supply when finished!)

« Last Edit: December 07, 2009, 05:09:24 AM by Grainger49 »