[ARC5] Circuit Help Needed

[Tom Lee]

Hi Ken,

The 6SL7 here is actually connected as a common-grid stage (the right 
half) driving a common-cathode stage in cascade. A cascode would have 
the plate of one section driving the cathode of the other (the "-ode" 
part of cascode).

The right-half of the 6SL7 is the error comparator -- it compares the 
reference voltage (applied to the grid) to a sample of the output 
voltage (applied to the cathode). That error is gained up without an 
inversion in going from cathode to plate and drives the grid of the 
other half of the 6SL7. That increases the gain even further, and also 
inverts in going to the plate, which drives the control grids of the 
paralleled 6V6s. There is no inversion in going from the grid to the 
cathode of the 6V6s, so with only one inversion around the loop, we have 
negative feedback, as needed.

--Cheers,
Tom

-- 
Prof. Thomas H. Lee
Allen Bldg., CIS-205
420 Via Palou Mall
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu
650-725-3383 (public fax; no confidential information, please)

On 2/10/2017 10:00 PM, Kenneth G. Gordon wrote:
> Mark:
>
> I just now realized something: the 6SL7 in your circuit is connected in a "cascode"
> arrangement, and is NOT paralleled at all.
>
> I found the necessary schematic and will draw it up in an easier to understand format and
> send it to you as a .JPG.
>
> Sorry for the confusion on my part.
>
> Even so, it IS a standard electronically regulated variable HV supply.
>
> What confused me was that the control tube is a triode: normally one uses a High mu
> pentode in that service.
>
> More later,
>
> Ken W7EKB
>
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