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previous: Ken Gilbert how large are the plate resistors?<... -- 6/30/1999 8:30 PM

Re: preamp design ruminations

7/1/1999 10:27 AM
anonymous	Re: preamp design ruminations Ken, you said your Rp are 100k, Rc = 10k ... 22k. This stage will behave similar (dependend on load) as the second stage in Marshall's 2203. There cut-off happens first. Cutoff clipping is of the razor blade type. Hence the transition to distortion for that stage is not smooth. What Soldano does may have the following intent: The last (4th) stage has a not too high Rc=1.8k. The 3rd stage uses Rk=39k, Rp=100k bypassed with 1nF. Hence the output swing into the last tube is not large which keeps the grid current low. The low Rc with the last stage will first run in soft grid current clipping and then in sharp cutoff. As long as the 4th stage reaches grid current clipping earlier than the 3rd stage reaches cutoff clipping, the overall transition to distortion will be soft.

7/1/1999 10:27 AM

anonymous

Re: preamp design ruminations

Ken,

you said your Rp are 100k, Rc = 10k ... 22k.

This stage will behave similar (dependend on load)

as the second stage in Marshall's 2203.

There cut-off happens first. Cutoff clipping

is of the razor blade type.

Hence the transition to distortion for that stage

is not smooth.

What Soldano does may have the following intent:

The last (4th) stage has a not too high Rc=1.8k.

The 3rd stage uses Rk=39k, Rp=100k bypassed with 1nF.

Hence the output swing into the last tube is not

large which keeps the grid current low. The low Rc

with the last stage will first run in soft grid

current clipping and then in sharp cutoff.

As long as the 4th stage reaches grid current clipping

earlier than the 3rd stage reaches cutoff clipping,

the overall transition to distortion will be soft.

Replies:

GFR There's a large (470K) resistor in ... -- 7/1/1999 11:57 AM