Old JVM mods from previous owner

Redguitar

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I got an email from the previous owner about some of the mods he did to the 410H.

Could anyone translate what he wrote, into the actual sonic change he was after? As in, he did a few mods to achieve what audible results?

Here's what he had to say a few years back...

"Glanced at the schem just now and the first stage would be a 100k plate (stock 150k) with a 2.7k/0.68uF cathode resistor and cathode bypass cap.

4th stage plate would be 100k replacing the stock 220k.

Clean channel would be swapped to Fender values in the tone stack with a 100k slope etc... Think I left the 20k mid pot alone since it just adds more range some people put a 22k across the mid pot to make it closer to the 10k mid Fender uses.

4th channel has a fixed version of the Mesa faux presence control. Mesa Recto's don't have a traditional presence control that works in the NFB loop this was an idea I read on the JVM forums and tried out that I liked."
 

gregr

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Dropping the plate resistors to 100k drops the gain and compression. It can also tame fizziness.

The modern mode of the Recto is a passive low pass shelf after the treble control. It will soften the top end. FWIW, the vintage mode does in fact use traditional presence control in the NFB loop.

The Fender mod on the clean channel should be self-explanatory.
 

Redguitar

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Thanks. That helps to Know what I don't need to do/mod.
 

gregr

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If you like it the way it is, I’d say leave it.

I don’t have anywhere near the level of knowledge/experience with changing the operating point of a gain stage as others around here, so I’d love to hear what they have to say.
 


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