Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: topbrent on August 18, 2010, 07:10:54 am
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Over on freestompboxes.org, there was a discussion about the /13 CJ-11, and a somewhat unorthodox "anti-bright cap" that went from the wiper to ground on the volume pot.
The CJ-11 has a ab763 front end and a 100pf bright cap mounted on the volume pot as blackface fenders usually do, and a 250pf cap from the wiper to ground. The afore mentioned "anti bright cap"
One poster, "sagajam" had this to say about the design:
"That 250pF could be so called "Anti-bright cap", when volume is turned up it starts to dump more and more treble to the ground.
It works like bright cap but opposite.
That could cure the fizziness I had with higher gain settings...
When the volume is turned down the 250pF becomes less effective, just like the 100pf bright cap becomes less effective when the vol is turned up. That way the cleans are nice and bright and gain is less fizzy."
Any thoughts on this design from the day crew?
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You have half of a James tone stack there. Look at the bass pot on a JTS.
With respect, Tubenit
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I'm pretty sure Carvin does this on several of their amp models. Their topologies are fairly similar across the Legacy, MTS, and Vintage series and I believe they all have either or both a bright and anti-bright cap on the gain pot.