Negative Feedback resistor value for bass

[pbman1953]

Another question on the Super Twin. I see that the stock NFB resistor is 820 ohms but that was for a guitar amp. I use it as a bass head. Plus,  I see for the SVT they used a 47k and Traynor used a 100k.


What would al think would be the right values to test out?

[sluckey]

Fender used the 820Ω/100Ω NFB resistors in a lot of the blackface amps, including many blackface Bassman amps. Don't get confused by the feedback resistor values in other amps that use a different power amp circuit. Maybe replace the 820Ω with a 470Ω in series with a 5K pot. Then experiment. I suspect you will spend a lot of wasted time and eventually go back to the 820Ω.

[pbman1953]

You're probably right, someone suggested a 1.5k. Any thoughts on that? Thanks!

[sluckey]

Try it and let your ears decide. What is your goal? The stock values work very well, especially for a clean bass power amp. Nice balance between fidelity, stability, and reliability. Most of the people you see tinkering with NFB are guitar players that are trying to get a bit of dirt in the power amp. That's OK for guitar, but not so for bass. IMO, a bass power amp should be powerful and clean. The original circuit already gives you that.

[pbman1953]

Based on your experience and help from the past, I'll leave it


Thanks!