Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: floyd on March 10, 2013, 11:06:00 am

Title: 220K vs. 470K mix resistors ?
Post by: floyd on March 10, 2013, 11:06:00 am

How would using 470K channel mix resistors instead of 220K affect tone in , for instance , an AB763 circuit ?

Title: Re: 220K vs. 470K mix resistors ?
Post by: tubeswell on March 10, 2013, 12:15:33 pm

470k resistors would decrease the AC load on the previous stage(s) compared to 270k resistors (by increasing the resistance to ground on the 'passive' side/channel that is feeding into the mixing resistors). This results in marginally less signal attenuation, but marginally more S/N noise.

Title: Re: 220K vs. 470K mix resistors ?
Post by: HotBluePlates on March 10, 2013, 12:27:33 pm

If there are coupling caps in series with them, it will also shift the roll-off point downward.

That said, the values are generally chosen due to other circuit values, so it doesn't really benefit you to tinker them.