Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: punkykatt on May 10, 2017, 10:43:28 am

Title: 6G6 Bassman bass channel resistor?
Post by: punkykatt on May 10, 2017, 10:43:28 am

The 6G6 Bassman,  the bass channel has a 1m resistor across the plates of valve 2. What is the purpose of this resistor?  Thanks Punky

http://el34world.com/charts/Schematics/files/fender/Fender_bassman_6g6_schem.pdf (http://el34world.com/charts/Schematics/files/fender/Fender_bassman_6g6_schem.pdf)

Title: Re: 6G6 Bassman bass channel resistor?
Post by: sluckey on May 10, 2017, 10:56:36 am

That's a local negative feedback resistor. Don't think of it as a resistor connected across the two plates even though it really is. Think of it as a resistor connected from the plate of a triode back to the grid of that same triode. It has to connect through a coupling cap to block the dc voltage from reaching the grid. Rather than use a separate cap Fender just used the existing .05µF coupling cap.

So, resistor from plate (output) back to grid (input) equals negative feedback.

Title: Re: 6G6 Bassman bass channel resistor?
Post by: punkykatt on May 10, 2017, 11:59:14 am

Thank you sluckey,  I see it now.