No bass control.

[mumford]

http://ampgarage.com/forum/download/file.php?id=15642

My first design overall has been a success, but it has one problem--the bass control does nothing. I've tried rewiring it, and even switched it from a FMV to a brownface using new parts without any change. I'm wondering if some component is filtering out the bass? The only thing I saw in my schematic that I thought could be a problem is the cathode cap on V3 (6SL7), but I changed it to 6.8 uF with no change. Any idea?

[mumford]

The link is to the schem.

[Drumslinger]

Why do you have the Bass going to .047uf and the mid going to .1uf? swap em around. Bass to .1uf and mid to .047uf and then give it a go.

[mumford]

I've wired it several ways, I am fairly certain the problem is not in the tone stack.

[Firestorm]

The 50K value you selected for mid pot pretty much knocks the bass control out of the picture except when the mid is turned all the way down. You could try something more standard for the mid pot. And since you're running the tone stack from a low impedance source, try a smaller slope resistor: maybe 47K.

[VacuumVoodoo]

Get Duncans Tone Stack Calculator from http://www.duncanamps.com/tsc/ and see what replacing the 0.1uF with 22nF will do.
Now you have several suggestions...

[10thTx]

I think you will find the bass and mid both work well independently if you wire it like this. The values in blues are the ones I personally prefer.

with respect, 10thtx

[mumford]

Thanks, everyone. I will try those suggestions.

I rewired it to a two knob brownface stack the other day, and the bass control still does nothing. It really seems like I should be getting something unless I have filtered out those frequencies?

The brownface stack I built was the one listed on Adam's Tone Stacks, shown below: (image from http://amps.zugster.net/articles/tone-stacks#Brownface)
[img:196:282]http://amps.zugster.net/images/articles ... ks/6G5.gif[/img]

[Jana]

Mumford,

With that 10K resistor wired like that, you only have the equivalent of a 9K pot for your bass control.

Unless you have a cap between the plate and the input to this tone stack, you are also providing a DC resistance to ground for the plate voltage from the tone driver stage. And, that resistance is changing with the setting of the bass control.