How to add a mid boost...

[Gaz]

I've built an amp with bright and dark paralleled stages into an anode/'tweed' mixer, which directly feeds the phase inverter. There is no tonestack in the amp, and I don't have enough gain stages to add one anyway.

I'm finding the bright/dark volume controls very versatile, but wish there was a way to do a mid-boost switch. Can anyone suggest a way to do this, or point me to another amp that uses a mid boost switch?

I'm not too worried about insertion loss - I have a ton of extra gain without the normal tonestack, but can't afford the gain losses of a normal tone stack.

Thanks for any advice...

-Alex

[black_labb]

what about a Low pass and a high pass filter. you could use a pot to adjust the break frequencies.

to cut the highs you could use a presence control if you have -ve feedback. you could create a low pass in the -ve feedback to cut the lows as well.

[Wakculloch]

The Burman preamp used a seperate mid control like this:-see attatchment.
Can't remember what it sounded like, havn't seen one for years.

[Gaz]

Thanks a lot, I might try that. Now I'm thinking just ditching the anode mixer and using the extra gain stage to do a bandaxall, but... I think this'll have to be another thread...

[Merlinb]

The BigMuff style tone control can be arranged to give a mid boost. Adding more pots can do funky things to the response.

[thumbs]

What about the treble bleed cap across the volume control? If you use a higher value cap it will bleed mids as well. You could make it switchable and keep your controls the way they are.

[tubeswell]

PV C30/DB has a mid-boost. This is in the Tone Stack, and the stock set-up consists of an extra cap (.047) with resistor (220k) to ground, both in parallel with the treble (270p) cap. The resistor is bypassed when the switch is engaged making the two caps in parallel. The sound is awful IMHO.

[Gaz]

Thanks all. I decided to do a Baxandall/James tone stack, which yields a nice mid bump with the bass and treble down. I think I'll add a switch to parallel another cap for a mid boost as described here