Framus Mid Control - What can I do with a DPDT?

[j-stylez]

This is the full schematic. The tone circuit as shown in the ltspice diagram above is inserted instead of the single mid control circuit that is still shown in this drawing. I havent updated it yet.



Ignore the Red line. The tone circuit is inserted on a 250k push pull pot between the right end of the Red line and the volume pot.

[j-stylez]

I have made another derivative of the Framus mid control, maybe this one is interesting for you @walkman?



A 100k resistor is added to the mid cut circuit (R1 in the schematic). The DPDT switch is wired so it selects a different coupling cap (47n vs 1n) and jumpers R1 when the 47n cap is selected to give the standard mid cut control. This changes the control to be a both mid and high cut, but due to the higher overall attenuation of bass frequencies it gives you (relatively) a control over how loud the bass is compared to the rest of the frequencies.

I wired the switch so that the 47n cap is always left in the circuit, to prevent high voltage DC on the switch. The 1n cap is simply switched in series AFTER the 47n cap. In series, the capacitance is still close to 1n when it is switched in (a little bit lower), but the 47n cap always blocks the dc from the switch for when the 1n is bypassed.

I thought this up for an amp of mine where I just didnt have the control over the relative level of treble and bass that I wanted, so I added the DPDT switch to be able to change the bass response. At the same time, the pot now also controls the treble frequencies. Overall, this is a more lossy control now, so you get a drop in volume when you use the 1n/100k setting. I like it, because it gives a different flavor to my amp at the flick of the DPDT switch. I especially like this for lower level practicing volumes in my room.

I use this in a 6V6, sort of 5f11 style amplifier right after the first gain stage.

[nickb]

Good to see you getting to grip with LtSpice so well

Can I make a suggestion that I think will help to communicate your idea? Create sub circuits for the potentiometer and switch. You can then parameterize them and drop them into your schematic. I think it makes it easier to simulate and to see what is intended. Attached all files as zip.




fmc.zip

[walkman]

That last set of curves looks good as well.... I’d really like to try it out. I have a build in mind and hope fully can get this into it, and let you know.

[ToneHenge]

In case you're interested, I've played with a similar mid control circuit I found in Merlin's book (of course) that has an adjustable center frequency. I found it pretty useful once you tune the sweep properly - gives you an approximation of some Fender and Marshall mid sounds. Note R1+R2 comprise a 1M pot, and R4+R5 comprise a 100K pot: