Bridged T Mid Control

[stephenl]

Interested if anyone has seen a mid control like this used in a guitar amp and opinions of its effectiveness.
Anyone interested in running a simulation?

Bridges T Filter.jpg

[Mr. Lime]

The control would have a deep mid cut while the dual pot shifts the notch from left to right. Theoretically cool but very lossy in practice I would guess. Probably more useful in clean amps as in high gainers.

[brewdude]

I am very interested in this idea—I suppose it would be a parametric mid control. I have been thinking of the mid knob as kind of a clean/overdrive or clear/mud control lately.

[Mr. Lime]

Lately I was playing with the Tone Stack Calculator to see how I can take use of a bridged T mid control in a simple James stack.
I came up with this arrangement which is basically a sum up of the controls of the first post's schematic.

As already mentioned before, it's quite lossy so I highly recommend a low impedance source like a cathode follower to drive it.
R1/R2 would have to be a tandem pot with additional limiting resistors. I chose 33k for those resistors and a 250k dual pot.

In high gain preamps where the distortion is created before the tone stack or in clean preamps, this circuit offers a very wide and useful range.
There's less interaction between the controls than in the FMV stack while treble and bass are responsible for how deep the mid notch actually is. The mid control (dual pot) shifts the notch from left to right. Bass frequencies decrease when mid pot values increase but that shouldn't be too much of a problem.

[fabiomayo]

I put an alternative form of the bridged-T in my 5F1 circuit as a test and I generally like it, but it is quirky.

1- It's very lossy. So it reduces gain and may need to be adjusted along with the volume control. I don't find this too problematic though. My use case is to tighten the sound to either (a) make more 'blackface' cleans, or (b) to use higher gain from pedals, which benefits from the lower bass and mid-scoop.
2- I've added a switch to either 500Hz higher Q or 800Hz lower Q. The plan was to remove the switch after some tests, but I kind of like it. At extreme settings (ccw), 800Hz is too muffled and 500Hz is more useful. At subtle settings (cw, less mid-cut), the difference between the filters is subtle but still useful, 500Hz obviously cuts more bass and leaves the sound a bit more 'sparkly' while the 800Hz keeps more of the bass.

At extreme settings, it creates an airy sound, for 'acoustic-like' strumming. I typically use more subtle settings, that simply cleans up and tightens the tweed sound a little.

PS: I first saw this alternate form in Merlin Blencowe's preamp book, but also here: https://robrobinette.com/5e3_Modificati ... id_Control

5F1-AlternateBridgedT-MidControl.png