Ever done this to the SWTC design .... Mid scoop ?

[Derringer]

I'm most likely re-inventing someone else's wheel here but in trying to retain some highs while reducing some mids and giving the low end some more mush .... this idea came to me.


Why not just run a really low value cap from lug 1 to 3 so that those highs stay put?



I originally was using a 20K pot but it seemed to pull the mids out too much for me ... more metal sounding than I wanted.


I have it at the tail end of a Tonebender MKII style circuit now, directly off the collecter of Q3, with the tone-pot lug 1 going to the output cap, then to the level-pot.

In the middle of the pot's swing the mid-scoop is most noticeable. At the far ends the scoop effect tapers. This effect was even more dramatic with the larger tone-pot. I'm assuming that this is because at the far ends of the pot's swing, the effect of one capacitor overtakes the other.

I like it better than the fixed t-notch designs I was playing with before ... and I suppose it is just a quicker/dirtier variation of those designs.

[Dragonfly]

Really cool idea...i'll have to check it out and see exactly what its doing. Seems like a different way of getting a tone control that responds similarly to the Shin-Ei FY-2 (with scoop mod)

you might look at Jacks mods for more ideas...  http://www.muzique.com/lab/swtc.htm

[Rob Strand]

> I'm most likely re-inventing someone else's wheel here but in trying to retain some highs while reducing some mids and giving the low end some more mush

I believe it cuts the highs and the mids notch is slightly less of a notch.    Absolutely valid form of EQ and works fine.   As I recall the EBS amplifiers (whatever Marcus Miller started to promote after he went away from SWR) use a similar frequency response however that may have used a more fender stack type of circuit to achieve it.

The more traditional way to reduce the notch depth alone, ie. leaving the low/high balance alone, is to add a resistor in series with the bottom cap.

Another other way to mod the circuit is to add a resistor in parallel with the bottom cap, that effectively cuts the bass (ie. boost  highs)

You can of course combine the two idea.

These circuits are quite close to Fender/Marshall EQ stacks.  The input series resistor mod is like the high-end drop you get when you connect a F/M stack to the plate output compare to that of a cathode follower output.

[Derringer]

Cool.

Thanks for the info Rob!


Dragonfly: Oh yeah, I've been ALL up and down Jack's SWTC page! Thanks!

[Mark Hammer]

Great idea.  Like any type of passive tone control, its success depends on the marriage of context and control.  I.E., there will be situations where it is exactly what the doctor ordered and others where builders will say "I tried it, but it didn't really seem to add very much".

Fair enough.  Still, a good idea.

Note that if one used a dual-ganged pot, you could use one section for the "lower half", as shown in the diagram, and use the other section as a variable resistance in series with the treble bypass cap.

Alternatively, you could have two treble bypass caps of different values, wire up the second pot section so that each outside lug goes to a different bypass cap, and the wiper of the second section is tied to the "output".  This would adjust between two types/depths of treble bypass, at the same time as provide a different location for any midscoop.  It'd require a bit of tinkering, and I can't imagine it would provide any "orderly" tonal change that corresponds to our normal thinking about tone-shaping, but it would certainly yield different tonal "characters" at each point in the knob rotation.

[earthtonesaudio]

I tried this once and didn't like how the scoop was only at the middle of rotation, so I put a resistor in series with the right side of the pot.  That helps. 
Also if you put a variable resistor in series with the cap on top, you have a separate presence/treble control.  You could label them "mid" and "treble."

[Derringer]

Great idea.  Like any type of passive tone control, its success depends on the marriage of context and control.  I.E., there will be situations where it is exactly what the doctor ordered and others where builders will say "I tried it, but it didn't really seem to add very much".

Fair enough.  Still, a good idea.

Note that if one used a dual-ganged pot, you could use one section for the "lower half", as shown in the diagram, and use the other section as a variable resistance in series with the treble bypass cap.

Alternatively, you could have two treble bypass caps of different values, wire up the second pot section so that each outside lug goes to a different bypass cap, and the wiper of the second section is tied to the "output".  This would adjust between two types/depths of treble bypass, at the same time as provide a different location for any midscoop.  It'd require a bit of tinkering, and I can't imagine it would provide any "orderly" tonal change that corresponds to our normal thinking about tone-shaping, but it would certainly yield different tonal "characters" at each point in the knob rotation.

Right on ... thanks for the ideas!

and you mentioned I can't imagine it would provide any "orderly" tonal change that corresponds to our normal thinking about tone-shaping, but it would certainly yield different tonal "characters" at each point in the knob rotation. ... which I think is spot on because I would totally describe this tone function as character adjustment.


and earthtonesaudio ... also .... thanks for the ideas!