Contour/cut control - useless?

[mr_hankey]

I’ve been using and tweaking a Two-Rock style contour setup on my #102-ish build for a long time and I’ve been unsuccessful enough that I’m starting to wonder whether the concept itself is flawed rather than just my implementation of it.

To me it sounds good on paper - instead of using a presence control (which in my experience is largely set-and-forget, permanently on 7 on my 6G6-B Bassman) you take the control off the panel and hardwire it and add a tone control across the PI plates, giving an option to control treble after the preamp. See John Mayer schematic below. You may also know it as the Vox cut control.

As you might imagine, the amp becomes unpleasantly bright and peaky with the presence stuck on 10 so you turn the contour down to compensate. The issue is that the contour takes an overly wide chunk out of the high end before it can soften the specific frequencies that get overemphasised by the presence.

I’ve tried different cap and pot values and as well as presence cap values (which was more fruitful than tweaking the contour itself) and ended up discovering that putting an adjustable resistor in series with the presence cap is what’s needed to target the correct segment of the high end. Yes, in the end I arrived back at a fully traditional presence control and made the contour control redundant.

Has anyone else experimented with this and have you found a way to make it worth having on the front panel?

The best solution I can think of is to combine it with an internal presence trimmer but by that point you’re really only doing it for the sake of being able to put a contour control on the panel and not because it’s actually more usable.

[rdavy]

Is it possible you have the pot wired backwards, considering it is an audio taper pot?

[katopan]

I originally put in a Vox style Cut Control on my Marshall 18 Watt style build. Very different amp to yours but I also found it to be pretty useless. Not much later it was ripped out and the front panel hole used for a VVR pot.

[Roe]

I originally put in a Vox style Cut Control on my Marshall 18 Watt style build. Very different amp to yours but I also found it to be pretty useless. Not much later it was ripped out and the front panel hole used for a VVR pot.

I like a noload pot to keep the vox cut control out of circuit since it loads the phase inverter slightly (you can hear the difference). I mostly keep it disconneced but sometimes it is good to have if the setup sounds overly bright in one application (e.g., telecaster at low volume). It is better to remove treble late in the circuit than at the start (e.g., guitar tone control) if you want to keep overtones, harmonics, and detail

[Colossal]

I originally put in a Vox style Cut Control on my Marshall 18 Watt style build. Very different amp to yours but I also found it to be pretty useless. Not much later it was ripped out and the front panel hole used for a VVR pot.

I found the exact same thing in the 18W (Lite IIb) amp. It needed nothing more than Volume and Tone.

[mr_hankey]

I like a noload pot to keep the vox cut control out of circuit since it loads the phase inverter slightly (you can hear the difference). I mostly keep it disconneced but sometimes it is good to have if the setup sounds overly bright in one application (e.g., telecaster at low volume). It is better to remove treble late in the circuit than at the start (e.g., guitar tone control) if you want to keep overtones, harmonics, and detail

'Useless' might be wrong word because I agree with all of that in theory (I had mine on a push-pull pot to take it out of circuit) but it certainly didn't keep the overtones and detail - it chopped all of it off. The logical step was to try a smaller cap but that sounded even worse IMO.

[Roe]

I like a noload pot to keep the vox cut control out of circuit since it loads the phase inverter slightly (you can hear the difference). I mostly keep it disconneced but sometimes it is good to have if the setup sounds overly bright in one application (e.g., telecaster at low volume). It is better to remove treble late in the circuit than at the start (e.g., guitar tone control) if you want to keep overtones, harmonics, and detail

'Useless' might be wrong word because I agree with all of that in theory (I had mine on a push-pull pot to take it out of circuit) but it certainly didn't keep the overtones and detail - it chopped all of it off. The logical step was to try a smaller cap but that sounded even worse IMO.

tweaking the values does help a bit here. I reduced the cap a little but do not remember the exact value

[FUCHSAUDIO]

A cut control (especially in an amp with negative feedback), isn't really a great idea.