Benefit of dual ganged gain pot controlling 2 gain stages?

[adew]

Earlier this year I built an Orange-Marshall mashup, marrying an OR-15 preamp with JCM800 style PI and power section. Took a bit of effort to make it work, but it sounds great and I’m happy with the end result.

One feature of the OR-15 preamp (Dark Terror and Rockerverb, too) is the use of a dual ganged gain pot, one side between V1a and b, the other between V2a and b triodes. I replicated this in my build but didn’t give it much thought at the time, which brings me to my question.

What is the benefit of this arrangement? Why not a single gain between V1a and b only, as is typical in so many designs?

Thanks in advance for any insights!

[pdf64]

For the same degree of max gain / overdrive, I suppose it could be used to facilitate a better user interface, cleaner settings less of a hair trigger.

[JD0x0]

Yeah, what PDF said. I think it helps give a smoother gain roll up, in certain circuits.
There's some higher gain circuits, where you'll notice you can dial in a clean sound at the lowest settings, but it feels like a 'hair trigger' as PDF64 described, where it immediately jumps out of clean territory into full grit when you turn the dial up. A dual ganged setup can help smooth out that transition, without losing gain at max settings in the way a fixed voltage divider would do.

[xtian]

Agree. I built a Tiny Terror: https://ampgarage.com/forum/viewtopic.php?t=28411

And I found the Volume control to be very pleasing and smooth.

[brewdude]

That seems counter intuitive to me... seems as if turning up two volumes at the same time would increase twice as fast.

I always wondered if it would be useful to have a dual gang pot wired such that one gain would go up while the other goes down... it probably would be more of a voice or texture (pre/post blend?) control—probably be difficult to balance well

[roberto]

I've done it, you need linear pots with resistors in series, but of course the volume changes so it is a texture and not a gain per se.

[martin manning]

I always wondered if it would be useful to have a dual gang pot wired such that one gain would go up while the other goes down... it probably would be more of a voice or texture (pre/post blend?) control—probably be difficult to balance well🤔

That has been done in FX loops for a wet/dry balance control.

[adew]

Thanks for the replies everyone. After posting my question I started to think more about this and came to the same conclusion, ie that it allows smoother control over low gain settings. I also wondered whether it helps to get a clean (ish) tone that would otherwise be difficult to achieve in a single high gain channel.
What I can say with certainty, echoing xtian's comment, is that the gain control is very smooth below mid-way on the dial.

[pdf64]

I think it might also help to improve the signal to noise ratio for low / clean settings, ie compared to a single control, with the second potential divider being fixed at a high level necessary for the lottsa overdrive capability.