dual linear potentiometer for adjusting feedback

I've seen topics on this forum discussing adjusting feedback resistors, including suggestion of reducing resistors ( 7 & 8 values) and running in series with a pot. Has anyone done this with a ST-120 and/or any specific recommendation - manufacturer and value? I'd expect one would want to use a very high quality pot for the application.

Thanks in advance

any particular reason why you are considering such a mod on the ST120?
The ST120 is pretty much as good as it gets.

If I'm reading this right ...

There was a dual pot mod you could use on older VTA boards to balance the AC, but the newer VTA boards have Constant Current Source (CCS)  which is adaptive and performs this function automatically under normal operation. It also has the mystery R39 for tailoring the board to a specific tube set if required ...

Seems to me you'd be better served just upgrading the VTA board to the CCS version?

How old is your ST120? This feature was added a couple years ago. Look for the two transistors between the tube sockets ...

Thanks for everyone's comments, and why is a fair question.

While my current speakers do not incorporate a HF compression horn, I'm leaning that way for my next build (and using my ST120 for the mid and high frequency sections, so not too concerned about affects on bottom end), and I've read that slight adjustments to feedback can make subtle enhancements to sound of a horn (not looking to remove all NFB). Similar are comments of people positively comparing their horns when moving from solid state amps to tubes.

Before my ST-120 I was using a small adjustable tube buffer pre- my solid state amp and found- subjectively of course, an improvement in sound.

Then I saw this Hafler HA75 Tube head amp with adjustable negative feedback;
http://audioxpress.com/article/Hafler-HA75-Tube-Head-Headphone-Amplifier.html
and got me to post this inquiry.

If I could only leave well enough alone- but that's 1/2 the fun of this.
Andy