$$$$ Review on Universal Gain Adjusters. $$$$
In short, I see people asking advice on universal gain controls, and I've owned a bunch. I'm not affiliated with any product listed nor do I claim to be a scholar or think I write as such.
I used a SainSmart DSO-201v1 to do the distortion testing coupled with a voltage meter for testing of linearity.
Pros and Cons of each:
1) Pac LC-1
Pros+
a) Feels very sturdy/well built
b) Very steady while turning with good resistance
Cons-
a) RCA's come disconnected easily from board
b) Extremely Non-linear. Touchy at first while barely any adjustment after halfway.
c) Introduced a great deal of distortion to the signal compared to the others
2) MT Audio/CT Sounds
Pros+
a) Built in Voltage Meter that is adustable for accuracy
b) Feels Sturdy
c) Push knob for amp on/off
Cons-
a) NOT Sturdy, broke in a week (meter broke, still usable for gain)
b) EXPENSIVE
c) Most Distortion
d) Most Non-Linear
3) NVX XBRC
Pros+
a) Linear
b) Cheapest
c) No Distortion
Cons-
a) Feels like its the cheapest
b) Weird mount that it slides on (actually broke it during initial install
c) All others had removable knobs, not this one
d) Turns TOO easily, even when barely brushing with leg hand.
4) EFC RLC by Scosche
Pros+
a) Only one tested that had a "knotch" at dead center
you could feel while turning to give you some non-visual aid.
b) Extremely Linear with ZERO distortion introduced
c) Only one that hasn't broken (6+ months and ticking)
Cons-
a) RCA's not labeled input and output (seriously? how easy is that?)
b) RCA's seem slightly smaller and have lost connection without being taped
THE WINNER IS:
For my money I would buy the EFX RLC all day and twice on Sunday. Durable, linear, no distortion, notch halfway, SOLD! NVX seems ok while fragile. I've only had it a little over a week, so we'll see.
You can take my advice or not, but at least be respectful as to not disuade others from sharing their reviews int the future.
I am not making a dime regardless, just decided to try to give back to the community from which I have learned so much. I started to show the whole "Taylor Fade" style, but that is such a pain in the butt! Big ups and props to him for doing what he does because I could not imagine the work associated with it.
Hope this helps somebody somewhere sometime. Thanks
**Update August 21, 2015***
Apparently in the year that I have owned the Scosche EFX, they have started to label the input and output on the outside. So I will be removing that con from their review. Could have been the manufacturers that accidentally left it off or maybe they just listen to their customers. Either way, cudos for the fix!***
****Removed the NVX knob after a week, TOO SENSITIVE TO ADJUSTMENT. Could actually be dangerous if you have children DO NOT USE, HIGHLY DISAPPOINTED IN NVX for this crap. Distortion and nonlinearity I can live with, but please don't set me up to make my kid deaf. Ac stiff fart will make it turn up to 85%!!!***