The Fog Lifter does exactly what it says it does, it gives your amp life
A few years ago, networking with other local MTS users LoD21 and MYDEMISE realized that the amps were reacting very differently with some of their favorite modules.
They would get a module sounding killer in one of their heads and then swap heads and it would sound noticeably different in the next head.
No matter how painstakingly precise modders try to be with their mods, there are always slight variations in tone from module to module. Part tolerances vary, tube types, tube age, etc... all make subtle differences from amp to amp, but the results they were getting we more drastic than that.
After exhausting every possibility - I won't go into them all, but TRUST me, no stone was left unturned! - LoD21 and MYDEMISE decided to take the chassis out and examine them for differences. Once apart it was noted that the values of caps and pots on the density boards were different. After much research LoD21 found out that the Lynchbox had a different presence/density board and after introducing the Lynchbox, they just started putting that boards in all the RM100s. The head that sounded the best had what the guys at Randall called the "old" density board. I'm guessing it was the first run of density boards that were closest to Bruce's original spec, but could be wrong. LoD21 got the last 2 Randall had, installed them and BAM the heads all sounded much more similar
A year later I bought a second NOS RM100H from Rob and had him inspect the density board before he shipped it to me. His findings were the same as ours, the values were matched to a Lynchbox, not our other RM100Hs. We got the values to Rob and he modded my density board and all was good
As always, Rob played around with things a little more and found ways to make an even bigger impact with the upgrade and the Fog Lifters were born!
I agree with what others have said and with the fact that you will hear the biggest impact in your higher gain tones. The difference is very apparent even with clean modules, but when you get a Snakebite, Ubersonic or serious high gain monster in there, watch out! It's like they're jumping out of the cab to attack you!
One word of advice that has served me well is to pick your favorite module that has the least low end and set your Fog Lifter to favor that module. Then pop in your modules that have more low end and reduce it accordingly. You get more uniform thump this way. Some of the modules have less low end by design and those are the ones that benefit the most from Fog Lifters
It's the best 40-45 bucks you're gonna spend on your amp, trust me!
Keep the Faith!
H