RM 20 mods

[okstrat]

So I have two RM20s and decided to mod one. Basically upgraded the signal path with better caps, changed some resistors, etc. Heck, even put a pair of blue LEDs in there.

Gave the amp an extended high end and to my ears a little more natural response. Pretty cool, I run the presence about 2 notches less than I did before, and the amp has more 'air' - high end that you don't really notice unless it's gone. I know that sounds weird, but it's like upper harmonics that are very subtle and don't grate on your ears - no ice pick here.

Next is to mod one of my spare RM100s

Pete

 

[derker]

Interesting! Could we get any more info, or is this some top secret stuff? 8)

 

[okstrat]

Interesting! Could we get any more info, or is this some top secret stuff? 8)

I'm a little hesitant to go into a whole lot of "step by step" detail because there are lethal voltages in your amp and you WILL lose your warranty doing this... but the basic idea is to replace caps and resistors in the signal path. I used the same values, didn't really 'mod' it other than replacing parts for same value, just parts I like to use. One good/bad thing is that it really extends the high end - if you think your Randall amp is on the dark side, this certainly brightens it up. But if you use your same old settings, it can get too bright/grating really fast. I like having a little bit of room on controls though instead of having them closer to max personally, but it's all a matter of taste.

Way I figure it is, if you can't tell what the signal path is on the amp, you probably don't have a whole lot of business messing around under the hood because of the voltages. There is a potential for getting zapped even from the preamp modules since there are power capacitors on it, but nothing like the full amp. Take it from someone who has been zapped - it's not fun. I've seen people on boards put instructions on how to do things and have them not followed correctly - in the case of tube amps, this literally can hurt or kill you. Not something I want to be responsible for.

Pete

 

[KillTone]

Pete - this is great news. Your module upgrades are awesome and help with the "darkness" but your new experiment sounds like the answer. Please let me know when you are ready to do this to RM100's.

I think you will have more work than you can handle.

Ron

 

[JKD]

The RM100s are desperately in need of something like this IMO...the RM20 not as much, as I think the EL84s help a lot..but even they are 'dark' .. major props Pete

I hear what you mean about 'air' though...sometimes you mess with Treble and Presence and you get 'hair' rather than 'air'...the first one being harsher, unwanted frequencies...the second one adding nice harmonics.

I still wanna hear what an OT swap does for the RM100 too...

 

[riff man]

the guy i bought my RM4 from is a very notable amp tech!! he told me he had done some sort of mod like this to my RM 4!!!

it's the GOOD STUFF!!

 

[derker]

Pete

Hey Pete, I appreciate the words of wisdom about doing amp mods. I'm well aware of the lethal voltages that hang around even after the power has been cut, which has kept me from trying anything silly to date. I was just curious whether you did any 'serious' mods; i.e. trying new component values, putting in a flux capacitor, etc. But that's really cool that you found improved the tone of the amp itself, just by changing the quality of the components and not the values. Just goes to show that there really is a difference.

Have you gotten a chance to compare Randall vs Egnater as far as the heads go? I feel like that might be the main difference between the two; the schematics are probably very close, with Bruce's "real thing" edging out because of the superior components, and possibly a tighter QC.