Amp mods part one

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okstrat

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Ok guys, who wants to tear into their MTS amps and do some mods?

First things first - do NOT do this if you don't have the knowledge to safely navigate the guts of an amp. You should at minimum be able to discharge your amp safely and be able to check to see if there is any voltage still present on the amp.

If you can't do the above, stop reading. Seriously. I don't want you to get hurt messing around in your amp. If you can't solder cleanly and neatly - same thing. I don't mean to be a jerk about this, but if you lack basic soldering skills, practice on something else before you goof up your amp. I and by extension, this message board, take ZERO responsibility if you goof up your amp or yourself by following info contained in this thread.

I'm not going to detail anything here that is amazingly hard, but if you lack basic skills ANY of this is going to be hard. We all have to learn somewhere, but your nice Randall amp is not a good place to begin. I'd recommend buying a really cheap piece of electronics at a thrift store and take it apart and practice soldering on it before you work on something cool like your Randall amp. :)

Ok, if you're still here... this is for an RM100.

Take your amp chassis out of the enclosure. flip it over. Look at the small circuit board behind the input jack. You'll see a circle with solder points all around it - this is the first tube your signal goes into. Look next to it and you'll see a big capacitor in brown (.1 uf on my amp, should be the same on yours.) This is a coupling capacitor, it behaves like C3 on our modules - it affects how much low end goes into the amp. It 'couples' gain stages of the amp to each other.

Any changes you make here will change the low end of ALL of your modules, so think carefully. You can either replace it, or... put a switch in. You'll need to drill the face of your amp underneath the channel switch, so think twice and drill once... you can either put a three way toggle that will give you three positions like a cap switch on a module, or go nuts and get a 5 or 6 way switch that is a rotary. It's a little tight in there, I'd recommend just a plain old 3way dpdt (double pole double throw) switch.

Typically you don't hear a change unless it's double, so you could set it up for .2, .047 and .1 to get stock and one step tighter and one step bassier. Or go .1, .022 and .047 to get stock and two tighter. If you have switches on your modules, you can use this to get the entire amp 'close' and then fine tune each module, as it will be different gain stages affected.

Pete
 
droptrd said:
Nice! Is this what the RM Kirk has in it?

Nope, his has power supply mods. I actually just bought a lynch RM100 with factory Kirk mods... haven't opened it up yet, should be interesting! :)
 
okstrat said:
Ok guys, who wants to tear into their MTS amps and do some mods?

First things first - do NOT do this if you don't have the knowledge to safely navigate the guts of an amp. You should at minimum be able to discharge your amp safely and be able to check to see if there is any voltage still present on the amp.

Discharging the amp consists of using a 1k resistor on the power supply caps? Is this correct. Then using the multimeter to check for any residual voltage across the power section?

If this looks correct is there a schematic that can be had to verufy the correct path of the PSCs?
 
im gonna check into this...

my main problem is the overall tightness of the amp........


ive read that the Egnater version Mod50/100s have a tighter more modern feel which is due to the different components used in the power section..

is that true?

i want to get rid of the spongy..i know they built the RMs to appeal to a wide varitey of players, but im just tryin to narrow it to my field..
 
TheHunter said:
okstrat said:
Ok guys, who wants to tear into their MTS amps and do some mods?

First things first - do NOT do this if you don't have the knowledge to safely navigate the guts of an amp. You should at minimum be able to discharge your amp safely and be able to check to see if there is any voltage still present on the amp.

Discharging the amp consists of using a 1k resistor on the power supply caps? Is this correct. Then using the multimeter to check for any residual voltage across the power section?

If this looks correct is there a schematic that can be had to verufy the correct path of the PSCs?

There are a lot of ways to discharge an amp, found on the internet. I really don't want to give step by step examples because you're dealing with potentially lethal voltages and I sure as heck don't want the liability. Look around on the net, you'll find lots of info.

Pete
 
paintkilz said:
im gonna check into this...

my main problem is the overall tightness of the amp........


ive read that the Egnater version Mod50/100s have a tighter more modern feel which is due to the different components used in the power section..

is that true?

i want to get rid of the spongy..i know they built the RMs to appeal to a wide varitey of players, but im just tryin to narrow it to my field..

The RM probably has some 'sag' built into it so some of the vintage modules work better, ya know?

Changing the first coupling cap value can tighten it up a bit, but will be different than messing with the power section. I might have some power section mods later, this one is fairly easy. There's quite a bit of wiring over the top of the power section on an RM100...

Pete
 
Thats awesome. My biggest complaint with my RM is the lack of low end. Im getting enough right now, but im cranking the hell out of the lows and res. Thanks for the info Pete.
okstrat said:
paintkilz said:
im gonna check into this...

my main problem is the overall tightness of the amp........


ive read that the Egnater version Mod50/100s have a tighter more modern feel which is due to the different components used in the power section..

is that true?

i want to get rid of the spongy..i know they built the RMs to appeal to a wide varitey of players, but im just tryin to narrow it to my field..

The RM probably has some 'sag' built into it so some of the vintage modules work better, ya know?

Changing the first coupling cap value can tighten it up a bit, but will be different than messing with the power section. I might have some power section mods later, this one is fairly easy. There's quite a bit of wiring over the top of the power section on an RM100...

Pete
 
is this mod more beneficial then just doing c3 on the module?, or would you be interested doing this if changing c3 on the module wouldn't give you enough tightness? my rm100 has plenty of bass for me and my modules are pretty tight in the low end just from changing c3's. my modern i went from a 47 to an 1.5 and it tightened right up and my grecto is a an 01 and i beleive my kh-3 is an 01 as well. they all seeem pretty tight.i don't use a whole lot of density maybe 9 o clock. seems like cool mod though thanks for sharing 8)
 
It's a different spot in the chain, so it's going to have a different effect on the tone than the module C3 mods.

If you don't want to commit to a switch/hole drilled on your amp, then go in and either halve or double the cap on the amp and see if it makes a useful difference for you. If not, then don't do it.

Pete

maximus1 said:
is this mod more beneficial then just doing c3 on the module?, or would you be interested doing this if changing c3 on the module wouldn't give you enough tightness? my rm100 has plenty of bass for me and my modules are pretty tight in the low end just from changing c3's. my modern i went from a 47 to an 1.5 and it tightened right up and my grecto is a an 01 and i beleive my kh-3 is an 01 as well. they all seeem pretty tight.i don't use a whole lot of density maybe 9 o clock. seems like cool mod though thanks for sharing 8)
 
have you been able to look over the KH power supply differences to see what might be done to change the low end on the RM yet?

im definitely lookin at doin the 3 way on the amp though..
 
paintkilz said:
have you been able to look over the KH power supply differences to see what might be done to change the low end on the RM yet?

im definitely lookin at doin the 3 way on the amp though..

haven't had a chance lately to scratch my *** lol... been crazy busy and waiting on parts so I can get a bunch of modules out the door. Should have a chance to do this hopefully in a week or two.

Pete
 
well would a OT swap help with the "sag" too...

thinkin OT change, and the 3 way C3 on the amp...

im lookin at VHT deliverance tight...if i can achieve it with the randall im happy, as i like the saturation alot more with it
 
paintkilz said:
well would a OT swap help with the "sag" too...

thinkin OT change, and the 3 way C3 on the amp...

im lookin at VHT deliverance tight...if i can achieve it with the randall im happy, as i like the saturation alot more with it

There are also some tricks in the power supply you can do - not sure if the KH is doing it or not... I'll have some interesting stuff soon, I promise. :)

Pete
 
will this mod get some of the stiffness out of the amp and make it more saturated or gainy sounding?, at low volumes my amp sounds stiff and kinda weak gainwise but cranked up a bit it's alot gainier than it you would have expected. i know that a 100 watt amp has to be cranked to sound right but i was wondering if maybe i had too much bass to start with like the value of the cap on the chassis maybe being too high. do you know what i'm trying to say :wink:

I don't think the amp is that stiff, personally... but changing that cap to a larger value will be something like a C3 swap on a module. Actually, the more bass you have in a module (with a larger say, C3 cap) the MORE gain you have too. It's like a funnel - the larger C3 values are wider mouthed, the smaller ones are more constrictive.

Might want to try changing the value of that cap on the amp to double or half and NOT use a switch - see if it makes a noticeable difference.

Only bad thing about drilling a hole in an amp is that it's not something you can go back on once you do it.

Pete
 
Uhm, my response is the last half of Maximus' note above. I think it's time to backup the database! lol
 
guess i'll just have to try, its really only stiff at low volumes, which isn't really an accurate portrayal of the amp anyway. i can't believe some people say they are not getting enough bass out of it though. :shock:
 
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