The RICH Mod: 2 Questions and a Story

(The mod seems to be a popular topic around here lately, but this is entirely coincidental )

The story first; As some of you will know, ages ago I installed the RICH master in my 2204 (late 70s pcb) 50w Marshall. RICH showed me first how to set it up as a 1987 early 70s steelface, then jump the channels together, then stick the master in, so it was a three-part process.

So, I thought, well, nobody uses the second channel, cos it sounds like shit, right? So, very cleverly I decided that if the first channel is so good, why not duplicate it in the second channel? Have like a double-first channel, if one is so good, double it!

So, I duplicated the cap and resistor setup of Ch 1 going into the first valve, I stripped out the 320uF cap and the 2.7k resistor and replaced them with .68uF cap and 820ohm resistor.

All this time I've been complaining about too much treble. All this F*cking time... I couldn't dial it out, the damn amp was trebly even with the presence and the treble off! I just never made the connection...

Then yesterday I read something on the web about how amps work, and how the higher the value of a cap the more bass frequencies it allows through with the high frequencies. HELLO? MCFLY? HELLO?

So tonight I changed the .68 cap back to a 330uF. Then I plugged in to test it.

It's after midnight here, I've been playing for an hour, I couldn't put the f*ckin Goldtop down, what a revelation! One, what a great sound! Two, what kind of asshole am I?! The neighbours are going to be complaining, but it'll be worth it

Lesson? Next time someone who knows what they're talking about shows me how to do something, I'll Listen, then do it *their* way!

So, two questions:

1. I haven't got a 2.7k resistor in the house to replace the 820ohm still in Ch2. Can anyone tell me if this is a big deal?

2. RICH, I remember reading a post from you to NOCD about the mods to your 50w, you removed all the 68k resistors going into the first preamp valve. What's that all about, what does that do?

Cool, Sean! And F**K your neighbors. I had my rack full throttle at 3:30am last week (280W total), and only the dog knew the doorbell was ringing.... It was the neighbor....

I have an 86 2203, what is this majical mod all about? I'm curious, cause I saw a jcm800 mod kit at torres electronics, but it looked rather expensive for an amp that already sounds good. But more is better, which is why I bought my Boogie rack. Tell me about this rich thing. And tell me again about the rabbits, george......

It's a master volume that allows you to drive the hole off your preamp (all three valves) to get as much gain as exists in the amp, at low volumes, see the FAQ page for the instructions.

The 2203 is a 100w MV, right? Mine had the factory master as well, and as you know they're shit. BUT, your amp has two channels, so it can be converted. This master is the dog's bollocks.

Snags, you try that shit over here and you go to jail

From the factory Channel 1 has the 2.7 K resistor and the .68uf cap, and channel 2 has the 820 resistor and the 320uf cap. I usually run both resistors at 820 because you get a little more gain, but its that cap that will really change the sound, so running an 820 resistor in both spots isn't going to hurt, plus the 100 watt reissues are like that anyway. Some of my heads are wired like yours, where I wired both sides of the tube the same way, but it depends on if the head needs it, or what speakers its getting plugged into. There is another pair of caps coming off of the first tube, channel 1 has a .0022uf, and channel 2 has a .022uf. I usually leave it this way, because replacing the .022 for another .0022 may be too much of a good thing. The other thing is just how much of channel 2 you have into the mix, too much will make it too muddy, or maybe even trebly/buzzy with the 2 sides of the tube wired the same, so you need to watch how much of channel 2 your putting into the mix.

As far as the 68K resistors go, I read somewhere that they were used to isolate one guitar's pickup signal from another should 2 guitars be plugged into the head at the same time. YEAH RIGHT, make sure you wear the patented homo harness with that one. Who the F**k operates on the homo plan and plugs their buddy into THEIR amp in this day an age is beyond me, so I removed them, because that sticks my pickup signal directly into the first tube without the tone sucking "homo" resistors stealing my signal. Jump a wire across each one and you're done if you want to try it, it works real good.

What, lose the 68k resistors and I get MORE gain??! Seriously? I wanna do it now, at 01.45 in the morning

F*ck, how many pints do I owe you at this stage?

Its weird, you kinda get more gain, but better note definition. I like it that way, it F**king rips! I do some other crazy stuff too, but lets go 1 step at a time.:lolspin

You may find yourself using even less of channel 2 if you do this, so you may have to adjust your channel 2 signal.

Sean, the woman that rang my bell is the one who leaves her dalmation (that barks nonstop) in her back yard when she goes out in the evenings. I don't go to jail, and the f**king dog doesn't either. I have an understanding with my neighbor.

Thanks man, I'll get back to you, I better get some sleep, we have a "team-building exercise" day in work tomorrow till about 10 o'clock tomorrow night, f*ckin great. Talk to you in two days

I rewired my reissue so that both chanels run the 820 and .68 caps, and had to put the .0022 in place of the .022 on the other channel. I also remopved all the 68K resistors on BOTH tubes. I think maybe i should just put a couple back.

My Marshall JCM 800 is a 100w Mv single channel with hi-lo inputs. Actually its one of the best sounding Marshalls stock I've heard. Its not overly bright, and has nice gain and grind. I was just hoping to get more out of it. More is always better, isn't it? Any help would be appriciated! The model # is hard to read, its either 7203, or 2203....pretty scribbley writing.

I don't know how much difference this makes over taking it out altogether, but I've bypassed that 68k resistor that hooks upto the ECC83's grids with a 330pF cap (courtesy of Trace Allen over at Ampage)

Take the 470pF bright cap off the gain pot as well - not needed in this amp IMO.

There's some other things that are nice in this amp too like putting a 0.68uF cap across the 820ohm cathode resistor on the second ECC83.

Changing the 10k cathode resistor on the first ECC83 to 4k7 also helped things out.

I changed the 33k slope resistor to 47k too, but I might change that back.

Use screened cable on the grids to cut down on the noise too - quick and easy to do and your amp will love you for it :smokin

:!

Ed! Try sticking one of those blue 100v 330uF caps you sent me in Ch2, instead of the .68uF you put in there. It's probably a function of the individual amp, but it deffo made a big difference in mine Looking fwd to playing it some more tomorrow....

Ian, thanks for the extra ideas, it's all grist to the mill...

Sean, I think i sent you all I had. I guess I'll have to go get more huh?

Hey, I've got one left if you want it?

Can't find the Rich mod in the FAQ's.
Where is it??

No thanks, Sean, I can just walk across the street and get some more where yours came from.
They don;t have everything but they have a lot of NOS '70s and '80s stuff.

You actually sent me two types, the other is a Sprague 330uF 60v, so I went with the higher voltage. I've no idea if the voltage part is relevant or not.

I think the preamp still deals with low voltages, but you were smart to go with the higher volts.
I'm happy with it for now, Sean. Things might change when RICH gets his hands on it again in October.