Looking for the dookie mod

[J M Fahey]

Just checked those fuzzy schematics: the Dokie Mod *basically* converts a standard Plexi into a rough JCM800 Master Volume.
Compare both schematics side by side and youŽll see.
And I gess part of the sound comes from using them full blast; at low levels JCM800 tend to be fizzy, but youŽll never notice that full blast.

If you already heve a regular JCM800, just play with it.

May be mistaken, but in general used JCM800, being more abbu8ndant, are way cheaper than similar Plexis.

[John G]

Is this better ??
John

[nosaj]

The thread name make me think someone wanted a mod to sound like crap.

nosaj

[J M Fahey]

[ATTACH=CONFIG]42895[/ATTACH][ATTACH=CONFIG]42896[/ATTACH]Is this better ??
John

Yes, thanks.
Put it side by side with a JCM800 and compare, in fact itŽs probably what was originally done to old Plexis to increase gain: on a regular series made Plexi they wired one of the input channels in series with the other, instead of in parallel, basically adding a clean 50X gain stage in the signal path.
So they disconnected a pair of inputs, connected the output of the one they left to the input grid of the other, let it drive the unmolested tone stack driver, and connected the second volume control *after* the tone stack as a Master volume.

That exact same configuration was somewhat polished, gain of the second stage was reduced and signature changed by cold biasing, and it became the JCM800.

But today you donŽt need to buy an expensive early Plexi and mod it, many suggest just playing with a cheaper JCM800 (as good as the other, but itŽs more abbundant on the market because itŽs newer and tons were made and sold in the 80Žs), you simply equalize it a little darker or to be more precise, with somewhat more mids, and of course play it with Master on 10, or you slightly mod it "backwards" into the crude original version which is what the Dokie mod is.

I remember there was an intermediate version, before the JCM800, called simply the "Master Volume" and even earlier, reember reading English Magazines (yes, I am that old) about "an amp Marshall had modded for Ritchie Blackmore which gave him more predictable sustain" which must have been something like this , and even earlier (I know, I know, I belong in a retirement home by now) remember reading that "Ritchie Blackmore had trouble in some venues because he did not have enough sustain so now he plugged into a miraculous box which gave him all he wanted" which of course was the Germanium powered Dallas Booster ... also the secret behind early Eric Clapton .... you donŽt believe a plain guitar (pre Di Marzio and high power pickups) plugged straight into an old Marshall had so much sustain unaided, do you?
Even less a plain Strat !!!!!!!
Jimi Hendrix of course used a Fuzz pedal, but the others did not,yet all had unbelievable sustain.

You could add a clean boost box between guitar and unmolested Marshall and achieve the same sound as Green Day, since the first extra stage is also clean, distortion appears later in the chain..

[Mr. Bill]

I actually know a little bit about this amp. It's one of my favorite Marshall tones I've heard. The amp is a 1959 SPL reissue modded by Martin Golub at LA Sound Design. At it's essence, it's basically just modded to 2203 specs with the cascaded gain stages and an FX loop added. I've seen a couple gut shots of people who claim to have had the mod done, and they're different from each other. I'm sure Martin mods them by ear, so no two will be exactly the same component wise. The schematics posted online are "best guesses" from others who have seen pictures of the inside of a version of the mod.

A cascaded SPL will get you in the neighborhood.

[spy]

I'm resurrecting the thread as I'm into Dookie mod these days and these schematics are the cleanest I found. Is this an orange drop .001u coupling cap between V1a and Gain pot? Isn't this too low?

Also, I think 220K at the grid (input) of V2a has to be before the 470K for an appropriate voltage divider, or not?

[Leo_Gnardo]

I'm resurrecting the thread as I'm into Dookie mod these days and these schematics are the cleanest I found. Is this an orange drop .001u coupling cap between V1a and Gain pot? Isn't this too low?

When cascading gain stages for an overdrive effect, it's good practice to limit the low end response in the first stage. Too much bass and the tone gets bogged down badly. Yes in an ordinary amp 0.001 uF would make for a thin weedy tone.

I've found similar necessity in guitar tone to drive fuzz boxes & overdrive preamps. My main test guitar has two single coils, a typical selector switch: bridge / both / neck. There's also a polarity toggle. With the selector in the "both" position, if I flip a pickup into reverse polarity, the guitar tone gets very thin, nothing anybody would want to hear. BUT if I use that "out of phase" setting to drive a fuzz, overdrive box, or amp with cascaded gain stages, then I get a terrific tone - clear without flubby excessive bass getting in the way.

[tedmich]

The thread name make me think someone wanted a mod to sound like crap.

nosaj

Have you heard Green Day?
Seriously though its an exceedingly tall order to think you can approximate a modern "album tone" with a simple amp mod or a pedal.

The closest you can come is to approximate a bands live tone but even that is a highly processed affair nowadays.

[spy]

I'll try that .001 but I think I'll stick with something larger like .01

So true tedmich!

Adding, though, a stage is a pretty nice mod if you need more gain.