• Welcome to ADA Depot - A Forum To Support Users of ADA Amplification Gear.


Lets get Technical > All Things Tube All about preamp and power amp Tubes.

Main Menu

mod 4 questions

Started by fart boy, March 25, 2016, 05:00:34 PM

Previous topic - Next topic

fart boy

Hi guys, new here, great place. So i want to get an mp1 and do mod 4 to it.
I have a basic understanding of schematics and tube preamp circuits,
but im having trouble understanding the first coupling section and the clean ch
in general.

1. What is the purpose of the -15v feed to the cathodes of the first two stages?
     To increase volume of the od chs? Mod 4 calls for its removal.

2. What is the signal path of the clean ch? Cathode to cathode, out of the plate
     to the other two stages, 4 stages total?

Basically I want to fatten it up and make it a tad bit more harmonic edgey saturated.
.022 coupling caps throughout, lower 1st two cathode resistors, higher 1st two cathode
bypass caps, the Marshall value 3rd cathode 10k, and maybe some 470/470 1st and 3rd.
I want to stick with that and use a switchable boost to tighten. Then if I want more, I'll do the
100p low passes, and the Soldano 3rd plate snubber, and the 3.666 od pot repositioing.

What I dont want is to dirty up the clean. Will I?


Hey FB, welcome  :wave: , I'm not across the Mod 4 but others here will be able to sort you out  :thumb-up: . One comment though is my mate MikeB decided to just do the noise mod and replace the tube board (keeping it stock but new) as he didn't want to loose (dirty up) the clean.  He'll also do the MDRT as that's a very worthwhile upgrade regardless.
Basically any mod that adds a 3rd tube (3TM) will dirty the clean, hence MJMP uses MP1 3TM for dirty sounds and MP2 for his cleans.
Studio Rig: Stuff; Live Rig: More Stuff; Guitars: A few

fart boy

Cool, thanks 4 the reply. So it seems like if i do dirty up the cleans, it wont be
too much to where i cant turn down the clean ch gain enough. Ive heard yputube
videos on the 3.666 clean and those seem fine, but ive not come across any mod
4 videos except only on dirty with a vol prob.


Well since the clean and distortion channel are on the tubeboard changing something will have an effect on both voicings.As you can see on the first stage are 2 fet's which switch in and out the 2 33µF caps.Also Fet Q5 will switch in and out when you change from clean to distortion.