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by dehughes
Tue Nov 07, 2017 7:41 pm
Forum: Technical Discussion
Topic: Two different types of plate caps in use?
Replies: 13
Views: 1604

Re: Two different types of plate caps in use?

Removed them...don't notice much difference either way. Leaving them out as less is more, IMHO. :)
by dehughes
Mon Nov 06, 2017 6:15 pm
Forum: Technical Discussion
Topic: Two different types of plate caps in use?
Replies: 13
Views: 1604

Re: Two different types of plate caps in use?

Whenever I used a 0.1uF capacitor in parallel with the filter capacitor it was because V1 was like 35cm from the filter cap. The 0.1uF capacitor was not physically located right next to the filter capacitor as it was shown on the schematic. The 0.1uF capacitor was physically located at the V1 end o...
by dehughes
Wed Nov 01, 2017 8:19 pm
Forum: Technical Discussion
Topic: Two different types of plate caps in use?
Replies: 13
Views: 1604

Re: Two different types of plate caps in use?

Stevem wrote: Wed Nov 01, 2017 6:38 pm I was gonna say, my God 10 uf ciramic s must be huge and act like a Microphone all on there own!
Fixed, to avoid future confusion.
by dehughes
Wed Nov 01, 2017 5:00 pm
Forum: Technical Discussion
Topic: Two different types of plate caps in use?
Replies: 13
Views: 1604

Re: Two different types of plate caps in use?

Pull 'em out. See what you think. Put 'em back in. That should satisfy your tinker mode for a while. :mrgreen: OH BELIEVE ME, I want to, but the older, wiser part of me says to ask here as you guys know more and can likely save me some effort. (However, if no replies by noon PST today, then there's...
by dehughes
Wed Nov 01, 2017 3:58 pm
Forum: Technical Discussion
Topic: Two different types of plate caps in use?
Replies: 13
Views: 1604

Re: Two different types of plate caps in use?

I don't think this is going to effect"Tone and Feel" as you say.... it's more about avoiding un-wanted noise artifacts, oscillations... etc. things that pop up in a high gain amp.... TT Oh cool. Thanks. I notice such caps are not used in "classic" Marshall-type circuits. Would removing these caps m...
by dehughes
Wed Nov 01, 2017 3:09 pm
Forum: Technical Discussion
Topic: Two different types of plate caps in use?
Replies: 13
Views: 1604

Re: Two different types of plate caps in use?

I see a 10nF in parallel with a regular 10µF electrolytic. The small cap is used because it reacts better for fast transients so it's more efficient at filtering fast noise spikes. Ah, sorry, thought that was "uf"...thanks. So how is this "better", or, how does this setup express itself in tone and...
by dehughes
Wed Nov 01, 2017 3:49 am
Forum: Technical Discussion
Topic: Two different types of plate caps in use?
Replies: 13
Views: 1604

Two different types of plate caps in use?

Hi all, On my Marshall JCM 2000 DSL 50, in parallel with the electrolytics on the 12AX7 plates I see they have ceramic caps of the same value. That is, the plates have both a 10uf electrolytic as well as a 10nf ceramic cap wired in. Never seen this before. What is the purpose of this? Thanks in adva...
by dehughes
Wed Sep 13, 2017 3:37 am
Forum: Marshall Discussion
Topic: Marshall JCM 2000 DSL 50 mods
Replies: 19
Views: 6313

Re: Marshall JCM 2000 DSL 50 mods

I figured it out! The Red Channel is MUCH better now...prefer it over the Joey Mods by far. Lemme figure out how to post a PDF and I'll share. Key was removing components just as much as it was changing the value of others....less is more. Only thing left is to increase the value of one of the volta...
by dehughes
Wed Sep 06, 2017 6:27 pm
Forum: Marshall Discussion
Topic: Marshall JCM 2000 DSL 50 mods
Replies: 19
Views: 6313

Re: Marshall JCM 2000 DSL 50 mods

dpin, yep, that's the schematic and it correlates to my generation of PCB. Thanks. Yeah, as I understand it, the "left area" on that section of the schematic is for the Green Channel whereas the right side (right of the relay....C10 on over) is for the Red Channel. If that's correct, then there appe...
by dehughes
Tue Sep 05, 2017 2:02 am
Forum: Marshall Discussion
Topic: Marshall JCM 2000 DSL 50 mods
Replies: 19
Views: 6313

Re: Marshall JCM 2000 DSL 50 mods

Alright, here's where I am with this: Main Board: Removed C9 entirely (100pf from the first gain stage plate to the cathode) and replaced C12 (the first gain stage Ck, a 4uf electrolytic) with a .68uf Sozo and lowered the same stage's Ra (R13) from 220k to 100k while raising Rk (R14) from 1k8 to 2k7...
by dehughes
Mon Sep 04, 2017 6:49 pm
Forum: Marshall Discussion
Topic: Marshall JCM 2000 DSL 50 mods
Replies: 19
Views: 6313

Re: Marshall JCM 2000 DSL 50 mods

Will do, thanks. I have a JAN '80s 12AT7 and an older RCA cleartop 12AU7 ready to try in the PI, once I put my amp back together. I'm trying an altered version of the Joey Mods....pretty much identical, save for I'm going to run a .68uf cathode cap w/o the 1000pf plate cap on the first gain stage (h...
by dehughes
Sat Sep 02, 2017 3:41 am
Forum: Marshall Discussion
Topic: Marshall JCM 2000 DSL 50 mods
Replies: 19
Views: 6313

Re: Marshall JCM 2000 DSL 50 mods

Oh cool! I'll definitely try that.

Does the AT7 kill the "Marshall thing", though? I mean, IIRC, the PI circuit is pretty standard setup on the DSL when compared to other Marshalls, yes?
by dehughes
Mon Aug 28, 2017 6:21 pm
Forum: Marshall Discussion
Topic: Marshall JCM 2000 DSL 50 mods
Replies: 19
Views: 6313

Re: Marshall JCM 2000 DSL 50 mods

I replaced the 470 pf bright cap across the Red Channel gain pot with a .0047uf Sozo NextGen and noticed a definite improvement.

In fact, if I could keep this tonality, yet reduce the overall gain on this channel, I'd be pretty close to content. Any suggestions?
by dehughes
Mon Aug 28, 2017 4:15 am
Forum: Marshall Discussion
Topic: Marshall JCM 2000 DSL 50 mods
Replies: 19
Views: 6313

Re: Marshall JCM 2000 DSL 50 mods

One thought I had was to just INCREASE the value of the "bright cap" on the Red Channel gain pot (C12). I have some higher value caps (.0047uf and .022uf ) and was wondering if throwing one of those in place of the 470pf cap that was C12 might add low end yet not deviate to much from the amp's origi...
by dehughes
Sun Aug 27, 2017 6:25 pm
Forum: Marshall Discussion
Topic: Marshall JCM 2000 DSL 50 mods
Replies: 19
Views: 6313

Re: Marshall JCM 2000 DSL 50 mods

Phase Two of mods has begun. :) Removed C12 on the "front board", which served as a bright-cap across the Red Channel's Gain pot. Not a fan of it installed, prefer it somewhat now that it's removed, yet the Red Channel still sounds "congested" for lack of a better word. I've seen the following mod s...