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Just re looked at you layout and the changes you made to the screen supply. With what I have experimented with the value of the first stage coupling cap and the screen changes to me made the big change in the the low end tightness (or compression at the output).

There so many things in this amp that can be a gentle change good or bad.

I originally tried the extra 1K in the screen supply like you but found it to be a slight change . Did not try the extra 220k's to ground. Then did an over kill thing with 2 470R's. Along with messing a round with .0022 .0047 .0068 .01 .022 in the first stage (which to me the lower values could sound a little to bright depending on the looseness of the output stage) . Lets just stay I've been in a few different configurations . When I ended up trying a separate 100Rs and then messing a round with the coupling cap's again I was almost there .

It's just so much of an adventure on how in a tone search of one choice can effect the other

Ended up with just a separate 220R's for the screen resistors. With the standard power supply dropping resistors . Went with a first stage coupling cap .022. To me this gave me the right tightness in the low end when pushed in to higher gain. Others might say there's too much compression and the amp has lost the looseness they once had. Its all a delicate balance of what makes you grin when you slam a power cord play a cunking riff or hang on to half bent vibrato note on the edge of screaming feed back!

Just something else for others to chew on, in all of our tone chasing quests .

Thanks for that info Sasafraz,I used a .022 cap inbetween the first and second gain stage.
I did a lot of listening tests,starting from the stock schematic.I am not sure I like the 220K's to ground off the screens,really need a switch,and to A/B at gig levels to see how much difference that makes.
I have been busy and haven't had time to mess with it this past week.But I really think it's almost there...I want to try 12V regulated heaters,and extra gain stage and a few other tweaks.
The amp really is excellent built per design,with the EZ81 the voltages came out just right.
I have just been trying to get the gain I want w/o a pedal or too much white noise.
The Egnater is only one channel and uses a dual ganged gain pot to get clean to high gain sounds,but its a little too bright for my tastes. What I like about it is the very low noise floor even at max gain.
I think that is from the low pass filtering via caps from GK like you mentioned before.
The input of the Egnater uses a 10K grid stopper.
My goal is to just have my guitar-wah-delay+reverb-A/Bfootswitch-amp to switch between clean and OD channels,(maybe make FX loop and put delay+reverb there)I think the Plexi MKII is a good start,and an excellent amp as is.I just like to mod,and learn while tone chasing,for me its as much fun as actually playing my guitar.

I find this thread interesting because I love the Jimmy Page Plexi Super Lead tones from 1973 at Madison Square Garden in The Song Remains The Same.

I built a Trinity sIII v6 a few years ago. While I think it's a great, great amp, the idea of it being more like that TSRTS tones is interesting.

As I best I can understand it, my Trinity 18 sIII amp's first channel (the one with 5 controls) is voiced like a vintage JTM type Marshall. And the second channel (the one with just Volume and Tone controls) is voiced like the original Marshall 18 watt tremolo channel.

From what I learned a few years back, the first channel in the Trinity Plexi build has a bit more gain than mine, but the boost is more or less a clean boost. This channel is the one for Plexi type cleans. The second channel (2 knobs) is supposed to be the "original plexi lead channel".

Is all this correct?

I'm guessing it would be quite a task to convert my couple year old sIII's first channel to anything like the Plexi specs. Maybe not, but it sure seems like the Plexi must have a lot different going on with a totally different boost and all.

Therefore, I'm wondering how hard it would be to convert my sIIIs second channel (the Volume and Tone channel) to the Plexi build specs. Are we talking massive rewiring surgery or just a few components here and there?


Admittedly, I'm sort of kicking myself for not building the Plexi version in the first place. But now, I'm just trying to figure out:
1) which channel would be easier to convert
2) which would give the most bang for the buck difference between channels with an A-B box.

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Go Buckeyes!

I would onlY change the TMB channel. It requires .022 coupling caps instead of .01 , a few resistors, and an optional silver mica cap. It will take a few hours to make the changes.

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Wow, that sounds much simpler than I thought. Are there instructions anywhere here for how to do that?

_________________
Go Buckeyes!

Well you really just have to compare two layout diagrams, get the parts, and make the changes.
Do you have the Red turret board or Black turret board?

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Mine is red. My entire build is documented in this thread:

viewtopic.php?f=7&t=3010

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Go Buckeyes!

Suggest you start a new thread, and model your update after this one - viewtopic.php?f=7&t=2464

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Sorry for the thread hijack.

I'll definitely check that other one out and start a new one as the time to do this approaches.

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Go Buckeyes!

No worries on the thread hi jack I do it too...
I basically built the Plexi V6 then changed it to the Plexi Lead MKII by using the different schematics and layouts from the resource section.

Sorry I haven't got the sound clips up,I have been busy and haven't even been able to pick up my guitar for awhile
On the plus side I did buy Merlin's book and have been able to read a couple chapters from it.
Really amazing info in it for us tube amp hacker types
I also picked up a used version of "Practical Electronics for Inventors" this is like a complete electronics info treasure trove so glad I bought them both.
After reading some of Merlin's book I want to redo the input of my Plexi build a little.
He has amazing advice for lowering noise,removing heater hum,ect,ect.

The kids are with the soon to be ex wife,I might get in the garage and get those clips done for you.
I have some more mods planned and that way you guys can hear the differences.
I actually haven't touched the amp since I got it dialed in as posted earlier,I built a Clyde McCoy wah for it,then started working on an active volume/stereo panner pedal.
So I can use this amp with my other DIY 18 watter it sounds awesome running stereo through them both.
Then got side tracked with some personal issues
I will keep this thread updated as I change the amp,and answer any questions I can.

Guys can you make a demo video of the amp, so we can hear it in action?
Your mods seem very interesting.