Getting started with 50w plexi

[DarkKnigh_t]

Greetings
First of all i have to say hello and Im amazed with the amount of knowlage and support on the forum and i hope you can help me too

Im a beginner at amp building but ive been building guitar pedals for years.
I want to build a 50W plexi the problem is there alot of versions and mods and instructions so im a bit lost here xD
I would like to make a lead series with more gain. As i read the 1978 is the way to go? correct me if im wrong please. And I would like to know what about the master volume mod? What does that bring? More gain at lower volumes?

I will buy all the parts by myself step by step as i get with it.
If someone can point me to some guides and documentation wiring and layout that would be amazing as i said im a bit lost in all the documentation on the forum

Thank you very much for all your help!

[vh junkie]

Instructions:
http://www.metroamp.com/downloads/50_WA ... CTIONS.pdf

More good stuff... 50w is a 1987...
http://home.comcast.net/~mamp17/1987%20Layouts.html

Master Volumes lower the overall output

[danman]

Try to pick one layout and set of instructions for your first build as there are many floating around out there. The instructions that VH Junkie linked would be a great set to use. For a beginner, trying to mix different companies layouts and instructions can get very frustrating. Check out Valvestorm.com for your parts. He has everything you need for the build except the transformers which you can source yourself. Do plenty of research ahead of time and learn the different variations of the lead circuit. It stayed mostly the same for years, but there are a few small component value differences that make the later models a little gainier and brighter. You may even prefer the 2204 circuit which has a pre-pi master volume which will allow you a little more gain at lower volumes.

[DarkKnigh_t]

By 2204 you mean jmp or jcm?
the problem is i live in croatia so ordering parts from the states will cost a fortune :/ i have to find sellers from europe thats the problem :/
Thank you for the links thats just want i need!

[danman]

I prefer the late 70's JMP 2204 over the JCM 800 50 watt circuit but both are excellent choices. I do tend to play my 1986 clone more than any other though. I added the Larmar ppimv to make it more manageable at home though.

[DarkKnigh_t]

I prefer the late 70's JMP 2204 over the JCM 800 50 watt circuit but both are excellent choices. I do tend to play my 1986 clone more than any other though. I added the Larmar ppimv to make it more manageable at home though.

What would be the difference then between the JMP and Plexi? I played both but i mean circuit wise? I also prefer the JMP. Adding the PPIMV is a must for me since I live in an apartment xD

[danman]

The 2204 master volume circuit and the 1987 lead circuit are both part of the JMP line. Plexi's are just the early version of the 1987 circuit which later became metal face panels in 1969 I believe. The 1987 circuit didn't change much over the years. It did become slightly brighter and more aggressive because of changes in the NFB circuit and a couple of component value changes. The 2204 master volume circuit came around in 76-77 I believe and it allowed for even more gain because of the cascaded inputs. It also had a master volume which allowed for more preamp gain at lower volumes. With the 1987 circuit, you really need to crank it to achieve the overdrive. You can add a ppimv to the 1987 which will allow you to achieve the preamp distortion without upsetting your neighbors. You should try to play both types of circuits or at least check out some videos to get an idea of which one you prefer.

[DarkKnigh_t]

The 2204 master volume circuit and the 1987 lead circuit are both part of the JMP line. Plexi's are just the early version of the 1987 circuit which later became metal face panels in 1969 I believe. The 1987 circuit didn't change much over the years. It did become slightly brighter and more aggressive because of changes in the NFB circuit and a couple of component value changes. The 2204 master volume circuit came around in 76-77 I believe and it allowed for even more gain because of the cascaded inputs. It also had a master volume which allowed for more preamp gain at lower volumes. With the 1987 circuit, you really need to crank it to achieve the overdrive. You can add a ppimv to the 1987 which will allow you to achieve the preamp distortion without upsetting your neighbors. You should try to play both types of circuits or at least check out some videos to get an idea of which one you prefer.

Thats just what i needed to know thank you very much!
Does anyone have by any chance dimensions for the chassis sizes and hole placements cause i will try to make it locally here in my country or maybe a europe seller that sells them?

[neikeel]

Try this:

[DarkKnigh_t]

Try this:

This looks pretty interesting. Is there a bit more detailed explained and a fuller picture? I can see 3 volume pots and only a part of the layout. :/