JMP 50W Lead/Bass Build

[bbaug14]

Hey everyone, just wrapped up a 50W JMP build. This is my first ever completely ground up amp build. I've modded/fixed tons of amps in the past, but I finally got around to actually building one from scratch. I sourced most of my parts from Valvestorm and Rob was very helpful. OT is a Mercury Magnetics over sized to make it sound more like a 100W. I was torn between this one and Marstran/Merren, but I'm glad I went this way because it sounds HUGE!!!! Just barely fit in the headshell (about 1/8" clearance). Lots of guys on other forums give MM a bad wrap compared to some of the competition, but if it's good enough for my Wizard, it's good enough for me. PT is a Marstran and Brian was great in delivering it right to my doorstep. Puts out 432V, which is exactly what I was looking for with this build and why I went with Marstran over MM.

I also installed a Lead/Bass switch in one of the speaker jacks. It switches the tone stack, split/shared cathode, and bypass cap on V2a. Works perfectly and does exactly what I was hoping. I find myself really digging the bass spec right now, but that could change as things settle in. Nails that Kossoff tone.

And of course, the pics....

 

[lespaul6]

Looks fantastic... where did you get the headbox/tolex? I would love to take a class on how to build these things and proper soldering etc.

 

[bbaug14]

Looks fantastic... where did you get the headbox/tolex? I would love to take a class on how to build these things and proper soldering etc.

I got the Headshell from Valvestorm, but as I understand it, it's a MOJO headshell.

 

[J-Rodger]

Nice amp but not a MARSHALL no ?

 

[LP Freak]

Great job!

 

[74JMP]

Nice amp but not a MARSHALL no ?

Is your FryGuy amp a Marshall dan?

 

[skoora]

I thought about trying to do the same kind of lead bass switch for my Metro but couldn't figure out an easy way to do it on one switch. Plus after some simple experimentation I discovered I liked split cathode without the V2a bypass cap so left it that way. The difference between split and shared cathode was extremely subtle. The V2a bypass cap made more of a difference. Your build looks killer.

 

[Jofipe]

Looks very nice! that sure is a huuge OT for a 50w. What chassis/kit did you use?

 

[J-Rodger]

Needs goop for 80's tone ...


Srsly tho for a kit thats nice.

 

[rottingcorpse]

I love seeing threads like this where people are making amps. Nice job. Very jealous.

 

[bbaug14]

Just so everyone knows, its not a kit. I sourced all the parts myself. I got the chassis from Valvestorm and had to drill out the new OT locations, ground points, and an extra cap can location (under the board). Its basically a 68 Lead/Bass spec with a few tweaks here and there. Nothing major changed though. Overall, I'm very happy with it.

 

[Shask]

Very nice looking! very clean!


I actually pulled my amp out over the holidays and have been tweaking it. It is a 2203 based amp, but has extra gain stages, depth mods and such. It does not look as nice are yours any more though, lol. I have soldered and re-soldered and re-soldered a hundred times tweaking the sound, so it is not very pretty anymore. Sounds massive though

 

[bbaug14]

Very nice looking! very clean!


I actually pulled my amp out over the holidays and have been tweaking it. It is a 2203 based amp, but has extra gain stages, depth mods and such. It does not look as nice are yours any more though, lol. I have soldered and re-soldered and re-soldered a hundred times tweaking the sound, so it is not very pretty anymore. Sounds massive though

I was torn between the 68 spec and 2203/2204 platform. In the end, I figured my Wizard covers all things 2203 and building one would have been a little redundant. I built this one to have as a "basement" amp for home use. Who knows though, I may build one in the future. Love the 2203/2204 sound with a few very minor tweaks here and there.

I'm amazed how well this amp sounds as a clean(ish) platform. A couple dirt pedals and this would be a gigging machine if need be.

 

[Shask]

Mine started its life as a 1959 Plexi build. Amazing dynamic clean sound. If I wanted a clean amp for pedals I would have kept it, but since I am a metal guy, I needed to add several gain stages

 

[J-Rodger]

Im always amazed at 60's & 70's MARSHALLS simple by design, they definitely got it right.

 

[74JMP]

Im always amazed at 60's & 70's MARSHALLS simple by design, they definitely got it right.

dan I thought you always shit on PCB amps??? and here you are posting pics of them?? would dave from ROCKSYSTEMS approve?

 

[bbaug14]

Here's a few minute clip of my noodling through some riffs this morning. Gives you sort of an idea how it sounds, though the quality is not that great. I chopped out some of the video here and there so it wouldn't be so long, so pardon that.

http://youtu.be/WGAcNY_WT10

 

[bbaug14]

Thanks guys!

Here's a quick clip of the Bass side. Same settings as the Lead clip, just on the bass settings. Sorry about the flubs (might be a bit out of tune in the cold basement) and don't mind the occasional sound of kids in the background if it made it on the video. I ran downstairs to throw something together...

https://youtu.be/8Ri4ZeKBVIY

 

[mrTapp]

Here's a few minute clip of my noodling through some riffs this morning. Gives you sort of an idea how it sounds, though the quality is not that great. I chopped out some of the video here and there so it wouldn't be so long, so pardon that.

http://youtu.be/WGAcNY_WT10

Nice build