Mods/upgrade for '79 JMP 2203

DeanS · Post by **DeanS** » Fri Feb 02, 2007 5:50 am

Hi, I'm new here and wanted to find out about my options for upgrading my Marshall. Not really looking to change the tone but merely to enhance it ie more of what it has- if you know what I mean.

thanks

Flames1950 · Post by **Flames1950** » Fri Feb 02, 2007 6:01 am

When I had a '78 2204 I felt like it needed something more too, I tried all sorts of mods to the poor thing......only to finally decide that Marshall wasn't so far off in the end, and that the amp sounded best in stock form, cranked, with a boost for leads.
I finally converted it to a non-master circuit, which was closer to what I was really after. But I wouldn't do that to another at this point in time, you'd ruin any value the amp has as a vintage piece.

DeanS · Post by **DeanS** » Fri Feb 02, 2007 6:55 am

Flames, I take on board what you're saying- but are there any mods that are worthwhile without 'butchering' the amp.

Oh by the way mine has 5881 valves as standard- if that makes any difference.

St August · Post by **St August** » Fri Feb 02, 2007 7:06 am

So what is it exactly that your looking for tone wise?

MacGaden · Post by **MacGaden** » Fri Feb 02, 2007 8:08 am

DeanS wrote:Flames, I take on board what you're saying- but are there any mods that are worthwhile without 'butchering' the amp.

Oh by the way mine has 5881 valves as standard- if that makes any difference.

5881

DeanS · Post by **DeanS** » Fri Feb 02, 2007 9:17 am

Yep, absolutely standard. The front panel has an extra logo/graphic near the 'JMP' sayimg 'Marshall 5881'. I believe these amps were made for export (I am however UK based) and due to the shoddy/unreliable EL34 valves that were available at the time they decided to ship them with the more robust military grade 6l6 ie the 5881.

Tonewise I'm looking to brighten the tone as its quite dark without boosts etc.

JD · Post by JD » Fri Feb 02, 2007 9:42 am

You may want to look to go to either EL-34s or if you are really looking for bright then 6550s. Most do not like the 5881 sound in the Marshalls. You can always look at speakers, tubes, and pickups to shape the sound and leave the amp be.

MacGaden · Post by **MacGaden** » Fri Feb 02, 2007 11:56 am

DeanS wrote:Yep, absolutely standard. The front panel has an extra logo/graphic near the 'JMP' sayimg 'Marshall 5881'. I believe these amps were made for export (I am however UK based) and due to the shoddy/unreliable EL34 valves that were available at the time they decided to ship them with the more robust military grade 6l6 ie the 5881.

Tonewise I'm looking to brighten the tone as its quite dark without boosts etc.

Do you have pictures ? As far as I know Marshall changed to 5881

MacGaden · Post by **MacGaden** » Fri Feb 02, 2007 12:04 pm

As for mods/upgrades: Check this: http://marshall.redpt.com/clay/mv_marsh ... cuits.html

HIn · Post by **HIn** » Fri Feb 02, 2007 12:33 pm

MacGaden wrote:As for mods/upgrades: Check this: http://marshall.redpt.com/clay/mv_marsh ... cuits.html

Nice site. I found that changing the slope resistor to 47K was the most effective mod for me on my 77 JMP 2203. Still liking my JTM 45 better and when I get some time will start tweaking the JMP but after working on a PTP not looking forward to the PC JMP.

DeanS · Post by **DeanS** » Sat Feb 03, 2007 5:53 am

MacGaden wrote:As for mods/upgrades: Check this: http://marshall.redpt.com/clay/mv_marsh ... cuits.html

Thanks for this- enough here to be getting on with.

jerrydyer · Post by **jerrydyer** » Wed Feb 14, 2007 4:09 pm

my main amp is a 79

jerrydyer · Post by **jerrydyer** » Wed Feb 14, 2007 4:10 pm

except the preamp looks like this now

jerrydyer · Post by **jerrydyer** » Wed Feb 14, 2007 4:10 pm

like this now.. he he

atbear · Post by **atbear** » Thu Feb 15, 2007 2:50 am

HIn wrote:
MacGaden wrote:As for mods/upgrades: Check this: http://marshall.redpt.com/clay/mv_marsh ... cuits.html
Nice site. I found that changing the slope resistor to 47K was the most effective mod for me on my 77 JMP 2203. Still liking my JTM 45 better and when I get some time will start tweaking the JMP but after working on a PTP not looking forward to the PC JMP.

What did that do?