Marshall Head Modded - Holy Cow

**jemaholic** · #1 09-13-2009, 09:04 AM

I've been through scores of guitars over the years, but I've used Marshall amps exclusively for the last 30 years- (got my first stack in 1979.) Last year I sent Jim Marshall two pics -one from 1979 and one recent pic of me playing my double stacks. Suprisingly, he mailed me a very nice letter back and put the pix up on the official website for awhile.

Two years ago I bought a new Marshall DSL 100 full stack to augment my live rig (JCM900 full stack) and last week I decided to make some mods to it. I recently modded my JTM60 and wanted to try it on a stack.

I replaced the output transformer with a Mercury Magnetics FatStack, added a power choke and replaced position 1 through 4 preamp tubes: position one with a NOS real Mullard 12AX-7 and the other three with JJ's 12AX-7's. Position #1 in the preamp stage is the key to shaping your overdriven gain tone.

Ureeka! I've found THE SOUND. The change is so drastic (for the better) I'm just floored. Normally the gain stage on this model loses much of the bass range, but now it's fat and warm with rounder highs. Think early EVH. The cost of the mod is about $450 but the transformation is unbelievable. Can't wait to mod the other Marshalls now!
So if you're thinking of Marshall mods - consider these changes -you will love the end result.

GuitarEvan07 · #2 09-14-2009, 03:01 AM

Wow Cool! Nice!!!

UV-7-BK · #3 09-14-2009, 06:31 AM

Great to hear dude!!! Ive always had a soft spot for Marshalls, but they have never been dirty, raw or angry enough...maybe this might sway me!!!!!!

Andy43 · #4 09-14-2009, 12:25 PM

Did you mod it yourself or send it somewhere? I've been thinking about modding my Laney by swapping the tranny.

**jemaholic** · #5 09-15-2009, 03:52 PM

It was done by a local guy - Bell Labs in CT. Andrew does great work. Unfortunately, I am incapable of doing electrical stuff - just ask my wife :^)

jazzedout · #6 09-15-2009, 05:53 PM

Slightly off topic: I have a JTM30 which I don't use much. What mods did you do on the JTM60? Would like to have a few ideas to improve my JTM30... Thanks!

buddroyce · #7 09-15-2009, 08:22 PM

A good power transformer makes a HUGE difference

A lot more than most people think it does.

**jemaholic** · #8 09-16-2009, 07:44 PM

Quote:

Originally Posted by jazzedout

Slightly off topic: I have a JTM30 which I don't use much. What mods did you do on the JTM60? Would like to have a few ideas to improve my JTM30... Thanks!

On the JTM60 I replaced both the power transformer and the output transformer with Mercury Magnetics. It was cool because they had not made a power transformer for that model yet so they included a letter stating it was the first one produced.

All tubes were replaced with matching JJ's - those amps tend to run hot so I had a small fan installed to keep the tubes cooler. We also changed some of the caps to a lower value which gave it more low-end without sacrificing the midrange- and lastly we replaced the stock Celestion with a Celestion G-12H reissue 12" speaker.

Hope that helps.

jazzedout · #9 09-17-2009, 01:39 AM

Great! Thanks!!

teokiatuan · #10 09-17-2009, 01:43 AM

Quote:

Originally Posted by buddroyce

A good power transformer makes a HUGE difference

A lot more than most people think it does.

It does??

My tech told me that there was no way a power transformer could affect tone.
weird

Teo

EmJay · #11 09-20-2009, 10:04 PM

awesome!!

bhuard75 · #12 09-22-2009, 02:15 PM

i also did similar upgrades to my randall rm100. installed a mercury magnetics output transformer and choke. upgraded all the preamp tubes, the preamp and power section got jj83c gold pins and the effets loop got a tung-sol 803 goldpin. the power tubes i went with SED el34's in V2 & V3, and sed 6L6's in V1 & V4. biased them on the hotter side of the voltage scope rating.

once the MMOT finished burning in after about 30hrs of play time..... the amp is significantlly clearer. its crazy how much of a difference there is and how much of a difference this upgrade makes. it'll ruin you for all amps that dont have the highest quality components in the power section.

jl2556 · #13 09-26-2009, 12:50 PM

Quote:

Originally Posted by teokiatuan

It does??

My tech told me that there was no way a power transformer could affect tone.
weird

Teo

That's a lie. If that's true, why wont Mike Soldano let
Deyoung (the company that builds his transformers)
sell the ones for his amps to anyone else......

racerevlon · #14 10-11-2009, 08:53 PM

I have a handwired Marshall 1974X combo--do you think a OT swap would benefit the tone or should I just not mess with a HandWired Marshall? BTW--I love the tone already...

Thanks!

Race