cr7r9":9vejn1eq said:
What can be changed in the circuits and components to make them exactly to spec of the original amps (assuming that there are some differences. Also obviously skipping the hand wiring)?
If we are talking strictly about component "
specs", the biggest difference between the original 1959, 1987 and JTM45's and the re-issues is that the power supply filtering is wrong on the re-issues. Marshall just slammed in 50uf x 50uf cans everywhere.
The filtering on the 2203 re-issue is correct, as are the coupling cap values and resistor values in all the re-issues, for the most part.
If we are talking about component
quality, then it's night and day across the board between the re-issues and the old stuff.
The shitty little box caps Marshall sticks in everything now sound like ass, and the transformers are lack-luster to say the least.
Getting the filtering right, and pulling the board in a re-issue and changing out the caps for something like the Synergy Royal Mustards will help a lot. However, that can be an exercise in frustration because the PCB's are single-sided crap, without through plated holes, and it's far to easy to blow a trace if you're not careful. Then you're still stuck with the mediocre OPT...
By far, the best solution these days is to just build a clone from scratch. Do your research and source good quality components and build the circuit you want. It will be way cheaper than buying the Marshall re-issue, and sound exponentially better.
The other option is to just buy the original, but be aware that they can really be hit and miss. In the last couple of months I've had a 73 SuperBass, a late 70's 2204 and an early 80's 2203 through here for filter caps, new tubes & bias etc.. and only the 2203 had the Mojo. The 2204 was mediocre, and the completely stock SuperBass sucked donkey balls.
YMMV