Apparently , there is no reason that this circuit does not work. Do not worry about the fixed Bias, thus is simpler.
Do not expect a similar sound to JTM1 or JTM45. But you will have a good study amplifier.
Cheers
Re: Marshall JCM1H or JTM1H schematics
Posted: 26 Jun 2016, 00:39
by mavrim
Matec, so good to see you posting here again!
That jcm1 schematic turned out to be a fun build. Wish I had followed it from the beginning of my build, but the schematic wasn't complete then. I did find that R29 which is a 1meg resistor, should connect from V1A pin 7 to ground. It is shown as being connected between C22 and R28 to ground.
A buddy of mine actually cloned his own jcm1 and had boards made up. He sells his clone on eBay. They are built into lead 12 sized chassis and fit right into your own lead 12 combo or head. Search eBay for jcm 800 clone silver jubilee.
Re: Marshall JCM1H or JTM1H schematics
Posted: 26 Jun 2016, 00:44
by mavrim
Cloned jcm1. Search eBay
Re: Marshall JCM1H or JTM1H schematics
Posted: 26 Jun 2016, 15:53
by Matec
Hello mavrim.
I doubt there is a big difference between R29 connected between the ground and the V1a grid, and R29 connected between the ground and the C22-R28 node.
There will be many clones of Marshalls 1W, manufactured by talented people. This is really good. Your friend seems to be doing a great amplifier.
Cheers.
Re: Marshall JCM1H or JTM1H schematics
Posted: 31 Aug 2016, 14:16
by Matec
Hello everyone.
Here is a video and sample of axehack, who set up his own JTM1.
Fatmoocow wrote:This is a great thread. As a learning exercise I've been reworking the JTM1 to more closely match the real thing. Full disclosure I don't really know what I'm doing.
Thus far I've taken the power amp and added a long tail pair to split the signal in front of the 12au7. I'm not sure that this will work at all. In a perfect world we'd want fixed bias as well, but I don't have the skills for that.