Metropoulos Forum

Hi Folks,

I'm gonne be documenting the build on my blog (http://liam2204build.wordpress.com/) for those who are interested!

Thanks!

There are 2 video clips of 2204 on your link, but these amps are not the same. JMP 2204 and JCM 800 2204 are different.
JMP has less gain on a high channel (3 gain stages) and the low channel is more usable. JCM 800 has 4 gain stages on a high channel, and the low channel is just for an option. I use it with Maxon AD-80 (the old one), and heavy modified BOSS CE-2 chorus, and the result is outstanding! But it's not so good on it's own.

Why are you using Metal Film Resistors?

You talking about me?

Haze13 wrote:There are 2 video clips of 2204 on your link, but these amps are not the same. JMP 2204 and JCM 800 2204 are different.
JMP has less gain on a high channel (3 gain stages) and the low channel is more usable. JCM 800 has 4 gain stages on a high channel, and the low channel is just for an option. I use it with Maxon AD-80 (the old one), and heavy modified BOSS CE-2 chorus, and the result is outstanding! But it's not so good on it's own.

I am puzzled.
Apart from some early oddball JMP50 2204s from 76/77 which had a non-cascaded front end the JMP 2204 and JCM800 have exactly the same number of preamp tubes in the same configuration with the same number of gain stages with V1b (0.68/2k7 cathode cascaded into V1a 10k via 22nf couplers a 470pF/470K and then to V2a. These then feed in to the cathode follower tone stack on V2b with V3 being the PI.
Where did you find the 4 stager

I was talking about JMP 50 from 77... And about JCM 800 I always forget that cathode follower doesn't count as a gain stage. Sorry about that!
It's only my first year in the Faculty of Engineering, and the only thing that we learning is a math and the physics! Damn!

Haze13 wrote:I was talking about JMP 50 from 77... And about JCM 800 I always forget that cathode follower doesn't count as a gain stage. Sorry about that!
It's only my first year in the Faculty of Engineering, and the only thing that we learning is a math and the physics! Damn!

Keep going with the maths and physics too they will be very important later!

Haze13 wrote:There are 2 video clips of 2204 on your link, but these amps are not the same. JMP 2204 and JCM 800 2204 are different.
JMP has less gain on a high channel (3 gain stages) and the low channel is more usable. JCM 800 has 4 gain stages on a high channel, and the low channel is just for an option. I use it with Maxon AD-80 (the old one), and heavy modified BOSS CE-2 chorus, and the result is outstanding! But it's not so good on it's own.

Okay,

1) There is only one 2204 video on the blog. The first video is a Suhr SL68, so a plexi style amp. Second one is the 77JMP

2) Marshall JMP 2204 and JCM800 2204 are the same amps, circuit wise. Just a different head box

axeman wrote:Why are you using Metal Film Resistors?

The only metal films I am using is are the 1 ohm 1% bias resitors of the power tubes. Other than that its is carbon films and metal oxides as per the metro 50w BOM.

The green ones are metal oxides, the majority will be carbon film but i didnt post any pictures of those.