Metropoulos Forum

LOL, thanks for the kind words. Some of this stuff is great, some of it is a bunch of B.S. It's just a shame you have to spend so much time and money to find out.

Great info post
I try, just for my curiosity, a lot of ceramic caps for signal path bypass and treble control and definitively is a problem of choice. NOS and new brand sound very different and have a very particullary sound and don't work good for me. Silver mica or styroflex caps is better choice in my oppinion for this position.
Also use WIMA MKP10 caps for overall coupling capacitors. Very good neutral and balanced caps, but,unfortunately, just in short radial leads shape.
Anyway can choose ceramic caps for best stability reason in high gain stages.

Funny thing, I haven't tried changing small signal caps in my Marshall build, but in a Fender Super Reverb, I put in a 330pf polystyrene cap and while it sounded good clean, it did not do well with distortion (pedal).
But I'm thinking in this circuit, the distortion is generated mostly in the later stages. So maybe I should try it again.
I'm not sure I like the sound of silver mica. It's got a "bite" to it. The ceramics give a nice smooth tone. I think the styrenes should be clear and detailed without the harshness of the mica.

Great review!

My experience with the JCM800 2203 (year 1982) loaded with a Metroamp PTP-board and some mods of mine is that the brand of caps and resistors do indeed make the amp sound different and in my case better compared to the original. After the board change the Sozos sounded softer than original Marshall's legos, but the shrill was still there. The surprising change for the better, for my ears anyway, was replacing Metroamp's UF4007 diodes to IN5408 which I got from a local electronic shop for about 0.20 € a piece. When I switched the amp on and played some power chords I couldn't believe my ears how much the new diodes opened up the sound, made all higher frequencies more musical and pleasing. Now I can dial treble and precense to 10 and the sound is bright of course but in a tasteful and pleasing manner. The change is unbeliavable. There is also a bit more gain which is ok.
Now I should play B.B. King's song "The 'shrill' is gone"

The next step is to fine tune the middle pots frequencies, a parametric eq would be great for the 2203...

funny that my experience with the silver mica vs ceramic is opposite of yours. To me, the silver mica just sounds hi-fi whereas the ceramics sound gritty and lo-fi...Which is what I want in a marshall clone.

Matti wrote:Great review!

My experience with the JCM800 2203 (year 1982) loaded with a Metroamp PTP-board and some mods of mine is that the brand of caps and resistors do indeed make the amp sound different and in my case better compared to the original. After the board change the Sozos sounded softer than original Marshall's legos, but the shrill was still there. The surprising change for the better, for my ears anyway, was replacing Metroamp's UF4007 diodes to IN5408 which I got from a local electronic shop for about 0.20 € a piece. When I switched the amp on and played some power chords I couldn't believe my ears how much the new diodes opened up the sound, made all higher frequencies more musical and pleasing. Now I can dial treble and precense to 10 and the sound is bright of course but in a tasteful and pleasing manner. The change is unbeliavable. There is also a bit more gain which is ok.
Now I should play B.B. King's song "The 'shrill' is gone"

The next step is to fine tune the middle pots frequencies, a parametric eq would be great for the 2203...

What about UF5408 diodes?

You still on the forum gnugear

Old thread (what isn't on this forum lol). But I wanted to point out that neither a UF4007 nor a UF5408 is a FRED. They are "ultra fast" recovery versions of the 1N4007 and 1N5408. But they are not FREDs. FRED = Fast Recovery Epitaxial Diode. And they are very different from a typical axial diode used in Marshall builds.