Express preamp board layout

[Colossal]

I put this [attached] drawing of an Express preamp board together, mostly for my own purposes but thought others might get some use from it. Ken used used perfboard with 0.265" centers and flea clips for mounting components. There has been much discussion and lively debate over the attributes that make the Express what it is. Tremendous attention has been paid to specific details to recreate those qualities and have been painstakingly documented by many here.

In looking at the layout and locations for each component on the Express preamp board, I couldn't help but indulge myself in some private speculation about the choices Ken made. Did Ken place each component specifically at the chosen locations based on a carefully planned spatial distribution choreographed to arrive at a precise balance of controlled chaos? Or, is it more simply that he arrived at the board dimension based on the physical limitation imposed by the six-pack of electrolytics located adjacently and then just arranged the preamp parts where they made sense? It is clear that he put the tube locations where they would be a minimal distance from their supporting circuitry to create a short path.

Considering the output section at the far left of the board, the orange drop output coupling caps, PI plate loads, and grid leak/bias resistors seemed cramped with respect to the fairly large amount of real estate allocated for the phase inverter. I'm wondering if Ken began laying out the components from the input, worked his way from right to left, and things simply got a bit cramped at the end. Some of this would have been imposed by the perfboard itself since turrets were forced to sit specifically on an available hole.

Thinking about this, I thought that Ken might have used perfboard certainly for the convenience where many of us today just work up a turretboard using a template overlay on a piece of G10 and a drill press. So, I thought it might be interesting to consider what if the perfboard had been based on 0.25" centers instead of 0.265". Locating the components on 1/4" centers provides some relief for the output section, giving the components more breathing room (if such a thing has any relevance or detriment to the Express design?).

Anyway, take it for what it's worth and thanks for indulging my ramblings. I don't place any value on mojo, only real science, but it was interesting to consider what KF might have been thinking in laying out the Express and particularly because he considered the most subtle of things to be relevant and contributory to an amp's overall tone.

[UR12]

I think first and formost he used store bought perfboard that came from the factory with .265 centerd holes. Then he took what was available to him and placed the components on the board so that he would have the best setup to run the wire from the board to the preamp tubes.

[M Fowler]

Good job Dave (colossal) and will useful for those wanting to build thinks just a little bit different on their TWs.

Mark

[Structo]

Nice drawing!