Fender oriented the Ajax caps with the ground towards the...

[rooster]

Funny, I never noticed this before. On Fender amps, noticeably the BF series using the Ajax Blues, the ground is oriented towards the tubes. This ground is indicated by a thick black line after the printing of the part value.

OK, so I've just noticed that the Ken built TW amps have reversed this direction and have the ground indicator going towards the pots.

Shitzbah! I have built my Expresses with the ground indicator pointing towards the tubes and things seem to be fine. In fact, I have always heard that Fender did this correctly, placing the shielded foil side of the cap towards the highest voltage, as found in typical B+ shielding layouts.

Anybody have some insight into this?

[martin manning]

It's not necessarily the highest voltage that you want the banded end connected to. To get lowest noise you want to have the lead connected to the capacitor's outer foil connected to the circuit node with the lowest impedance to AC ground. Generally that will be "upstream" with respect to the signal flow, so in the case of coupling caps that will be towards the plate.

Maybe in the past the band or bar marking did reliably indicate the outer foil lead, but in modern caps it does not not seem to mean anything, and you have to find it for yourself by connecting the cap to a scope or across the input of an amp and listen for the lowest hum. Aiken has a good article on this. See http://www.aikenamps.com/index.php/wher ... capacitors

[rooster]

.....so Martin, you're saying that Ken did not adhere to the cap direction philosophy?

Or that he did, and he found every OD to be marked incorrectly?

[martin manning]

I don't think I can answer either one of those questions.