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Old April 28th, 2012, 10:19 AM   #1 (permalink)
birddog01
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Location: Michigan, in the palm of the mitten
Age: 57
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5e3 pot wiring differences

Hey all, I've started back on my 5e3 I got from Dave when he was just starting out and its been a while so I'm refreshing myself with the different layouts and such and going through old links and photos I saved.

One thing I noticed is there seems to be some variations on the original fender scheme. Webers and the Fender layout for the pot volume and tone controls are the same. The .0047uf cap goes to ground off the tone control. Another I was looking at from Cieratone shows the .0047uf cap between the tone and one volume pot and the volume pot to ground.
Wondering if there is any sonic differences in these two variants for one?

Also in searching old build threads I bookmarked I was reading Bob Urbans first build thread.

http://www.tdpri.com/forum/shock-bro...marsh-5e3.html

There was a discussion between Bob and ThermonicScott on wiring the volume controls so there wasn't that abrubt volume change problem.
Modifying similar to the Brown Deluxe, minus the tone control jumper for the normal channel?
Bob chaged his and had positve comments on it. He had a diagram posted in the link but its not there anymore.

Scott explained it like this:
When the "top" (for lack of a better term) of the pot is connected to the previous stage and the wiper to the next, you have a simple voltage divider and the load on the previous stage stays the same (usually 1Meg).

When you're out to mix two channels, you don't want one of the controls to be able to "turn off" the following stage by directly grounding its grid (as the above control would do if you turned it all the way down), so you either want some series resistance after each input (brown and later Fenders), or for each volume control to present the same load to the following stage regardless of its setting (tweed).

The scheme used on the 5E3 and nearly every two-channel Fender up to that point gave a solution with the lowest parts count, and worked well enough that they didn't feel the need to change it for a while. It varies the load on the previous stage (1Meg when the volume is all the way up, 0 when it's all the way down). This changing load has the effect of varying the gain of the previous stage, rather than dividing off the signal. Someone else could probably do the math better than I, but suffice it to say that gives a different response to the controls.

Can anyone share any expierience with this or have a link to a diagram or layout?
thanks!
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