Non Madbean GGG EA Trem Fixed Volume?

[Pedro Fontacos]

Hi all I have a question I built a GGG EA  Tremolo a while back and I want to just get a fixed volume without having a volume knob so basically just a resistor of some value.  I'm not sure.  I'd like to be approximately 1dB above unity To compensate for the perceived volume drop.  Thanks!

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[Pedro Fontacos]

I'm sorry I'm having difficulty pasting the link from GGG's website here

[RobA]

You want to replace the Volume knob and just have a fixed volume? Probably the best solution would be to replace the 25k pot with a 25k trim pot. It would be straight forward and you could then set the output to just where you wanted it but still not have a knob on the outside.

[Pedro Fontacos]

You want to replace the Volume knob and just have a fixed volume? Probably the best solution would be to replace the 25k pot with a 25k trim pot. It would be straight forward and you could then set the output to just where you wanted it but still not have a knob on the outside.

Hi RobA and yes, exactly.  I considered a trim pot but couldn't find one from mammoth for a 25K that's why I decided to put a fixed value resistor Instead.

[RobA]

I don't know why they chose a 25k for the output pot, but I'd guess that a 20k or 50k would work fine here. You could give it a try.

If you really want to use fixed resistors, it will need two. They should be setup as a voltage divider with one hooked to ground, one hooked to the output of C2 and the connection to the output coming out of the center of the two. The best thing to do to get the values you need would be to set the pot you have in there to where you want it to be and then measure the resistance on the two sides of the pot. You should measure both sides because the pot probably doesn't actually add up to 25k. So, to get the actual values for the voltage divider, you need both the 1 to 2 and 2 to 3 R values from the pot.

[Pedro Fontacos]

I don't know why they chose a 25k for the output pot, but I'd guess that a 20k or 50k would work fine here. You could give it a try.

If you really want to use fixed resistors, it will need two. They should be setup as a voltage divider with one hooked to ground, one hooked to the output of C2 and the connection to the output coming out of the center of the two. The best thing to do to get the values you need would be to set the pot you have in there to where you want it to be and then measure the resistance on the two sides of the pot. You should measure both sides because the pot probably doesn't actually add up to 25k. So, to get the actual values for the voltage divider, you need both the 1 to 2 and 2 to 3 R values from the pot.

Thanks for the info RobA, I never realized a pot in this configuration is a voltage divider thus requiring 2 resistors.

I can't wait for the Madbean Phobos; the EA kits are so sloppy once you've seen a Madbean.  Installing 2 resistors in place of the pot is going to be a royal pain because of the hokey layout.

[RobA]

You are welcome. I haven't built one of these, but I just took a look at the layout doc and you are right, it is going to be a pain. If I were doing it, I think I'd actually do the two resistors at the foot switch. You need one resistor going to ground. This one replaces the 2-to-1 on the pot. This one will almost certainly be the bigger of the two resistors. And you need one coming from V3 pad. This one replaces the 3-to-2 connection on the pot.

If you have your foot switch wired like the one in the build doc, ground is the center lug on the foot switch and the lug in the bottom right conner is the input from the pot. So, you can take the resistor that goes to ground and put it between the center lug and the bottom right lug, Then wire the other resistor from the input lug directly to the input wire. I'd actually use a small wire coming off the foot switch lug and then wire this resistor to that and the other side to the wire coming from V3. Just solder it directly to the wire and then wrap it in electrical tape. That way, you have a little flex where it goes into the foot switch.