Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: slowferrari on February 12, 2023, 05:11:40 pm
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This is gonna get long winded, so I'm gonna gloss over some details.
I'm doing a 6AQ5 jcm800, but I feel like my chassis is too small (11x7x2) for all the knobs.
I stripped it down to gain, tone, and volume knobs, but I'm not sure how to approach the presence control. I was going to use an on-off-on switch with two different caps for a couple of ranges, but now that I'm marking my drill locations, the damn thing still seems too crowded.
What's the best way to eliminate the presence control? Leave out the cap and pot completely and only retain the 4k7 resistor to ground? Maybe I should just tie the 100n cap to ground and just have it always dimed? Or maybe I should just ditch the feedback, like the 18W?
I'm pulling my hair out. Any advice is welcome.
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Put presence pot next to output jack on the chassis rear?
--Pete
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Mock up a temp pot and use your multimeter to get the ideal value for your ears, and install a fixed resistor.
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For reference here are examples of Fender long tail phase inverters WITH and WITHOUT presence controls. The cap and pot are gone and there's just a low value R to ground.
47 or 100 ohms are common in that position.
I'm a minimalist, so in some of my builds I like to delete controls that tend to only have one good setting. Less knobs to fuss with, more time to play.
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Leave out the cap and pot completely and only retain the 4k7 resistor to ground?
yes