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In a trem circuit that operates by linking the LFO cathode with a separate preamp cathode, a good place to put the footswitch is on the line linking the two cathodes; it starts instantly (at least in my circuit) and at the same time very positively shuts up any pulsing bleed-through. However, there is a pretty considerable pop when switching. Any way around this? A cap across the switch doesn't seem to do anything, and adding resistance to the line I would think would affect the bias point. Any ideas? Maybe some really low-ohm resistors in the line (like 10 ohm etc.) Looking for ideas!
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Your switch closure is changing some voltage relationship.
Would be real helpful if we had a clue what the circuit was you are working on.Education is what you're left with after you have forgotten what you have learned. -
Definitely changing a voltage relationship, oh large and mighty Sumo flyer! The preamp cathode R is 1.5K, 25uF bypass. The first stage LFO oscillator cathode is tied to this - has no R of it's own. This is basically a Supro 1624 circuit, but being a Supro, it is grounded in 87 different places with little preamp filtering and there is bleed through of the pulsing when the trem is shut off. I put the second stage cathode on the speed pot switch and I put the first stage cathode on the footswitch. However, now the footswitch pops (the original footswitch setup worked fine, but allowed the pulsing bleed through). I can live with the pop, as at this point I now have the amp very, very quiet even w/ both volumes wound up to 10, and it's not a deafening pop. But, of course I can't help wondering if there is some way to snub it a bit. What is happening is the LFO is suddenly allowed a cathode path to ground, and the preamp cathode goes from "seeing" 1.5K to a shared resistance, 3K I guess.Comment
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I don't have a Supro1624 print to look at, and don;t see one at Schematic heaven. I can get a general feel for what you escribe, but short of drawing it up myself, can you link to a schematic?
OK, I am looking at the S6424, seems to fit your description. You can;t switch that cathode in and out without getting some noise. The left half of the tube is the LFO and the right half is the driver. The switch interrupts the LFO signal from getting to the driver, but enough component lead and what not exist to pick it up as crosstalk, I'd bet. Try grounding the top of the intensity control. Does that eliminate the bleed through?Education is what you're left with after you have forgotten what you have learned.Comment
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