Potato Cakes
Well-known member
Hello, Everyone,
I am working on a unique project where a 1:1 (600R:600R) is in the middle of the circuit then uses buffer afterwards to unbalance the signal for the rest of the chain. Because of the level coming off of the transformer, I have to utilize a U-pad so as to no clip the input of the buffer. The client requested adding a high frequency roll off so quickest way I could think of is to use the Hi Cut circuit found in Vox amps, as shown in the top drawing. I ran into the same issue I have when I implement this on various push/pull amps which is the useful range is only last 1/4 of the turn. So I lowered the value of the potentiometer to 2k but then encountered a new issue where the signal was high passed until the full amount of high pass is engaged. I've messed around with a couple more capacitor changes but ended back to 250k and 1uF for this circuit. I used reverse log, log, and linear pots with similar results.
So the next idea is to use a dual gang pot and have separate circuits both referencing ground as shown in the bottom drawing (the pots labeled 10k should be 20k). The goal is to get the rate of audible change to be closely matched to the range of movement of the potentiometer. Of course, I could always add a low pass filter after the buffer and then add another buffer for make up gain for the insertion loss, but it would be simpler if this could accomplished passively.
I don't have a dual gang 10k pot to try this to I'll have to get one and report back.
Thanks!
Paul
I am working on a unique project where a 1:1 (600R:600R) is in the middle of the circuit then uses buffer afterwards to unbalance the signal for the rest of the chain. Because of the level coming off of the transformer, I have to utilize a U-pad so as to no clip the input of the buffer. The client requested adding a high frequency roll off so quickest way I could think of is to use the Hi Cut circuit found in Vox amps, as shown in the top drawing. I ran into the same issue I have when I implement this on various push/pull amps which is the useful range is only last 1/4 of the turn. So I lowered the value of the potentiometer to 2k but then encountered a new issue where the signal was high passed until the full amount of high pass is engaged. I've messed around with a couple more capacitor changes but ended back to 250k and 1uF for this circuit. I used reverse log, log, and linear pots with similar results.
So the next idea is to use a dual gang pot and have separate circuits both referencing ground as shown in the bottom drawing (the pots labeled 10k should be 20k). The goal is to get the rate of audible change to be closely matched to the range of movement of the potentiometer. Of course, I could always add a low pass filter after the buffer and then add another buffer for make up gain for the insertion loss, but it would be simpler if this could accomplished passively.
I don't have a dual gang 10k pot to try this to I'll have to get one and report back.
Thanks!
Paul