Hi all,
I'm playing around with the idea of a parametric eq pedal primarily used with a guitar rig live, so it would typically see high source impedances and be connected to high gain devices either before or after, like a distortion pedal or high gain amp.
I've built one based on the SSL 82E02 schematic (which is a Wein bridge eq I believe?..) and the eq itself is functioning well. When I have it plugged into a clean amplifier it sounds great with either a guitar or bass connected. A couple problems appear though when followed by a distortion pedal or plugged into a high gain amp.
The first issue is just overall noise level. It's quite a bit noisier than I was expecting throughout pretty much the entire frequency spectrum. I've mostly ruled out the power supply being the main contributor. I've run it on various voltages (+/- 9V, 12V, 15V) using linear regulators and charge pumps, and also my bench supply which is pretty clean. The noise doesn't change much. It appears as if the circuit itself just generates a fair bit of noise. Again, really only a noticeable issue when adding heaps of gain after it.
The second issue is that the frequency and Q pots make quite a bit of scratchy noise when adjusted. It's not really a problem when adjusting the eq while audio is running through it, and again not noticeable through a clean amplifier, but with a high gain amp it's very noticeable when adjusting the controls and not actively playing.
So I guess my questions for anyone familiar with the SSL eq's are, is it to be expected that it wouldn't work very well in my application? I've always assumed they were fairly low noise but I guess acceptable noise level depends on the application (console use vs with a high gain guitar amp). Are there other topologies that are lower noise (SVF maybe?) that might be better suited for guitar?
Anything I can do to improve the scratchy noise when adjusting the frequency and q pots, or is this just inherit to the design? I believe this is caused by changing DC operating levels but I feel like the design probably also depends on that happening..
Appreciate any advice!
I'm playing around with the idea of a parametric eq pedal primarily used with a guitar rig live, so it would typically see high source impedances and be connected to high gain devices either before or after, like a distortion pedal or high gain amp.
I've built one based on the SSL 82E02 schematic (which is a Wein bridge eq I believe?..) and the eq itself is functioning well. When I have it plugged into a clean amplifier it sounds great with either a guitar or bass connected. A couple problems appear though when followed by a distortion pedal or plugged into a high gain amp.
The first issue is just overall noise level. It's quite a bit noisier than I was expecting throughout pretty much the entire frequency spectrum. I've mostly ruled out the power supply being the main contributor. I've run it on various voltages (+/- 9V, 12V, 15V) using linear regulators and charge pumps, and also my bench supply which is pretty clean. The noise doesn't change much. It appears as if the circuit itself just generates a fair bit of noise. Again, really only a noticeable issue when adding heaps of gain after it.
The second issue is that the frequency and Q pots make quite a bit of scratchy noise when adjusted. It's not really a problem when adjusting the eq while audio is running through it, and again not noticeable through a clean amplifier, but with a high gain amp it's very noticeable when adjusting the controls and not actively playing.
So I guess my questions for anyone familiar with the SSL eq's are, is it to be expected that it wouldn't work very well in my application? I've always assumed they were fairly low noise but I guess acceptable noise level depends on the application (console use vs with a high gain guitar amp). Are there other topologies that are lower noise (SVF maybe?) that might be better suited for guitar?
Anything I can do to improve the scratchy noise when adjusting the frequency and q pots, or is this just inherit to the design? I believe this is caused by changing DC operating levels but I feel like the design probably also depends on that happening..
Appreciate any advice!