Originally Posted by maguire
I'm wondering if anyone has experience with an Agro pedal producing a high pitch constant feedback sound.
Yesterday I ran an active stingray through a compressor and into the Agro. When I turned both the saturation and volume dials past 3/4 turn, the pedal made a high pitched feedback sound. I could eventually balance it out so 1/2 volume and 3/4 saturation did not create the whistling sound. But anything past 3/4 on both and it would whiiiiiiiine like crazy.
This wast first time using the pedal. I bought it used. Anyone know if I have a bum pedal or maybe just overloaded it with signal?
I thought it should be able to handle the input signal.
Thanks in advance for any information/ experience!
Here is a slightly technical explanation of what happens and why from our very own Goran Stankovic. I hope it is helpful and answers your concerns.
Best, Dave B.
Any time a signal is passed through a circuit that contains filters and/or inverters, the phase of the signal is altered.
When a signal is passed through multiple circuits or a circuit with multiple filters, its phase can get altered to a point at which the output of a circuit can become in phase with the input, given that the feedback path between the two is provided. At this point the circuit will start oscillating – feed backing.
Every electronic circuit that contains a gain stage is subject to this behavior.
Exactly when the circuit will become unstable and start oscillating will depend on the amount of gain in the circuit, and the parameters related to the feedback between the output and the input of the circuit.
If a particular system (made out of multiple effects) oscillates at one setting, reducing the total gain in the system will make it stable again.
Quality and position of cables (routing on the pedal board for instance), shielding (or the lack of it) of the instrument and pickups, proximity of the instrument to the amplifier and/or cabinet are some of the factors that can increase the amount of feedback between output and input of the circuit, and make it more prone to oscillation.