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I got some motorboating going on im my amp. Its a jcm800, and the motorboating occurs in conjunction with turning the volume and gain controls up. With the gain around 6 or above, the motorboating occurs with the master volume around 4, and vica versa. What are some ways i can troubleshoot and eliminate certain possibilites or solutions?
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One major cause of motorboating is bad filter caps. Filter caps are not only used to remove ripple from the power supply, but also serve to decouple the amp's stages from each other, which is why each stage has it's own. As the caps age and capacitance drops, the decoupling at low frequencies suffers and the amp becomes unstable at low frequencies as the gain is turned up, essentially creating a feedback loop through the power supply. What you are experiencing is low-frequency oscillation.
Time to recap that JCM800. Great amp!
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