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gareth magennis gareth magennis is offline
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Default Pultec EQP clone problem

On Tuesday, 2 February 2021 at 23:13:16 UTC, wrote:
gareth magennis wrote:
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Any thoughts on this? I'm getting rather frustrated.

** Motorboating in audio stages that do not use NFB is caused by supply rail coupling of imposed signal from the later stages back to the first stage - usually at a sub sonic frequency.

The inter-stage coupling caps are way too large at 270nF - try 22nF instead for each.

This shifts the -3dB point up to to 7 Hz.

Increasing the PSU filter caps - by paralleling with a 47uF - will also help reduce LF coupling.


..... Phil




Yes, customer was reporting a "tick" every couple of seconds.