[gareth magennis]

On Saturday, 27 February 2021 at 16:57:06 UTC, Scott Dorsey wrote:
wrote:
Don Pearce wrote:

The frequency of the ring is determined by
the LC circuit that is being struck by that edge.

** So a linear circuit with a resonance creates a new frequency ?

Does not do so with a sine sweep.
You bet it does! You get close to the resonance and it kicks off... you
don't need to be right on the resonance, you only need to be in the
ballpark.

This is the basic principle that makes bandpass speaker enclosures do
what they do. You don't need to put that one bass note into it... any
bass going into it will come out as that one note.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."



Well I think I might go for the mod of 100 ohms in series with 0.01uF, as this seems to best address the obvious catastrophic ringing this unit has, even though I have been unable to recreate the 90 Hz oscillations the customer encountered when connecting the unit via a patchbay.

Fortunately, the unit has an XLR output and a parallel TRS output, so the mod can be incorporated into a TRS jack, so the customer can insert the mod or remove it at will.
The mod does have a slight HF rolloff, so perhaps if the 90Hz problem is not happening, he can at least get his full frequency response back.

Seems to me this is a serious design issue that was overlooked, the mod is a sticking plaster.