While back in a different thread i was talking about a modified whammy circuit i came up with, that was even before the simulation physicalized on a breadboard by me with subjectively excellent results.
I recently turned that into a full blown preamp and have been visiting local hobbists for an audition. However last weekend it ran into a problem when connected to an old sansui amp. One channel went into oscillation, dc spike to the rail and almost blew the amp and the speaker!
I know the sensible thing to do now would be to actually learn simulation and catch the mistake in digital domain, but i also wanna solve this issue physically since the circuit is already built.
So i'd like to ask what kind of test jig i can build for a preamp output that will torture test the circuit. A massive cap to the ground, perhaps?
I recently turned that into a full blown preamp and have been visiting local hobbists for an audition. However last weekend it ran into a problem when connected to an old sansui amp. One channel went into oscillation, dc spike to the rail and almost blew the amp and the speaker!
I know the sensible thing to do now would be to actually learn simulation and catch the mistake in digital domain, but i also wanna solve this issue physically since the circuit is already built.
So i'd like to ask what kind of test jig i can build for a preamp output that will torture test the circuit. A massive cap to the ground, perhaps?
Assuming what happened was oscillations caused by the interconnect's capacitance, you should have a large enough output resistor and test how a square wave behaves with capacitive load. A 100ohm resistor is sufficient in most cases. Where is your circuit?
Yeah, it would be nice to have the schematic here for future reference and learning. I tend to worry about failures in preamps, because they can do a lot of damage at this point in the gain chain. A protection circuit on the preamp output might be worth investigation.
It very well could have been the amp section’s input capacitance. If I recall correctly, I used to know of one that was 2000pf shunt capacitance at the input.
It very well could have been the amp section’s input capacitance. If I recall correctly, I used to know of one that was 2000pf shunt capacitance at the input.