BillFitzmaurice.info

Hey now. I've rented a Traynor YBA100 - I DEFINITELY want one now, it really is dynamite - It has a resonance switch which disables the negative feedback loop of the power section & "provides a bass boost at the impedance peak of the speaker cabinet." Is anyone able to say where that might be with a Jack? It sure gets the dishes & cutlery moving in the kitchen & you can feel what it does when engaged. It sounds kickass, my worry is that the frequencies it's boosting are low enough to cause unnecessary excursion in the driver on gigs. The head supposedly has a 2nd order cutoff at 30Hz. Anyone have experience with such a thing?

There are two impedance peaks with the J12. All ported cabs have two impedance peaks, so right off the bat the information from Traynor is inaccurate. This from the owner's manual:
'Pushing in the switch reduces the damping factor and allows the resonance of the speaker cabinet to be more pronounced.' That isn't a totally accurate description of what damping factor does. This is: http://www.cartchunk.org/audiotopics/DampingFactor.pdf
In any event run the switch in whichever position it sounds best.

Amazing, thanks so much. The information I had was from an email around the time production was starting up.
Cheers, Bill.

So that pretty much bunkifies what my initial thoughts were, but makes me wonder more in depth about what a negative feedback loop actually does. Apparently has something to do with phase. I'll go read up...

Negative feedback is the feeding back of a small amount of signal from a later part of the circuit to an earlier part, usually from a tap on the output transformer back to the phase inverter. Negative feedback flattens and extends the frequency response, reduces distortion, and reduces the effective output impedance of the amplifier, which increases the damping factor. Tube amps naturally have a very low damping factor, so using negative feedback to increase it is generally looked on favorably. SS amps naturally have a very high damping factor, which some say makes SS superior. The point made in the linked pdf is that once you get above a damping factor of roughly 50, which a well designed tube amp is capable of, any additional damping factor doesn't do anything that's audible. So when you see SS amp manufacturers making a big deal about have damping factors of 200 and more take it with a grain of salt.

Oh! Nicely done! I love this place.