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Strange experience / class D content

#22
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#23
okcrum said:
It's more likely the cab impedance goes a little wonky - fifth fret A will have a different distribution of spectral energy than open A (IOW tone is different).
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agedhorse said:
This is exactly what my first suspicion is too.
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I'll third that. If you eq things a bit, the open A will likely elicit the same behavior as well, but the note up the neck gives you (by virtue of pickup spacing) more fundamental. Down at the bottom end of our instruments is where speakers have wildly varying impedance, and somewhere near (but not precisely at) resonance, you're going to get a very reactive load that's demanding a lot of current with a phase relationship that's not friendly to the output electronics. That is almost certainly what the protection circuit is not happy with, and is putting the amp into "armadillo mode" over.

I had an amp early on in my career that would put out 100 watts into 8 ohms, 200 into 4 - solid as a rock, provided it was a resistive load. Through my bass cabinets, it would fold up pretty early on a couple notes in particular and, although it didn't thermally shut down, the protection circuit would make it distort horribly. I originally though it was just lack of power, so I bought a 500 watt amp (which was a very big amp in that day), thinking it'd be a bit louder. It went a LOT louder - it didn't have the same limitations, and was happy with a reactive load - anyway, once I figured out what was up, it all made sense.
 
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#26
I'd say you were nearing max output of power amp into the cab, and that one note hits a resonance in the cab or impedance drop in the speaker that draws more current, overloading amp.

Also in general I'd say your amp isn't powerful enough for loud rock, if you guys actually play loudly. Love my class d, but headroom it ain't got much of. Extra wattage in class D amounts to headroom in more classic, "transformer size matters" amps.
 
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#30
KeithPas said:
Weird. Almost sounds like a compression issue.
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That crossed my mind as well.

I also worry it may be a cab resonance issue like I once had on another set of cabs.

Anyway, I'll tote over another, more powerful Class D amp next time to try and narrow things down. Maybe a second bass as well.

I'm hoping that the little Taurus was just not up for the job.

Thanks for the input everyone!
 
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#35
I thought you had a 200 watt Tarus?

If you are overdriving a small amp into an "unfriendly" load, the protection circuitry that's built into many amps (not just class D) can generate unpleasant artifacts even if they do not shut down.
 
#36
agedhorse said:
I thought you had a 200 watt Tarus?

If you are overdriving a small amp into an "unfriendly" load, the protection circuitry that's built into many amps (not just class D) can generate unpleasant artifacts even if they do not shut down.
Click to expand...

Thanks. I thought it was 200 watts but I came across the thread when I bought it. It was said to be 300 watts.

Anyway, all's well that ends well. The Taurus is back home as a practice amp.
 
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