I decided to take my amp to work and see how it looked on our scope, I found some 15 ohm 900w resistors I used to make a load bank at 7.5 and 5 ohms. I used my phone hooked to my audio quest dragon fly as the source. The amp exceeded the rated power just fine, but when I ran a square wave through it i see what could be ringing. Can someone tell me what could be the issue. I'm still in the learning phase of this hobby. I replaced the power supply caps and replaced the rectifer with some high current shockley diodes we had laying around. Thanks.
I used my phone hooked to my audio quest dragon fly as the source.
Before you rip your amp to shreds looking for a problem it may not have, you need to eliminate your phone and the dragonfly as the cause of the ringing.
There is a pretty good chance the amp is doing exactly what it's being told to do by poor input devices.
Put one more channel of the scope at the input and compare graphs perhaps?
Yep ... Do a null test ... one channel on the input, one on the output... then level match them, invert the output (if necessary) and ADD... the scope's output would then be the difference between input and output waveforms. A graph of amplifier errors.
So it's the dragon fly. I don't have my power amp with me today to test it again but the dragon fly was clearly causing the ringing. I tried it with and without a resistor and the ringing looked better with a 56 ohm resistor. Is ringing something that can be audible? Could that explain why I feel like I wasted 200 bucks on a the dragon fly? Lol
The ringing is I believe due to an IIR brickwall filter - its clearly ringing at about 20kHz right on the filter edge, looks like a high order Chebyshev filter or similar. Audio DACs can't produce square waves outside their bandwidth limit, for this you need a pulse generator or arb. function generator.
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