AB(x) testing of Power Amplifiers
I had to do it. Once again I was convinced that I hear a difference in a sighted test, so I had to prepare a properly level matched A/B test. Two amplifiers, both of 2 x 50W/4ohm rated continuous sine power.
The relay used was just what I had in stock – a 6 amps TYPE6013 with 3 switching contacts. Hopefully this type can be disassembled and the first think I had to do was to brush and clean the contacts, as their contact resistance was creating non-linear distortion, which must be avoided.
So this is the photo of the DIYed A/B test circuit.
I made a test with 2 different music samples, Beethoven's No.7 Symphony (Wiener Philharmoniker, Simon Rattle) and Rolling Stones, “Anybody Seen My Baby”. Before the test, the level was matched with a 1kHz sine and with the pink noise, measured at speaker terminals. Matching at about 0.07dB.
So what? Though I did not expect it, there was a difference. The class D was punchier, with better impact on bass and better distinguishing of instruments, and also more dry. The class AB was more on the mellow side, but tending to blend, melt. Average power was about 4W on the Stones sample. The symphony has much more difference between loud and silent parts so speaking about power is difficult. No clipping, of course.
I had to do it. Once again I was convinced that I hear a difference in a sighted test, so I had to prepare a properly level matched A/B test. Two amplifiers, both of 2 x 50W/4ohm rated continuous sine power.
- conservatively designed class AB, with acceptable distortion up to 0.02%/1kHz/4ohm/30W
- class D TPA3255, AIYIMA A07
The relay used was just what I had in stock – a 6 amps TYPE6013 with 3 switching contacts. Hopefully this type can be disassembled and the first think I had to do was to brush and clean the contacts, as their contact resistance was creating non-linear distortion, which must be avoided.
So this is the photo of the DIYed A/B test circuit.
I made a test with 2 different music samples, Beethoven's No.7 Symphony (Wiener Philharmoniker, Simon Rattle) and Rolling Stones, “Anybody Seen My Baby”. Before the test, the level was matched with a 1kHz sine and with the pink noise, measured at speaker terminals. Matching at about 0.07dB.
So what? Though I did not expect it, there was a difference. The class D was punchier, with better impact on bass and better distinguishing of instruments, and also more dry. The class AB was more on the mellow side, but tending to blend, melt. Average power was about 4W on the Stones sample. The symphony has much more difference between loud and silent parts so speaking about power is difficult. No clipping, of course.