Some measurements of my latest power amplifier

[AussieAmps]

I recently was able to purchase the Q403 and after a reasonably steep learning curve, I am able to share my results.
I am currently using the internal attenuator, but I will be building a lower impedance attenuator in the near future.

I did add a binding post Case Ground point to the Q403, this help a lot with the minimizing the LF harmonic spikes to practically nothing as shown in the FFT results.

The measurements shown are of course limited to around 200 Watts into 8 Ohms as set by the Q403 attenuator.

Gambit Mono Block Power Amplifier.

300 Watts sine wave into 8 Ohms Maximum

600 Watts sine wave into 4 Ohms Maximum

1200 Watts sine wave into 2 Ohms Maximum

THD+N - 0.00055% 1khz @ 200 Watts - 8 Ohms un-weighted

THD+N - 0.0015% 20kHz @ 200 Watts - 8 Ohms un-weighted

THD+N - A Weighted 1 kHz @ 200 Watts - 0.00043% THD+N

THD+N - C Weighted 1 kHz @ 200 Watts - 0.00037% THD+N

[restorer-john]

Well done!

But, your 20kHz THD+N test with a 45kHz measurement bandwidth is a problem. There is only one (1) harmonic considered, so the number is not accurate at all. You need to extend the measurement bandwidth to slightly above 80kHz to get 3 harmonics in the measurement at a bare minimum.

On your webpage, you also have a THD vs Frequency where the bandwidth is also clearly truncated. This makes the THD+N appear (incorrectly) to go down at high frequencies when all that is actually happening is the opposite due to the harmonics falling outside the measurement bandwidth.

You should fix that.

[AussieAmps]

Thanks so much John for your reply.
Ok, I have re-measured the Gambit Amp with a 96kHz bandwidth and measured the THD+N to 45kHz.

Cheers Anthony