This is a review and detailed measurements of the Class D Audio (the company) CDA-250C Power (speaker) Amplifier. It is on kind loan from a member. The CDA-250C costs USD $495 from the company direct which barely sneaks it into affordable class.There is not a whole lot to look at on the face of the unit:As you see, the unit is made in USA. I suspect the case is generic Chinese though given the DIY look and feel it has.The power button is oddly in the right side of the unit.The back panel sports very large speaker jacks which is nice:Unfortunately there are no balanced inputs even though the holes seem to be made for them.Another miss is lack of any safety or regulatory certification.In testing, the CDA-250C ran completely cool. I could not feel slightest rise in temperature of the case whether I touched the top, left or right, which is really good.Let's start with our usual dashboard at 5 watts of output:I was pleased to see the unit working well enough to allow me to measure it down to DC and hence the DC offset. Many recent switching amplifiers make my analyzer go crazy if I DC couple of it.SINAD (signal over distortion and noise) is rather low and seems to be driven by high noise floor than distortion products (which are below 100 dB).Signal to noise ratio is disappointing:We can't even clear the CD's 96 dB at either 5 watt. We barely get there with 200 watts of output (which is already pretty distorted).The news gets pretty ugly when I measured THD+N versus frequency at six different power levels:We have multiple problems here. At both low and high end of the frequency spectrum we have rising noise and or distortion. The higher the power, the worse they get.At low power outputs (around 1 to 2 watts), low frequency noise seems to escalate which may be due to power supply noise.To top it all, two channel are wildly different than each other. One seems to be a lot more susceptible to noise than the other.Let's look at the spectrum of 1 kHz tone with wide bandwidth and see if we can figure this out:I should have run this without my external filter but let's run with it anyway. We see our usual spikes in hundreds of kilohertz due to switching frequencies. But we also see a rise in noise around 50 kHz or so. The previous test uses 90 kHz bandwidth so this peak will impact the measurements. Note again the channel mismatch.Let's rerun the previous test, this time by limiting the bandwidth to 22.4 kHz. Note that this means that we can't capture anything past second harmonic for the high frequencies (hence the reason the levels artificially drop there):The graph becomes somewhat cleaner especially at low output level (in red). But otherwise, the signature issues with distortion/noise remain.Let's run our typical power versus distortion test. Note that 1 kHz tone is used for this test so doesn't incorporate the issues we see above:We have good bit of power reaching 178 watts into 4 ohm before clipping sets in. FYI, I have refined this test to give us more resolution near max power so it is a bit unfair to previous products I tested. Still, this is quite a bit more power than the two reference amps in the graph.When I get a chance later, I will test the output impedance versus frequency. And a frequency response test which I just realized I forgot to run too.Getting nearly 200 watts/channel into 4 ohm for a US made power amplifier for $500 is not bad. Outside of that, you have to close your eyes to many flaws. These noise and distortion issues way dwarf anything upstream. As such, I don't see the Class D Audio CDA-250C in any kind of high fidelity system. Our search will continue for something with Hypex NC400 performance but at half the price.Needless to say, I can't recommend the CDA-250C but you can judge it for yourself and your application based on above data and decide.------------As always, questions, comments, recommendations, etc. are welcome.Sometime a man just needs money for really no obvious reason. This is one of those moments. So pleaseusing: https://www.patreon.com/audiosciencereview ), or https://audiosciencereview.com/foru...eview-and-measurements.2164/page-3#post-59054 ).