Having recently made a test to compare the BehringerMods DEQ2496 DAC and ADC, looped through 10X, against an original direct CD rip, I think it is a good idea to try a similar test with a power amp.
Here I have used the same digitally extracted music samples as the DAC/ADC test only this time I have passed one set of samples through my DAC/Pre -> Alesis RA500 amp -> AudioSmile Kensai speakers. I have then tapped the signal off the back of the speaker posts into my ADC to record what the amp is actually doing when driving a pair of real speakers.
Doing this, it is possible to compare the original files to those which have been through a DAC, Amp and ADC to see if the equipment chain is transparent or if it can be detected.
Having listened to the files before posting this, it is my opinion that the difference between them is very small and helps to show how a powerful and neutral amplifier can be had for very little money today. The Alesis is £190 and has 120watts per channel.
This simple image shows the test method:
The Fun Part
Here we have 4 samples of music. Each sample has an 'A' and 'B' version. One of these is an original file and one has been through the DAC, Amp, ADC chain. The identity has been hidden to help avoid bias. You can download the files and simply listen to see if there is an audible difference between them and if so, which you prefer.
Please not not post your findings as others may want to try this test in the future. Send me a PM if you'd like to know the identity of the files.
If you wish to make this test more concrete then please download this ABX comparator and check if you can reliably identify each file. This is necessary because even with the identity of the files hidden a preference could still be formed. Using this utility to identify X and A or B allows us to really know if a difference can be heard between the samples. A video showing how to use the program is at the bottom of this post.
Sample 1 - Jazz:
Sample 2 - Metal:
Sample 3 - Classical:
Sample 4 - Speech:
How to use ABX Comparator