Here are some frequency response graphs done by playing white noise through each of the amps and the HE-500. I used an app and the mic on my phone. Unfortunately it seems the mic on my phone isn't very sensitive to bass, especially sub-bass. Also remember this is done with the mic of my phone, probably not a world class recording device.
*The WA7 test used the stock silver cable rather than Moon Audio Blue Dragon copper cable. Also used single ended TRS plug instead of balanced XLR setup.
A few things that can be noted here that matches up with my observations is that the Emotiva does look to have the most neutral curve. Also I noted that the Lepai sounded warm and more tubey than the Emotiva, and it has a similar looking curve to the Sophia Baby. In fact, I've found other people mention in various places that Class-T amps have a tubier sound than other solid state classes.
Once again I want to remind everyone I don't know how accurate these curves are through the device I'm using and also that curves don't tell you the whole story. Only by listening yourself could you get an idea on how each amp sounds.
I have came up with new configuration by using the WA7 with the Emotiva as a preamp. Since the Emotiva is pretty neutral, the result is that you can really hear the sound of the WA7 and its tubes, but now the WA7 outputs plenty of power to drive the HE-500. Honestly, the sound rivals that of the Baby Sophia and had I known to do this before, I probably would have never gotten the Baby Sophia. The bass is still less impactful than the Baby Sophia and it's somewhere in between the Baby Sophia and Emotiva, but there is definitely a warmer tube signature. The biggest improvement though is that I find the WA7+Emotiva to be more transparent and have better transients than the Baby Sophia.
And yes I made a graph.
Edited by Sonido - 11/2/13 at 9:15pm