Originally Posted by Bill-P
It's not all that bad, but it does make the Mad Dog overly thick and syrupy... if you are into that.
I'd agree that O2 is very neutral. E12? Not so much. I have tried E12 with a lot of headphones... and I'm sure you can ask any other E12 owner to see if E12 is a neutral amp. In essence, E12 is probably more neutral than other Fiio amps, but it's very far from transparent... or even clean. There is a very slight emphasis in the lower midrange, and the overall sound is a bit on the mellow side.
I'm not against some slight added warmth in order to smooth out the music, but... it was really overly warm and dark to me.
And yes, I have tried both amps with other headphones. See here for some impressions:
I didn't mention the Mad Dog, because I didn't really like the presentation out of either of those amps. I tried E12 with 2 different Mad Dogs (one from Dan's table and one from a different room) to make sure it wasn't just me.
Maybe I had a bad seal with the new pads? I don't know, really... but sincerely, I would still recommend Mad Dog to other people looking for a good closed headphone under $300. I really liked it a lot out of the Meridian Explorer. The sound opened up, and it was only lacking a tiny bit of the articulated bass of the LCD-2. Everything else was equal. Mad Dog + Meridian Explorer is still less than the price of a used LCD-2, so I think it's some serious value.
The C&C BH did a pretty good job. I preferred Output 1 to keep the thick, syrupy mid of the Mad Dog. Switching SF and LF to On helped cleaning the sound for me, and brought the sound signature to something more natural, but the lush/smoothness was retained because I think that's how Mad Dog was originally intended to be.
It's not perfect, of course. I think I still prefer the Meridian Explorer... (sorry to sound like a broken record, but it does sound pretty good out of the DAC), but for a portable setup, I'd say C&C BH is the better fit for Mad Dog than other amps.
And you can see very clearly I don't rate C&C BH very highly against E12 or O2 for any other headphone. I just think Mad Dog is a special case.