Yep, as originally posted, I opted for a Apheared47 or CHA47, a variant of the CMOY. To answer rascal's question, the ouput load resistors are 47ohms.
This is the schamtic of one channel:
http://i54.photobucket.com/albums/g101/D0Hbert/aph_47b.gif
From my limited understanding, this amp is called the a47 because of the 47ohm resistors tied to the ouput. The schematic I think was based on a burr brown application note entitled: Double The Output Current To A Load With The OPA2604 Audio Opamp.
The input cap (.47uf) and the resistor (100kohm) forms a high pass filter thats cuts somewhere in the 5hz region I think and these are connected to Opamp1's (+) input. Opamp1's (-) line has to resistors, to adjust the gain of the amp, in this schematic, the gain is around 3 (10/4.7+1). Output of opamp1 is tied directly to the (+) input line of the Opamp2. What I don't understand is the need to connect the (-) input of the Opamp2 to the output. The 47ohm resistors are used to reduce noise/hiss from the output. Please correct me, but these 2 resistors are inside the feedback loop? This is the ideal position I think, less side effects from what I've read. Ideally, however, there shouldn't be any resistors in series with the output, it should give the amp much better control over the drivers of your cans, but at the expense of some possible hiss/noise. Also, its is much better to use lower values since higher value resistors are noisier.
That's my limited understanding of the schematic and how the amp works. Hope it helps.
the 47ohm resistors are there to equalise load current, IC1a provides all the gain, while IC1b in a non-inverting buffer with a gain of 1, now output of the gain opamp, IC1a is buffered by IC1b, so any output in a appears at input of b. two opamps can deliver more current than just one, this is not so hard to imagine...
this is just one of those circuit trick used by designers to lower output impedance and thus be able to deliver more current. if you have a quad opamp you can do this trick on it also...
@ferds,
finally....it's about time you show your creations....more choices, the better....