Do you feel you want more gain or is it something else?
I have a D10 and it didn't really push them loudly enough for me to achieve decent headroom.
Since the Q701's have an impedance of 60 ohms I would guess that the D12 is running out of current.
A higher authority (Top Flight) advised me to try using LMH6643 from the Op Amp rolling kit, this Op Amp can output up to 75 milliAmps.
In addition it has a very low output impedance.
I'll try the LMH6643 Op Amps out when I get some free time and report back..............
If you need still more output current from your D12, you might also try the AD8397 in L/R. As it has built-in buffers, it is best to use it with the bypass (dummy) buffers. IMO, it does a better job in the L/R position than the AD8532 considering overall tonal balance. SQ is similar to that of the LMH6643 but with more muscle.
LT1678 will do that. Quite detailed and transparent.
Unfortunately they don't source/sink a lot of current, can you recommend a good buffer? Any idea what buffer is shipped with the D12?
If you seldom go above the 12:00 position with your volume control, I think the LT1678 would still work well with bypassed buffers and give you the SQ that you are looking for. I can tell very little difference between it and other L/R opamps with buffers as far as driving ability. I really like the sound of the LT1678 and often use it as the optional opamp for several Topkits. You might try it with the LMH6643 as buffers. Should be a very good pairing.
This was what I got from my HiFlight Topkit For my Grado 325is'. I can put up the ones for my um3x if you like. I just have to open my D12 up.
Using the LOD from the iphone uses the phone's DAC, which then passes the analog signal into the D4/D12 for amplification. The dac in the D4/D12 is not used; you can only use it via usb/optical/coax.
I've tried using the LOD on my iPod to D12 Aux In............I wasn't too impressed, I thought the bass was too loose.
I normally use a Wadia 170i with my iPod, I use the digital output on the Wadia to the D12 spdif.
Unfrotunately I can't walk down the street with it, but it's nice for sitting outside on my deck. LOL