K701's require a lot of current in my opinion so even if they are low impedance they still need good levels of power. Perhaps it is an excuse to try a PB2!
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..............
OK,
I pulled all the op amps out and replaced the buffers with dummy buffers.
First I tried using the LMH6643 in the centre L/R . Waddaya know, D12 has no problem driving my Q701s, good tight punchy bass with an open middle and treble.
Then I replaced the LMH6643 with an AD8532, a bit noisier which was fixed by reducing gain to +3 dB and turning the volume up a bit. So far I'm still trying to figure what the difference is, but the AD8532 does something to the midrange.
My theory is that the Q701s need a lot of current (both the op amps I swapped in can supply a fair amount of current into the load).
More later.
OK,
I pulled all the op amps out and replaced the buffers with dummy buffers.
First I tried using the LMH6643 in the centre L/R . Waddaya know, D12 has no problem driving my Q701s, good tight punchy bass with an open middle and treble.
Then I replaced the LMH6643 with an AD8532, a bit noisier which was fixed by reducing gain to +3 dB and turning the volume up a bit. So far I'm still trying to figure what the difference is, but the AD8532 does something to the midrange.
My theory is that the Q701s need a lot of current ( both the op amps I swapped in can supply a fair amount of current into the load.
More later.
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.
Hi Topflight,
I prefer the LMH6643 sound, but what I am really looking for is more clarity and transparency.
I very rarely turn the volume past 12 o'clock.
regards, Chris
Hi Topflight,
I prefer the LMH6643 sound, but what I am really looking for is more clarity and transparency.
I very rarely turn the volume past 12 o'clock.
regards, Chris
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.
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
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