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
This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
By continuing to use this site, you are consenting to our use of cookies.
