Dual opamps have very high isolation and to all intents and purposes behave totally independantly... I would go with whatever makes for the best PCB layout.
The channel separation of a pickup is what ? 20 to 40 db at a guess, crosstalk of LM4562 opamps in shared package is 112db at 20Khz.
Very good point... in fact its a certainty.
Grado PH-1
I have a modified Grado PH-1 and have a few suggestions to offer. First, upgrade the power supply. I use the Hagerman Bugle Power Supply wired for +\-15VDC. I also rolled many opamps (NJM4556, OPA2134, 2xOPA627 and 2xOPA827 on Browndog Adaptors) and found the OPA627s on Browndog to be my favorite. The nominal voltage for OPA627 is +\-15VDC which is why chose to increase the power supply from Grado's +\-12VDC (that and I only had 15 volt regulators on hand). I also bypassed the 2 (Solen?) 5.1uf coupling caps with a couple of 0.1uf Vitamin Q's.
The results, I'm very satisfied, to say the least. OPA627 is much quieter than OPA2134 and NJM4556 as well as more dynamic. Very low hiss and plenty of gain for my 0.5mv Grado Sonata cartridge. The bass is beautiful, full and tight and the treble is smooth and not sibilant. OPA827 was a very close second, a very good sound value . I haven't tried OPA637 yet but I hear it's superior.
As much fun as it was to roll opamps, upgrading the power supply was a huge improvement. The preamp became much more dynamic, fuller and less background noise.
I have a modified Grado PH-1 and have a few suggestions to offer. First, upgrade the power supply. I use the Hagerman Bugle Power Supply wired for +\-15VDC. I also rolled many opamps (NJM4556, OPA2134, 2xOPA627 and 2xOPA827 on Browndog Adaptors) and found the OPA627s on Browndog to be my favorite. The nominal voltage for OPA627 is +\-15VDC which is why chose to increase the power supply from Grado's +\-12VDC (that and I only had 15 volt regulators on hand). I also bypassed the 2 (Solen?) 5.1uf coupling caps with a couple of 0.1uf Vitamin Q's.
The results, I'm very satisfied, to say the least. OPA627 is much quieter than OPA2134 and NJM4556 as well as more dynamic. Very low hiss and plenty of gain for my 0.5mv Grado Sonata cartridge. The bass is beautiful, full and tight and the treble is smooth and not sibilant. OPA827 was a very close second, a very good sound value . I haven't tried OPA637 yet but I hear it's superior.
As much fun as it was to roll opamps, upgrading the power supply was a huge improvement. The preamp became much more dynamic, fuller and less background noise.
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