Was the architecture of the OPA627 changed sometime ago? I see that the BP version has better specs all around than the AP, costs more and is less available. Does the BP version have a different design than the AP or is it simply better quality control? Will the BP stay current?
I am using the OPA627BP extensively in a 4 stage phono preamp. Recently, in addition to the second and third stages, we tried the 627 in the first stage. This stage's impedence can vary from 30 ohms to 47K ohms depending on the cartridge. We noticed that at about 300 ohms the 627 starts to feel the burden of the lower impedence and it's output is reduced proportionally to the lower input impedences.
Now, it still sounds very fine; even at 30 ohms/reduced output, but I'm wondering if I am playing with fire in the long run. I considered the OPA1611 but the 627 just sounds so good. Given that;
1. Do you think the 627 will be OK under a low impedence condition long term...and
2.Do you recommend the 1611 or another opamp that would be more acceptable of input impedences that can range from 30ohms -47kohms?
Thanks
Mark