I just had an MC installed in an original blueberry by Mark. The previous owner got rid of it because of some noise he was experiencing in his system -- I've only had it for about a month. I replaced the tubes (with cheap, stock tubes) and that solved the problem. From my perspective, it was simply a noisy tube.
Mark told me if you change the tubes on a Blueberry you have to have them tested for Low Noise output. In his words, the Blueberry is "merciless" on noisy or humming tubes. I'm no audio expert, but what makes the Blueberry excellent for the value and such a great pre-amp is also its biggest flaw - you're going to hear it if something is off because it's way more sensitive than most pre-amps at that price.
I know that this doesn't answer your question but it's interesting because I've heard this complaint before but I haven't experienced had any issues with this yet.
My .02 is to check the tubes for noise and keep the amp.
Mark told me if you change the tubes on a Blueberry you have to have them tested for Low Noise output. In his words, the Blueberry is "merciless" on noisy or humming tubes. I'm no audio expert, but what makes the Blueberry excellent for the value and such a great pre-amp is also its biggest flaw - you're going to hear it if something is off because it's way more sensitive than most pre-amps at that price.
I know that this doesn't answer your question but it's interesting because I've heard this complaint before but I haven't experienced had any issues with this yet.
My .02 is to check the tubes for noise and keep the amp.