Ed, while there more similarities than differences between VK60 and VK75, the VK75 has an additional PCB for power regulation that improves performance.
BAT VK55 vs VK 60
the 60 appears to be an older model (95?) vs the newer 55. Is the 55 an improvement in sound, notwithstanding its slightly lower power? is it worth the extra $500 or so?
Also, I'll be running it with a Shindo preamp, which is single ended. So is this a waste since the BAT is engineered to be balanced and this is their raison detre. I've heard that it may be a bit noisier or have hum in SE mode.
Also, I'll be running it with a Shindo preamp, which is single ended. So is this a waste since the BAT is engineered to be balanced and this is their raison detre. I've heard that it may be a bit noisier or have hum in SE mode.