Kgturner,
Have you tried putting a "cheater" plug on your Malbec amps to get rid of the hum? I have a friend that has a Grange preamp and he could not get rid of a loud hum it had developed. He was ready to send it to Kevin Kovac, and he just happened to plug a power cord into it that did not have a ground. The hum disappeared! It plays perfect now.
Have you tried putting a "cheater" plug on your Malbec amps to get rid of the hum? I have a friend that has a Grange preamp and he could not get rid of a loud hum it had developed. He was ready to send it to Kevin Kovac, and he just happened to plug a power cord into it that did not have a ground. The hum disappeared! It plays perfect now.