here is what kevin covi had to say:
"The hum is coming from the 101D's, and unfortunately hum (and microphonics) are all-too-common attributes of directly-heated triodes."
i sent him a picture of my setup to which he stated:
"I can see right away that the Cab power supply is too close to the preamp, as are the components sitting on top. The DHT's are quite sensitive to external fields so it is essential to keep them far away from any equipment that contains a power supply. The output transformers are also susceptible in this way. The extremely high sensitivity of your speakers just compounds the problem. You also might try building electrostatic shields around the 101D's. As an experiment try placing an empty tin can over each tube to see if the hum goes away. Or maybe aluminum foil. Either way make sure the shields touch the chassis to shunt the noise to ground."
"The hum is coming from the 101D's, and unfortunately hum (and microphonics) are all-too-common attributes of directly-heated triodes."
i sent him a picture of my setup to which he stated:
"I can see right away that the Cab power supply is too close to the preamp, as are the components sitting on top. The DHT's are quite sensitive to external fields so it is essential to keep them far away from any equipment that contains a power supply. The output transformers are also susceptible in this way. The extremely high sensitivity of your speakers just compounds the problem. You also might try building electrostatic shields around the 101D's. As an experiment try placing an empty tin can over each tube to see if the hum goes away. Or maybe aluminum foil. Either way make sure the shields touch the chassis to shunt the noise to ground."