Hi Michael,
Have you tried changing the 6SN7s? See this thread from 2012, in which you participated. It seems that the VAC Renaissance amps can hum if heater-to-cathode leakage is excessive in the 6SN7s.
Also, I would suspect that you have two problems present, one internal to the amp that is causing the hum with the volume control at min, and a different problem which adds to the hum when the volume control is raised. If you’ve found that lifting the AC safety ground on the preamp or the amp does not affect either problem, the cause of the second problem figures to be somewhere upstream of the amp.
Also, DC offset by definition is zero Hz, and so it would not cause a hum. And as you realize it is very unlikely to be present in the case of an amp having transformer-coupled outputs.
Best regards,
-- Al
Have you tried changing the 6SN7s? See this thread from 2012, in which you participated. It seems that the VAC Renaissance amps can hum if heater-to-cathode leakage is excessive in the 6SN7s.
Also, I would suspect that you have two problems present, one internal to the amp that is causing the hum with the volume control at min, and a different problem which adds to the hum when the volume control is raised. If you’ve found that lifting the AC safety ground on the preamp or the amp does not affect either problem, the cause of the second problem figures to be somewhere upstream of the amp.
Also, DC offset by definition is zero Hz, and so it would not cause a hum. And as you realize it is very unlikely to be present in the case of an amp having transformer-coupled outputs.
Best regards,
-- Al