A lot of good comments have been made, and, yes, it certainly seems possible that the condition of the tubes in your line stage preamp may be a factor. Especially given the unusually high 30 db gain that the preamp provides. I'll add the following to what has been said:
First, it appears that your system includes an unusual multitude of different power conditioning products. Some such products do unusual things with the power line grounds, which very conceivably could result in some setups in hum, noise, and/or sound quality issues. I would suggest that for experimental purposes you simplify the setup as much as possible, eliminating all of those things, as well as any components that are not necessary for vinyl playback.
Also, when you do that try temporarily using a cheater plug (a 3-prong to 2-prong adapter, with the ground not connected to the wall plate screw) on the AC plugs of each of the remaining components, one at a time. That will break any ground loops that may be contributing to the problem.
Also, it's not clear from your system description photos where the turntable, phono stage, and preamp are located, relative to the components that are shown. If any of them, or their associated cabling, are located near the power amp or the power conditioners, that may be contributing to hum pickup.
Finally, I see that the default settings of your Acoustech PH-1P when in LOMC mode result in an input capacitance of 10,000 pf, which seems wacky to me and could result in excessive sensitivity to RFI pickup. Jonathan Carr, who designed your cartridge, has said in past threads here that in general load capacitance that is applied to LOMC's should be kept as low as possible. 10,000 pf is extremely high. I'm not sure if that value can be readily changed in the Acoustech to the moving magnet default of about 200 pf, by changing the position of an internal jumper. If it can be readily changed, I would suggest that you do that and reassess the sonics it provides in LOMC mode, without the head amp.
Good luck. Regards,
-- Al
First, it appears that your system includes an unusual multitude of different power conditioning products. Some such products do unusual things with the power line grounds, which very conceivably could result in some setups in hum, noise, and/or sound quality issues. I would suggest that for experimental purposes you simplify the setup as much as possible, eliminating all of those things, as well as any components that are not necessary for vinyl playback.
Also, when you do that try temporarily using a cheater plug (a 3-prong to 2-prong adapter, with the ground not connected to the wall plate screw) on the AC plugs of each of the remaining components, one at a time. That will break any ground loops that may be contributing to the problem.
Also, it's not clear from your system description photos where the turntable, phono stage, and preamp are located, relative to the components that are shown. If any of them, or their associated cabling, are located near the power amp or the power conditioners, that may be contributing to hum pickup.
Finally, I see that the default settings of your Acoustech PH-1P when in LOMC mode result in an input capacitance of 10,000 pf, which seems wacky to me and could result in excessive sensitivity to RFI pickup. Jonathan Carr, who designed your cartridge, has said in past threads here that in general load capacitance that is applied to LOMC's should be kept as low as possible. 10,000 pf is extremely high. I'm not sure if that value can be readily changed in the Acoustech to the moving magnet default of about 200 pf, by changing the position of an internal jumper. If it can be readily changed, I would suggest that you do that and reassess the sonics it provides in LOMC mode, without the head amp.
Good luck. Regards,
-- Al