Streetdaddy
The problem with a noisy tube is that it may test well but still be noisy. I have a Hickock tube tester. While it performs several important tests it doesn't test for noise. Buying from a reliable tube vendor, Andy of Vintage Tube Services immediately comes to mind, is a good way to go if you call him and talk to him and tell him what's going on. In addition to being a tube merchant he is extremely knowledgable in general and can possibly give you greater insight into other possible causes and the MOST probable cause. If you are on a budget and just want to get the unit up and running the FIRST thing I would do is to buy a CHEAP reliably tested tube from a guy like Andy to see if it IS the tube. After the problem is resolved THEN you can consider different tubes which DO make a difference in the MHDT DACs. Hope this helps you going forward.
The problem with a noisy tube is that it may test well but still be noisy. I have a Hickock tube tester. While it performs several important tests it doesn't test for noise. Buying from a reliable tube vendor, Andy of Vintage Tube Services immediately comes to mind, is a good way to go if you call him and talk to him and tell him what's going on. In addition to being a tube merchant he is extremely knowledgable in general and can possibly give you greater insight into other possible causes and the MOST probable cause. If you are on a budget and just want to get the unit up and running the FIRST thing I would do is to buy a CHEAP reliably tested tube from a guy like Andy to see if it IS the tube. After the problem is resolved THEN you can consider different tubes which DO make a difference in the MHDT DACs. Hope this helps you going forward.