OK so I took my amp apart and put it back together and I can't find any mistakes. First I want to decrease the hum. Maybee lower the voltage. I have a GZ34, A choke between, a 22uF and a 33uF is there a better way to configure my power supply to decrease hum how would i do a tranformer coupled using a choke possible? I hear louder than normal 60 cycle hum.. More than i like anyway. thanx for any help..

What kind of resistance do you have going to the pre-amp tubes? What kind of capacitance do you have after this? Is the hum coming from the output tubes or drivers/pre-amps? Removing drivers will tell. Do you have the plates of the output tubes connected before or after the choke? Connecting after decreases hum. The choke must be capable of handling this load. Are you using a full wave rectification system? (Center tapped high voltage winding with ends feeding two plates of a full wave rectifier type tube) If, for some strange reason, your high voltage supply does not have a center tap, there are ways of achieving full wave rectification with a winding with no center tap. Either four solid state diodes may be wired as a full wave rectifier, or two dual diode rectifiers, each with electrically separate cathodes. If, for some reason your transformer is not equipped with a split high voltage winding, I can tell you how to construct a full wave rectifier using a single phase winding.

20 to 30 MFD is usually enough for filtering purposes in a full wave rectification system. Going as high as 50 or 60 MFD may improve matters. Using too high of a capacitance, especially right at the rectifier, can blow the rectifier (or cause arc-over) with the start-up surge. If you are using a tube, I assume it is a 5U4. A 5Y3 will be a bit more fragile, therefore capacitance should be kept below 60 MFD with this type of tube.

The Hum is coming from the output as far as I can tell. It is there with only the output tubes in. (no other tubes in the picture). I even disconnected the other stages b+ to check this. I think I have the plates conected before, so I will try after. cHoke is a 16H 100 or 150mA Hammond so should handle. Center tapped full wave GZ34 I am using. Lat question is I have built a star ground in my amp. everything grounds to it but I don't have it connected to the chassis. I have the safety ground connected to the chassis and one side of the of the AC(120) connected to the chassis
via a .05uF cap. should I ground circuit ground to the chassis as well? Also I read that you are supposed to connect shielding of the signal wire of the first stage the the plate of the tube you are running to is this right and leave the (shielding end) at the input jack dissconnected or cut of?

:What kind of resistance do you have going to the pre-amp tubes? What kind of capacitance do you have after this? Is the hum coming from the output tubes or drivers/pre-amps? Removing drivers will tell. Do you have the plates of the output tubes connected before or after the choke? Connecting after decreases hum. The choke must be capable of handling this load. Are you using a full wave rectification system? (Center tapped high voltage winding with ends feeding two plates of a full wave rectifier type tube) If, for some strange reason, your high voltage supply does not have a center tap, there are ways of achieving full wave rectification with a winding with no center tap. Either four solid state diodes may be wired as a full wave rectifier, or two dual diode rectifiers, each with electrically separate cathodes. If, for some reason your transformer is not equipped with a split high voltage winding, I can tell you how to construct a full wave rectifier using a single phase winding.
:
:20 to 30 MFD is usually enough for filtering purposes in a full wave rectification system. Going as high as 50 or 60 MFD may improve matters. Using too high of a capacitance, especially right at the rectifier, can blow the rectifier (or cause arc-over) with the start-up surge. If you are using a tube, I assume it is a 5U4. A 5Y3 will be a bit more fragile, therefore capacitance should be kept below 60 MFD with this type of tube.

That Really made a HUGE difference putting the HV for the output transformer after the choke. Now it is perfect except I notice when I turn the bass all the way on either channel it hums a bit could I improve on this somehow?

:The Hum is coming from the output as far as I can tell. It is there with only the output tubes in. (no other tubes in the picture). I even disconnected the other stages b+ to check this. I think I have the plates conected before, so I will try after. cHoke is a 16H 100 or 150mA Hammond so should handle. Center tapped full wave GZ34 I am using. Lat question is I have built a star ground in my amp. everything grounds to it but I don't have it connected to the chassis. I have the safety ground connected to the chassis and one side of the of the AC(120) connected to the chassis
:via a .05uF cap. should I ground circuit ground to the chassis as well? Also I read that you are supposed to connect shielding of the signal wire of the first stage the the plate of the tube you are running to is this right and leave the (shielding end) at the input jack dissconnected or cut of?
:
:
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::What kind of resistance do you have going to the pre-amp tubes? What kind of capacitance do you have after this? Is the hum coming from the output tubes or drivers/pre-amps? Removing drivers will tell. Do you have the plates of the output tubes connected before or after the choke? Connecting after decreases hum. The choke must be capable of handling this load. Are you using a full wave rectification system? (Center tapped high voltage winding with ends feeding two plates of a full wave rectifier type tube) If, for some strange reason, your high voltage supply does not have a center tap, there are ways of achieving full wave rectification with a winding with no center tap. Either four solid state diodes may be wired as a full wave rectifier, or two dual diode rectifiers, each with electrically separate cathodes. If, for some reason your transformer is not equipped with a split high voltage winding, I can tell you how to construct a full wave rectifier using a single phase winding.
::
::20 to 30 MFD is usually enough for filtering purposes in a full wave rectification system. Going as high as 50 or 60 MFD may improve matters. Using too high of a capacitance, especially right at the rectifier, can blow the rectifier (or cause arc-over) with the start-up surge. If you are using a tube, I assume it is a 5U4. A 5Y3 will be a bit more fragile, therefore capacitance should be kept below 60 MFD with this type of tube.

Glad the hum is reduced. I would shield all signal wires to the chassis, and also have B- connected to the chassis (center tap of the transformer). Make sure that any wires that have been shielded that connect to B+ have no possibility of touching the shield, or a short will occur.

Usually the wire leading from the jack to the grid of the first audio tube is shielded to the chassis. You may use shorting jacks in your amplifier that short out when the guitar plug is removed. This reduces the tendency of the amplifier to "nare" hum when instruments are removed.

Thomas