The left channel of the amp is buzzing loudly and the volume control does not turn the channel off. When I put it in the zero position a signal is still routed to the channel. I've replaced all the cables and verified that the mixer is good.

First of all remove the wires to the cartridge. With the amp on, touch each of the wires to the cartridge with your finger. one at a time. On one you should hear a loud buzz on the left and on another a loud buzz on the right.
If you get no loud buzz on the left. There is something wrong with either the connections between the deck, or the pre-amp of the amplifier. This will not effect any other function on the amp such as tape or cd.
If you do get a loud buzz on the left, check the cartridge connection or replace the cartridge.

Most likely a faulty cartridge. To check disconnect the leads to the cartridge. With the amp switched on touch each of the wires one at a time with your finger. On two you will have little or no response but on one you should hear a buzz on the left and on the other a buzz on the right. If the buzz are equal in volume then the cartridge is faulty. If the buzz is weak on the left, then that suggest a faulty pre-amp stage in the amp. This pre-amp only affects the record deck, so you won't get it on other functions.

Hi,

Did you left the amp on overnight with a guitar hooked up to it?

Many amps these days have an IC that controls the volume and other functions such as bass and treble. You need to follow the wiring from the volume control to where it meets up on the PC board, or follow the circuit if the control is mounted direct to the board. As this is on one channel you have the good channel to compare it with. If you are lucky there will be two of these IC's one for each channel. If not then the volume control connections will all go into one IC. Putting a insulated tool on parts of the amp will cause it to buzz when it's on, on each channel. That way you can find the faulty IC. But don't short any of the pins of an IC together.

I'm thinking you have an open shield ground on the RCA input side. Connecting speaker inputs possibly restores the ground. Try connecting the high level inputs then disconnect the remote end of the cables (floating the grounds).

Then get out an ohmmeter and find that open circuitor or bad solder joint between RCA ground and real ground in the speaker's amplifier. Or.... if speaker ground kills the hum and you want to use RCA Line Level input to the sub, just connect one minus speaker output on your source amp to one minus on the sub's amp.

That would depend on the preamp. Name it. A true preamp outputs a variable signal.

It's not clear from the manual what the state of the volume output is without the VCA. Most amps default to full ON and the preamp attentuates the signal with a volume control. Try it with a signal that fades in slowly so you can intervene if it gets too loud. If it's full ON a preamp will control its volume.

change the plugs on the chords.or both.they loose their resistance.good luck.

You need to determine if the fault is in the pre-amp section or power amp part. Look around for damaged or burnt parts. If you turn up the volume on the left channel and you hear a weak signal then the pre-amp will be OK. If not then start with that section. Remember the right channel will be the same as the left so compare the parts. If it looks odd in the left it might be the faulty part!
You can apply the Buzz test! Being careful not to touch the power supply parts, touch the two channels in various places with a srewdriver. On the right you should get a buzz showing the signal is there, so touch the left in the same place! And so on...PS don't short anything with the screwdriver!

Sounds like your master volume is turned up too much. The channel volume will make the squealing go away(caused by high gain and humbuckers). The best thing to do is dial in your favorite presets and change the channel volume to the correct level with the master volume where you usually keep it. I use my Spider Valve at master volume at about noon and the channel volume between nine o'clock and noon. Let me know if this does not solve the problem......