First of all, let the seller know about the problem. Handle this however you want.
If you have a digital multimeter and know what your doing, you could check the amp and preamp to a known good ground. This would at least tell you where the voltage is coming from.
The hum being louder in one channel doesn't sound normal either IMO.
The voltage being present on the amps cabinet can be dangerous. It could be capacitance somewhere causing it, or something that may have been worked on. Sometimes some amps do have a small voltage on them from moisture if the amp was cool, and can have condensation in them also.
If the amp has a grounded plug, make sure the outlet is properly grounded. If it just has a two prong plug, try reversing it in the outlet, if the prongs (plug) are the same size, allowing the reversal to be done, plugging it in. Check and try the preamp for the same (plug reversal).
If you try reconnecting this equipment, make sure you unplug everything (from outlets) first, before making, or changing any connection. With this voltage difference, if you plug something in and the center pin (RCA) makes contact first, before the outer shield does, it will feed that voltage to the delicate transistors (amp or preamp) and damage them. So be careful with this, and most important, make sure you don't get shocked.
Some amps will hum with nothing plugged in them. A shorting plug (RCA) on the inputs of the amp will prevent this. Some people make their own (the center pin is shorted to the shield), or you can buy some like these in this link.[http://www.mcmelectronics.com/product/27-5335&scode=GS111&CAWELAID=240971936]
If you have a digital multimeter and know what your doing, you could check the amp and preamp to a known good ground. This would at least tell you where the voltage is coming from.
The hum being louder in one channel doesn't sound normal either IMO.
The voltage being present on the amps cabinet can be dangerous. It could be capacitance somewhere causing it, or something that may have been worked on. Sometimes some amps do have a small voltage on them from moisture if the amp was cool, and can have condensation in them also.
If the amp has a grounded plug, make sure the outlet is properly grounded. If it just has a two prong plug, try reversing it in the outlet, if the prongs (plug) are the same size, allowing the reversal to be done, plugging it in. Check and try the preamp for the same (plug reversal).
If you try reconnecting this equipment, make sure you unplug everything (from outlets) first, before making, or changing any connection. With this voltage difference, if you plug something in and the center pin (RCA) makes contact first, before the outer shield does, it will feed that voltage to the delicate transistors (amp or preamp) and damage them. So be careful with this, and most important, make sure you don't get shocked.
Some amps will hum with nothing plugged in them. A shorting plug (RCA) on the inputs of the amp will prevent this. Some people make their own (the center pin is shorted to the shield), or you can buy some like these in this link.[http://www.mcmelectronics.com/product/27-5335&scode=GS111&CAWELAID=240971936]