On May 5, 2017 at 12:19, Ernie Gilman said...
You're doing what I sometimes do: you're letting words get in the way of finding a solution. You're defining grounding in an accurate but too narrow way. Ground and grounding mean different things in different situations.
In talking about turntables, "ground" is the reference point from which voltages are measured. This is usually the chassis of the preamp that the cartridge is connected to. Grounding is connecting together the chassis of the different components in a system.
Turntables had a ground wire and new ones may or may not have this. I have seen situations where disconnecting this wire caused the hum to stop. I already called this 'equipotential' vs actual grounding- not much else should be needed, other than the knowledge that the turntable ground may need to be connected to the preamp/AVR ground, although I forgot to mention that Pin 1 might need to be disconnected in the event that it's the cause of the hum.
If one were to connect up a turntable that had a ground wire by plugging the RCA cables into a preamp and connecting the ground wire to an earth ground, the amount of hum would be AMAZING! That's because what's meant is chassis ground, not earth ground. Chassis ground might be connected to earth ground for other reasons. For instance, if you have an AM antenna on an AVR, connecting the chassis to earth ground makes the antenna signal appear stronger.
I know this and it's the reason connecting the ground wire is optional. However, it might be possible to reverse the power plug if the turntable is old enough. FOr a 1980s model, that can't happen unless someone installed a grounded power cord or clipped the + tang on the plug.
RS is not necessarily dead.
That's an excellent tool and will do EXACTLY what buzz's suggestion of a headphone will do: if hum is present at the output of the turntable all by itself, it will prove that the turntable itself is causing the hum. If there's no hum when using headphones or an amp like this, that means the problem is due to something about the interconnection of the turntable with other products. That's no proof, however, that messing with the connections of chassis or other internal parts, dare I say circuit grounds, of the turntable will solve the problem.
But the best way (and the reason the battery-powered amplifier/speaker works best) is because it's completely isolated until the signal cable is inserted. Using a headphone amp that uses a wall wart or any other connection to the AC supply raises the risk of some kind of interaction.
Well, if RS isn't dead, I'll paraphrase Frank Zappa- "RS isn't dead, it just smells funny".
FWIW, I went to the only local RS store last week and if RS had hired the guy (and others like him) behind the counter years ago, they might not be in this position. They hung their hats on the wrong products.
