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In Reply to: not to hurt you posted by djk on November 1, 2016 at 15:46:47:
It's there to induce audible hum to allow you to polarize the cord properly.
Does it say that in the guitar amp's owners manual?I sure could see where it could cause a ground loop hum when the HOT mains line was connected to the capacitor making the chassis Hot when referenced to any grounded object, that is connected to the service neutral conductor, (The Grounded Conductor). Such a connection could be made with the body of a guitar player.
What if the guitar amp, metal chassis, was sitting on a wood table all by itself isolated/insulated from any grounded object. Would reversing the plug change the noise floor of the amp heard through the speaker? If so can you be sure it is due to whether the cap is connected to the AC mains neutral line or the Hot line. Theory for use of the cap should show the best place is connected to the neutral line. The grounded conductor, Correct?
What if the amp had a lower noise floor when the cap was being fed from the Hot AC mains line? How does the amp know one line is the hot ungrounded conductor and the other line is the grounded conductor without a reference to ground of any kind?
As for hurting a person that maybe playing a guitar hooked up to the amp when the chassis is hot referenced to earth ground, (the source service neutral conductor), I have read the old paper condensers were very unreliable and prone to excessive AC leakage. If the guitar player was playing the guitar totally isolated/insulated from any grounded object, (not referenced to the service neutral), then the player should be safe. But what if?
I agree with what Ralph said in his post below. Back then the designers didn't really understand grounding and noise reduction.
I also agree with FenderLover. Anybody that owns one of the old amps with the paper condenser, capacitor, should remove the cap and rewire the amp using a 3 wire cord and plug.
The guitar amp may operate just the same or better without the cap connected to one of the AC mains and the chassis.
Below is a link for the schematic wiring diagram for a McIntosh MC 60 mono amp. The design is for 1956. You will note the designer of the amp did not use the cap.
Food for thought. I know of at least one person with a pair of MC 60s that has both AC power plugs orientation plugged into the wall outlet the same direction. The guy is a member on the Steve Hoffman Audio Forum. He says the way he has them plugged in now yields the lowest noise floor for the sound he hears through the speakers of his audio system. The Why? My guess he has both power transformers primary windings of the MC 60s connected to the hot and neutral for the proper polarity orientation.
I wish he would verify 100% the polarity is correct for each transformer with a volt meter. What he did was to check the power cord of each amp for the identified neutral conductor marking on the cords. In his case the identified conductor has a raised ridge that runs the entire length of the cord. He then made sure that side was plugged into the neutral contact side of the wall receptacle. Use of a volt meter would tell him 100% for sure.
Edits: 11/02/16
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Follow Ups
- RE: not to hurt you - jea48 11:23:22 11/02/16 (1)
- RE: not to hurt you - triamp 01:20:11 11/07/16 (0)
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