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Topic: Peavy Classic Twin Ground question |
Carter York
From:
Austin, TX [Windsor Park]
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Posted 18 Jun 2002 6:29 am |
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Howdy y'all,
I play through a Peavy Classic Twin, and there is a "Ground" toggle switch on the back of the amp, with a 'center' setting, then a setting marked '+', and a setting marked '-'. Can someone elaborate on this for me? I've never changed it from the center setting, and everything seems ok...
Thanks alot,
Carter York |
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Donny Hinson
From:
Glen Burnie, Md. U.S.A.
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Posted 24 Jun 2002 2:01 pm
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Well Carter, if you're not having any problems, you cam leave it where it's at! The three positions give 3 different grounding schemes (provided everything is as it should be) to reduce noise, and eliminate that dreaded "bite" you get when you touch any other equipment and your rig at the same time. The way I would set my switch is to plug a cord into the input, and turn the amp about half-way up. Now if you hold the cord by the insulation near the plug on the opposite end of the cord (don't touch the metal plug itself), and work your ground switch, you might hear 2 or 3 different hum levels. The position that hums the least is the "right" one.
Oh yeah, if you're still getting "bit" by another piece of equipment, do the same with that one.  |
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Bob Metzger
From:
Waltham (Boston), MA, USA
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Posted 24 Jun 2002 9:00 pm
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Without referring to the Peavey schematic, there are two generally incorporated philosophies for a three way switch in the AC section of a MI amp. The most common is to have a large capacitor switched between either the hot or neutral AC line and ground. That is to say, one end of the capacitor is connected to a ground point, many times it's the star ground point. The other end is switched between either side of the AC line and in the center position, the cap is connected to neither side, essentially out of the circuit. In a 3 prong AC grounded plug situation this cap, which filters line noise to ground, is of a minimal help in serious reduction of line noise, although occasionally it can help. This type of switch and cap filtering helps alot in a two prong AC cord, where there is no ground pin. However, this two prong system can be really unsafe (and very dangerous) and many people refuse to play high voltage equipment fitted with two prong cords. I concur. I always change them out to 3 prong cords with a ground pin for safety and I recommend you do the same before you're asked, as every musician is at least once in their career, to play on the rainsoaked cement stage barefoot; a truely shocking turn of events.
The other way you see a three way switch employed in the AC section is to reverse the hot and neutral lines. This can be of some help and I feel it's generally more useable than the 'filtering cap' idea. This is exactly the same thing as turning the AC wall plug around 180 degrees in the wall socket, except with the ground pin ruining the symmetry, that is not possible. (Hey, that's why those ground pins are always broken off.)
Depending on the era of Peavey amp you have, I think it's possible to have either of these systems but to be absolutely sure, one must consult the proper schematic for the unit involved.
On the other hand, if it ain't broke, don't fix it!
I guess enquiring minds want to know,
Bob M. [This message was edited by Bob Metzger on 24 June 2002 at 10:02 PM.] [This message was edited by Bob Metzger on 25 June 2002 at 11:28 AM.] |
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