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What position should ground switch be in?

M

mr80htz

May 15, 2018
801
694
#1
Hey talkbass peolle, iihave a question that your wisdom could answer. I have just bought a Traynor YBA 1 Bass Master...love it. It has a ground loop switch on the back. What does it do? What position should it be in? Thanks peeps. :)
 
#3
If this is an older amp with a two-prong cable plug you should have it updated to a three prong "modern" plug and cable. Much safer that way. It should not be a very expensive job if you take it to a tech. I had and liked a YBA-1 many years ago. Wouldn't mind having it now.
 
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#4
Hi mr80htz :)

mr80htz said:
It has a ground loop switch on the back. What does it do? What position should it be in?
Click to expand...

A ground/ lift switch disconnects your XLR D.I out from the amp' s ground connection. (in the "lift" position)

That way the amp' s ground is not connected to the table' s ground.
(to avoid a ground loop between amp and mixer, which can lead to a ground hum)

Raf Seibert said:
As a rule, newer amps with proper grounding don’t have this problem, but older amps may. The switch does the same thing as taking a two prong plug out and plugging it back in the other way.
Click to expand...

monty-python-no-o.gif


Your amp will still be grounded!!!!!!! (via its three prong power cable)

Never ever use an amp that is not grounded! You will risk your life!!!!!

I hope I can save some lives here! :laugh:


may the bass be with you

Wise(b)ass
 
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#5
Raf Seibert said:
If the amp does not hum, leave it alone. If you have a strong hum, try changing the ground loop switch to the other position. As a rule, newer amps with proper grounding don’t have this problem, but older amps may. The switch does the same thing as taking a two prong plug out and plugging it back in the other way.
Click to expand...

If it's like the Fenders of the same era, the ground switch does NOT operate as if you inverted the two-prong power plug. Instead, it just shunts a capacitor to ground across one leg of the power cord or the other. Many people remove this cap, as it doesn't really help much with hum and can cause a deadly fault condition if the cap fails as a short. I have to say, I've never actually known of a case of that cap failing that way, but I guess it doesn't hurt to be safe about it. You definitely should have a three-wire power cord and plug put on it.
 
#7
Oh...my boner. I just presumed the OP had an original YBA-1. I'm not aware of any amp that ever employed a 'ground reverse' circuit that just swapped the two power lines as if the plug had been reversed, but all my tube amp experience has been with Fenders and Ampegs.
 
#8
Wisebass said:
Hi mr80htz :)



A ground/ lift switch disconnects your XLR D.I out from the amp' s ground connection. (in the "lift" position)

That way the amps ground is not connected to the table' s ground.
(to avoid a ground loop between amp and mixer, which can lead to a ground hum)



View attachment 3307405

Your amp will still be grounded!!!!!!! (via its three prong power cable)

Never ever use an amp that is not grounded! You will risk your life!!!!!

I hope I can save some lives here! :laugh:


may the bass be with you

Wise(b)ass
Click to expand...
Back in the day, I would touch my bass strings against the guitar players or a mike stand and look for sparks.... That's how you know to flip the ground switch... just another tip from your old uncle Dbase ;)
 
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#10
Redbrangus said:
I'm not aware of any amp that ever employed a 'ground reverse' circuit that just swapped the two power lines as if the plug had been reversed
Click to expand...
Peavey for one did that. There was no ground switch, instead they used a DPDT center off power switch. You flipped it in whichever direction gave less noise.
If it's like the Fenders of the same era, the ground switch does NOT operate as if you inverted the two-prong power plug. Instead, it just shunts a capacitor to ground across one leg of the power cord or the other. Many people remove this cap, as it doesn't really help much with hum and can cause a deadly fault condition if the cap fails as a short.
Click to expand...
It did work, really well. I've never heard of a confirmed instance where the cap shorted out, that much seems to be urban myth. What would happen a lot was a shock when touching your strings and the metal parts of your instrument while touching another amp, or anything connected to another amp, like a mic. You couldn't get a full on 60 Hz AC zap, because the cap didn't pass 60 Hz AC to the chassis, it only passed the high frequency harmonics of that 60 Hz AC. They had to do it this way because back when there was no third wire connection from the chassis to ground it was the only more or less safe way to ground the chassis.
OP, it the amp has a two wire cord get it retrofitted with a 3 wire by a qualified tech.
 
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#11
Thanks folks. It's a '71 Traynor and has had a 3 prong outlet installed on the chord. Don't know if the ground switch has been disconnected internally. I was just wondering which position the switch should be in
 
#12
mr80htz said:
Thanks folks. It's a '71 Traynor and has had a 3 prong outlet installed on the chord. Don't know if the ground switch has been disconnected internally. I was just wondering which position the switch should be in
Click to expand...

If the circuit is still intact, whatever position makes the amp quieter. Just because there is a three-prong plug, that doesn’t necessarily mean that the ground circuit has been disabled. You’d have to look inside the chassis to know for sure.
 
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#13
Rick James said:
Peavey for one did that. There was no ground switch, instead they used a DPDT center off power switch. You flipped it in whichever direction gave less noise.
It did work, really well. I've never heard of a confirmed instance where the cap shorted out, that much seems to be urban myth. What would happen a lot was a shock when touching your strings and the metal parts of your instrument while touching another amp, or anything connected to another amp, like a mic. You couldn't get a full on 60 Hz AC zap, because the cap didn't pass 60 Hz AC to the chassis, it only passed the high frequency harmonics of that 60 Hz AC. They had to do it this way because back when there was no third wire connection from the chassis to ground it was the only more or less safe way to ground the chassis.
OP, it the amp has a two wire cord get it retrofitted with a 3 wire by a qualified tech.
Click to expand...

I totally agree that the potential danger of the so-called 'widow-maker' cap has been way over-blown in some quarters...I never heard of it being an actual problem in the wild, either. IME, the Fender-style 'ground-reverse' switch did help some with HF-type hash on power lines, like fluorescent or neon buzz, but didn't really help on the 60/120 Hz hum that was more often the problem. And I certainly remember being zapped more than once holding my bass and contacting a 'hot' mic or another amp. I once saw a guitar player draw a spark about 3/4" between his lips and a mic...Yikes! That proved to be a problem with his vintage guitar amp, IIRC...I'm just glad that didn't happen to me. And I've also seen many 'seasoned' players touch their plugged-in instrument to a mic without holding on to the strings to test for a potential 'bite'. Probably not a bad idea, even in these modern times.
 
#14
I haven’t been killed by the “death cap”, but I have been bitten by them a couple of times. After that, any amp I bought got a 3 prong cable and a proper chassis ground as the FIRST thing I did to it. If a used amp came with a 3 prong plug, I’d open it up and make sure it was connected properly.
 
#15
I may be wrong, and I love to be corrected, but I believe I heard from an old amp designer that chassis doesn't always necessarily mean ground. Particularly on a much older amp, which is more likely to not have a three prong power cord with a ground. Just adding a grounded cable to any amp without one without confirming the circuit design can be a bad idea. Again, correct me with documentation if I am wrong.
 
#16
dbase said:
Back in the day, I would touch my bass strings against the guitar players or a mike stand and look for sparks.... That's how you know to flip the ground switch... just another tip from your old uncle Dbase ;)
Click to expand...

After you touched your bass strings against the guitar players and saw sparks, what happened then?

I assume you advertised for new guitar players?
 
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#17
Wisebass said:
Hi mr80htz :)



A ground/ lift switch disconnects your XLR D.I out from the amp' s ground connection. (in the "lift" position)

That way the amps ground is not connected to the table' s ground.
(to avoid a ground loop between amp and mixer, which can lead to a ground hum)



View attachment 3307405

Your amp will still be grounded!!!!!!! (via its three prong power cable)

Never ever use an amp that is not grounded! You will risk your life!!!!!

I hope I can save some lives here! :laugh:


may the bass be with you

Wise(b)ass
Click to expand...
VERY TRUE DONT DO IT :thumbsup:
 
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