MC-250 cord swap?

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MC-250 cord swap?

Postby NSP » Thu Jul 12, 2012 7:12 pm

Just picked up a McIntosh MC-250 with the original two prong power cord. Is it advisable to swap it out for a three prong or will the two prong into my power conditioner be ok? If a swap is the way to go, can anyone point me in the right direction as to the procedure? I've done some searching but haven't found anything. Thanks folks!
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Re: MC-250 cord swap?

Postby JonnyBoy » Thu Jul 12, 2012 7:34 pm

I would like to hear the story behind it too, mine has a 2 prong and I have wondered if it would be best to establish a ground to the amp. I run mine through a power conditioner too and its never acted abnormal. It does have a fuse for shorts and current spikes, but I would think grounding it would be a good idea to me.

I am still using a two prong and it works great.
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Re: MC-250 cord swap?

Postby tcsned » Thu Jul 12, 2012 8:14 pm

My MC2100 has a grounded plug so I'm guessing it had been replaced. Doesn't seem like it would be that difficult of an operation - finding where to ground the plug would be the only issue. The main issue of not changing it is possibly getting shocked by a microphone. Been there, done that, ain't no fun.
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Re: MC-250 cord swap?

Postby waldo041 » Thu Jul 12, 2012 9:04 pm

you only need 1 path to ground, anymore and you could create ground loops. if the preamp is grounded with a 3 prong then the amp can be 2 prong or vice versa. they are grounded together with the cable that links them or at least should be. however a power conditioner is not sufficient if both the power and pre amps are 2 prong, you will become the path to ground.

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Re: MC-250 cord swap?

Postby NSP » Fri Jul 13, 2012 5:33 am

waldo041 wrote:you only need 1 path to ground, anymore and you could create ground loops. if the preamp is grounded with a 3 prong then the amp can be 2 prong or vice versa. they are grounded together with the cable that links them or at least should be. however a power conditioner is not sufficient if both the power and pre amps are 2 prong, you will become the path to ground.

~waldo


Thank you Mike. As always, appreciate your input. I'm using Brad's pre, so I should be good to go. I'm happy that I can keep the mac in it's original condition.

Peace,

-Tim
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Re: MC-250 cord swap?

Postby Smolder » Fri Jul 13, 2012 6:51 am

I picked up an mc-50 last week... the first thing I did was put a three prong grounded power cord in it. Absolutely no way I'm playing a guitar through an amp, whether in my basement or on stage, without it being grounded. Life is too short already.
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Re: MC-250 cord swap?

Postby mgbills » Fri Jul 13, 2012 10:17 am

I had my Mc2100 serviced by Classic Tube Audio (Vancouver, WA). He's a one guy shop. Pat reiterated Mike's point. These amps were designed to be used in a system, and that system was grounded at 1 point. He recommended not changing the cord in my application.
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Re: MC-250 cord swap?

Postby TRG » Fri Jul 13, 2012 11:36 am

I swapped out the 2 prong cord on my 250 for a 3 prong IEC inlet, so that I can just remove the plug when transporting and plug back in when ready. Been working great for me...
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Re: MC-250 cord swap?

Postby Smolder » Fri Jul 13, 2012 11:54 am

mgbills wrote:I had my Mc2100 serviced by Classic Tube Audio (Vancouver, WA). He's a one guy shop. Pat reiterated Mike's point. These amps were designed to be used in a system, and that system was grounded at 1 point. He recommended not changing the cord in my application.


I hear that... but that system was for home audio back in the day when grounded household wiring was not the code standard. The main reason that the audio guys like the two prong is to remove the ground loop and subsequent hum. It's just a bit different when you holding a conductor and stepping up to a mic that may or may not be grounded compatibly. If you are running a pair of macs, you can address any loop issues in front without lifting the ground. Just my opinion though.
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Re: MC-250 cord swap?

Postby mijknahs » Fri Jul 13, 2012 12:00 pm

It shouldn't be too hard to replace the cord if the new cord is a similar gauge/thickness.
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Re: MC-250 cord swap?

Postby tcsned » Fri Jul 13, 2012 12:33 pm

TRG wrote:I swapped out the 2 prong cord on my 250 for a 3 prong IEC inlet, so that I can just remove the plug when transporting and plug back in when ready. Been working great for me...

That's a good idea . . .
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Re: MC-250 cord swap?

Postby waldo041 » Fri Jul 13, 2012 1:34 pm

Smolder wrote:
mgbills wrote:I had my Mc2100 serviced by Classic Tube Audio (Vancouver, WA). He's a one guy shop. Pat reiterated Mike's point. These amps were designed to be used in a system, and that system was grounded at 1 point. He recommended not changing the cord in my application.


I hear that... but that system was for home audio back in the day when grounded household wiring was not the code standard. The main reason that the audio guys like the two prong is to remove the ground loop and subsequent hum. It's just a bit different when you holding a conductor and stepping up to a mic that may or may not be grounded compatibly. If you are running a pair of macs, you can address any loop issues in front without lifting the ground. Just my opinion though.


a mic or pa system that does not have the same earth ground as your rig will shock you everytime REGARDLESS if you have 2, 3 or 4 - 3 pronged components within your rig. you become the path of least resistance everytime. fact is, you only need 1 earth ground within your rig and anymore is only providing a second path that can and usually does create a hum. if you are wanting to ensure you do not get lit up by the mic, a continuity tester with one probe on the ground pin(pin 1= earth pin) of the mic cable and one to your ground pin of your rigs outlet usually will tell you if you have the potential of getting shocked.

~waldo
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Re: MC-250 cord swap?

Postby tcsned » Fri Jul 13, 2012 9:03 pm

waldo041 wrote:a mic or pa system that does not have the same earth ground as your rig will shock you everytime REGARDLESS if you have 2, 3 or 4 - 3 pronged components within your rig. you become the path of least resistance everytime. fact is, you only need 1 earth ground within your rig and anymore is only providing a second path that can and usually does create a hum. if you are wanting to ensure you do not get lit up by the mic, a continuity tester with one probe on the ground pin(pin 1= earth pin) of the mic cable and one to your ground pin of your rigs outlet usually will tell you if you have the potential of getting shocked.

~waldo

sorry to derail a but, but Waldo, are you saying to put the continuity tester into then ground of the outlet the rig will be plugged into and on the ground pin on the plugged in mic cable with the PA on (I assume) and if it lights up then I'm gonna light up? I've got a gig at a club next month at a club that a regularly get a good night of shock therapy.
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Re: MC-250 cord swap?

Postby waldo041 » Fri Jul 13, 2012 9:13 pm

tcsned wrote:sorry to derail a but, but Waldo, are you saying to put the continuity tester into then ground of the outlet the rig will be plugged into and on the ground pin on the plugged in mic cable with the PA on (I assume) and if it lights up then I'm gonna light up? I've got a gig at a club next month at a club that a regularly get a good night of shock therapy.


yes and no. yes to the locations for the probes of the continuity tester. no, if the continuity tester lights up the two systems (your rig & PA) are on the same earth ground and you should not get lit up. but if the tester does not light up be sure to have a windscreen for the mic because you are gonna get lit up.

also, first you should always check your rigs outlet with one of these outlet testers, and if at all possible the pa systems outlet as well.

Imagehttp://electrical.hardwarestore.com/15-62-circuit-voltage-testers/receptacle-tester-281667.aspx

this will most of the time be sufficient, but the continuity test diagnosis whether or not they have lifted the ground somewhere within their system, knowingly or unknowingly.

if all these tests test OK. then you might want to look into something with the phantom power. turn it off in your mic's channel if possible. they could have a shorted cable sending 48 to 50Vdc to your lips.

~waldo
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Re: MC-250 cord swap?

Postby tcsned » Sat Jul 14, 2012 5:30 am

Thanks Waldo, that makes sense. See if I can have a electrocution free gig this time :-)
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