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110 (or 120) vs 220

Hi,

IF an amp can operate at both 110 and 220, and a dedicated circuit is being installed for that amp, is there an advantage to a 220 v circuit? Or is the answer "it depends on the amp"? Or is the answer simply "no"?
128x128jimspov
jimspov's avatar
jimspov OP
60 posts
 
Hi jea48,

That's a pretty thorough response - thanks. If it is against code I won't do it.

I presume that IF the unit was designed to run at 220-240 (as well as 110-120) that most of your concerns would be alleviated? Running other equipment off of the same circuit is theoretically possible with a voltage converter. But ya, I'd have to give up my new Zu mains cable. :(

Btw, thanks for pointing out that my country doesn't show up. I live in Canada and did enter that info, but for some reason it is not coming through on Audiogon. I've sent an e-mail to  support@easypost.com.


jea48
4,481 posts
 
I presume that IF the unit was designed to run at 220-240 (as well as 110-120) that most of your concerns would be alleviated?

Only if one of the 2 Line conductors feeding the equipment was a neutral, a grounded conductor.

One Hot ungrounded conductor. The other Line a neutral grounded conductor that is at earth potential.

In the US or Canada this can be achieved cheaply by using an autotransformer.

It can step up 120 to 240 where the neutral is common. The 240V out maintains the 120V feed common neutral.

Example:

http://www.toddsystems.com/geninfo.html

https://www.canadatransformers.com/what-is-autotransformer/


You can also do it by using an isolation transformer.

One secondary winding lead, leg, of the 240V out is intentionally connected to ground making it the neutral, the grounded conductor. This method is a lot more involved. It is not for a layperson without any experience with isolation transformers.

gs5556
1,236 posts
 
For an amplifier to be designed to run on either 120 or 240 it must have two fuses, one for the hot and one for the neutral. When it is running on 120, the fuse on the neutral is just dead weight and does nothing but provide continuity. When it's running on 240, that "neutral" is now doing duty as a hot conductor and can pull short circuit current under a fault -- hence the reason for the second fuse. Don't forget to change out the fuses to a lower (usually half) amperage since the current draw is now half at 240 volts.

If there in only one fuse then do not run it at 240 regardless if there is a split primary with a switch or jumpers capable of conversion or else you will run the risk of what jea48 outlined above.

Also, you should not run other equipment off a 240 circuit. Theoretically, you can pull power off one leg and feed it to a 120 outlet and run a neutral  back to the panel but that is against code because it unbalances the circuit. The correct way is to leave it dedicated. That circuit will have a 2-pole circuit breaker feeding a 250 volt receptacle (6-15 or 6-20) which has the blades rotated at a 90 degree angle (horizontal) so that you cannot accidentally plug a 115 volt appliance into that outlet, resulting in a pretty fireworks display.

Your electrician knows how to wire everything up if you decide to go with 240.
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jimspov's avatar
jimspov OP
60 posts
 
Ok. If the amp isn't designed to do both with no modifications from me then I don't want to do this. (I have a call in to the manufacturer).

I have a CPAP machine and it will automatically switch from 110 to 220 it I switch the power cord. Guess it isn't so simple for an amp!

For the interconnects, I was referring to a converter that you plug into the wall and then you plug the ancillary equipment into it. The converter takes 220 volts from the wall and converts to 110 for the equipment to use.
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