Check the potential from the chassis to house ground with a volt meter. The lower voltage is the correct position.
14 responses Add your response
1.) Get a simple volt/ohm meter.
2.) Detach interconnects and speaker cables from the amp.
3.) Attach a *bi-polar cheater plug to the three-prong
plug on the amplifier power cord.
4.) Set the VOM to AC volts with an approximate range
of 0-100 VAC.
5.) Remove the trim plate from the wall outlet.
6.) Plug the amplifier power cord (with cheater plug
attached) into the wall socket. Do not turn on the
7.) Using the VOM, measure the voltage between a point on
the amplifier chassis (a bare metal spot like a
chassis screw or some unpainted part of the chassis)
and the galvanized metal mounting frame of the duplex
wall outlet. Note the reading.
8.) Remove the plug from the wall socket, rotate it 180
degrees and re-insert it into the socket. (The plug
blades are now in new slots) Measure the voltage again
as you did in #7.
9.) Whichever plug **position gave you the lowest reading
on th VOM is the way you want to plug in the amp (or
any other device you may wish to measure, into the
* A bi-polar cheater plug is a cheater plug (three prongs in, two prongs out) which has had the wider (neutral) blade filed down so it will fit the narrow outlet slot when you turn it over 180 degrees in step 8. You can't buy them, you have to make them.
** If you want to ground your amp (using all three prongs) but the best position (as determined above) leaves you with the ground prong out of line with the hole in the wall outlet, get a cheater plug with a green wire coming out of it. File down the wide blade so you can plug the power cord into the wall in the most desireable orientation you determined in step 9, and then wire the little spade connector on the cheater plug to the screw that holds the trim plate onto the wall outlet (you may have to use a longer screw).
I gather from your post the low position in off is correct.
I noticed you said to do the measurements with the power to the
off. I've had some amps that measure low in "off", but measure high when on. Reversing the plug the amp will be high when off, low when on, which is the way I leave it connected. Is this wrong?
Robbyg, Stuartbranson, Tbg:
Robbyg: The reason one makes the measurements with the component off, and all input/output connections detached is because what your trying to determine is how all the component's various circuits "grounds" combine and where that total is positioned electrically -- i.e is it closer to the "hot" blade of the power cord or the "neutral" blade of the power cord. Depending which way the blades of your equipment's power cord are oriented relative to the real "Hot" and "Neutral" of the electrical service in your wall, you'll get a bigger potential difference or "leak" in one position or the other. The position with the smallest leak will give you the least hum in your system when the component is finally turned on.
Stuartbranson: You little devil!! Of course you could, but what about when you start to get oldtimers disease like me, and forget what you did where. Or what if someone buys your house and can't understand why they keep getting shocks from their vacuum cleaner!!
Tbg: Soooo....you like a little electrical stimulation once in a while, do you?! "Higher leakage voltage" indeed! Listen: Audiophiles are a dying breed, so please be careful, we need you. If you find yourself craving higher and higher leakage voltages, please, email one of us before it's too late, your body fries your computer and you lose all contact with the outside world!
On some components with advanced power supply designs, "balanced power" will lower the performance quite noticeably. Before investing in such a device, you should check with the manufacturer of each component to find out if is suitable for use with such a device.
Here's a post i made about Noise, Hum and AC Polarity a few years ago. It may explain a few things to those that have questions or are confused about what to do. Sean
One of my friends was using a preamp that i was very familiar with. We discussed a few things over the phone and i told him that he had the polarity reversed on the preamp. I told him how to verify this and once he checked it, it was reversed as i had suspected.
After changing the polarity and listening for a while, he told me that he had never heard that big of a difference when playing with the AC on any component before. The reason why the differences were so obvious? This specific product has a built in noise trap / transformer damping circuit that requires specific polarization to work properly. Without the proper polarity OR using balanced power, that circuitry is completely negated and the preamp will never work or sound nearly as good as it can.
This is why i said that one should check with the manufacturer of the gear before investing big money in what could be a major step backwards in their AC systems. It is also the reason why i've touted high quality isolation transformers, as they will only strip away the noise without altering the polarity of the signal. Sean
Sean, my experience with asking manufacturers about using ac filters or transformers is that they always say it is better plugged directly into the wall. I have often found they are wrong, however.
Until I got the IsoClean transformers, I had always found transformers smeared the sound and slowed the transients.
Nsgarch, initially I found that leakage voltage measurement failed to be a guide for better sound, but the ultimate problem I had was with hum with phono caused by the ground of the turntable not really seeing a ground when plugged into the Equi=Tech. When I plugged directly into the wall, I had no hum. This turnout to be caused by my not having everything plugged into the Equi=Tech. I did not have my big subwoofer amp plugged into it.
John Tucker has suggested that the ground fault circuit on the Equi=Tech is responsible for my problems and suggested that I remove it. I just gave up and sold the Equi=Tech.
Running balanced AC to some gear and not to others within the same system is the same thing as introducing a ground loop. That's because the difference in voltage potential from hot to neutral varies with the way that each component is receiving their power.
In one method, you've got 120 volts of potential on the hot and the neutral tied to ground. In the other, you've got 60 / 60 volts divided between the hot and neutral. This is why filtering inside the gear becomes ineffective when used in balanced mode i.e. neutral is no longer at ground potential but has become an active part of the AC feed. Since most filters shunt the noise to neutral or ground, you've removed the "dumping ground" for the noise from the equation. This means that the noise remains in the gear and further contaminates the other components tied into that same balanced AC feed.
Once again, all of these types of systems introduce further non-standardized variables into the system. Rather than opening up the door for more problems, why not just optimize the standardized system that you've already got and we've been using for years? Using this approach, you're guaranteed that your components will work optimally with little chance for negating built-in design features and circuitry.
Until gear is actually designed and built to be run strictly on balanced power, introducing balanced AC as the source of power will provide rather unpredictable results in any given system. Sean
For everyone's info, and for what it's worth vis-a-vis our discussion about mixing balanced and unbalanced power:
I had about an hour and a half conversation with Brent Jackson (who is the CEO, chief engineer, etc) of ExactPower on this subject to see what he'd say (especially since I use both of his units, the EP regenerator and the SP balanced unit -- and do so only because I'm in an apartment now. When I had a house it was dedicated circuits with high-speed diodes on the breakers for surge protection and that was it!)
Anyway, his recommendation for using both units together was to put the EP regenerator at the speaker/amp end and plug in the amp, both (CLS) speakers, the subwoofer, and (using a longer 12 ga. PC) the SP balanced power unit, which I have near the source devices.
First I listened with all ground pins connected. It was pretty quiet except the sub which had some barely perceptable 60 ~ hum. So I started putting ground lifters on the devices plugged into the regenerator. That got any residual noise/hum, so I haven't messed with polarity yet on those devices (but you know I will ;-)