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mtl777 26th February 2009 08:49 PM

Plug GTQ2 to power conditioner or wall outlet?
Hey guys, sorry for this newbie question. I was advised to plug my GTQ2 mic preamp directly to the wall outlet rather than to my ONEAC CY1115 power conditioner (passive isolation transformer). The way I understood the advice, in a residential area like where I live where there are no electrical disturbances from heavy machinery and the like, the power is already clean. Adding a power conditioner is unnecessary and will even make the power quality less than ideal. Is my understanding correct? If so, I'd like to know what's the explanation for this. Prior to this, I had always thought that good power conditioners are supposed to improve the power quality or at least not degrade it, no matter whether the power is already clean or not. And I think my power conditioner is of good quality as ONEAC is a reputable manufacturer. Not having doubts on the advice, I just want to understand why.

Thanks in advance for your help! :)

dmills 28th February 2009 06:35 PM

If the power supply is even halfway right then power conditioning is pretty much irrelevant in most cases.

Just plug the benighted thing in, it will be fine either way.

There are a couple of reasons to be wary of power conditioners unless you know (as in have measured) that you have a problem:

1: Cheap 'surge protection' often means shunting surges to ground, and while this should not have any effect on properly designed balanced audio gear, it can add noise to unbalanced kit or to poorly done balanced audio stuff.

2: Tap changers can if implemented less then perfectly produce very strange voltage waveforms when tap changing.

3: Feroresonant transformers can do some odd things when presented with high crest factor loads.

4: Most surge suppression that is not installed right at the distribution board has a Ze value far too high to help with the sort of common mode surge that something like lightning induces.

For these reasons if I was selling a product about which I was confident in the power supply design, I would probably rather it was plugged straight in unless there was an known, identified and quantified reason to use a power conditioner.

I have never really understood the whole paranoia about power in the audio world, power supply design is well understood and is not at the end of the day rocket science (Especially for something small signal like a mic preamp).

Mad Dans rules for power supply design:

1: Ensure the unregulated rail keeps the regs in regulation at minimum rated mains voltage, bottom of capacitor rating tolerance, maximum load and minimum supply frequency.

2: Ensure the heatsinks can cope with maximum load at maximum supply voltage.

3: Do not make the caps bigger then you need to! It increases the RMS current in the transformer and rectifier (and thus the IIR losses), it also costs money and space.
Also remember to calculate the ripple current and make sure it is within ratings.

4: Bridge rectifiers get a 470nF cap across each diode to reduce RF generation.

5: Power inputs get a two stage mains filter fitted (Mostly to control conducted emissions).

6: If building high value digital electronics, and particularly if using a switchmode topology, fit an over voltage crowbar.

Regards, Dan.

mtl777 1st March 2009 04:01 AM

Thank you so much for the explanation! :) I'm not really knowledgable enough to understand all of it, but I get the idea.

I guess it applies especially for audio gear. But what about computer gear such as my PC, monitor, printer, scanner, etc.? Would it also be better to plug them directly to the wall? I hope it doesn't matter as much with these equipment since they do not pass any audio. I just really want to find a good use for my ONEAC as I would not like this relatively expensive ($150) "power conditioner" to go to waste and become a useless doorstop. :D

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