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I lived off grid for ±28 years in the NC mountains. After no electricity for several years, we made a little hydro system with a large battery bank and inverter, that system slowly shifting as tech and climate changes evolved, both changing notably over that time. The annual rainfall remained about the same, ±60 inches a year, but as things changed, it became less and less regular. For years, in the hotter times of summer, about once a week it would rain, seemingly in part from evaporative localized cloud development. But gradually, weather patterns shifted, and there were longer and longer dry spells between heavier downpours. The ground dryer, and rains bigger, unable to take it in, less and less was retained, and more and more ran off down stream. Though still 60 inches of rain per year, my lowest gallon/minute average in high summer went from 90 gpm in ’83, to about 20 gpm over the about 24 years we used that system.
Luckily tech changed also, though in this case for the better. Relative to inverters, I went from a pretty good (for the time) “modified sine wave” that mimicked a sine wave by overlaying a lot of squares to look sort of like a sine wave, but still with a lot of noisy corners on those square’s edges. I used an isolation transformer with it for the stereo, and this helped, but the inverter, in a small building well away from the house, buzzed a lot, and the iso transformer buzzed a lot too, presumably from the noisy power it received, so I had to make a little house for it outside also. Not surprisingly, my then NAD amp transformers buzzed notably too, and you could hear the buzz without music from the ADS L1090, 90 db speakers. Still, considering this was the best I could do, I got used to it, loving the music while watching for better tech.
Next was a Trace modified sine wave inverter that was supposed to be much closer to true sine, and it was notably less noisy than the earlier behemoth. But still buzzing transformers, in the inverter, iso transformer, and the amp.
Getting closer, and over noise, I found an Exceltech (sp) “true sine wave” inverter, designed for sensitive equipment, especially medical, and supposedly steady and quiet. And though getting this close to a true sine was really expensive then, they made smaller units, and I got one just for the audio circuit. The best yet by far, no more Iso Transformer, but still noisy transformers in particular.
In the later 90s, after a lot of back and neck damage from being rear-ended by a tractor trailer at high speed, and us nearly stopped, I needed a pugmill to wedge clay for me in our pottery, and an electric wheel I could stand up at. The pugmill needed a lot of power (for a small off-grid system anyway). So I got a “close to” state of the art, larger Trace “pure sine wave” inverter. Designed to be tied to the grid, its power was said to be as, or more, reliable and good quality than the grid, making interchangeability possible. The relatively low measuring noise was acceptable by the grid standards, but I don’t think the noise nice audio can pick up and convey was the criteria. It was less noisy than the previous setups, but I guessed part of that was that the whole system was making less noise, including reduced, but not gone and EMF and RFI from the Inverter. I still had amp transformer hum and minor noise from the speakers… more than I have now, but finally getting pretty good (though I bet it would drive me nuts with my 97-98 db speakers now).
With MMs experience, it looks like this tech has progressively continued to improve. But I also know there are a lot of inverters and small backup systems out there, and there will be those that are less noisy than others, so research makes sense to me. And as I pointed to, seems to me it is not necessarily just the inverter in a lot of cases, but how it, and the battery are fed. Also, from researching and seriously upgrading my RV solar system recently, I gather it is still true that “true” or “pure” sine wave inverters are “flexible” relative to noise… So though I don’t have good answers, I feel confident that for very low noise audio, checking pretty carefully into various inverter based backup setups is a good idea. Aside from audio folks that maybe MM can point us to??? off grid Hamm radio operators seem to be pretty good “noise sniffers.”
Yours is an exciting story for me MM! Glad you broke through!
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Power Conditioning (Read 1304 times)
