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In Reply to: RE: Just the opposite posted by Sondek on March 24, 2016 at 13:55:06
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Your old (pre self limiting) Corvette. You can run it up to 300 rpm over the redline. But you sadly found out running up 400 rpm just blew up your engine. You took it up to 300 rpm over numerous times. but 400 just was the step too far.
Speaking of steps. stepping UP to the edge of the Grand Canyon. No problem. A half step further, and you are sleeping with the angels.Another car example: Tire pressure too low? Not a problem at even only 14 psi.. Drive all day. When that same tire on the same roads started it's final day at 13 psi. After an hour It blew out. Who would have thought?
Nascar is a prime bunch of endless examples of those tiny 'too far' things that causes a series of further events and a crashed car.
I can go on and on, but the thing is there are plenty of examples of specific points where things change drastically. This guys transformer just happened to be at such a point between 115 and 120 volts
Edits: 03/25/16
all I was saying is that I am surprised in this particular case that only a 5 Hz difference is "too far" or "too much". For example, if you are one foot from the edge of the Grand Canyon, it would be ok to step forward 6 inches. But I certainly don't doubt you at all, in this case.
So, I reset my re-generator back to 120v and the buzzing came back. Reverted to 115v and buzz substantially reduced. The buzzing never went completely away, but is very much less noticeable @ 115v output from the re-generator. I am by no means expert in physics of transformers, but one thing to offer is that these are not your run of the mill garden variety transformers. These amps are specifically designed to drive electrostatic panels. Those trannies output thousands of volts not hundreds. Again, not sure if that has any bearing on what I am witnessing, but I am here to tell you that reducing the voltage does have an effect in my case. Quite audible. There may indeed be other factors at work here, but in the end the transformers run quieter and that's all I really care about.
Are these direct-drive OTL amplifiers? Oh, I guess you did mention they are from your Acoustats. Very cool. I use Beveridge 2SW speakers in one of my systems, also direct-driven. Although such amplifiers do put out high-ish voltage, sometimes the output voltage is much further increased after the secondaries, by use of voltage doublers, which is at the expense of current. But very very little current (at very very high voltage) is required to drive an ESL directly. Anyway, whatever one might have expected in terms of the effect of the AC voltage on vibration of the transformer, I don't doubt your direct experience. And those are probably unobtainium transformers, should one of them blow, so you are right to be conservative. I feel the same way about the power transformers in the Bev DD amplifiers.
BTW, Beveridges also very cool. Working ones are scarce as hens teeth. I'd love to hear them. Too damned bad we live so far apart.
You are right. Direct drive OTL's. In reading Jim Strickland's notes on the copy of the schematic I have, the transformers output ~2,200 volts. He then employs voltage doubler to bring what the tubes see to ~5,000 volts.
So, 3200V across the stators. But they are not like conventional ESLs in that the diaphragm does not carry a charge; the diaphragm is low impedance (coated with aluminum)and driven, I think, along with the stators. Why this works, I have to sit down and re-think every time. However, because of the lack of high tension on the diaphragm, in fact the panels have lasted for 30 years, by and large. It's the amplifiers that cause problems. I am endlessly thankful for the help of "Steve O", an inmate on TubesDIY, who is also an EE and an owner of Bevs. Steve held my hand long distance as I solved a vexing problem with one of my amplifiers, which after all was done turned out to be a bad solder joint on one capacitor in the output circuit. After a while, I figured out it HAD to be something stupid like that, because I had been through and rebuilt the entire circuit, pretty much, and the amp was still oscillating.
If the buzz is still there you probably have a ground loop. Regenerators act like an amp circuit. I lifted my ground to my regenerator per PaulMcGowan and gone.
After talking to him and Charles Hansen of Ayre I have lifted all my safety grounds with excellent results. What a difference.
ET
Wouldn't ground loop be audible through the speakers? As far as lifting the safety ground, no way. Not with something that outputs 5,000 potentially lethal volts. Out of the question.
I never use regens onan amp. I'd consider if the load used less than half the potential current of the regen.
Regens are notorious for squashing dynamics when you even get just peaks near the max potential of the regen.
ET
The PurePower unit runs everything through lead acid batteries which actually are capable of delivering more current than is available from the wall - for short periods obviously. As such, things never poop out. I've never experienced squashed dynamics with this setup.
I think you misunderstood me. It's about the output of the regen not it's input source. I think 3000 Watts out is the largest one made by the manufacturer you have which is hefty and would provide 25 amps of current. Still no regen made by anyone should be used with amps if you are going to use much more than half to two thirds of the regens potential output. Headroom for peaks is critical. That's when dynamics get compromised.
Just add up the consumption in Watts of all the devices plugged into it. Knowing the consumption of all you plan to plug into it should be a very important factor before purchasing a regen.
ET
I think I understand now what you were saying. I did all that volt amps watts computation before I bought it for exactly the reason you said and the 1500+ model offered more than double my estimate. There is a LCD on front which, among other things, constantly shows % of capacity used. Most of the time it never goes above 25%. If all components in the system are powered up it will sometimes hit 50%. I've never seen it exceed 50% on the display. No idea how accurate that display is, but it does suggest at least that my estimate vs. its capacity may be where it was intended to operate.
Awesome. My P 300 has that too and it reads slow so it won't show peak draws but it never goes above 10-20% so I'm fine. Sounds like you have the headroom you need as well. I was told by someone wiser than me that these regens are like an amp and need headroom. They need it even more when power amps are connected.
ET
So far I've been really happy with the PurePower, which is a good thing as they have a fairly poor record of customer service. This is my second unit purchased from them. The older one is supplying power to my plasma. Actually, this is my third unit. The very first one suffered some internal shipping damage and did not function properly. They hadn't been in business very long at that point and customer service was quite good as they were trying to build customer base. The defective unit was replaced PDQ with no hassle. Since then I've read some real horror stories about servicing issues. Knock wood, no problems here. Regarding peak supply, the use of the batteries in their design and their ability to provide a little extra insurance in addition to the excess capacity against peak draw was a major factor in descison to go with PP as I knew I wanted to run the servos through it. So far it's worked out fine.
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