Regulated AC...thought some of you might be interested

[bushroot]

http://www.herbach.com/Merchant2/mer...egory_Code=PWS

[zigzagflux]

I would be a little hesitant to use something like this.

Not sure exactly what the TO-3 transistor is for, but it's either to measure the AC or control the output.

Regardless, there are three common methods of regulating AC:

First is to rectify to DC, and invert back to AC. Some use straight square wave inverter, some are stepped (quasi) sine, and others are full PWM sine. All three of these are rich in some spectrum of harmonics, which are usually not friendly for audio. Side note: the first two products are great for most non-audio devices, that rectify the square wave back to dc.

Second method is SCR or triac phase control. Simple, down and dirty, and horrible for audio, due to steep wavefronts and all around nasty harmonics.

Third method is ferroresonant, which of any has some potential, but they have drawbacks also. The sine wave is not necessarily a clean sine wave, but is typically a little flat-topped. This may actually be a benefit with rectification, but I do not have the experience to have tried it with an audio device. Their source impedance is quite bad, implying you would need a very overrated unit to provide a suitable source for your circuit. I think the worst part of these units are the incredible expense, weight, and heat.

I would put your picture in some unknown version of the third method, but it's not completely ferroresonant. I can't really tell what the large device in back is.

There are some other esoteric methods such as paraformer and eddy current, but those are rare.

[EC8010]

There's a fourth. I have an Automatic Voltage Regulator (AVR) that consists of a motor-driven variac driving a series buck and boost transformer enabling a sinusoidal regulated 240V 10A supply. It's big and it's heavy (of course).

[zigzagflux]

Quote:
"There's a fourth."

Absolutely. These are typically between 1 and 3% regulation, and have a fairly slow response time.

[kevinkr]

Actually there are pure sine power sources for audio applications, for example the Powerstation series from PS Audio.. They are rather expensive, but they are clean and very tightly regulated. <1% no load to full load. Most models are also frequency agile over a limited frequency range.

I have a close friend who uses one in conjunction with his pre-amp, a Sony SCD-1 and a few other odds & ends. Occasionally I feel motivated to clone something similar, but the amount of work involved is too considerable.

Not sure how much merit the approach has, I have always preferred good line filtering, but have not been able to A/B in my own system..
Currently I have dedicated power feeds less than 10' from the panel and limited to non existant filtering.

Of course YMMV..

[EC8010]

Originally posted by zigzagflux
... and have a fairly slow response time.

That's right, but fast enough to keep valve heaters at a constant temperature (which is what they were desgned for)

[Duo]

I have a small collection of ferroresonant transformers around my place. I use a few of them for audio, but you are heavily limited in power obviously. I don't use them for amplifiers, but have tried them on CD transports, turntables, etc.

They are nice for regulating line level problems and eliminating lots of noise. Only really useful I find with equipment that has problems with line level variation.

[Brian Beck]

A number of years ago, a buddy of mine bought a huge new-surplus AC regenerator. I don’t recall the brand, but it was good for many, many kilowatts. It might have been from Square D or GE. It was about the size of a dishwasher, without exaggeration. This device, obviously not designed for audio, rectified his 240 volt two-phase line power, created a crystal-controlled 60 Hz oscillation which was amplified by powerful internal amplifiers. He planted this beast in a distant spare bedroom on a pallet since it had noisy cooling fans. He ran what looked like dock-to-ship power cables from this room, down the hall, to his stereo in the great room. His stereo at that time consisted of a pair of stripped Quad 63s with a variety of tube and transistor amps. Needless to say, he was single. I mention all this because the difference this regenerator made to the sound of his system was rather alarming. It was a lesson for me. This guy always knew how to throw together a good-sounding system, but I had never heard Quads play with that kind of pristine clarity and sparkling detail before, and I knew his equipment well from before the AC regenerator took up residence. My friend moved out of town a few years later and we’ve lost touch unfortunately. But that experience made a believer out of me regarding very serious power regeneration. I haven’t attempted to match that level of power conditioning in my own set-ups yet, but in an upcoming new house building project, I may make provision for something like this in the plans.

[bushroot]

At the moment, I only have a 5KVA isolation transformer.

[smoking-amp]

Leslie Wanlass had the patents on the saturable reactor regulator, #3443198,3679962,3679966,3683269 from 1969. Transistor would be the DC current controller.

Don