"No, I don't think you can divorce the senses from each other if your intent is to recreate a live experience. It doesn't even have to be music, and sounds will do fine. Especially those woodland sounds meant to relax a person. Smell-a-vision anyone?"
While this is surely true, sitting in an empty concert hall at a rehearsal listening with your eyes closed can shut out the sights, smells, feel of the chair and you can become absorbed in the sound alone. Few if any distracting noises. Besides, when the hall is empty, that's when it sounds best to me. In case you haven't guessed, I'm a reverb freak. Have been all of my life. You could say a concert hall, opera house, or cathedral is the ultimate natural reverb chambers for music, each one best suited for a particular type. How important is it? Somewhere I heard a story that several years ago symphony orchestras and their audiences were descending 150 feet into an ice cave in Russia because of the acoustics there. Now that's what I call a sacrifice for better sound.
Fifty years ago, the power line was 'relatively' free of high frequency interference, the stuff between 10kHz and 500kHz. Then E-I power transformers were the norm, computer circuits were confined to specific locations, very few people had microwaves, telephones were analog, FAX was isolated to specific locations, etc. Then, simple power supplies worked OK.
For today's AC, I use a slightly different approach:
I start with E-I transformers, because that is what we used in the CTC Blowtorch. I chose the lowest coupling capacitance, between windings transformer that I could find, that also had good regulation, and could be purchased directly from the manufacturer.
This transformer is relatively plain looking, probably throws out a hard to filter, hum field, BUT it works very well to transfer line AC to ISOLATED power supply AC. No TOROIDS! This is the key.
The AC is then rectified by 8 discrete high speed-soft recovery time rectifiers. This is to REDUCE RFI generation in the turnoff off of the diodes. Then the final output of these diodes loads 1 medium sized electrolytic cap. NOT 2, 1. Why? (more later)
For today's AC, I use a slightly different approach:
I start with E-I transformers, because that is what we used in the CTC Blowtorch. I chose the lowest coupling capacitance, between windings transformer that I could find, that also had good regulation, and could be purchased directly from the manufacturer.
This transformer is relatively plain looking, probably throws out a hard to filter, hum field, BUT it works very well to transfer line AC to ISOLATED power supply AC. No TOROIDS! This is the key.
The AC is then rectified by 8 discrete high speed-soft recovery time rectifiers. This is to REDUCE RFI generation in the turnoff off of the diodes. Then the final output of these diodes loads 1 medium sized electrolytic cap. NOT 2, 1. Why? (more later)
It's a start! You may not know this, BUT toroid transformers have a fatal flaw, they couple high frequency line noise into the circuitry. When they were first introduced, perhaps 40 years ago, for power supply operation, we ALL fell for them. You know, quiet, both physically and electrically, better regulation, and more efficient. What a combination, and still a GOOD device for ANYTHING except audio-video, for the most part. Still, most of use are still forced to use toroids for power amplifiers, it is just too difficult to source a D-core transformer. (more later)
The ultimate power transformer, today, seems to be either a split C, D, or R core. I have not studied the differences between these units, but they are generally better, all else being equal, than either an E-I or a toroid transformer, because they perform more efficiently than an E-I, and have winding isolation to keep the high frequency noise out of the power supply. It is almost line garbage rejection for free. (more later)
Only if you don't bother to order them with an electrostatic shield between the primary and secondary.
se
Dual, split bobbin U-I core transformers also have good isolation between primary and secondary.
se
john curl said:
That's interesting about the toroids.
Also, what about RF/EMI inlet filters?
Recently someone contacted me about a possible noise problem with his system. He said that weeks after he purchased some active speakers his ears started hurting, and he developed mild hyperacusis, which is increased sensitivity to sounds (for those that don't know).
His speakers used a very high end amp module, one used in other well received commercial amps. He had tried everything, with room acoustics, preamps, etc. He even had a pro installer come in and analyze system and acoustics and get everything set up correctly.
Anyway, he decided to get a power line conditioner and see if that solved the problem. He later told me he was just sitting in the room reading for an hour and had the speakers turned on, but not other components. He then found his ears hurting bad and ringing and sensitive to many sounds.
He said he noticed no buzz or hum from the speakers, but said there must have been some noise coming from the speaker hurting his ears.
I've had this same experience with the noise that hurt my ears. I was just sitting and reading in our music room with our system on, and after a while it felt like some sound was hurting my ears. I thought I could faintly hear some noise, but it wasn't easily discernable.
I can say I've never really "heard" the noise that hurt my ears. I still use these amps with a power line conditioner (which solved the problem), and when I put my ear up to the speaker mid and tweeter ( 97 dB sensitivity ), I think I can make out faint sound, not sure, but it doesn't hurt with the power line conditioner.
I think all amps got to have some RF/EMI inlet filters. I mean the designers of these amps say they are immune to RF/EMI but that's not the case, IMO.
My next preamp is using batteries!
John
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Almost everyone, who is not a total amateur in electrical engineering, knows this.
John's rather hyping the drawbacks of toroids, but you're now hyping the value of an electrostatic shield. It can help, assuming there's a nice clean earth connection. Clean earths (i.e. low inductance) aren't so common in my experience. If you have a noisy earth, or no earth at all, you're back to the same as having no shield.
A very good question. A mixed blessing if they incorporate Y capacitors as do most of the pre-packaged ones. A good common-mode choke though is invaluable, preferably one with segmented windings. Or even use two in series, of different construction so they attenuate in overlapping bands.
That's not true. Probably most very good electrical engineers don't know much about transformers or audio, because it's not their area of expertise.
john curl said:
Sorry for the off topic John. I'm really interested in hearing more about power supplies and the Blowtorch.
abraxalito said:
Hadn't thought of that. Good Idea.
Moving on, the very next stage is a common mode choke, the largest that I can practically buy, loaded by 2 large electrolytic caps. It is these caps that set the 'ground' that is fully floating and unconnected to the transformers. This also creates sort of a pi filter of an initial cap, dual choke, and output caps, whose center tap between them is the 'ground' for the power supply. (more later)
You said toroids have a fatal flaw. That is exaggeration, its not at all fatal its just undesirable. The inter-winding capacitance of toroids might be up to 10X worse than R-core for example. Its definitely a drawback, but by no means fatal as a better CM choke can be used to help compensate for that.
And that's entirely reasonable.
If it genuinely hurts, but you can't hear it, then it must be a significant amount of ultrasonic power. This ought to be visible in a spectrum plot. Not necessarily coming in on the mains, could be an unstable amplifier module.
Many years ago, when I was a student, the student union common room had an 'ultrasonic' burglar alarm. They always switched it on at 5.30pm. I could not 'hear' it, but I knew when it was on and found it unpleasant to sit in the room. I can only describe it as a mild pain in the ears.
DF96,
I've replied to your post in the thread here:
http://www.diyaudio.com/forums/everything-else/181793-rf-audio-5.html#post2450768
So I don't hijack JC's thread.
I've replied to your post in the thread here:
http://www.diyaudio.com/forums/everything-else/181793-rf-audio-5.html#post2450768
So I don't hijack JC's thread.
Finally, I am not going to go into a further description of the power supply in the CTC Blowtorch. Most have little idea of what I am describing, in any case, but most of the rest is described in enough detail in part 1 of this thread. Please go back to some of the early messages in part 1 to get a more complete picture. I will say that there are 3 active regulators for each stage, after the passive filtering that I just described.
Why so many? Why 4 turbo drives in a Vector auto? Same basic reasons, not because we WANT to spend more time and money, BUT because we want to make sure that EVERYTHING is covered. This increases our investment in the product and the customer has to pay for it, in the end.
Is it necessary? Well, no more than a Bugatti, Porsche, or even a high end Mercedes is 'necessary' just more fun to use for those who are so inclined.
Why so many? Why 4 turbo drives in a Vector auto? Same basic reasons, not because we WANT to spend more time and money, BUT because we want to make sure that EVERYTHING is covered. This increases our investment in the product and the customer has to pay for it, in the end.
Is it necessary? Well, no more than a Bugatti, Porsche, or even a high end Mercedes is 'necessary' just more fun to use for those who are so inclined.
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