Ed-
Do you have a current probe? Monitoring the current waveform can show a lot of what is happening. The interactions between conduction angle, load, transformer saturation etc. are easier to visualize as waveforms than spectra.Usually the stiffer the voltage the bigger the current peaks, and as such more radiated noise. If you have a scope with waveform math you can display the instantaneous power which is also very interesting. Sinewaves are not the best source for rectified power.
Do you have a current probe? Monitoring the current waveform can show a lot of what is happening. The interactions between conduction angle, load, transformer saturation etc. are easier to visualize as waveforms than spectra.Usually the stiffer the voltage the bigger the current peaks, and as such more radiated noise. If you have a scope with waveform math you can display the instantaneous power which is also very interesting. Sinewaves are not the best source for rectified power.
the conduction period of the rectifiers when used to charge the capacitors of a DC supply that follows. You get a short conduction phase with a very high peak current followed by a period of no current in the diode. a swinging choke would help, but at the currents involved in a power amp it soon gets big and cumbersome.
It the incoming mains is rich in third harmonic then the diode gets more time to charge the capacitor.
Demian has a good point. While I appreciate the time and effort that Ed is putting into these power supply examples, they are (for me) difficult to interpret, and ANOTHER VIEW might be equally revealing and add to the real understanding of the problems and tradeoffs. Decades ago, somebody gave me a HP current probe from the early '60's that used obsolete (mercury)batteries and was germanium based. It was difficult to get going, yet, it gave me SERIOUS INSIGHT as to the difference between typical and high speed rectifier diodes. It was SO OBVIOUS with the current waveform that I then stopped using ordinary diodes in my best designs. You will find that the Blowtorch, Para JC-1,2,3, all use high speed-soft recovery diodes, everywhere where they are in continuous use such as in rectifier service.
I would like to point something out to Gapapag, something of interest. Last night, watching a TV program on 'How They Do It' they showed the construction of AIRSTREAM trailers, a popular travel trailer type from the 1930's. They specifically pointed out that they construct them with AIRCRAFT GRADE ALUMINUM, yet they are just a trailer. Why? I think it is the why they can be polished to a quality finish as well as other physical qualities. They would not use 'trashcan grade aluminum' or whatever, if they could get the same results. Our choice of AIRCRAFT GRADE ALUMINUM was made for us by the machinist that we went to, not by us. In mentioning it, here, in context of the CTC Blowtorch, I was only passing on what I was told, and the fact that someone who tried to make the same sort of case for themselves might consider that there are different grades of aluminum.
The 'heart' of our 'success' with the CTC Blowtorch, by anyone (so far as we know) who has used it, is because we DID OUR BEST to make it as good as possible. Not for some commercial enterprise, where cost vs quality, or 'proof' of WHY we chose the most exotic and expensive passive parts in many locations (so that we made no 'knowing' oversights at the time of its design and construction) because we were serious about making the best preamplifier that we could.
If I were making a recording, and it was my job to be a technical consultant, as I have done on several occasions, I would try my best, in the same way, to do the BEST JOB POSSIBLE, not to some typical commercial standard, or the most cost effective way.
By the way, this can 'tick off' the regular people who make audio for film, recording, and PA when you insist on 'the best way' rather than settling for the status quo, and I am pretty sure I would 'tick off' a number of people here, who do/or did audio for a living, commercially. That is the trade-off for doing a 'world class' effort in a commercial world.
I would like to point something out to Gapapag, something of interest. Last night, watching a TV program on 'How They Do It' they showed the construction of AIRSTREAM trailers, a popular travel trailer type from the 1930's. They specifically pointed out that they construct them with AIRCRAFT GRADE ALUMINUM, yet they are just a trailer. Why? I think it is the why they can be polished to a quality finish as well as other physical qualities. They would not use 'trashcan grade aluminum' or whatever, if they could get the same results. Our choice of AIRCRAFT GRADE ALUMINUM was made for us by the machinist that we went to, not by us. In mentioning it, here, in context of the CTC Blowtorch, I was only passing on what I was told, and the fact that someone who tried to make the same sort of case for themselves might consider that there are different grades of aluminum.
The 'heart' of our 'success' with the CTC Blowtorch, by anyone (so far as we know) who has used it, is because we DID OUR BEST to make it as good as possible. Not for some commercial enterprise, where cost vs quality, or 'proof' of WHY we chose the most exotic and expensive passive parts in many locations (so that we made no 'knowing' oversights at the time of its design and construction) because we were serious about making the best preamplifier that we could.
If I were making a recording, and it was my job to be a technical consultant, as I have done on several occasions, I would try my best, in the same way, to do the BEST JOB POSSIBLE, not to some typical commercial standard, or the most cost effective way.
By the way, this can 'tick off' the regular people who make audio for film, recording, and PA when you insist on 'the best way' rather than settling for the status quo, and I am pretty sure I would 'tick off' a number of people here, who do/or did audio for a living, commercially. That is the trade-off for doing a 'world class' effort in a commercial world.
Oh please, John. "AIRCRAFT GRADE ALUMINUM" is just an overly-hyped buzzword for 6061, which even Wikipedia notes is "one of the most common alloys of aluminum for general purpose use." I'm sure they even make trash cans out of it.
se
Steve Eddy,
You are correct that all 6061-T6 aluminum should be made to the same standards whether the aircraft grade name is applied or not. But that is to say that you couldn't use 7075-T6 in its place, wouldn't really make any difference in an audio chassis, but in a plane the two alloys have different properties that are chosen for specific purposes. Yes aircraft grade would somewhat distinguish this material from junk recycled material that is just cast aluminum, but it is an oft overused term at this point in time.
ps. In aircraft the designation is only used along with chemical analysis and quality control to have a paper trail and certification of the material that it does in fact meet specific standards. It is a traceable quality standard. The aluminum coming into a qualified shop sure better be marked with grade and producer if you are going to use it for a flyaway part.
You are correct that all 6061-T6 aluminum should be made to the same standards whether the aircraft grade name is applied or not. But that is to say that you couldn't use 7075-T6 in its place, wouldn't really make any difference in an audio chassis, but in a plane the two alloys have different properties that are chosen for specific purposes. Yes aircraft grade would somewhat distinguish this material from junk recycled material that is just cast aluminum, but it is an oft overused term at this point in time.
ps. In aircraft the designation is only used along with chemical analysis and quality control to have a paper trail and certification of the material that it does in fact meet specific standards. It is a traceable quality standard. The aluminum coming into a qualified shop sure better be marked with grade and producer if you are going to use it for a flyaway part.
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Yeah, but it's not like anyone who's machining or fabricating aluminum parts, even for cheap mass market gear, are using junk recycled material. Even the cover on my little $99 Schiit Magni headphone amp is using 6061.
Yeah. But I don't see any wings on the Blowtorch.
se
Or how 'bout "MARINE GRADE"?
se
Seems to be tugging on a memory but I cant quite recall it, wasn't there some interest in "old" aluminum from marine usage for use as low background materials on cryostats and the like?
Thanks
-Antonio
Sure. But it doesn't change the fact that there's nothing particularly special about the use of 6061. As I said, my $99 headphone amp uses it too. So to brag about the Blowtorch being made out of "AIRCRAFT GRADE" aluminum isn't really saying anything. It's just more chest thumping.
se
The point of this discussion or the many others, over the years, is to put forth what we found that worked in making the CTC Blowtorch, having to make it attractive enough to sell in Japan and elsewhere, and not just among our friends and ourselves, who would have put up with a plastic box, IF we felt that it was just as good.
I will also tell my personal history on package design, over the decades.
First, I used steel enclosures, often custom fabricated by others. They were strong, looked pretty good when painted properly, and made a good shield from magnetic and electrostatic fields. The only notable exception was the Mark Levinson preamps (he preferred aluminum for some reason) and for heat-sinks. I kept using steel chassis for master recorder electronics and studio boards, but when I started Vendetta Research, I first went back to pretty plastic cases, internally sprayed with a conductive coating for electrostatic shielding. It worked pretty well, at first, but we could not find a large enough plastic box for the final version of the phono preamp or Xover, so we made cases of aluminum put together with metal bolts or screws. These cases worked pretty well, BUT they did not shield against a nearby power transformer. The sides were also somewhat flimsy and the bolts could loosen up with time or movement.
For the Blowtorch, my business partner, (the guy in charge of the cases) found that THICK aluminum worked pretty well, so long as it was continuous and not put together with bolts. Therefore he had first units aluminum welded (however they do it) but the guy who did the welding always seemed to have a beer in hand, so we decided to have the chassis 'hogged out' leaving as much aluminum as possible for shielding. We actually got down to 60Hz or so for some shielding (not much) but wonderful shielding at somewhat higher frequencies. This chassis shields pretty darn well, (better than the Vendetta did), is mechanically strong (doesn't rattle or ring), and looks pretty good, without any seams, except for the bottom plate. It made a wonderfully stable platform for the Shalco switches, that we found worked best.
On the other hand, it made the unit easier to sell to people who could easily afford it, but demand a certain level of attractiveness and substantialness.
We thought that making the case heavier than just about any other, would not distract from sales, and we also put on a substantial set of machined knobs, that could remind one of Dolly Parton, at the beginning. Later, I insisted that we reduce the knobs to a MM size, because the original knobs made the unit look like it was tipping over, and the stress on the shafts on the switch and volume controls could not have been good. In any case, we did most of what we did for a good reason, and we will never regret it.
I will also tell my personal history on package design, over the decades.
First, I used steel enclosures, often custom fabricated by others. They were strong, looked pretty good when painted properly, and made a good shield from magnetic and electrostatic fields. The only notable exception was the Mark Levinson preamps (he preferred aluminum for some reason) and for heat-sinks. I kept using steel chassis for master recorder electronics and studio boards, but when I started Vendetta Research, I first went back to pretty plastic cases, internally sprayed with a conductive coating for electrostatic shielding. It worked pretty well, at first, but we could not find a large enough plastic box for the final version of the phono preamp or Xover, so we made cases of aluminum put together with metal bolts or screws. These cases worked pretty well, BUT they did not shield against a nearby power transformer. The sides were also somewhat flimsy and the bolts could loosen up with time or movement.
For the Blowtorch, my business partner, (the guy in charge of the cases) found that THICK aluminum worked pretty well, so long as it was continuous and not put together with bolts. Therefore he had first units aluminum welded (however they do it) but the guy who did the welding always seemed to have a beer in hand, so we decided to have the chassis 'hogged out' leaving as much aluminum as possible for shielding. We actually got down to 60Hz or so for some shielding (not much) but wonderful shielding at somewhat higher frequencies. This chassis shields pretty darn well, (better than the Vendetta did), is mechanically strong (doesn't rattle or ring), and looks pretty good, without any seams, except for the bottom plate. It made a wonderfully stable platform for the Shalco switches, that we found worked best.
On the other hand, it made the unit easier to sell to people who could easily afford it, but demand a certain level of attractiveness and substantialness.
We thought that making the case heavier than just about any other, would not distract from sales, and we also put on a substantial set of machined knobs, that could remind one of Dolly Parton, at the beginning. Later, I insisted that we reduce the knobs to a MM size, because the original knobs made the unit look like it was tipping over, and the stress on the shafts on the switch and volume controls could not have been good. In any case, we did most of what we did for a good reason, and we will never regret it.
Actually the war between Edison and Westinghouse (DC vs AC) is often presented as AC won because you could distribute it with transformers. As electric power was first used for lighting either would work and the distribution advantage strongly tilted to AC. However the first motors were push-pull devices that would only run on DC. These gave way to rotary version that also required DC. It was the invention of the induction motor that allowed AC to compete for motor energy. DC motors are still used when the current to torque property is needed. Although with power semiconductors and variable speed drives AC motors can now match that.
But how would you explain to someone how an induction motor works, when the moving part is just a hunk of metal? (The universal motor that runs on AC or DC also took a bit to get working well and they are limited to small motors.)
i mentioned this first to Audioxpress and will offer it to them when and if ever finished. Besides Jan isn't talking to me...
The snubber is a well known circuit. Probably became popular in the mid sixties.
Demian,
Around here we have a rule, you don't ask if we have ... you ask where it is! As my shop is small (Only 1/2 Acre) I often have more than one of anything. For example there are screwdrivers for the woodshop, metal working area, electronics bench, assembly bays, backline rental and even the paint shop. Of course my secretary also has her own set.
I was looking for my clamp on ammeter last week and still haven't found it. I do have my wideband hall effect Tektronix one and several current transformers. One is built into my AC line isolation unit.
However what I am doing is a tutorial on power supply design. When I had one of my magnetics' courses, the prof teaching the course gave out an answer sheet after you took the final exam. One of the questions was what would happen if you cut a pair of toroid cores in half and then built a transformer using 1/2 of each. One of us got the answer wrong. He showed that it would combine the properties of both, I got it would be the average of them. (I think he forgot L went to L/2.) (Or there may be more than one opinion on how to do things... but I am always right!
)Now the issue in designing a power supply that is being addressed at the moment is how noise gets into the power supply. The plot I showed used a low distortion sinewave source. The distortion shown at the low frequencies was due to nonlinear magnetic behavior. There was also high frequency noise, that was not coming in from the AC line! (I don't want to get into the mechanism that causes this because it gets into actual physics and life is too short to argue with...)
Now a transformer will also pass any AC line noise. That is shown by frequency response plots. (Also depends on load).
The other issue I should touch on is efficiency or power loss. When the transformers are used at 10% high line voltage, 50 hz. and full load they heat up. Not as much an issue at 60 hz. The increased eddy current losses are not as great as the reduced saturation losses.
Now flux leakage as it induces voltage into a chassis is also being measured. There are simple methods to deal with this from construction, orientation, spacing and if required shielding. I could show magnetic field strength models or use a probe, but that is method not results.
The common B-H loop is useful for showing hysteresis and saturation. Although I have designed transformers, inductors and cores, and used the magnetic data, here the emphasis is on complete power supply results.
Now if there is some data you would like to see, please let me know.
I think already shown has been diode switch off is a function of diode and transformer. But I will get into more detail once I get past just the transformers.
ES
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