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Q: experimental power supplies
Okay - here's definitely an UNUSUAL question... and I'm pretty sure that
nobody's ever messed with this stuff on such a scale... BUT I was reading some of the web pages on the BBC Radiophonic Workshop about how they pulled all the balancing transformers from alot of their equipment and were able to get superior sonic results - it was in the spirit of this, and knowing that alot of people like audio upgrades beef up power supplies to get greatly increased clarity and dynamics - it kind of got me wondering about the possibility of gutting the power supplies from some of my outboard equipment and feed them directly with +24V or what-have-you from a master supply located remotely. Has anybody heard of anyone experimenting with this??? I expect that doing so would achieve two things: 1. tighten up the clarity and dynamics (generally improve signal quality), and 2. prevent interference from xformers in adjacent rack pieces. I've certainly had problems with this and have had to rack stuff up to 5U apart to avoid this. Any Ideas?? Sincerely, Jonathan |
#2
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experimental power supplies
"Jonathan Dewdney" wrote
Any Ideas?? Your idea has it's merits. The classic situation is a UPS which converts AC to DC then converts the DC back to AC just so that the power supplies in our equipment can convert it all back to DC. There must be a lot of extra noise and cost of components in all that. It would be a much better idea to have a single UPS which then distributed DC at a couple of different voltages to all the equipment in the studio. -- Anthony Gosnell to reply remove nospam. |
#3
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experimental power supplies
"Jonathan Dewdney" wrote in message
Okay - here's definitely an UNUSUAL question... and I'm pretty sure that nobody's ever messed with this stuff on such a scale... BUT I was reading some of the web pages on the BBC Radiophonic Workshop about how they pulled all the balancing transformers from alot of their equipment and were able to get superior sonic results - it was in the spirit of this, and knowing that alot of people like audio upgrades beef up power supplies to get greatly increased clarity and dynamics - it kind of got me wondering about the possibility of gutting the power supplies from some of my outboard equipment and feed them directly with +24V or what-have-you from a master supply located remotely. Has anybody heard of anyone experimenting with this??? I expect that doing so would achieve two things: 1. tighten up the clarity and dynamics (generally improve signal quality), and 2. prevent interference from xformers in adjacent rack pieces. I've certainly had problems with this and have had to rack stuff up to 5U apart to avoid this. Any Ideas?? The classic way to increase isolation of individual circuits from a common power supply is to distribute well-regulated DC at some higher voltage such as 32 volts or higher, and use on-board regulators to bring it down to say, 24 volts. |
#4
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Q: experimental power supplies
In article ,
Jonathan Dewdney wrote: Okay - here's definitely an UNUSUAL question... and I'm pretty sure that nobody's ever messed with this stuff on such a scale... BUT I was reading some of the web pages on the BBC Radiophonic Workshop about how they pulled all the balancing transformers from alot of their equipment and were able to get superior sonic results Yes, bad input transformers can sound bad. Removing them can improve things. However, some transformers sound really good and can solve a lot of ground issues. So, I don't think it's an automatic win to get rid of audio transformers. it was in the spirit of this, and knowing that alot of people like audio upgrades beef up power supplies to get greatly increased clarity and dynamics - it kind of got me wondering about the possibility of gutting the power supplies from some of my outboard equipment and feed them directly with +24V or what-have-you from a master supply located remotely. Has anybody heard of anyone experimenting with this??? One thing that using a shared power supply will do is make all of your devices have a common ground through the power supply ground. This might be a good thing, but it might also be bad. Normally, if a device has a power transformer, the power supply ground is created inside of the power supply circuit and can be connected to the grounds associated with the audio IOs by the designer of that piece of gear, and that piece only. With a shared power supply, you get a shared ground, so the relationship between gear is in many ways more complicated than if power transformers are used. Maybe it won't cause problems, but there will definitely be a more complex and interconnected ground scheme when a shared supply is used. I expect that doing so would achieve two things: 1. tighten up the clarity and dynamics (generally improve signal quality), A larger and more complex ground system wouldn't automatically make the think that you'd go in that direction at all. Actually, I'd expect more of the opposite. With a more complex and interconnected ground, I would think that crosstalk and the like would be worse. Also, with a shared DC supply, any variation on power suppy rails would be shared among several devices, and that should work to increase the interaction of devices with each other and probably reduce clarity. and 2. prevent interference from xformers in adjacent rack pieces. I've certainly had problems with this and have had to rack stuff up to 5U apart to avoid this. Toroidal transformers would be a better idea IMHO. They have very low radiated fields, and you can put them in a box to reduce fields further. Any Ideas?? If you try something like this, also consider what happens when a device fails and draws a lot of current. When you combine supplies for several pieces of gear into one large supply, a fault situation might not be high enough to trip the larger supply with its high combined current rating. Old large computers built in this way used to have smoke detectors installed at the top of each rack to detect this fault situation. A better way might be to use local regulation, but you still have a problem if a regulator fails and starts to hammer the main supply. Best of luck, Monte McGuire |
#5
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Q: experimental power supplies
Jonathan Dewdney wrote:
Okay - here's definitely an UNUSUAL question... and I'm pretty sure that nobody's ever messed with this stuff on such a scale... BUT I was reading some of the web pages on the BBC Radiophonic Workshop about how they pulled all the balancing transformers from alot of their equipment and were able to get superior sonic results - it was in the spirit of this, and knowing that alot of people like audio upgrades beef up power supplies to get greatly increased clarity and dynamics - Removing audio transformers was very popular in the seventies. I think in general it's a good idea, but others will disagree. I am not a fan of audio transformers in the signal path if it can be avoided. it kind of got me wondering about the possibility of gutting the power supplies from some of my outboard equipment and feed them directly with +24V or what-have-you from a master supply located remotely. Has anybody heard of anyone experimenting with this??? This, however, is mostly a silly idea. What good is removing the power supply going to do you? I expect that doing so would achieve two things: 1. tighten up the clarity and dynamics (generally improve signal quality), Why will it do this? and 2. prevent interference from xformers in adjacent rack pieces. I've certainly had problems with this and have had to rack stuff up to 5U apart to avoid this. This will definitely be the case... BUT now you will have a huge honking power supply at the bottom of your rack. You aren't eliminating the problem, just moving it. You'd probably gain more just by replacing crappy transformers in low end gear with low-magnetic-leakage types. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
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Q: experimental power supplies
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#7
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experimental power supplies
Here is a solution I am using for powering some mic pres I am
designing... It is a remote PS unit that will provide +- 15VDC, +- 24 VDC and +48VDC. All from high capacity linear supplies. The +-15 supplies are for monolithic pres and the +-24 is for 990C base pres. I haven't added the +-24 supply yet but there is a bay for it inside and holes for multi pin XLR's on the back once I get going on the 990C preamps. The pres I build for other people have integral supply boards with external transformers. Here are some picture links: http://www.mixposse.com/attach/Pre_P...pply_Front.jpg http://www.mixposse.com/attach/Pre_PowerSupply_Rear.jpg The remote supply really keeps low level hum down to a minimum. |
#8
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Q: experimental power supplies
Jonathan Dewdney wrote:
Okay - here's definitely an UNUSUAL question... snip Hi Jonathan, Not all that unusual, in fact, Rane tried exactly that setup with their gear several years ago, calling the system "Remote AC Power" or RAP, not to be confused with this newsgroup or the musical styleG! It didn't seem to take off in the marketplace, for whatever reason. There used to be a great application note describing the system in their library... but it doesn't appear to be there at the moment. There is an article that talks about the history: http://www.rane.com/pdf/note133.pdf And if you email their support desk I'll bet they'll find you a copy of the original if one still exists. They are pretty good like that. OK, I've experimented with this sort of thing a lot, mostly looking to eliminate transformer mechanical hum, ground loops, radiated noise, etc. I have a couple of thoughts... My first attempt was a single transformer feeding several devices. Each device was modified so that I could apply the appropriate voltage to the input of the local bridge. Sadly, since some of the gear has unbalanced I/O I ended up creating a loverly ground loop... next. The next attempt was a bunch of smaller transformers located remotely feeding the same gear. It actually worked quite nicely, but just lacked a certain elegance. While I knew up front it was going to be a nightmare, I tried distributing DC as well. As was expected, the groundloop problem was pretty bad. Well, now, what the heck! Everything is going back to a common ground, and even though there are loops, I really shouldn't be having such a problem. What to do? Well, it might sound a bit wierd, but I basically built a differential low voltage distribution network, carefully groomed the ground paths, and voila... a workable solution. In fact a very good solution. Except that it will be a LOT of work to implement. Still, I am considering it for the next version of the studio... If you take this approach, you will need to pay careful attention to the paths to ground. The first step is probably to make sure that all "pin 1" type problems are addressed. Since I use a single pair for both balanced and unbalanced gear this turned out to be reasonable. I also made sure that EVERY piece used three conductors for power - hot, neutral, and safety ground. AND, all audio grounds are home runs to a central ground located in the patchbay racks, and all power grounds are home runs to the ground at the transformer, which is located at the service entrance. Pros: All the benefits of low voltage distribution, all the benefits of differnetial distribution, enforced star groundingG Cons: A lot of work to implement, all the gear has to be modified. Certainly was an interesting experiment though. |
#9
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Q: experimental power supplies
Thanks all for your input. It's just an idea I was flitting about in my
head. I use alot of naim playback gear - they're bullish on supplies... and offer upgrades via beefier power supplies. Seems to hold true from what I'd heard with my own ears. At any rate, it struck me as downright weird that tape decks had power supplies located in them and that the EM might be consequential to such a machine. I removed the P/S from my A810 to a remote enclosure and what it did to the sound quality was nothing short of amazing! SO I tried the same thing with a Yamaha REV5. Same. Unless I'm just hearing things with my delusions. This also relates to my SSL power supply I'm selling (see other post, same date) - which would be the means to do something like this - though I think I secretly don't want to (why I'm selling the thing)... but I thought I'd get some opinions before I actually did. The only big problem is that I'd have to start reverse-engineering every piece of gear I have. But maybe that's what college students are for (think EE dept..! exploitation....). At any rate, I want to respond to the individuals who already responded here... 1. Monte, good points. I think Bill clarified how the ground issues might be solved. And yes, I AM using a toroid for my one experimental supply. 200VA with two votage rails. The failure issue is a good one. And one I need to consider. 2. Scott! Thanks for your input. You'd be surprised at what a little more juice will do for headroom! I promise you. The rack would be located at least eight feet away. And yes! the idea WOULD be to move the problem. More juice and (literally) move the problem away! I expect I would see MORE benefit from my lower-end gear... since the one design feature that tends to distinguish low end from high end is the power supply. But like I said - I'm just kind of thinking out loud here - not prosetylizing. 3. Mike... Sorry I shouldn't have brought up both issues at once perhaps. The two are quite separate in my head and so they should be in yours. Sorry to make you think I was confusing them. Balancing transformers are just that and power transformers have nothing to do with them. I'm not even thinking of induced hum. Think about it. You have a complex LCR or even digital network in a piece of rack gear. All the voltage drops are carefully calculated by the designers. Then you immerse this whole damn thing in a pool of 60Hz magnetic fields, all located in varying positions around it. Do you think this thing is operating within spec? At ALL?? Really... think about it. Isn't it kind of amazing that the gear works at all? I first got clued into the whole notion (as an interesting or not so interesting sidebar) in the 80s when I was trying to play guitar through a Midiverb which was sitting atop a guitar amp. It started making this CRAZY honking sound until I placed the unit several feet away. 4. Bill... thanks for the ideas. And for being encouraging. I'd really like to pick your brain about this further. sincerely, JW Dewdney in article , Bill Thompson at wrote on 3/2/04 12:22: Jonathan Dewdney wrote: Okay - here's definitely an UNUSUAL question... snip Hi Jonathan, Not all that unusual, in fact, Rane tried exactly that setup with their gear several years ago, calling the system "Remote AC Power" or RAP, not to be confused with this newsgroup or the musical styleG! It didn't seem to take off in the marketplace, for whatever reason. There used to be a great application note describing the system in their library... but it doesn't appear to be there at the moment. There is an article that talks about the history: http://www.rane.com/pdf/note133.pdf And if you email their support desk I'll bet they'll find you a copy of the original if one still exists. They are pretty good like that. OK, I've experimented with this sort of thing a lot, mostly looking to eliminate transformer mechanical hum, ground loops, radiated noise, etc. I have a couple of thoughts... My first attempt was a single transformer feeding several devices. Each device was modified so that I could apply the appropriate voltage to the input of the local bridge. Sadly, since some of the gear has unbalanced I/O I ended up creating a loverly ground loop... next. The next attempt was a bunch of smaller transformers located remotely feeding the same gear. It actually worked quite nicely, but just lacked a certain elegance. While I knew up front it was going to be a nightmare, I tried distributing DC as well. As was expected, the groundloop problem was pretty bad. Well, now, what the heck! Everything is going back to a common ground, and even though there are loops, I really shouldn't be having such a problem. What to do? Well, it might sound a bit wierd, but I basically built a differential low voltage distribution network, carefully groomed the ground paths, and voila... a workable solution. In fact a very good solution. Except that it will be a LOT of work to implement. Still, I am considering it for the next version of the studio... If you take this approach, you will need to pay careful attention to the paths to ground. The first step is probably to make sure that all "pin 1" type problems are addressed. Since I use a single pair for both balanced and unbalanced gear this turned out to be reasonable. I also made sure that EVERY piece used three conductors for power - hot, neutral, and safety ground. AND, all audio grounds are home runs to a central ground located in the patchbay racks, and all power grounds are home runs to the ground at the transformer, which is located at the service entrance. Pros: All the benefits of low voltage distribution, all the benefits of differnetial distribution, enforced star groundingG Cons: A lot of work to implement, all the gear has to be modified. Certainly was an interesting experiment though. |
#10
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Q: experimental power supplies
Bill Thompson wrote in message ...
--snip-- ....Rane tried exactly that setup with their gear several years ago... ....I also made sure that EVERY piece used three conductors for power - hot, neutral, and safety ground. ---snip--- Just to be picky, if your power cord has a black wire, a white wire, and a green wire, the white wire isn't the neutral, it's the grounded conductor (connected to ground at the service entrance and insulated from ground everywhere downstream of that) and carries the exact same current as the black wire, and the green wire is the grounding conductor and carries no current unless something goes wrong. If you have a black wire, a red wire, and a white wire then the black and the red are the "hot" wires and the white is the neutral, although it is still not supposed to be connected to ground anywhere except all the way back at the service entrance. Is that Rane thing the one where they use an oversize wallwart and an RJ-45 plug? |
#11
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Q: experimental power supplies
In rec.audio.pro, (Monte P McGuire) wrote:
In article , Jonathan Dewdney wrote: ... it was in the spirit of this, and knowing that alot of people like audio upgrades beef up power supplies to get greatly increased clarity and dynamics - it kind of got me wondering about the possibility of gutting the power supplies from some of my outboard equipment and feed them directly with +24V or what-have-you from a master supply located remotely. Has anybody heard of anyone experimenting with this??? One thing that using a shared power supply will do is make all of your devices have a common ground through the power supply ground. This might be a good thing, but it might also be bad. One feature of well-designed equipment is that the ground connections of the input and output connectors are carefully chosen inside the unit so if there is significant leakage current through ground, it doesn't show up in the signal path. Bill Whitlock of Jensen Transformers has written some excellent articles on this and related causes of hum and noise (so much so that you can probably solve all your hum/ground loop problems without using any audio transformers!), and I urge anyone who wants to add, change or rearrange, or is having problems with ground connections to read his articles. Go to http://www.jensen-transformers.com/ and click on 'white papers' and read the articles on that page. Of course, there's a lot of equipment that's not designed well as far as internal ground connections, so connecting to this main DC power supply ground might actually increase their ground-loop hum immunuty. I recall that Mr. Whitlock proposed a test where 60 Hz current injected through an input or output's 'pin 1' ground connection and another ground on the same piece of equipment, and the 'signal' generated is measured on the output. This is an excellent test for immunity to ground loop problems. Normally, if a device has a power transformer, the power supply ground is created inside of the power supply circuit and can be connected to the grounds associated with the audio IOs by the designer of that piece of gear, and that piece only. With a shared power supply, you get a shared ground, so the relationship between gear is in many ways more complicated than if power transformers are used. Maybe it won't cause problems, but there will definitely be a more complex and interconnected ground scheme when a shared supply is used. I expect that doing so would achieve two things: 1. tighten up the clarity and dynamics (generally improve signal quality), I think a better solution would be to beef up the power supply (and perhaps other things such as ground connections) in each piece of equipment. Things that can be done: Put 0.1 uF caps (at appropriate voltage rating) directly (using as short leads as possible) across each rectifier. I also like to put 0.1's across the AC input (transformer secondary) and DC output, just for overkill. This keeps several posssible RF interference problems from happening. These can go on the inputs and outputs of voltage regulators as well, but there's the possibility of capacitive loading making regulators unstable, so be careful with that (read data sheets, app notes, and books such as Pease's "Trobleshoorting Analog Circuits"). Replace the main filter cap(s) with larger value. Problems with this are that if you have a 'stiff' transformer (one that can provide a lot of current - wall-warts generally can't), you may need to replace the rectifiers with ones with greater peak current capability. Also, since the peak current will be greater and the conduction angle of the rectifier charging the cap will be lower, this pulls a more non-linear current waveform with even more harmonic content from the power line, which may be picked up by not-well-designed, er, uh, 'sensitive' equipment. A larger and more complex ground system wouldn't automatically make the think that you'd go in that direction at all. Actually, I'd expect more of the opposite. With a more complex and interconnected ground, I would think that crosstalk and the like would be worse. Also, with a shared DC supply, any variation on power suppy rails would be shared among several devices, and that should work to increase the interaction of devices with each other and probably reduce clarity. and 2. prevent interference from xformers in adjacent rack pieces. I've certainly had problems with this and have had to rack stuff up to 5U apart to avoid this. Toroidal transformers would be a better idea IMHO. They have very low radiated fields, and you can put them in a box to reduce fields further. Any Ideas?? If you try something like this, also consider what happens when a device fails and draws a lot of current. When you combine supplies for several pieces of gear into one large supply, a fault situation might not be high enough to trip the larger supply with its high combined current rating. The solution would be to have an appropriate fuse at the power input of each device. One problem with this is it raises the impedance of the power supply as seen by each device. Old large computers built in this way used to have smoke detectors installed at the top of each rack to detect this fault situation. A better way might be to use local regulation, but you still have a problem if a regulator fails and starts to hammer the main supply. A fuse between the main supply and each local regulator would work fine here, as the impedance the final circuit sees is that of the local regulator. Best of luck, Monte McGuire ----- http://mindspring.com/~benbradley |
#12
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Q: experimental power supplies
unitron wrote:
Just to be picky, if your power cord has a black wire, a white wire, and a green wire, the white wire isn't the neutral, it's the grounded conductor Wow... I didn't know that. I've always heard it described as the neutral (connected to ground at the service entrance and insulated from ground everywhere downstream of that) and carries the exact same current as the black wire, although that is my understanding of how "neutral" is connected, and how it works. and the green wire is the grounding conductor and carries no current unless something goes wrong. agreed. If you have a black wire, a red wire, and a white wire then the black and the red are the "hot" wires and the white is the neutral, although it is still not supposed to be connected to ground anywhere except all the way back at the service entrance. also agreed... though I know a lot of folks use red in "three-way" switching arrangements as the line that might be hotG! Is that Rane thing the one where they use an oversize wallwart and an RJ-45 plug? That's the one! Thanks for the info on house wiring... Bill |
#13
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Q: experimental power supplies
Bill Thompson wrote:
unitron wrote: Just to be picky, if your power cord has a black wire, a white wire, and a green wire, the white wire isn't the neutral, it's the grounded conductor Wow... I didn't know that. I've always heard it described as the neutral (connected to ground at the service entrance and insulated from ground everywhere downstream of that) and carries the exact same current as the black wire, although that is my understanding of how "neutral" is connected, and how it works. Right. The white wire is the neutral. In a typical installation, it is bonded to the ground at the point where the building ground enters the system, which is normally the service entry panel. It's being used as the current return, not the green wire. But this is the terminology that electricians use, and that you will find in the NEC book. The thing is that this terminology is different than the terminology that electronics guys use... Electronics guys will talk about the ground being the current return, and the safety ground ("Chassis ground") being a different thing. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
#14
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Q: experimental power supplies
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#16
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Q: experimental power supplies
unitron wrote:
Speaking of neutral wires, I'm thinking of starting up a new thread of the bi-wiring off of a single amp discussion, this time centered on whether one could do so with 3 wires instead of 4, one hot for the woofer, one for the tweeter, and a common return. Whadda ya think? :-) Should work, provided: 1) the amps are ground-referenced on the low side not bridged. 2) you're aware of the potentially higher current flow in the common wire. This would surely only give half of the biwiring advantage, which is questionable to start with... -- Mark. http://tranchant.plus.com/ |
#17
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Q: experimental power supplies
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#18
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Q: experimental power supplies
unitron wrote:
A single phase 3 wire 240 Volt circuit has 2 "hots" and a neutral and theoretically no current flows in the neutral. Where I am, the Netherlands, such a circuit has one 'hot' wire (phase), one 'null' wire (neutral) and one 'earth' wire (ground). Current only flows when something conductive between phase and neutral is connected, so you can't claim these are *both* hot wires. When I measure between phase and neutral I see 230 V; between phase and ground also 230 V; between neutral and ground there's 0 V, i.e.: one hot wire. Obviously I can't comment on colors used where you are (overhere phase is brown, neutral is blue and ground is green/yellow), but maybe some more can be added about the term 'neutral'. It is called that because in the way power is generated - commonly in a rotary/ 3-phase manner - the point where the three phases share their common connection is the neutral point, or null. Therefor this is not a second 'hot' and neither the same as 'ground' (unless one wants it to be, and connects it to ground). Now aviation, that's where life is simple: there's only 'hot' or 'plus', and the rest is all the same; neutral, minus, ground, safety ground, chassis ground, static ground, lightning conductor, aircraft frame, sigh.. No earth though :-) Luck, Arjan -- ----Real email: news then at then soundbyte then dot then nl---- |
#19
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Q: experimental power supplies
Arjan P wrote:
unitron wrote: A single phase 3 wire 240 Volt circuit has 2 "hots" and a neutral and theoretically no current flows in the neutral. Where I am, the Netherlands, such a circuit has one 'hot' wire (phase), one 'null' wire (neutral) and one 'earth' wire (ground). Current only flows when something conductive between phase and neutral is connected, so you can't claim these are *both* hot wires. When I measure between phase and neutral I see 230 V; between phase and ground also 230 V; between neutral and ground there's 0 V, i.e.: one hot wire. That is how a 120 volt circuit in the US works. The US 240V three-wire connections come off of a transformer with a center tap on it, and the center tap is bonded to ground. (This is basically "balanced power.") It's the same way that 460V circuits in Europe work. Obviously I can't comment on colors used where you are (overhere phase is brown, neutral is blue and ground is green/yellow), but maybe some more can be added about the term 'neutral'. It is called that because in the way power is generated - commonly in a rotary/ 3-phase manner - the point where the three phases share their common connection is the neutral point, or null. Therefor this is not a second 'hot' and neither the same as 'ground' (unless one wants it to be, and connects it to ground). Now aviation, that's where life is simple: there's only 'hot' or 'plus', and the rest is all the same; neutral, minus, ground, safety ground, chassis ground, static ground, lightning conductor, aircraft frame, sigh.. No earth though :-) Ground return through aircraft frame is BAD! BAD BAD! Yeah, I know cars do it... --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
#21
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Q: experimental power supplies
Scott Dorsey wrote:
That is how a 120 volt circuit in the US works. The US 240V three-wire connections come off of a transformer with a center tap on it, and the center tap is bonded to ground. (This is basically "balanced power.") It's the same way that 460V circuits in Europe work. Mmh, I'm not aware of those circuits at all, could be my ignorance but as far as far as I know there's either single phase 230V or 3-phase 400V. Which is the effective voltage between two phases of 230V with a 120 degree phase shift. Interesting, with the center tap. Ground return through aircraft frame is BAD! BAD BAD! Yeah, I know cars do it... Huh? Maybe you're talking about composite aircraft, but airframe ground return is all there is on today's aircraft, since it cuts the amount of cable = weight in half (outside the studio I'm an avionics engineer). The only exceptions to it are antenna and pickup wiring and data lines obviously. On the newest Airbus designs they're even considering increasing main power for certain systems from 115V/400Hz to a higher level to further decrease cable weight. Luck, Arjan -- ----Real email: news then at then soundbyte then dot then nl---- |
#22
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Q: experimental power supplies
Jonathan Dewdney wrote:
Okay - here's definitely an UNUSUAL question... and I'm pretty sure that nobody's ever messed with this stuff on such a scale... BUT I was reading some of the web pages on the BBC Radiophonic Workshop about how they pulled all the balancing transformers from alot of their equipment and were able to get superior sonic results Yes - audio transformers aren't the smartest things to have in the signal path. - it was in the spirit of this, and knowing that alot of people like audio upgrades beef up power supplies to get greatly increased clarity and dynamics Clarity ? You might get better dynamics in a power amp by upgrading the PSU but that's another issue. - it kind of got me wondering about the possibility of gutting the power supplies from some of my outboard equipment and feed them directly with +24V Most decent gear needs 'split rail' supplies, i.e. + and - Volts and rarely 24V. or what-have-you from a master supply located remotely. Has anybody heard of anyone experimenting with this??? No, never. I expect that doing so would achieve two things: 1. tighten up the clarity and dynamics (generally improve signal quality), How ? You've been listening to the audiophile crowd who think 'one way' cables are cool too ? and 2. prevent interference from xformers in adjacent rack pieces. I've certainly had problems with this and have had to rack stuff up to 5U apart to avoid this. Bad equipment design then. Replace the cheap transformers with qualty toroids might be a good idea. Any Ideas?? Don't do what you just suggested. Graham |
#23
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experimental power supplies
Arny Krueger wrote:
The classic way to increase isolation of individual circuits from a common power supply is to distribute well-regulated DC at some higher voltage such as 32 volts or higher, and use on-board regulators to bring it down to say, 24 volts. This is fine for telecoms. As in telephone quality. Don't even get me started about ground return currents and the problems that will add. Graham |
#24
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Q: experimental power supplies
Arjan P wrote:
Huh? Maybe you're talking about composite aircraft, but airframe ground return is all there is on today's aircraft, since it cuts the amount of cable = weight in half (outside the studio I'm an avionics engineer). The only exceptions to it are antenna and pickup wiring and data lines obviously. On the newest Airbus designs they're even considering increasing main power for certain systems from 115V/400Hz to a higher level to further decrease cable weight. Don't you have 400 Hz eddy currents everywhere, and 400 Hz trash leaking into everything? My experience with aircraft stuff is mostly military craft, which are a soup of 400 Hz in spite of careful grounding and sometimes even shielded power lines. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
#25
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Q: experimental power supplies
"Scott Dorsey" wrote in message
Arjan P wrote: Huh? Maybe you're talking about composite aircraft, but airframe ground return is all there is on today's aircraft, since it cuts the amount of cable = weight in half (outside the studio I'm an avionics engineer). The only exceptions to it are antenna and pickup wiring and data lines obviously. On the newest Airbus designs they're even considering increasing main power for certain systems from 115V/400Hz to a higher level to further decrease cable weight. Don't you have 400 Hz eddy currents everywhere, and 400 Hz trash leaking into everything? My experience with aircraft stuff is mostly military craft, which are a soup of 400 Hz in spite of careful grounding and sometimes even shielded power lines. Agreed. The Hawk ca- 60s CW RADARs I worked with involved listening to Doppler tones in the audible range. I don't know how they picked the frequency of the RF. Perhaps conincidentally the RF carrier frequency chosen put all of the audio signals that were interesting well above 2400 Hz. Those days were still mostly about tubes and selenium rectifiers, though just a little germanium and silicon was creeping in. All you have to do is look at the Fletcher-Munson curves and compare audibility of 60 Hz to 400 Hz on say the 30 dB curve (something like 30 dB difference) , or 360 Hz versus 2400 Hz ( about 10 dB difference). OTOH, a line frequency of 1200 Hz or higher happily starts one back up the audibility curve for 3 phase full wave rectification. In the old days the most problematic aspect of 400 Hz was building synchronous motors that spun slow enough to do useful things without lots of gearing. Today, they would probably be DC servos. I don't think that power transmission losses are much of an issue below 10 KHz and lengths under 500'. Above 10 KHz self-inductance and skin effect start rearing their ugly heads, when losses have to be REALLY low and currents are high. |
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Q: experimental power supplies
Scott Dorsey wrote:
Huh? Maybe you're talking about composite aircraft, but airframe ground return is all there is on today's aircraft, since it cuts the amount of cable = weight in half (outside the studio I'm an avionics engineer). The only exceptions to it are antenna and pickup wiring and data lines obviously. On the newest Airbus designs they're even considering increasing main power for certain systems from 115V/400Hz to a higher level to further decrease cable weight. Don't you have 400 Hz eddy currents everywhere, and 400 Hz trash leaking into everything? My experience with aircraft stuff is mostly military craft, which are a soup of 400 Hz in spite of careful grounding and sometimes even shielded power lines. Yes, there's a lot more to it then saying 'all grounds are the same', and shielding equipment and certain wiring is essential. As is the electrical bonding of all structural elements to make sure return currents do flow in the shortest route (and static buildup gets discharged where the designers want it to go - from replaceable dischargers and not wingtips or flight control surfaces). A number that comes to mind for, say bonding of an elevator surface, to the reference (AC ground connection, usually aircraft nose) is 20 milliOhms. Most of the potential problems are being tackled in the design stage though; return paths are calculated and AC systems never share the same grounding location (to the airframe) with DC systems, and the same goes for shielding grounds. Not to mention the cable separations in different cable looms for different types of signals and systems and then also splitting different identical main systems from each other and their backups; this also for redundancy reasons. I think it's safe to say that here the difference between cars and aircraft become apparent, to say the least.. And then, the smaller the aircraft - the bigger the problems, since everything has to get crammed into the same tight space. Mmh, getting quite off topic, this one.. Luck, Arjan -- ----Real email: news then at then soundbyte then dot then nl---- |
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Q: experimental power supplies
(Mike Rivers) wrote in message news:znr1078350305k@trad...
In article writes: unitron wrote: Just to be picky, if your power cord has a black wire, a white wire, and a green wire, the white wire isn't the neutral, it's the grounded conductor Wow... I didn't know that. I've always heard it described as the neutral Don't let him kid you. An electrician will tell you that it's the neutral wire, and that the green wire is the safety ground wire. It's correct that the neutral wire is supposed to be connected to ground at one point only. That's why it's called "neutral" rather than "ground." Right, also that it connects to the center tap on the utility transformer and provides the reference for 120V circuits. |
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Q: experimental power supplies
Mark Tranchant wrote in message ...
unitron wrote: Speaking of neutral wires, I'm thinking of starting up a new thread of the bi-wiring off of a single amp discussion, this time centered on whether one could do so with 3 wires instead of 4, one hot for the woofer, one for the tweeter, and a common return. Whadda ya think? :-) Should work, provided: 1) the amps are ground-referenced on the low side not bridged. 2) you're aware of the potentially higher current flow in the common wire. This would surely only give half of the biwiring advantage, which is questionable to start with... Yes, but think how entertaining a thread about it would be :-) |
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