The other night I found some info on power transformers that I had tucked away for a while and never read ( like 25 years, lol!) the jist of it seems to be that a low impedance secondary is better at providing a fast burst of current which in turn will make for less ripple voltage at the first filter node.
So low impedance would make for the need of a low voltage secondary, or in terms of tubes a lower voltage power supply will have far less 120 hz ripple to start with.
Progressing with this train of thought then to me it would seem that a voltage doubling type power supply with on its own, or one with a excess of current will have a ripple advantage over a standard type and taking this further, a PT who's primary is run on 220 volt or better will also have a smaller ripple factor while being able to provide a higher secondary voltage!
Am I in the ball park with this?
Thanks for your thoughs!
Power transformer info?
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Stevem
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Power transformer info?
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
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Leo_Gnardo
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Re: Power transformer info?
After the first paragraph I think your train's running off the track. Don't worry, you are giving it some thought and that's good.
You could take a look over at Audio Asylum. There's a couple of guys who have been trying to advance their theories of optimum power supply construction. The first, foremost, and most beset with detractors is Jeff Medwin. Right behind is his friend and mentor Dennis Fraker. Jeff's been claiming for years that secondary windings (hi voltage) with super low resistance (10 ohms or less), and low R chokes (20 ohm limit here) are necessary. Also, minimum filtering, we're talking just a couple uF and chokes measuring a fraction of a Henry. You can get iron like that, it takes FAT WIRE so it's costly and takes up a lot of space. Not too many are inclined to experiment along those lines, but if you have the $$$ be my guest. I haven't closed my mind to his ideas, maybe you can build a superior hi fi amp this way. Oh, you're supposed to use super fat wire to do your connections within the amp. To the extreme: cut the transformer wires back as far as you can, splice on 3 or 4 parallel pieces of special oxygen free high purity copper, run that to your next connection, etc etc. You could spend hours and hours searching their threads for info on this, membership isn't necessary.
Maybe, if you follow his directions, you could build a superior sounding power amp. It would be very heavy and extremely expensive for home built. I have a customer who started building his own, or at least collecting the parts and having custom 12ga steel chassis made, in 2006 and hasn't finished yet. Perhaps he'll get to evaluate it sonically before he's old and deaf.
And that's just hi fi amp: power amp only. How it applies to preamp, expect it to be a continuation. With all this fat wire and huge transformers plus super sturdy chassis, it would be wise to keep the circuitry very simple.
You could take a look over at Audio Asylum. There's a couple of guys who have been trying to advance their theories of optimum power supply construction. The first, foremost, and most beset with detractors is Jeff Medwin. Right behind is his friend and mentor Dennis Fraker. Jeff's been claiming for years that secondary windings (hi voltage) with super low resistance (10 ohms or less), and low R chokes (20 ohm limit here) are necessary. Also, minimum filtering, we're talking just a couple uF and chokes measuring a fraction of a Henry. You can get iron like that, it takes FAT WIRE so it's costly and takes up a lot of space. Not too many are inclined to experiment along those lines, but if you have the $$$ be my guest. I haven't closed my mind to his ideas, maybe you can build a superior hi fi amp this way. Oh, you're supposed to use super fat wire to do your connections within the amp. To the extreme: cut the transformer wires back as far as you can, splice on 3 or 4 parallel pieces of special oxygen free high purity copper, run that to your next connection, etc etc. You could spend hours and hours searching their threads for info on this, membership isn't necessary.
Maybe, if you follow his directions, you could build a superior sounding power amp. It would be very heavy and extremely expensive for home built. I have a customer who started building his own, or at least collecting the parts and having custom 12ga steel chassis made, in 2006 and hasn't finished yet. Perhaps he'll get to evaluate it sonically before he's old and deaf.
And that's just hi fi amp: power amp only. How it applies to preamp, expect it to be a continuation. With all this fat wire and huge transformers plus super sturdy chassis, it would be wise to keep the circuitry very simple.
down technical blind alleys . . .
Re: Power transformer info?
Well, not exactly, although it will have a definite influence.Stevem wrote: the jist of it seems to be that a low impedance secondary is better at providing a fast burst of current which in turn will make for less ripple voltage at the first filter node.
To make my position clear: I design and wind my own transformers, and am a firm advocate of low loss supplies,firm, stable if at all possible.
A few others have a different opinion, and to a point, in one or two very specific circuits , not my way but I understand them.
What a low impedance transformer (not only the secondary but also the primary, which is in series with it, divided by turns ratio) can offer is:
1) less resistance , so less drop with load
2) the current burst will be higher , caps get charged in a few milliseconds, much less than 50% wall voltage frequency.
The ripple waveform will be different, sharper; faster attack, roughly same release time.
Basically no.So low impedance would make for the need of a low voltage secondary, or in terms of tubes a lower voltage power supply will have far less 120 hz ripple to start with.
There is a formula for ripple voltage and it's based on frequency, capacitance and load current; actual supply voltage does not get mentioned.
Progressing with this train of thought then to me it would seem that a voltage doubling type power supply with on its own,
No, exactly the opposite, voltage doublers have the highest vripple because line frequency gets effectively halved.
or one with a excess of current will have a ripple advantage over a standard type
Not clear what you mean:
a) if excess current capability, it's what I mentioned earlier as lower resistance supply, won't affect ripple voltage.
b) if excess current consumption, higher current absorbed means higher ripple voltage.
The formula I mentioned above.
Not at all.and taking this further, a PT who's primary is run on 220 volt or better will also have a smaller ripple factor while being able to provide a higher secondary voltage!
Primary voltage will be converted to secondary by winding the transformer with a certain turns ratio.
If you design for a different primary voltage, turns ratio will vary to compensate, ripple voltage will be the same.
What will change ripple, is going from 50Hz to 60Hz and viceversa, the higher frequency having lower ripple voltage.
Re: Power transformer info?
Delving even more deeply, the way transformers work is that the primary "charges up" the core magnetic circuit with energy in a magnetic field.
In the absence of any secondary current, the M-field sucks just enough current to be maintained by the volt-seconds of applied primary. The back-emf of the core M-field limits input current.
What the secondary does is to parasitically suck some of the energy out of the M-field in the core, which reduces the back-emf enough to let a just-balancing amount more energy in.
The consequences are that even of you make the secondary out of centimeter- or inch-thick silver bars, or even a room temperature superconductor, the resistance of the primary still shows up effectively in series with the energy out of the secondary.
You can get around this by making the secondary *and* primary wire resistance small by making them *both* out of inch-thick silver wire, but then you have to have an enormous magnetic core to limit the magnetizing current needed to pump the M-field up to maintain the transfer.
There is another ugly issue on the table: leakage inductance. No matter how low you run the wire impedance, some M-field leaks out. And the bigger the physical dimensions of the core, the worse the leakage is, so leakage inductance goes up as wire size goes up as a side effect of needing a bigger window. And leakage inductance limits current flow in the secondary too, just in a different way than resistance.
Transformer action was a hot technical topic back in the early 1900s, and was very thoroughly worked over by the technical hot shots of the time. It is possible to very thoroughly model what power transformers do with some existing models. It is arcane, and easy to handwave as mystical and so on, but really, this stuff was pretty well explored. In the last century.
In the absence of any secondary current, the M-field sucks just enough current to be maintained by the volt-seconds of applied primary. The back-emf of the core M-field limits input current.
What the secondary does is to parasitically suck some of the energy out of the M-field in the core, which reduces the back-emf enough to let a just-balancing amount more energy in.
The consequences are that even of you make the secondary out of centimeter- or inch-thick silver bars, or even a room temperature superconductor, the resistance of the primary still shows up effectively in series with the energy out of the secondary.
You can get around this by making the secondary *and* primary wire resistance small by making them *both* out of inch-thick silver wire, but then you have to have an enormous magnetic core to limit the magnetizing current needed to pump the M-field up to maintain the transfer.
There is another ugly issue on the table: leakage inductance. No matter how low you run the wire impedance, some M-field leaks out. And the bigger the physical dimensions of the core, the worse the leakage is, so leakage inductance goes up as wire size goes up as a side effect of needing a bigger window. And leakage inductance limits current flow in the secondary too, just in a different way than resistance.
Transformer action was a hot technical topic back in the early 1900s, and was very thoroughly worked over by the technical hot shots of the time. It is possible to very thoroughly model what power transformers do with some existing models. It is arcane, and easy to handwave as mystical and so on, but really, this stuff was pretty well explored. In the last century.
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Stevem
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Re: Power transformer info?
Wow! Thanks for all the info gang!
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!