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transformer upgrade?

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     Cannot see the secondary windings on the EI transformer. The toroid has dual secondaries. May not be compatible. 

  For many applications the limited bandwidth of an EI transformer is better. The noise is filtered out. 

  The picture shows a 70 volt line transformer. 

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The substitution may or may not be an upgrade, depending on the specific application. If the EI is an output transformer then substituting a toroid may well improve performance, in particular in leakage inductance and DCR of the windings. However if the EI is a power transformer the wider bandwidth of the toroid may be detrimental.

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10 minutes ago, Panelhead said:

     Cannot see the secondary windings on the EI transformer. The toroid has dual secondaries. May not be compatible. 

  For many applications the limited bandwidth of an EI transformer is better. The noise is filtered out. 

  The picture shows a 70 volt line transformer. 

Ignore the wiring and writing it's just a general picture to ask if an el transformer can be upgraded inside a LPSU to toridal transformer?

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13 minutes ago, opus101 said:

The substitution may or may not be an upgrade, depending on the specific application. If the EI is an output transformer then substituting a toroid may well improve performance, in particular in leakage inductance and DCR of the windings. However if the EI is a power transformer the wider bandwidth of the toroid may be detrimental.

its for one of these:

1752172448_SboosterBOTWLPSU(4x)a.jpg.0ed952474d46347e148cca478c712aca.jpg

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4 minutes ago, opus101 said:

If its a power supply transformer in an audio application then in my view it'll be a downgrade to change EI to toroid.

I just wondered because all the best and latest LPSU for audio seem to be either toroidal or R-Core these days in the more expensive builds.

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10 minutes ago, opus101 said:

The best for an audio application would be the one with lowest capacitance between the windings. Which is normally a split-bobbin EI. Both R-core and toroid have more capacitance than split-bobbin EI. Toroid comes in useful when you want very low radiated flux but in a wall-wart that's not a requirement.

thank you!

 

I just read this on the web:

"In the high tech world of audio, there are many different components that make up a single piece of equipment. In most powerful audio systems, you can find toroid transformers. These donut-shaped devices are taking over the audio industry. There are many advantages for using a toroid transformer, but the most valued characteristic of the device is that they do not radiate a magnetic field. This advantage makes them extremely attractive to the high-end audio equipment sector."

 

Yes sorry, I;m talking of LPSU's, not wall warts, not SMPS, see pic 'above', thanks!

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Notice the context there - '...in the most powerful audio systems...'. That to me indicates power amps. In a power amp, lack of radiated flux is a big benefit as the trafo's in the same box as the electronics. A power amp is a completely different application from a wall-wart type supply brick.

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2 hours ago, opus101 said:

Notice the context there - '...in the most powerful audio systems...'. That to me indicates power amps. In a power amp, lack of radiated flux is a big benefit as the trafo's in the same box as the electronics. A power amp is a completely different application from a wall-wart type supply brick.

yes I agree that a power amp is different to wall wart application! However, I'm not talking about wall warts I'm talking about LPSU's; the type Paul hynes builds and many many others, e.g. MCRU, BOTW, Pang, Baldwin, Jacobs, Linear Solution, etc. and all high-end Hi-Fi applications. 

However, I think in the case of the SBOOSTER that I gave a picture of up this thread, I have thought about the overall design principal and maybe wrongly (?) come to the conclusion that the PCB in that LPSU is designed to operate with that El transformer and it's not as simple as simply supplanting it with a toroidal transformer? i.e in order to use a toroidal transformer you would need to redesign the entire PCB to function correctly with it?   ...yes?

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54 minutes ago, opus101 said:

To me, the pic in post #5 is a very close relative of a wall wart, hence my 'wall wart type supply brick'. Is that called 'SBOOSTER' ? If so then its still a backwards step to exchange an EI for a toroid in that. 

yes it's an SBOOSTER/BOTW LPSU:

2048228734_SboosterBOTWLPSU(4x)b.jpg.9710fe48bb5155c63fd5aeaa3d21b32c.jpg

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12 minutes ago, JohnSwenson said:

There is no way to make a general "one is always better than the other". There is far more to a power transformer than just if it is EI or toroid. How the design handles high current pulses (does the magnetic circuit saturate) is very important for most linear supplies. The standard way these supplies work (large cap after diode bridge) produces high current pulses at the peaks of the waveforms, the transformer needs to be able to handle these. NOBODY specs this for power transformers.

 

So you either have to measure this yourself or significantly derate the transformers. This is why it is usually not good to spec the VA of a transformer near what steady state ohms law calculations say. Exactly how much? Who knows, it can vary all over the place depending on the circuit and the transformer. Some people say you should rate the transformer at 1.5 what the simple calculations say. Most of the time that works pretty well, but not always.

 

Several years ago I was working on a fairly high power PS design and decided to go with the empirical approach, I ordered a whole bunch of different transformers and tried them out in the real circuit. I found that most of the EI transformers were very close to their rated VA (almost no margin). Many of the large high power toroids  had fairly large margins. Thus for similarly speced transformers I got much better performance from the toroids. Thus for the specific PS design I was able to get good performance (properly handling high current pulses) from a toroid with a lower VA than a EI. This meant the toroid transformer was much cheaper.

 

On the issue of high frequency passing from one winding to another, a basic toroid has much more capacitance than a split bobbin EI. But you have to be sure the EI is split bobbin. This can mostly be alleviated by a toroid with a shield between windings. I found in my tests that a toroid with inter winding shield fared just as good as the split winding EI, and given the much lower price, it was the way to go.

 

For lower power PS I found the opposite. For some reason the small toroids were not nearly as good as the large ones. So for me at least I would go with a split bobbin EI for lower power (say less than 30 watts) but derate it to 1.5 simple calulations (say 48 VA instead of 30VA) and an inter winding shielded toroid for larger supplies.  Of course that is not always true for all designs.

 

I would not swap out a transformer in an existing design unless you really know what you are doing and can measure what is happening. There are so many ways you can make it worse, and only a few that will make it better, its usually not good odds of accidentally finding the better.

 

John S.

many thanks for this splendid analysis, some of which I understand (LOL), and this confirms what I thought in post #11, i.e. better not to tamper, better to leave it as it was designed! Subjectively to my ears personally, this does improve sound quality compared to the wall wart! I should hope that it would considering that it cost like £150 more than the £5 wart wart (LOL)!

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1 hour ago, JohnSwenson said:

There is no way to make a general "one is always better than the other". There is far more to a power transformer than just if it is EI or toroid. How the design handles high current pulses (does the magnetic circuit saturate) is very important for most linear supplies. The standard way these supplies work (large cap after diode bridge) produces high current pulses at the peaks of the waveforms, the transformer needs to be able to handle these. NOBODY specs this for power transformers.

 

So you either have to measure this yourself or significantly derate the transformers. This is why it is usually not good to spec the VA of a transformer near what steady state ohms law calculations say. Exactly how much? Who knows, it can vary all over the place depending on the circuit and the transformer. Some people say you should rate the transformer at 1.5 what the simple calculations say. Most of the time that works pretty well, but not always.

 

Several years ago I was working on a fairly high power PS design and decided to go with the empirical approach, I ordered a whole bunch of different transformers and tried them out in the real circuit. I found that most of the EI transformers were very close to their rated VA (almost no margin). Many of the large high power toroids  had fairly large margins. Thus for similarly speced transformers I got much better performance from the toroids. Thus for the specific PS design I was able to get good performance (properly handling high current pulses) from a toroid with a lower VA than a EI. This meant the toroid transformer was much cheaper.

 

On the issue of high frequency passing from one winding to another, a basic toroid has much more capacitance than a split bobbin EI. But you have to be sure the EI is split bobbin. This can mostly be alleviated by a toroid with a shield between windings. I found in my tests that a toroid with inter winding shield fared just as good as the split winding EI, and given the much lower price, it was the way to go.

 

For lower power PS I found the opposite. For some reason the small toroids were not nearly as good as the large ones. So for me at least I would go with a split bobbin EI for lower power (say less than 30 watts) but derate it to 1.5 simple calulations (say 48 VA instead of 30VA) and an inter winding shielded toroid for larger supplies.  Of course that is not always true for all designs.

 

I would not swap out a transformer in an existing design unless you really know what you are doing and can measure what is happening. There are so many ways you can make it worse, and only a few that will make it better, its usually not good odds of accidentally finding the better.

 

John S.

you have supplied the only convincing argument against replacing the transformer, better not to meddle and possibly degrade the power supplies efficiency by marrying a transformer to a PCB that it wasn't designed for! -   ...yes?

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