Hi and thanks for the explanation
Clearly it is much more complex than what i thought.
I remember this one, but it is solid state.
In the chassis on the right the toroids and i guess AC umbilicals to the power sections on the left.
An externally hosted image should be here but it was not working when we last tested it.
Regards, gino
Hi All,
searching in the forum I have found this, very interesting post that has changed my plans.
And complicates a lot my project 🙁
I have to rethink about the AC umbilical solution
Maybe it is not the right way at all. Here the DC umbilical is mentioned as the only good option.
I am a little sad for this. I like the AC umbilical so much more.
I have seen it used in some commercial products like Cambridge Audio dacs (actually they use both).
Thanks again, gino
searching in the forum I have found this, very interesting post that has changed my plans.
And complicates a lot my project 🙁
I have to rethink about the AC umbilical solution
Maybe it is not the right way at all. Here the DC umbilical is mentioned as the only good option.
I am a little sad for this. I like the AC umbilical so much more.
I have seen it used in some commercial products like Cambridge Audio dacs (actually they use both).
Thanks again, gino
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The quoted text in your last post refer to a PSU for a power amp. That it may be a high power one, larger currents through, and so on. Not your case. For sure your device it take lower than 1 A for 12v...
Good morning ! thank you very much again ! great news !
because as I said I am quite sold now on the AC umbilical solution.
Actually I have already a headphone amp using an external mains transformer to function.
And also a Cambridge Audio dac (however in CA they provide both AC and DC power solution for different dac models).
Yes ! using a cheap bench power supply I see 450mA of current draw at 12VDC. This makes about 5.4 VA. Very little consumption. I do not know why they specify 15W in the datasheet.
Anyway I should receive a 12V transformer soon ... a nice EI type 😱
As a start. If the result will be promising I will look for a R-core unit for sure.
However I have also two old Mascot psu.
They both have EI mains transformers if this can mean anything.
In this 1st phase I am focusing the regulators.
I am so sad to be limited intellectually but these power supplies and the search for the minimal noise the complete silence is very very fascinating.
It is really an art.
For instance I have found a very interesting video on youtube by Linear.
https://www.youtube.com/watch?v=WxhjLIu-vPg
The designer suggests to place ferrite beads both before and after the regulator to suppress high Hz noise (listen at 2:40)
I wonder if to place one small bead directly on the input pin and another on the output pin of the regulator chip could
actually improve PSRR at higher Hz where, like the designer says, the linear regulators have lower PSRR
(without creating negative side effects of course like magnetic noise or such ... ).
This is a very easy thing to test by the way.
Again if I were more gifted I would be a designer of something.
I have an enormous and sincere admiration for designers in general.
They are geniuses ... the world evolves thank to them.
Thank you very much again.
Kind regards, gino
P.S. however, do you live in Norway ? I live in Stavanger. I am an expat from the Spaghetti kingdom ...
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You may not mix switching regulators with linear regulators...
A main linear power supply, or a linear regulator may not need any ferrite bad, but good capacitive filtering. Such components are used also in advanced DC power rails filtering for some local sensitive stages of a device, or to prevent side HF noise (from oscillators, RF processing circuits) to be spread into the rest of the circuits around.
P.S. I live in Norway indeed. Also into Stavanger area...
A main linear power supply, or a linear regulator may not need any ferrite bad, but good capacitive filtering. Such components are used also in advanced DC power rails filtering for some local sensitive stages of a device, or to prevent side HF noise (from oscillators, RF processing circuits) to be spread into the rest of the circuits around.
P.S. I live in Norway indeed. Also into Stavanger area...
R core transformers have higher capacitance between primary and secondary than EI core or flatpack transformers by about four times, and about one half of torodial trafos. Interested should measure it .
Hi ! from what I understand the Man was a real genius.
https://en.wikipedia.org/wiki/Jim_Williams_(analog_designer)
I would give him some credit 😉
For me technical geniuses are the real prophets. They help human beings to live better. If the world would be ruled by good engineers it would be a much better place to live. I tried to be an engineer but failed miserably.
Unfortunately we are not gifted the same 😱
They gave me the degree for mercy ... i think they made a mistake 😉
Nice ! If you like we can have a coffee downtown sometime and chat a little about diy.
Have a nice day, gino 🙂
Hi and thanks for the very helpful advice.
From what i understand for the common regulators high Hz noise is a real challenge. So the idea is to block it, at least in part, at the transformer level before it can reach the regulator.
Okey ... there is also the diodes high Hz noise ... that is an added issue.
But imho mains noise can be very significant. The sound is much better during the night or the weekend; my guess is for less noise coming from the mains.
I do not know about PSRR of different type of transformers but it would be interesting to see some graphs.
I have just bought an isolation EI one to try out.
On the basis of your advice the next one will be a R-core for sure. Very soon.
I have just to check the right voltage. I have ordered 12VAC models.
They should be enough.
Thanks again, gino
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This could be due to DC Offset on your mains supply causing the transformer core to saturate.
It may require you putting a DC blocker in series with the Transformer input to stop this occurring.
Hi and thanks a lot for the helpful advice.
What is a dc blocker ? a special capacitor ?
Prior to the transformer, large electrolytic capacitors conduct the first couple of volts of the incoming AC, then diodes take over after the threshold voltage is exceeded.
A better explanation here.
Mains DC and Transformers
I usually use the setup as in diagram 8, using 33000uf 16v caps with 8 amps of ripple current capability.
Very useful with toroids, especially in the UK, where the mains voltage is often 240 vAC or more and 50HZ loads the core more than the 60HZ used in the USA.
Bryston used this system in their big Power Amps too.
A better explanation here.
Mains DC and Transformers
I usually use the setup as in diagram 8, using 33000uf 16v caps with 8 amps of ripple current capability.
Very useful with toroids, especially in the UK, where the mains voltage is often 240 vAC or more and 50HZ loads the core more than the 60HZ used in the USA.
Bryston used this system in their big Power Amps too.
you will never know for sure unless you try....
i have done it and it worked for me,
no reason for it not to work for you...
i would rather listen to folks with actual experience...
Hi and thanks again. I will try to understand a little.
I have always associated this difference in sound to higher noise in the mains during the working hours.
So isolation from mains noise is beneficial.
Kind regards, gino
No, that is not how a DC blocker works. The caps pass all the AC, and block the first few volts of DC. The diodes pass large amounts of DC (if present, which is extremely unlikely) and also protect the caps from overvoltage in the event of a serious overload such as a short. If DC is not the problem then a DC blocker does nothing useful. Note that the main symptom of DC on the mains is excessive transformer hum, not audio noise.MIKEVO said:
A toroid designed for 240V 50Hz in the UK is just as happy as a toroid designed for 120V 60Hz in the US. The thing to be aware of is that some cheap toroids (from China, perhaps?) are rated for 220V or 230V so may struggle in the UK where our 'EU-harmonised 230V' is actually 240V.
Absolutely no toroids here 😉
Again what convinced me to go for EI type is what I saw used in control panels power supplies ...
and also lab linear supplies ...
I have ordered an isolation EI type.
So it will provide also isolation from the mains.
Again what convinced me to go for EI type is what I saw used in control panels power supplies ...
and also lab linear supplies ...
An externally hosted image should be here but it was not working when we last tested it.
I have ordered an isolation EI type.
So it will provide also isolation from the mains.
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Incorrect on both counts DF as the Caps are only rated at 16 Volts and the voltage of UK AC mains is 340 Volts Peak.
The higher the frequency, the smaller the core in a toroid.
Hence the issue with USA made kit having the primaries split on their Toroidal transformers for UK use, same transformer, but no hum in the USA at 60hz, but hum in the UK at 50Hz.
Ive had problems for years, but I do agree, a properly designed Toroidal will hum an awful lot less and thats why UK made Power Amps hum less mechanically.
I think you need to do some more reading on electronics before you build anything, especially if mains powered. You need to understand how caps pass AC and block DC, for a start. Then you will know how a 16V cap can be safe on 240V mains - when used correctly, of course.MIKEVO said:
Absolutely no toroids here 😉
Again what convinced me to go for EI type is what I saw used in control panels power supplies ...
and also lab linear supplies ...
An externally hosted image should be here but it was not working when we last tested it.
I have ordered an isolation EI type.
So it will provide also isolation from the mains.
Be a bit wary of EI if you have DC on the mains as these can suffer with core saturation also, I have seen it several times.
If you have an issue, the Transformer will run quite warm and possibly hum quite loudly.
Some nice kit you have there.
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