power supply toroidal help

ebay.com/itm/LV30-Variable-V … 3384866145

i just found this on ebay.(didnt end up purchasing yet) i hope its good but i was just sort of guessing…:stuck_out_tongue: it uses the LM1085 linear chip
can i get some opinions?
and also i was looking at getting a 30va potted toroidal from altronics
altronics.com.au/p/m4315-pow … ansformer/
something like that
all help is much appreciated

Hi,
have a look at our post in this forum https://volumio.org/forum/mdxs-the-source-everything-t3643.html or our website with a comparison of regulators https://sites.google.com/a/architekturkonsulat.at/mdxs/home.
Unfortunately we didn’t have a LM1085 to test (there are just too many options available). For an off the shelf (ebay) regulator we liked the LT1963EQ.
As for the toroidial check for Nuvotem Talema - they can be found inside the “more expensive” audio stuff on the market. Noratel also makes a 30 VA 9 VAC (4x) # AA-021521 if you like to split things up.

ebay.com/itm/201209828911
this is the power reg i found based on the chip you recommended. will this be ok?
Ultra-low Noise <40μV Adjustable Voltage Regulator Module, Based on LT1963.

M4909A • 240/9+9 30VA Toroidal Transformer
thats the transformer i have ordered

You can connect your toroidal with a center tap and remove the marked diodes (maybe not really necessary but no guarantee) like this.

Why would I do that? Isn’t that the rectifier diodes? And if I want full amperage from the toroidal it would need to be 9v parallel. That would go straight to the AC input.

Actually looking at the circuit again I see your wiring does just put it into parallel. But is there a need to remove two of the diodes? Sorry if I’m missing something obvious. Would making a custom rectifier be just as easy as doing this?

Excuse my question Capedory, but do you have any background in electronics? :confused:

These articles might help:
allaboutcircuits.com/textboo … -circuits/
www.acoustica.org.uk/t/naim/powersupplies.html

Stephane, maybe you can help couchzombie. I have limited knowledge but I have built some power supplies* (mainly by looking at other good stuff) for pre-amps and volumio projects. They work fine and sound pretty good when compared to very expensive equipment. A full wave center tap rectifier is a common layout and it must have its reasons.
I would not run the two winding parallel.

OK I’ll stick with standard wiring. I’m losing half my current capacity if I use center tap. The reason for center tap to me looks like just to avoid using extra diodes and preventing excess voltage loss. I have plenty of voltage to play with.

A center tap on a transformer is needed when you need bi-polar Dc voltages.
On the circuit that couchzombie wants to use there is a Wheatstone bridge diode rectifier and a single polarity DC regulator. So no need to take off some diodes and wire the transformer in an odd way.
If the transformer has two separate output coils, you can wire them in series to have a greater output voltage or in parallel to have a greater current. You will have to take care connecting the right sides of the coils or you will have a near zero AC output (two identical voltages but in opposite phase).
One thing to consider is the unregulated DC voltage feeded to the regulator. If it’s too low the regulator will not work properly, if it’s too high it will burn and when it’s higher than the output voltage then it will have to dissipate the power not used by the application through a heat-sink ([Vin-Vout]*I).
So, if I had to put a power supply, it would be a switching power supply with good DC filtering and a linear regulator to provide a cleaner output. Remember that switching power-supplies are commonly used in medical instruments, measuring instruments and many other circuits where efficiency is needed.
I have built a low-noise trigger board for an astro-physical experiment with DC-DC switching converters and it has been detecting high energy cosmic rays with success for many years.

Oh, and last thing, if your ears are the only instruments you have to measure the results then comparing to circuits is absolutely non-sense.

OK cheers for that last comment. As long as I’m not in danger of burning something out with the combo I’m going with I’m happy.

Hi Stephane,
i haven’t been here for a while, but don’t want to leave this sentence uncontradicted.

Maybe bringing the centertap theme to this thread was not a good idea and lead to nothing but confusion (for a existing circuit). It came up, because we use the center tap as the beginnig of a star ground scheme in our setups where it is logical to us.

To come back to our ears. Of course beenig almost complete laymen we have needed, and we still will need some more passes of testing for consistent clearfication of musical improvements (of our approaches, tuningsteps and hacks). But, beeing systematical in our approach, we find what matters. E.g. after beeing very good at the end (with the regs) we found (with some help of the pinkfish media crowd, thank you…) out (what we read before but did not understand) that there is improvement by implementing crc in the psu (using PSUD for estimation, very nice…)… Experienced people would have done this first.

Talking only about psu’s you would be able to measure the better, but deciding for a dac, an oszilloscop will not help. Not in the last instance.

So we are developing slow, always and still improving, unprofessional, but i may say we’re having incredibly nice sounding volumio dacs at the moment that can compare to or outperform everything more or less expensive (like really nice lp12s, naim dacs etc) we have around at testing.
The result is only because of learnig tecnical basics, comparing to what others did, having some ideas, testing and comparing our built approaches with our ears. This makes absolutely sense and is not non-sense :slight_smile: