It is an audio myth that R core transformers are the best mains transformers for audio.They are recent design, have good look, and certainly better than toroids. Construction is identical to C core type save core design which is round( R). But their interwinding capacitance(indicator of unwanted noise reduction ) is lower than toroid-same as for C core, but higher than split bobbin EI core types or UI core low profile transformers,
UI core have balanced wound coils which reduce stray , harmful magnetic field(similar to R and C core).
If we measure primary to secondary capacitance of various transformers with the same voltage and current ratings the lowest reading will be with UI core, followed by EI( similar C, but radiate more magnetic field) , R core, C core and
toroids. But UI core transformes are generally available up to 100VA, so for power amps R core is the optimum.
For my preamps , headphone amps and phono preamps I am using outstanding Bulgarian ANG low profile UI PCB transformers which are available to 24VA max. current, in dual mono configuration.
UI core have balanced wound coils which reduce stray , harmful magnetic field(similar to R and C core).
If we measure primary to secondary capacitance of various transformers with the same voltage and current ratings the lowest reading will be with UI core, followed by EI( similar C, but radiate more magnetic field) , R core, C core and
toroids. But UI core transformes are generally available up to 100VA, so for power amps R core is the optimum.
For my preamps , headphone amps and phono preamps I am using outstanding Bulgarian ANG low profile UI PCB transformers which are available to 24VA max. current, in dual mono configuration.
If you put C core transformer in separate box results are the same as with R(ound) core transformer near the circuit. UI core low profile have slightly higher radiated field than toroids , but they have more neutral , more focused sound. It depends of whole PS and audio circuit design and PSRR.
For ultimate sound reproduction even the lowest radiated transformer(s) should be in separate enclosure. Mains polarity is also important . Factory markings are not always correct.
Either with an electricians screwdriver, or by testing voltage between common, phase and earth. Phase and earth should have 220V, common should be zero.
As I said , remove any kind of transformers in separate box if you wish to avoid electronic noise which degrade fine sound nuances. Mains transformers are some kind of mains filters , and UI are EI core the best for that purpose.
UI core low profile tansformers are self balanced wound, to focuse magnetic field inside the core, so they can be used inside the equipment ,with careful positioning and rotation if necessary.
If you wish to avoid separate PSU box, which is of course more practical, use large and wide 2U 19 inch rack enclosure and mount transformers as far as possible from the input circuit. Primare Audio did similar with R32 phono stage.Take a look at Pass XP-15 and XP-25 phono preamps. Less expensive model is single box .
No.... I just experimented this 57dB build with my friend´s 0.15mV cart and it sounded very good but lacking some gain.
After he heard it, I built a 48dB + SUT with external double mono psu for him with great results as you know
This experiment led me to believe it is better to have less than too much gain.
For instance, the same 57dB build does not work so good with my 0.8mV Benz.
It is ok with my DL103
After he heard it, I built a 48dB + SUT with external double mono psu for him with great results as you know
This experiment led me to believe it is better to have less than too much gain.
For instance, the same 57dB build does not work so good with my 0.8mV Benz.
It is ok with my DL103
I mean determine the correct polarity for the TX wires.
(I know how to determine polarity in the mains socket
)
Transformers primary can be connected to mains socket in two ways , but only one position is correct. If not, magnetic stray field is much higher.
The best way to determine the right position is to measure magnetic field around transformers. I have been using Elfix magnetic field detector for many years. Another method but very tedious is described by Vandenhul at his web-site.
I found that the polarity can only be accessed by ear. Common sense tells us that we should plug in the mains that way that the coupling capacitance is minimized.
I found when i wired my system that way that it sounded worse compared to the case when i just listened to each component separately and determined the position by ear. Discussing this with a friend that does a lot of fundamental research he came up with the explanation that capacitive coupling should not be minimized referenced to ground but similar to "both sides".
I found when i wired my system that way that it sounded worse compared to the case when i just listened to each component separately and determined the position by ear. Discussing this with a friend that does a lot of fundamental research he came up with the explanation that capacitive coupling should not be minimized referenced to ground but similar to "both sides".
Here the mains, filter, transformer and rectifier sections, and some notes
Read the information here
http://sound.westhost.com/psu-wiring.htm
Use a mains filter like this: schaffner fn-9264
http://www.google.nl/search?q=schaf...rtPage=1&redir_esc=&ei=-5MQT6WfCsP_-gbkk-GwAg
Use this for L4/L5 and L6/L7
http://www.diyaudio.com/forums/analogue-source/154210-mpp-354.html#post2819168
The rectifier diodes may (but not must be) of the Schottky type, almost any 1 Amp 100 Volt
device will do. It is advised to install the 'snubber' components (the 2.2 Ohm resistors and
100 nF capacitors) if the diodes are not of an 'fast recovery' type the resistors can be left
out (replace with wire bridges on the PCB).
Attachments
Last edited:
My listening test shows that magneting field measuring method is correct with every transformer type.
I use this common mode coil :CAF 0,6-100 - Stromkompensierte Drossel, 100mH, 20 - 30mm - Stromkompensierte Drosseln bei reichelt elektronik
Some prefer Panasonic 400 series ( Digikey ).
Some prefer Panasonic 400 series ( Digikey ).