Im about to build a four output 9v power supply with for my stompboxes.
Not because I try to save money, but because Im bored
I read a lot of ultra low noise supplies build with independent trafos. Is that reliable info or snake oil?
My plan is to use a 2x9v secondary trafo and two DB102/7809 circuits on each secondary for a total of four outputs.
Is my plan any better than running all four outputs from a 1x9v trafo via a single DB102/7809 circuit?
Will a 9v trafo be enough to meet the 11v minimum for the 7809 I plan to use due to the voltage loss of the bridge rectifiers (DB102) or should I go with a 12v?
https://www.tme.eu/en/details/bvei3821190/pcb-transformers/hahn/bv-ei-382-1190/
https://www.tme.eu/en/details/bvei4221225/pcb-transformers/hahn/bv-ei-422-1225/
Thx
Not because I try to save money, but because Im bored
I read a lot of ultra low noise supplies build with independent trafos. Is that reliable info or snake oil?
My plan is to use a 2x9v secondary trafo and two DB102/7809 circuits on each secondary for a total of four outputs.
Is my plan any better than running all four outputs from a 1x9v trafo via a single DB102/7809 circuit?
Will a 9v trafo be enough to meet the 11v minimum for the 7809 I plan to use due to the voltage loss of the bridge rectifiers (DB102) or should I go with a 12v?
https://www.tme.eu/en/details/bvei3821190/pcb-transformers/hahn/bv-ei-382-1190/
https://www.tme.eu/en/details/bvei4221225/pcb-transformers/hahn/bv-ei-422-1225/
Thx
Hi nanofarad. Thx for replying.
im not sure I get your point. The psu is for 9v stompboxes. I dont need 25v and the power dissipation in the 7809's would be huge.
I didnt purchase any of the parts as I needed confirmation on my design.
I can add another 2x9v trafo and make all four independent.
So you think 9v on the secondary will supply enough voltage to the regulators?
A very quick research show the design of LLC resonant psu's are very load depending.
The current draw varies from pedal to pedal.
9VAC rectified will give you like 12 VDC. = 3V only across the 7809
I should recommend a small trafo 12VAC.
Just to be on the safe side.
I should recommend a small trafo 12VAC.
Just to be on the safe side.
If I am doing the math right its 9*sqrt 2 = 12.7v rectified, minus ~1.4v bridge drop. So the 7809 see ~11.3v. True its a small margin, though this is with full loaded trafo.
12*sqrt 2 = 17v rectified, minus 1.4v bridge drop equals 15.6v for the 7809.
If a 100mA pedal is attatched the power dissipation equals 6.6*0.1=0.66w.
Its a tough call, I might go with 12v trafos.
Thx 🙂
Nah, not much if the transformer is underrated /small, you can also add small to-220 heatsinks (max input voltage is 35vDC for 7809). But i see lineup has a better solution.
Best regards
LLC converters have an operating point/frequency where the voltage is minimally load dependent. I used that feature. some low cost poweramp supplies are based on that principle.
I was under the impression smps' are very noisy.
Is an LLC the same as a buck converter?
I found 9v, 12w LLC converters on AliExpress at $5. But that will not address the issue about common ground by independent circuits.
LLC, means one capacitor 2 inductors, one inductor is the primary inductance of the transformer, the other is the leakage inductance of the transformer, or sometimes a separate inductor. By resonating them the current waveform is sinusoidal, lower in noise than the steep dvdt of flyback converters. The second advantage is that the transformer can be built using intended leakage inductance or poor coupling, allowing more insulation distance between primary and secondary, hence better noise isolation. I have played with gapped 3C20 toroid cores, having secondary and primary each on a half of the toroid, resulting in less than 5pf coupling capacitance.