Hello everyone. I recently finished my hybrid 12AU7/IRF510 headphone amp, and it sounds wonderful The problem is, there's a bit of hum every once in a while, and I think it's the power supply that's the problem. Here's a schematic for it:
Now I've tried building that schematic 2 times, but it outputs about 15 VDC I'm looking for a regulator schematic that inputs about 15-20 VDC and outputs 12.6 VDC. If anyone has any suggestions I would be really thankful
An externally hosted image should be here but it was not working when we last tested it.
Now I've tried building that schematic 2 times, but it outputs about 15 VDC I'm looking for a regulator schematic that inputs about 15-20 VDC and outputs 12.6 VDC. If anyone has any suggestions I would be really thankful
Changing RR1 from 120 to 270 Ohm will be quite enough.
Thanks, I'll do that and report back here
This device may require a minimum load current to function properly. I believe that
minimum load is 10ma. If you are powering it up without a load then the current through rr2 and rr3 may be below this minimum value. You might try just shorting
rr2 or placing a load on the output to se if this is the problem.
minimum load is 10ma. If you are powering it up without a load then the current through rr2 and rr3 may be below this minimum value. You might try just shorting
rr2 or placing a load on the output to se if this is the problem.
I think your Vin is too low, the LM317 needs about 3V to operate. As an experiment try increasing Vin, try about 18VDC that should prove the point.
Yeah... The National Semiconductor LM317 has a worst-case drop-out of about 2.5 V. I.e. the input voltage has to be at least 2.5 V higher than the output voltage. Allowing for a few volts of ripple, an input voltage of 18~20 V seems reasonable.
You also need a reasonably sized heat sink on the LM317. If the chip overheats, it'll enter thermal shutdown.
Three bad pots?! Actually, that sounds like you either didn't hook the components up according to the schematic or there's a cold solder joint somewhere.
~Tom
It seems the trim potentiometer wasn't properly working. Well, actually, not one, but THREE of them ! I am that unlucky. I bought a proper trim potentiometer so now it works.
Do you get 12.6 V out now?
~Tom
This device may require a minimum load current to function properly. I believe that
minimum load is 10ma.
Actually, it's a bit lower than 10 mA typically. It depends on (Vout-Vin). See the datasheet for details.
With 120 ohm from OUT to ADJ, you already draw 10 mA through the regulator. No additional load needed for regulation.
~Tom
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