Hi all, i put this in the analogue source forum since i'm building a supply for a phone pre amp.
Basically my problem (?) is this, the lm7815 gives 14.9 volts; the lm7915 gives 15.1 volts. Is this normal, and is this a problem when driving an op amp?
After rectification i get +-21.9 volts, so the toroid and rectifier seem ok.. Also i rebuild the whole thing a second time with fresh parts and a cleaner layout, but still the same difference.
I build a basic power supply, mix from the VSPS power supply and sound westhost pre amp supply. It has a 2*15 vac, 50VA toroid on it.
Thanks for any input!
Basically my problem (?) is this, the lm7815 gives 14.9 volts; the lm7915 gives 15.1 volts. Is this normal, and is this a problem when driving an op amp?
After rectification i get +-21.9 volts, so the toroid and rectifier seem ok.. Also i rebuild the whole thing a second time with fresh parts and a cleaner layout, but still the same difference.
I build a basic power supply, mix from the VSPS power supply and sound westhost pre amp supply. It has a 2*15 vac, 50VA toroid on it.
Thanks for any input!
The tolerance on the standard 7815/7915 is not the greatest. Make sure you have the decoupling capacitors fitted as shown in the datasheets, they should be mounted very close to the actual regulators. If they're not fitted, the output voltage can drift in and out of spec or even oscillate.
If you want a more accurate balanced supply, use a fixed 7915 for -ve and a variable LM317 for the +ve rail, then adjust the trimmer on the LM317 to exactly match the output from the LM7915.
If you want a more accurate balanced supply, use a fixed 7915 for -ve and a variable LM317 for the +ve rail, then adjust the trimmer on the LM317 to exactly match the output from the LM7915.
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