audio-gd said:
Once i built something very similar. Replacing the opamp with a differential mosfet pair, like a Pass preamp was an obvious improvement.
I wish someone will design a usb dac using a better usb chip.
Do the transistors in the power supply need to be matched or do we get away from that with the trimmer?
Hoping someone might have an answer. I etched a board to try this circuit and want to get the best performance but not sure if matching is necessary.
board I came up with
This is for the psu on the bottom of his 3 supply schematic. 100mmx146mm
Blue is top layer and green is bottom. When you see green disappear under blue its not the same trace but they are overlapping at that point.
This is for the psu on the bottom of his 3 supply schematic. 100mmx146mm
Blue is top layer and green is bottom. When you see green disappear under blue its not the same trace but they are overlapping at that point.
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hopefully someone will be interested enough to pop in and talk about transistor matching and if it is necessary on the +/- supply PSU.
I bought 50 of each small signal transistor and 10 of each larger transistor. Hope to not have to match them all, even though its not a real big pain. I imagine DC offset wont be a problem ;P but not sure what that trimmer does and want to make sure it does not make up for only small differences between +/-
I bought 50 of each small signal transistor and 10 of each larger transistor. Hope to not have to match them all, even though its not a real big pain. I imagine DC offset wont be a problem ;P but not sure what that trimmer does and want to make sure it does not make up for only small differences between +/-
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Built the supply tonight. Very nice results on the bench so far. Will hook it up to a headphone amp this weekend. Output voltage is accurate to about 3-4mV. Moves around in that area as long as ambient temp is steady. My sink is running about 46C right now. Will use a bigger one next time. If I blow on the sink the output voltage jumps around a lot til the temp of the sink stabilizes. Scoped the output and it looks fantastic.
Uriah
Uriah
Well, I built it to replace a battery supply on the headphone amp and it serves the purpose well. After some tweaking there is no distinguishable difference. Thats a good thing 🙂
Thing is very touchy with temp. The sun moved across the room and when the sunlight hit it the offset from +to- was a few volts. Will have to put a load on the transformer and heavier load on output to test further.
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