this is the schematic, i used two op amps (the ne5532 and the tl072) and two loads an weird 8ohm pair of iems and my hd559 the amlplifier seems to improve the bass extetion and current drive of my basic ugreen dongle and otherwise works fine but it makes a weird noise when its not plugged into anything, i sadly cant post the recording of this noise but its an high pitched noise simmilar to boiling water thats diffrent from the typical mains hum.
Usually for the non-inverting input, use a 10k/10k supply divider with a 10uF decoupling capacitor,
and a 100k resistor from the center of the divider to the positive input.
and a 100k resistor from the center of the divider to the positive input.
It is normal that an open input with hi-impedance produces excessive noise.
This disappears when input is shorted.
Either you short it if no source is present or you connect it to a source.
Open inputs are a call for problems.
Open inputs are a call for problems.
Well it obviously is shorted when in use, are there any headphone jacks that could automatically short the input when there is no cable inserted?
Ref: TI single supply vs multiple supply appnote
"TI appnotes say:"
Single-supply op amp design is more complicated than split-supply op ampdesign, but with a logical design approach excellent results are achieved.Single-supply design was considered technically limiting because the older opamps had limited capability. The new op amps, such as the TLC247X, TLC07X,and TLC08X have excellent single-supply parameters; thus, when used in thecorrect applications, these op amps yield rail-to-rail performance equal to theirsplit-supply counterparts.Single-supply op amp design usually involves some form of biasing, and thisrequires more thought. So, single-supply op amp design needs discipline and aprocedure. The recommended design procedure for single-supply op amp...........
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Despite what the math says, I found that it works better if both input pins are biased from the same reference..
"TI appnotes say:"
Single-supply op amp design is more complicated than split-supply op ampdesign, but with a logical design approach excellent results are achieved.Single-supply design was considered technically limiting because the older opamps had limited capability. The new op amps, such as the TLC247X, TLC07X,and TLC08X have excellent single-supply parameters; thus, when used in thecorrect applications, these op amps yield rail-to-rail performance equal to theirsplit-supply counterparts.Single-supply op amp design usually involves some form of biasing, and thisrequires more thought. So, single-supply op amp design needs discipline and aprocedure. The recommended design procedure for single-supply op amp...........
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Despite what the math says, I found that it works better if both input pins are biased from the same reference..
With your headphone HD559, 108dB/1Vrms sensitivity and 50ohm impedance, it needs 2.24Vrms, 45mA to drive it to 115dB, no one listen to this volume just so it has spare driving power. most modern signal source has enough voltage output, so you might not need so much voltage gain. Opa needs to be able to provide some current, 45mA is a very awkward range. most signal op amp is more comfortable driving 30mA ish current.
njm4556 is good choice.
njm4556 is good choice.