Hi all been using these chips for a while for my headphone amp.
The right channel is now heavily distorted and I've exhausted all options.
The circuit uses two LM380Ns, one per channel. Tried swapping them around to see if the fault moves channel, nothing still the same. Lifted the legs for VOut and soldered straight on to them to see if a component was causing it in the output stage, still the same, lifted the legs on the Vin and soldered a pot in line direct on to the chips, still the same, tried bridging the stereopot for mono to see if that is causing it, still the same. Output from the PC is fine tried headphones direct, tried 3 different headphones too and still the same.
Any ideas or anything I have missed? The fault stays on the right hand side no matter what and I and V supply is fine.
The right channel is now heavily distorted and I've exhausted all options.
The circuit uses two LM380Ns, one per channel. Tried swapping them around to see if the fault moves channel, nothing still the same. Lifted the legs for VOut and soldered straight on to them to see if a component was causing it in the output stage, still the same, lifted the legs on the Vin and soldered a pot in line direct on to the chips, still the same, tried bridging the stereopot for mono to see if that is causing it, still the same. Output from the PC is fine tried headphones direct, tried 3 different headphones too and still the same.
Any ideas or anything I have missed? The fault stays on the right hand side no matter what and I and V supply is fine.
Forgot to add, even if I mono the output on to one chip, it is still the same. It can't be the output jack I only fitted it from new last week and it hasn't been moved etc
Could You show the schematics you are using?
Anyhow, it should be straight forward. Easiest chip to get to function.....all right.
Always adviceable to add a pot on the input. Or at least a dropresistor. Is fixed 34dB gain in this.
Otherwise, I would rather use a discrete design for headphone amp. LM380 is...... poor.
Anyhow, it should be straight forward. Easiest chip to get to function.....all right.
Always adviceable to add a pot on the input. Or at least a dropresistor. Is fixed 34dB gain in this.
Otherwise, I would rather use a discrete design for headphone amp. LM380 is...... poor.
Don't have a schematic to hand, at the moment line level is connected to a pot and direct to the IC and the Vout goes straight to the headphones. The only other pins connected to the PCB are grounds, Bypass (not sure on the use for this) or Vs.
Yes it is poor but it is better than the motherboard audio. Next I want a TPA6120A2
Yes it is poor but it is better than the motherboard audio. Next I want a TPA6120A2
Check supply voltage on pin 14.
Check ground connections on pin 7 and pins 3-4-5-10-11-12, things won't work if either is missing.
Check output coupling capacitor on problematic channel.
Check ground connections on pin 7 and pins 3-4-5-10-11-12, things won't work if either is missing.
Check output coupling capacitor on problematic channel.
Does bypass need to be connected? It can only be one of three things left, bypass, something on Vs (I doubt this) or the output jack.
With nothing on the bypass pin you would be getting pretty terrible power supply rejection, but things should still work. A leaky bypass cap could potentially drag things down though.
Expected DC voltage on the bypass pin is about half supply.
Expected DC voltage on the bypass pin is about half supply.
Thank you for clearing that up for me, Voltage on bypass is half Vs on both IC's. So now I am stuck, right channel is completely distorted, and having swapped IC's and inputs and outputs it is still the same. The only thing left is Vs (supply is the same on both IC's) or the output jack that I very much doubt is at fault.
Is the line out from the sound card that is feeding the amp the same connector you're plugging the headphones directly into? Or is it a separate line out connection that is connected to the amp?
Just done some measurements right channel is over driving, So something on the right side must be dragging it to ground or floating, going to have a quick play with the circuit and see what I find.
Problem solved, it was the new output jack plug, even though it was working fine for a week and measures fine. Changed it and all working like normal now, so I am none the wiser.
Couplingcapasitors before the pots are adviceable.
This amp is internally compensated and bypassed, so if the voltage on the output differs from half the supplyvoltage, the device is defective.
Should be very straightforward this one, simple and easy actually.
This amp is internally compensated and bypassed, so if the voltage on the output differs from half the supplyvoltage, the device is defective.
Should be very straightforward this one, simple and easy actually.
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