I've built this headphone amp (before I knew about diyaudio): https://www.instructables.com/Make-a-Headphone-Amp/
I want to use it to amplify a mono signal into stereo headphones, so I put in a mono jack for input and ran the tip to both channels of the volume pot (the first thing in the circuit). My audio probe and plugging into a stereo audio recorder both tell me that the signal is getting to both channels in the (stereo) output jack, but through the headphones I get near silence. Any idea of what's going wrong? or suggestions for how to fix it?
UPDATE: the output signal stays the same strength even if I unplug the battery or take out the opamp. In fact, I put in a new opamp and got a loud signal through the headphones for a split second, which suggests I've done some bad wiring and blown the opamp somehow. (Any tips on why opamps blow much appreciated.)
Thanks!
I want to use it to amplify a mono signal into stereo headphones, so I put in a mono jack for input and ran the tip to both channels of the volume pot (the first thing in the circuit). My audio probe and plugging into a stereo audio recorder both tell me that the signal is getting to both channels in the (stereo) output jack, but through the headphones I get near silence. Any idea of what's going wrong? or suggestions for how to fix it?
UPDATE: the output signal stays the same strength even if I unplug the battery or take out the opamp. In fact, I put in a new opamp and got a loud signal through the headphones for a split second, which suggests I've done some bad wiring and blown the opamp somehow. (Any tips on why opamps blow much appreciated.)
Thanks!
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Hi Galu. Thanks for taking the time. I've corrected the link and added some new info. I had thought it might be a phasing problem, but now I think I'm blowing the opamp somehow.
Caspar
Caspar
The most likely reason for blowing the op amp is that the DC voltage is of the wrong polarity.
It may seem obvious, but have you connected the 9 V battery the correct way round - positive connecting to positive terminal of 220 uF capacitor?
It may seem obvious, but have you connected the 9 V battery the correct way round - positive connecting to positive terminal of 220 uF capacitor?
It does seem to be the right way round. Taking the opamp out of its holder I tested voltages at the different pins. Pin 8 was +9 volt. So were pins 3 and 5. Should they be? Also without the opamp, the sound signal was audible with a probe at pins 2 and 6 (as I expected) and also at 1 and 7, which I didn't. I guess it is going across the 68k resistors.
Pins 3 & 5 are the non-inverting inputs and will read positive. Pins 2 & 6 are the inverting inputs and will see the input signal. Same to be expected with output pins 1 & 7.
rayma will to be the man to go to if you let him see photos of your construction.
rayma will to be the man to go to if you let him see photos of your construction.
Hi again, both. Yes to both questions. I waited for daylight and got a better soldering iron, reflowed a few joints and - success! No sound comes through when the battery's unplugged and when it's plugged in the signal is definitely amplified. It's not the cleanest signal, but good enough for my purposes. Thanks for taking the time and sorry it was nothing more exciting than a case of bad soldering.
Caspar
Caspar
Pin 3 & 5 should be 4.5V, not 9V, you should check even if amp seems to operate.