Hi Guys,
Not sure if I am putting this in the correct section so apologies if not.
The sound from my PC is pretty dire (amp before so never a problem), just built up a amp based on the LM380N with a 15V 500mA regulated supply. All is working fine as I expect it would, It is basically the sound monitor from a matamp supernova.
Problem is it really starts clipping from 80% onwards, if I reduce the line input it is still the same. Any ideas or tips of things to check?
Wondering if the impedance of my headphones could be too high. Sensitivity 100dB/mW and 40 Ohm @ 1khz.
Not sure if I am putting this in the correct section so apologies if not.
The sound from my PC is pretty dire (amp before so never a problem), just built up a amp based on the LM380N with a 15V 500mA regulated supply. All is working fine as I expect it would, It is basically the sound monitor from a matamp supernova.
Problem is it really starts clipping from 80% onwards, if I reduce the line input it is still the same. Any ideas or tips of things to check?
Wondering if the impedance of my headphones could be too high. Sensitivity 100dB/mW and 40 Ohm @ 1khz.
Don't have the schematic at home or the software to draw one, would a picture suffice lol?
Can you post a link to a schematic, if you got it from somewhere?
Are there DC blocking capacitors at the inputs?
Unfortunately not this has been copied from a proven working designed product and no designs are available online etc. Basically it uses 2xLM380N's yep got some 10uF caps on the inputs.
All at work, have just got rid of all my personal test equipment due to space after a recent move.
Ok, then run a variable amplitude 1kHz triangle wave into it. See where it clips, on both polarities.
No need for a load. Is it close to symmetric? If the amp running on a single supply, is it still biased
to half the supply voltage at the outputs?
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Are you wanting me to inject something like 1khz and follow the input to the output and see where it starts clipping?
It is certainly clipping on the output, I can control the input from min to max (connected to PC) even on 5% volume from the PC it is still clipping. I could try changing resistor values on +Ve
It is certainly clipping on the output, I can control the input from min to max (connected to PC) even on 5% volume from the PC it is still clipping. I could try changing resistor values on +Ve
It does sound like there is not a DC biasing of the circuit to half the supply.
Without that, it would be like a half wave rectifier.
https://www.ieee.li/pdf/essay/single_supply_op_amp_design.pdf
http://www.ti.com/lit/an/sloa030a/sloa030a.pdf
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The clipping doesn't start until around 80% of the output volume, it doesn't matter what the input is, it is still the same.
Not really, can you sketch a schematic and post it? The guess would be that the amplifier uses only a single voltage supply,
but is not biased to half that voltage, for equal output swings in either polarity.
OK, maybe the DC biasing is off. Measure the DC output (before the output capacitor)
and see if it's close to half the 15VDC supply, or 7.5VDC from ground.
Okay will draw a schematic tomorrow everything is in boxes at the moment. Constant 7.3VDC output on both IC's even with the pot turned to 100%.
Anything else worth checking at the moment, I am only with a DMM until I get to work. I have a feeling my headphones are causing the problem with impedance, just connected some Senheiser headphones and all attenuation just went out of the window and got basically minimum output.
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