I tested with 34 ohms and 300 ohms headphones at 2 to 3 micro Watts (super loud!)
There was no obvious improvements at 34 ohms with 1 db better 3rds, worst higher harmonics (0.5db), but on the IMD 2000hz+2050hz, the third harmonics improved by 5 db. Conclusion: the LM456 don't care about output impedance as specified to drive 2K loads.
I noticed the headphone speaker can't produce a sine wave until at least 30 hertz, no issues with other forms of waves.
Udailey nice comment, the opamps have the required voltage to drive speakers but cant make enough current for the inductance and capacitance of a speaker.
There was no obvious improvements at 34 ohms with 1 db better 3rds, worst higher harmonics (0.5db), but on the IMD 2000hz+2050hz, the third harmonics improved by 5 db. Conclusion: the LM456 don't care about output impedance as specified to drive 2K loads.
I noticed the headphone speaker can't produce a sine wave until at least 30 hertz, no issues with other forms of waves.
Udailey nice comment, the opamps have the required voltage to drive speakers but cant make enough current for the inductance and capacitance of a speaker.
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Added information: I disconnected the (-) output of the differential opamps and connected one side to ground together. Surprise: sound natural instead of overwhelming.
This is explained 2 ways : 1. IMD gets better by 1.5 db. 2. Noise floor between 2 bass signals is considerably reduced by 5 to 10 db visually looking like a basket curve instead of a line.
This is explained 2 ways : 1. IMD gets better by 1.5 db. 2. Noise floor between 2 bass signals is considerably reduced by 5 to 10 db visually looking like a basket curve instead of a line.
Youre almost there...I think. The speaker has 8 ohms of resistance. This is much much harder to drive than your 300 ohm headphones. The higher the impedance the easier to drive. More impedance = less current at a given voltage. Voltage divided by resistance equals current. One volt through one ohm equals one amp. One volt through one thousand ohms equals one milliamp. Impedance is resistance to an alternating current like music.
Yes the inductance and capacitance matter but they pale in comparison to the lack of current the opamp has to drive 30ohm headphones.
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Udailey how can you explain the reduced distortion driving the headphones with only half the opamp differential outputs? -5db reduction of third harmonics
I wouldn't be able to explain anything going on in your setup as I doubt the information provided already.
Few opamps have a differential output. All opamps have a differential input. Unclear what you are doing here.gabdx said:
A few extra opamps in the signal chain? I have seen sound cards with full blown DSP chips in the path. You forget the target audience here. Many sound cards are made "to enhance your gaming experience." After all we really need the full effect when blasting the head off a zombie with a BFG. The second major target for sound cards is HT. Audiophiles are way down the list, unless you get a setup designed for recording (and playback) of live music.
I prefer to keep using my 10 year old M-Audio card. FR is within a few tenths of a DB from 6Hz to 40 KHz when looped back (line out to line in). One opamp between the converter and the output jack.
I said I connected the (-) side of the differential opamp output to ground and only used the (+) to connect the headphones. Previous to that I had (-) and (+) connected to headphones in a 'balanced' way. Do you guys know what a differential amplifier is ???
I know what a differential amp is. I know what an opamp is. I don't know what a "differential opamp" is.
I checked up on 'differential'. Seems to mean like 'different', like, you know. So I think he used 2 opamps. Seems obvious to me.
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