OPAMP tests 270 ohms
A friend was modifying a cheap headphone amp, and was wondering which OPAMP would work the best.
So I created a similar circuit and measured several different OPAMPS loaded with 270 ohms as a 'typical' headphone load.
Note: Don't only look at the headline THD figure - also note the harmonic distortion even for some that measured well.
Measurement parameters:
PSU: 15 - 0 - 15
Gain: 2.2
Output: 2.7V RMS
Load: 270 ohms
The various results are pictured below (click on an image to enlarge)
| OPAMP | THD | Notes |
|---|---|---|
| LM4562NA | 0.00027% | |
| NE5532N | 0.00160% | (Philips) |
| NE5532N | 0.00141% | (Signetics) |
| NE5532N | 0.00090% | (Texas) |
| NJM2043DD | 0.00101% | |
| NJM2068DD | 0.00090% | |
| NJM4558D | 0.00604% | |
| NJM4565DD | 0.00502% | |
| NJM4580DD | 0.00082% | |
| OPA2134P | 0.02294% | |
| OPA2604AU | 0.00132% | (sample #1) |
| OPA2604AU | 0.00139% | (sample #2) |
Click the images for a larger view
