OPA1622 Vs. OPA627 High Performance Op-amps Comparison

This op-amps comparison topic is actually boring, but at the same time, many of us still curious about what others think about it. The reason is simply because of the op-amps variation are hundreds and they are depends by the implementation.

The op-amps are considerably cheap and an interchangeable electronic components but they are not built for the same function. So in this discussion, I will focus on the modern Vs. vintage high performance op-amps in the simple non-inverting pre-amplifier gain stage.

The first candidate is the OPA1622. This op-amp is quite popular right now. It is made by Texas Instrument and it is the latest op-amps that built and designed by more modern technology.

The contender is the vintage OPA627 which is far older than the OPA1622. This OPA627 was made by Burr-brown long before the Texas Instrument acquisition. The production for this OPA627 is still continue but in the SMD version.

If I compares for both op-amps datasheet, I found that OPA1622 and OPA627 are both high performance op-amps intended for professional audio use.

The OPA1622 is dual op-amps in single die. This op-amp is built specifically for headphone amplifier application, preferable for the portable audio device which the current output is quite high enough, about 100 mV at 32 ohm load as per specification on the datasheet. It also can drive the load as low as 16 ohm without degrade the performance of this op-amp significantly.

In contrast, the OPA627AU is a single op-amp in SMD package. To make it works as a dual op-amps, I should put two pieces of OPA627 in a dedicated dual SMD to single DIP converter just like the OPA1622.

Deep down to the each op-amps specification, especially for THD, slew-rate, settling time and noise, the OPA627 is have so much better numbers than the OPA1622. Those numbers really surprised me since the OPA1622 supposedly being better.

But at the end, the specification cannot tell how the sound quality are and the real judgement is only by ears.

Is it?

In this comparison, I will using my "secret" DAC" that including the headphone amplifier. I post the detail in here.

The circuit is non-inverting amplifier gain stage with 2200 ohm feedback resistor and 1100 ohm inverting resistor to the ground. The amplifier gain is 3 times. Voltage supplied for each differential input op-amps are +10 volt and -10 volt using LM317 and LM337 linear power supply.

 OPA1622

I using this op-amps since the first time I finished built this DAC. I like the sound which is more neutral, open sound-stage, good details and musical imaging.

I was previously compares this OPA1622 with the other op-amps such as OPA2134, OPA2604, AD823, AD712, LME49720NA, and LM4562 which none of them, in this headphone amplifier application can match with the sound quality as near as this OPA1622.

OPA627AU

This OPA627AU is the most popular op-amps up to date.

In comparison with the OPA1622, I never thought that the difference will be audible enough for me to notice at the first time I swap them.

Continue to this OPA627 op-amps, I was quite shocked that the OPA627 can deliver better sound quality than OPA1622 in one specific music aspect.

It is on the mid-range.

OPA627 mid-range, especially for the vocals are a little bit more forward in the presentation but more presence and body. The difference for the OPA627 is far more realistic and more intimate. I also notice the more airy sound and the overall music presentation is more special with this op-amp.

Others than that, the OPA627 can deliver the same richness, same sound-stage and same detail as the OPA1622 does.

Again, I was shocked and I know this is not placebo effect. I initially felt that OPA1622 is the modern op-amps that probably can easily beat the OPA627, but it is not.

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