Comparison of several op amp combinations for CD analog output

Today I finally fixed my CD player. It's an old machine. I remember it was bought in 1996. It's a CDM12.1 that I worked hard to repair. So I took out some single op amps that I had in reserve before, and used the newly made "Dragon Edition" DAC for more than three hours to make a rough comparison. Because the equipment is not high-grade and the resolution is limited, and it may be that I spent a long time and concentrated, so that I almost lost my sense later, and I don't know if my memory and judgment are very accurate. To be honest, this difference is really subtle. For example, if the expressiveness of a certain effect is divided into 100 points, then a difference of 6 or 7 points is considered a very big difference. Therefore, if you don't use the same piece of music (a short section of no more than 20 seconds in a piece of music) to compare repeatedly, it is difficult to feel the difference. But since I have done it, I still write it down for reference only, even if it is spam! I will verify it later when I am interested and have the conditions:-)
The op amps involved in the comparison are: OPA627AP, LT1115CN8, PMI's OP37GP, LM318N, RCA's CA3140, AD's OP27G. Since there are only 4 OPA627 and LM318, and the rest have only 3 at most, the I/V conversion part can only use these two, and the buffer amplification and LFP parts are replaced by the above ones. Since it was a temporary impulse, I didn't deliberately choose the tracks. I just grabbed a "foreign folk song" and Bandred's "Dream Garden" (of course, both are D versions), and selected "Pigeon" and "Adagio in Minor" respectively, and used different combinations to compare the effects. The following uses the sound field, resolution, overtones, low frequency, human voice, and positioning as the content of the comparison.
The first one: OPA627 + LT1115. This is the most expensive combination here. Haha, I have been using this combination, so I almost don't feel it when I hear it:), but since it is a comparison, let's talk about it: the sound field is the widest, with a good sense of layering. The sound image is between the two speakers, neither protruding forward nor shrinking backward; the positioning is clear; the resolution is the highest, the details are clear and the sound is transparent; the bass is good, the diffusion is soft and soft, and there is a diffuse effect; the human voice is very magnetic and rich in overtones.
The second type: 6 LM318. As soon as I got on the machine, I suddenly felt a refreshing feeling. I felt that the impact of the bass was greatly improved. This may be due to the 318's conversion rate of up to 70V/uS, but it is a little stiff. The high-frequency overtones are rich, the sound image is somewhat protruding forward, and the human voice is more prominent. It's just that the sound field is a little narrowed, and the sense of layering is slightly lacking, but it is very subtle and almost difficult to distinguish. Maybe it's an illusion; the sound image positioning is still clear, and the resolution is still very high. Rich overtones and transparent sound.
The third type: LM318 + OP37. The impact of the bass is weakened, and the diffuse feeling is slightly stronger; the sound field is slightly narrow, the layering is average, and the sound image is between the two speakers, neither protruding forward nor shrinking backward; the high, medium and low frequencies are relatively balanced, and the overall feeling is quite satisfactory.
The fourth type: LM318 + OPA627. The sound field is basically the same as the first type, the impact is better but it feels a little hard, and the high-frequency overtones are rich; the sound image and human voice are also a little protruding forward, but the layering is better, and the voice line is clearer; the positioning is clear, the resolution is no different from the previous one, and the depth is still excellent.
The fifth type: LM318 + CA3140. The biggest feature of this combination is that the high-frequency overtones are the richest, there is a relatively bright sense of brilliance, and even a sense of burrs, but in general, it still feels very delicate; the bass is similar to the fourth type; the depth of the sound field is slightly worse, the thickness of the human voice is a little insufficient, and it feels a bit floating in front of the speaker; the sound image is clearly positioned.
The sixth type: LM318 + LT1115. This is a very distinctive combination. The bass sound is very powerful, but the spread is very soft. The thickness of the sound is also good, with a sense of convex and concave; the rest is basically the same as the fourth, but it seems to be slightly less delicate.
The seventh: LM318 + OP27. This is also a more distinctive combination. The sound field is the narrowest; the treble is somewhat compressed, the thickness of the sound becomes thinner, the high, medium and low frequencies seem to be in the shape of a pyramid, the resolution is slightly lower, and the diffuse feeling of the bass is more obvious; what is particularly interesting is that the height of the sound image is about 15-20 cm lower than that of other combinations.
The eighth: OPA627 + OP37. The sound becomes a little lighter, but the layering and positioning are still accurate, the bass is softer, and the rest is similar to the third.
The ninth: OPA627 + OP27. Similar to the seventh, the height of the sound field is reduced, the high frequency is somewhat compressed, and the resolution is reduced, but the thickness and depth of the sound seem to be better than the seventh.
The tenth: OPA627 + LM318. There is basically no difference compared to the fourth, at least I can't hear it.
Eleventh: OPA627 + CA3140. Similar to the fifth, the overtones are still very rich, but the high frequency is smoother and more delicate; the thickness of the sound is also thicker than the fifth, the position of the sound image is shrunk, and there is basically no floating feeling.

From the audition, we can roughly summarize the sound characteristics of the above op amp models. My favorite combination is the sixth one, which has been used on DAC. Because this combination is basically not inferior to other combinations in performance, but the cost performance is much higher.