A similar thread could be read here:
https://www.audiosciencereview.com/...burson-sparkos-sonic994-1612.3305/post-153240.
I did rolled out few opamps myself too, so I'm sharing from my so-called "experience" of rolling opamps.
- 1) In ASUS Essence One I swapped the default NE5532P opamps with MUSES01 in I/V stage and got an increased soundstage and a more...musical sound. I found out later that this was due to increased THD (mostly the 3rd and 5th harmonics) and probably some ringing and oscillations I haven't measured yet, so I swapped back the MUSES01 with LME49720 or NE5532P and I got the best THD+N out of it. Essence One seems to be very sensitive to opamps rolling, probably due to it's poor grounding and very thin traces; also, the joints between the PCB layers was very poor, especially on the power supply ground plane (0.1...0.2 Ohms).
- 2) Same Essence One, but now the Low-Pass Filter: swapped NE5532P with OPA2604 and got an increased soundstage and less "nasal" voices and saxophone. It was do the OPA2604 opamps oscillations, lot of ringing I saw with my scope and both opamps were overheating a lot. So, I did got back to the default NE5532P/LME49720 opamps.
- 3) Same EssenceOne, but on the Voltage-Gain opamps (the loop for the LME49600 buffers), I got a better bass with Burson V5i opamps. When I did a frequency response check I noticed a bit of thump on the low-end frequencies, so I had them swapped with the default LME49720. V5i might be OK for those willing a small bass boost, but not for me.
- 4) Matrix HPA-3B: swapped the default LME49860 opamps from the Voltage-Amplification Stage with the following: Burson SS V6/MUSES01/02/8820/8920 etc. I noticed a decrease of the background noise, even when using LME49720, despite it should be identical with LME49860 (who knows, maybe these LME49860 were fakes). In the end I left inside the OPA1652 due to the lowest DC-voltage on outputs (e.g.: about 1mV vs. the SS V6 (5...10mV), but all of the above opamps were having about the same THD, just the noise (and THD+N) was a bit higher on the LME49860, not sure why.
- 5) Same Matrix HPA-3B: swapped the default LME49860 with Burson V5i, but on the low-gain I got a strange noise coming out of my headphones. Seems that under some circumstances V5i are not so great for unity gain or even for <2X gains, but for higher gains seems to do well.
- 6) In Burson PLAY v1.6 I swapped the default JRC5532 with AD8599 in I/V and and AD8672 in LPF to decrease the noise. About the same noise decrease was achieved when using MUSES01/02 or MUSES8920/8820. Same opamps used in PLAY v2.2 did not showed any improvements, but the v2.2 had already a lower background noise than previous v1.6, probably due to increased ground plane on both sides of the PCB.
- 7) In Burson PLAYMATE Everest I swapped the default SS V6 Classic & Vivid opamps with LME49720 in I/V and JRC5532D in LPF and VAS stages. I wasn't noticing any sound changes, the THD+N was about the same with Burson opampd as with the TI & JRC opamps as well. Probably the huge ground plane and the improved PCB quality is not so sensitive to opamps like PLAY used to be in the past. However, worth mentioning that the Vivids are having a more energy on the trebles, not sure why, but I like the Classics more (same neutral sound as 5532 and 49720 opamps).
- 8) In Burson C3X I swapped the default SS V6 Vivid opamps with JRC5532D; I couldn't feel any change in audio, but the trebles are having somehow more details if Vivids are used, although the freq. response seems pretty flat to me...kinda odd. However, I will leave the JRC5532D inside due to the lowest output DC (2...4mV with 5532D vs. the 5...10mV with the V6 opamps).
- 9) I swapped the default JRC4556 buffer opamps from the Objective2 with MUSES8920, just to lower the DC-voltage from 3...3.5mV to about 1mV (kinda crazy and not recommended mod). Also, I did swapped the default JRC2608D opamp from the voltage-gain with OPA1652 opamp to further decrease the background noise (this can only be felt only for gains higher than 3X; for lower gains makes no sense to do this).
Subjectively, I noticed a different sound flavour when swapping opamps, but only in DACs/headamps that probably were not having a perfect ground plane or the PCB was somehow poorly designed (Essence One, PLAY v1.6, HPA-3B maybe). The only device where I really noticed that an expensive opamp might make sense is the Matrix HPA-3B where the difference between SS V6 Classic and the default LME49720 was very obvious with sensitive cans (I'm only referring to background noise here; the audio quality was about the same in an A/B test).
Also, the noise decrease when swapping the default LME49860 with LME49720 (or other opamps) remains unexplained to me, but difference was pretty big. Basically, doesn't matters what opamp I stick into the DIP8 socket, the background noise is still lower then LME49860. Test done with only one channel swapped, so it's quite easy to compare this way (also swapped the opamp for the other channel, background noise moved into the other ear).
Technically speaking, it's really hard to beat opamps like AD797, AD8599, OPA1612, OPA1656, so it might be safer to use one of these over the "exotic" ones, unless swapping opamps is really fun for you and you have enough money to spend on this hobby.