Note: I added in black plastic/glue from my 180W glue gun. This was to add support for the (SOIC-8 to DIP-8) adapter and capacitors, in order to isolate vibrations and increase the longevity of the mod.
Update July 2020:
I am now using this socket to hold onto dual Sparkos Labs SS2590, using a few adapters. This should put to rest any concerns over the mechanical stability of this mod! haha
Update June 2020:
The sAp-10 DIP-8 mod is still going very strong! I really couldn’t be any happier with how this mod turned out. Even though that soldering was far from my best work, the signal quality is superb. The added black plastic/glue, was essential in making that DIP-8 sturdy enough to allow rolling op-amps. I definitely wouldn’t want to be swapping in op-amps without that support. You’ll end up lifting the pads off the PCB, eventually.
If you do this mod on the sAp-10 and you happen to reverse the direction of the op-amp, you will blow the 250mA fuse, located near the plug. It’s a PCB mounted fuse and requires you to desolder the 4-Pin XLR PCB and the 3 pin header on the 1/4″ stereo jack. After that, you remove the copper standoffs and you can then remove the entire PCB. Replace the fuse with an equivalent fuse and put it back together.
At less than $200, the S.M.S.L. sAp-10 is a hefty contender in the field of balanced headphone amplifiers. However, it relies on one JRC 5532 surface mount (SMD) op-amp. I decided to upgrade this to a DIP-8 socket, so that I could try different op-amps. To achieve this I used a special adapter that goes from SMD pads to a DIP-8 socket. While I was in there I decided to go ahead and swap out the few SMD capacitors with full-size Panasonic FM capacitors.
Having the ability to swap the op-amp is a huge sonic advantage (to anyone with spare op-amps). Going from a JRC 5532 to a Burson Audio V6 Classic or a Sparkos Labs SS3602 made a clear difference.
The handful of remaining SMD capacitors are related to the power circuitry ICs (outside of the signal path).
I haven’t yet had the time to analyze the circuit to see what configuration the op-amp is in. It’s likely the first stage, in the headphone-level VAS (voltage amplification stage). Op-amps can serve a variety of purposes in a circuit: stages of amplification, voltage followers, buffers and filters (to name a few configurations). Swapping in full size capacitors helped bass response/headroom and seemed to improve rejection of buzz/hum. By lowering the SNR, the soundstage will naturally feel larger and more open.
Note: The flexible lead DIP-8 socket can be purchased at Burson Audio’s website.