Heres the QA550 with a few details of the upgrades I've tried
Info for the QA550 here http://www.qlshifi.com/en/wzcapi/qa550.htm
The three LDO regs was upgraded to Paul Hynes shunts, space is extremely tight in the QA550 so I went for the Micro shunts instead of the Z1703v3's. I believe the Microshunts are quite a new addition to Pauls range of regulators, I don't think theres a details page on his website for them yet but the price is a little higher than the Z1703v3's (£36 plus carriage) Paul mentioned these are harder to build and some of the main components are more expensive . They can't handle as much current as the Z170's so are better suited to light loads where space is limited .
Picture of the microshunts next to Z170 shunt reg and normal T0-220 sized regulator , it gives an idea how compact the Micro shunts are. Mr Hynes must have very steady hands making these
, you can see a lot of time goes into making these tiny discrete regulators, you have to see one in the flesh to appreciate how compact they are
Picture of installed shunts, all three are 3v3 types
The pair in the middle of the pcb was quite fiddly to fit, the legs had to be formed and soldered onto the pads so the regs body allow plug in of the crystal display, obviously an extension lead for the display can be made using a ribbon cable if you decide to re-house the QA550 and wanted to move the display to the front of the new case.
The regs run quite warm which is normal for a shunt reg, giving the regs as much free space as possible would be best if possible. Also for the main external psu, don't go much higher than the recommended 9v, if you go too high the smd 5v reg in the QA550 runs hot . I use something based around the diy PR3 module
When cold I found the sound of the modded unit was a little harsh so I left it on a few days to bed in (no listening during run in) , after this the sound now had improved focus and more extension in the lows to high's. The harshness was gone. The stock unit was a very good performer but imo the modded unit was a better all rounder .
A word of advice, Its important to let things run in before proper listening tests should be made . I'll add any updates as soon as available