QA550 SD card reader

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multibit16

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QA550 SD card reader
« on: 23 Oct 2010, 03:42 pm »
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  :D , 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

JDUBS

Re: QA550 SD card reader
« Reply #1 on: 24 Oct 2010, 05:36 pm »
Very cool application.  Would definitely like to hear more about this and your experiences with it into a DAC vs. whatever else you have tried.

-Jim

satfrat

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Re: QA550 SD card reader
« Reply #2 on: 24 Oct 2010, 11:40 pm »
Mighty sweet pictorial review, thanks for taking the time to do so during this mod.  :notworthy: 
 
Cheers,
Robin

multibit16

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Re: QA550 SD card reader
« Reply #3 on: 27 Oct 2010, 05:51 pm »
Very cool application.  Would definitely like to hear more about this and your experiences with it into a DAC vs. whatever else you have tried.

-Jim

Thanks Jim,
Sonically as a digital source supplying an external dac the performance from the stock unit and especially the modified one is very very good.  All my dacs locked onto it without problems. I think the stock unit was a better performer than say a stock Duet . Both QA550 and Squeezebox Duet are good performers after mods

The downside of the QA550 is its not very user friendly compared to something like a Squeezebox, it won't play hi-res files and limited to 44/16 material.  I've also heard a few people had a few problems getting it to read some of their WAV files,  since installing latest firmware I've had no issues in that area so far

Regards,
Leo

multibit16

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Re: QA550 SD card reader
« Reply #4 on: 27 Oct 2010, 06:14 pm »
Mighty sweet pictorial review, thanks for taking the time to do so during this mod.  :notworthy: 
 
Cheers,
Robin

Thanks for the kind words Robin, its much appreciated !

Regards,
Leo

jonners

Re: QA550 SD card reader
« Reply #5 on: 12 Nov 2010, 01:52 pm »
Leo -

Have you tried using the I2S output yet? I found that to be a significant improvement (into my TDA1543 NOS DAC).

John