SMSL AD 18 teardown

Have a set of used/wrapped to match furniture, set of Wharfendales 9.1’s for tunes in the living room and had this unit driving them probably going on a year now. Well it finally seemingly gave up the ghost…was frequently running through BT…me and the wife mostly from Spotify. The unit started to cut in and out and then nothing…not from BT, not from Aux, not USB. Not sure what stopped running? Rebooted, checked all the connections and googled stuff to no availal. The thing typically ran pretty warm and I got it second hand off the bay of e. I figured I’d open her up as I wasn’t able to find any teardowns nor problem solvers for my issue. Also went ahead and ordered the SMSL SA 100 from Ali as a quick and easy replacement. May upgrade late (open to reccomendations for amp/dac-amp BT combos)


Phase 1

-Simple removal of showing hex bolt front and back. 2mm + 1.5 mm
-Remove screw on speaker wire terminals

  • unscrew Bluetooth antenna
  • pull off volume knob
  • unscrew retaining nut on volume (10 mm) and Bluetooth antenna (8mm)


Phase 2

Shits not coming apart…well the back panel does. Simple Aluminium body. Front and rear pannels thread into the primary “tube” which also has grooves top and bottom that hold PCB…after looking to body see two screws on top of front panel behind the glass screen. Will require heat gun to remove sticky shit on glass. Heat Al body around glass, gently peel forward glass top to bottom gently- think replacing cell phone screen.
Unscrew two more hex (2mm) and almost there.

DO NOT PULL PCB or Pannels off yet!!!

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Phase 3

Don’t force out the PCB yet!!! The NFC has its antenna lightly glued to the glass piece on the top…you can remove it with your fingernail or with a thin screwdriver/narrow pry tool.

You will also need to disconnect the ribbon strip the runs to the front screen PCB. Pull up the two black tabs on either side. Then pull the white ribbon out. Take note of orientation…if you are planning to reassemble maybe mark one side - of outlet and ribbon with marker ( I totally forgot to do this - not too savy with electronics)


Phase 4 Innards

Here is where I am out of my depth…any EE folks here explain the insides to me? The heatsink in the center of the board seems odd…I guess it’s drawing heat from a chip in the center.

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Not an EE, but hobbyist.

Under the heatsink, you are going to find the MOSFETs responsible for the heavy lifting in the amplification.

As far as I can tell, the Op-Amp provides feedback to the TAS5508 (8-ch driver), the MOSFETs get their own power (higher drive voltage = higher efficency).

This here looks to be a discrete headphone amp:

If one of these ever goes dead, there are some probe points to check with a multimeter. If one of the rails (3.3V, 4.5V or 12V) is not present, try hunting, you at least know power is part of the problem.

A higher detail shot of this area could be interesting aswell:


Awesome ! Thank you! Yeah, let me rephrase that to EE knowledge…I too am hobbyist/tinkerer but better at larger physical mechanical things- bikes/electric skatboards, buildings…small circuits are a new/recent thing. Here is the higher detailed photo.


Thanks for the picture.

It is a power supply, a “beefy” 5V one with a 3.3V LDO and one chip I can’t find a convincing datasheet on.


@MazeFrame thanks for the tips, do you have any recommendations on sites to read up on how these components work by chance?

There are several sites and videos (and books).
Texas Instruments Training Resources

Digikey has some amazing videos on various electronics topics and Learning resources.

Element14 is the place that got me started and worth checking out, the people there are REALY knowledgable.