I was recently contracted to fix a one-of-a-kind HiFi DAC. As you may know, the A in A18 stands for AKM. It uses the AK4499.

The AKM factory in Japan burned for 48 hours in November 2020. No Casualties had been reported.

Since then, AKM DAC’s have been getting rare in HiFi gear. The Gustard A18 has been released just months before the fire. I recon It’s fair to say this DAC is rare! Especially at an initial price point of roughly 600USD.

The Issue

My contact told me the DAC was mostly generating noise, music was barely hearable at all. He already took it apart prior to shipping it my way. Here is Patient Zero:

Can you spot the Problem?

Let’s take a Closer Look!

They are using Ultra Low Noise Regulators from Texas Instruments.
Positive TPS7A47 Regulator on the Left.
Negative TPS7A33 Regulator on the Right.

I measured the resistance on the positive output rail, right on that burned Tantalum Capacitor, and see there, 3 Ohm Short. No wonder the DAC was outputting noise.

More often than not, It’s enough to remove the short to get a circuit back up and running. So I did and it works very well. That DAC Sounds Incredible. Way more detail than my, by comparison, bargain bin SMSL SU-8.

The Repair

I’d love to see if we can find the exact same capacitor to replace the burned one with. Here’s another close up:

Looks like a triangle Logo or “A”, followed by 226A.
Next line clearly reads: 71AH4 (Date code maybe?) 226 stands for the Capacitance Code: 22 * 10^6 pF. Or 22 μF.

Roughly measured I estimate the Case to be 1206.

Putting the capacitance and case size into Arrow’s parametric search in the Solid Tantalum Capacitor Section, yields ~200 results.

Looks like only KEMET and Kyocera AVX use Yellow Packages though! KEMET’s Yellow is a little brighter than the caps on the board! Their text is also rotated by 90°.

We are down to around 100 options. Kyocera AVX has this Capacitance and Case available in multiple Voltage Ratings and ESR.

Now, the A in 226A gets its meaning, according to the TPS Series Datasheet from Kyocera AVX. A indicates a Voltage rating of 10V. This only leaves a couple of models up for debate, as it all comes down to the ESR.

Let’s see if the Regulator’s Datasheet has any opinions on Output Capacitor ESR.

Damping of unwanted ringing can be accomplished by using a tantalum capacitor, with a few hundred milliohms of ESR, in parallel with the ceramic input capacitor.
– TPS7A47 Datasheet, Section 8.2.2.1 Capacitor Recommendations

Oh, That is on the Input, but the Output Capacitor burned. Datasheet does not mention its ESR at all!

I’ll get the Capacitor with 900mOhm ESR, as 900mOhm sound already pretty high for the Analog Supply.

So, here is the final part number: TPS A 226 K 010 ? R 0900

Quick Note:

• The K is 10% Tolerance, can be M for 20%
• The ? is Packaging, just make sure to get lead free
  • can be pure tin, gold plating, tin and lead, non RoHS …

Seems like the Engineers at Gustard made the somewhat high ESR work and validated it.

The Capacitor is worth no more than 30 cents, but broke a 600USD new and, I was told 300USD used, Highend DAC.

The DAC works again, but I totally forgot to take a picture of the newly installed capacitor, oh dammit. I hope more board scans make it up to you.