Home > General > Adding Input Capacitors to the Amanero Board

Adding Input Capacitors to the Amanero Board

September 24, 2012 Leave a comment Go to comments

Continuing from the previous post, I decided to consider some mods to improve its performance. Looking at the schematics [schematic 1][schematic 2], the input capacitors to the regulators are implemented as per-spec at 1 uF in value. I decided to add a larger capacitors to both of the regulators. Used 100 uF Oscons mainly because I had a bunch of them handy. Furthermore, using large input capacitors for regulators seems to be a “normal” thing to do for audio applications. Look at the Buffalo II board use of 100 uF OSCON SVPs as input capacitors into its 3 LT 1763 on-board regulators:

For the Amanero board 3.3v regulator, I added the capacitor to the first capacitor in the PI network (C27). This  further improves the filtering of the USB power. C27 is a “mere” 4.7 uF. At first I thought it was 47 uF and wrongly thought that it provided good filtering… maybe good but not as good as adding a 100 uF 🙂.

For the 1.8v regulator, I paralleled the 100 uF capacitor with its input capacitor (C31).

For C27, it was convenient and easy to piggyback the 100 uF capacitor. First add some solder to the pins of the capacitor, “mount” it to C27 and reheat the pins

For C31. the capacitor is too small (for me to work with), but there is a nearby ground via where I installed the (-) lead; for the + lead, I scratched off the solder mask in the power trace into the regulator, and soldered it there.

Doesn’t seem like a good solder joint since I only scratched a tiny bit of the solder mask but I tested it by wiggling it and measuring the continuity with the power input pin of the regulator.


The results are very encouraging. No longer do I see a “lingering” low level unlocks. The number of unlocks settles to zero after about one hour. In addition, the number of unlocks decreases at a faster rate than the Musiland, at least in the two tests I’ve done on the Amanero board.

Here is a plot of the results (44.1K sample rate, DAC DPLL set to “LOWEST”):

The test shows that the Amanero board, with the additional input capacitors performs as good, if not better than the Musiland 03 board. Same disclaimer applies: I’ve done just two tests…

For those interested, this is how I count the number of unlocks: [link]


(Update 9/25/12)

Decided to another tweak before doing a “long term” measurement: adding a small value capacitor to the USB power line.

There is currently a 4.7 uF capacitor on the USB power line. I have already added a 100 uF capacitor.

Adding .022 uF film capacitor seems to be a good idea in order to provide further bypass to the input power line. The capacitor can be installed under the board across terminals 1 and 4 of the on-board USB connector (top of the diagram is the connector side)

Now we have the following add-on capacitors to the USB power line:


Hmmm… Some “disturbances” in the morning hours. The last test I did on the Musiland, was cleaner. (Usual disclaimer… small number of tests…)

I did remove the piece of putty I had put on the top of the Crystek oscillator. Perhaps the problem is compounded by the vibrations? Maybe I should work on damping and mechanical isolation.

  1. qusp
    September 24, 2012 at 10:01

    interesting, seems like it will respond quite well to further tweaking of the power supply, even though at first glance you might think it was OK. you have to watch adding large caps in parallel with ceramics on the output with LDOs, not so much here as the consumer isnt far away, but they can ring if you have long leads. thanks for doing these tests mate!

    • BlogGeanDo
      September 24, 2012 at 15:58

      Likely won’t add to the output capacitors… Probably bypass the USB power with small value capacitors…

  2. qusp
    September 24, 2012 at 10:02

    i’m interested in playing with the reference voltages

  3. Bunpei
    September 26, 2012 at 04:29

    I am really looking forward to the similar test on the use of Ian’s FIFO!

    • BlogGeanDo
      September 26, 2012 at 16:27

      I will get to it. The Amanero was so simple to hookup, I had to tried it first. In any case, the order is to test from GOOD to BEST🙂

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  5. September 14, 2016 at 15:50

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  6. September 14, 2016 at 16:04

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