Home > General > Update to the Musiland Power Mod

Update to the Musiland Power Mod

Minimizing Switching Regulator Residue in Linear Regulator Outputs is an application note describing the use of ferrite beads to eliminate high frequency spikes from switching supplies.

Designers frequently use linear regulators to post-regulate switching-regulator outputs. The benefits of this approach include improved stability, accuracy, and transient response, along with lower output impedance. Ideally, markedly reduced switching-regulator-generated ripple and spikes would accompany these performance gains. In practice, all linear regulators encounter some difficulty with ripple and spikes, particularly as frequency rises.

The USB power feeding the Musiland MINI in my setup comes from switching regulators inside the computer and thus prone to have spikes [I can’t measure these with my low-end scope, but lets assume they are there].

These spikes cannot be filtered/attenuated by the linear regulator because of their high frequency. The reason is the following: ripple rejection of linear regulators can be 70 db or more at low frequencies, but this capability decreases as the frequency of the disturbance increases. In the MHz range, the ripple rejection is down to 20 db or less. Spikes at this frequency can pass right through. The following diagram shows the ripple rejection as a function of frequency for the LT1963 regulator. As you can see, at the higher frequencies, the ripple rejection is just not too great.

Low frequency ripples can be filtered with input capacitors. In my mod, I used 1000 uF capacitors and that should virtually eliminate all low frequency ripples.

For the high frequency ripples, the application note recommends the use of ferrite beads. I added ferrite beads to the inputs and outputs of the regulators. The photo below shows the ferrite beads to the inputs, one to each regulator.

[If you are starting from scratch, you can pull the ferrite off its lead, leave the positive lead of the capacitor long and just insert the bead to the lead the capacitor]


It is hard to say… But looking at the dropout (unlocks) behavior of Buffalo II, I would say there is some improvement on the frequency of dropouts. In any case, this is good practice (the use of ferrite beads). Twisted Pear Audio uses them extensively at the outputs of the on-board regulators.


  • The elegance of ferrite beads as a circuit design and problem-solving component [link]
  • Vishay ferrite beads app note [link]
  1. HJ
    May 13, 2011 at 19:22

    Why not just use USB Isolator (http://www.circuitsathome.com/measurements/usb-isolator), then you can use any HQ external PS instead of USB power
    Great improvement on SQ

  2. BlogGeanDo
    May 13, 2011 at 20:24

    Hello, I have tried battery power (4 alkaline batteries = 6v) on the USB Power lines, but I couldn’t hear any differences in sound, so I’m happy with USB power. Even with the power mod, I can’t tell for sure whether the sound is better now. I can tell you it sounds “equally good”. But since this is diy audio hobby, trying to get the interface with the lowest setting for the DAC’s DPLL, it a worthy goal🙂. Plus learning the physics/engineering theory behind the mods is also a fun thing to do. I am familiar with the ADUM isolator. It is spec’ed for USB Full speed (12 MHz). I am waiting for their high speed version.

    • alex
      February 1, 2012 at 22:42

      Hello, so it’s not possible to use the ADUM for Musiland or could it support it no matter of full speed secs?

      • BlogGeanDo
        February 3, 2012 at 08:14

        If you mean ADUM for the USB, then it is too slow for USB2 speeds…

  3. hj
    May 16, 2011 at 03:03

    Well for me the improvement is real, but I’m using cheap DAC (DIR9001+PCM1793), maybe my sensitives to input signal, and yours is much better and have advanced self-correction feature

  4. BlogGeanDo
    May 16, 2011 at 17:47

    Sure. In addition, different people have different sensibilities. Some people can hear things more than others and younger people can hear higher frequencies. My hearing, although very good for my age tend to fall under the “can’t hear much difference camp”. However, in my experience, it is the accumulation of several improvements that result in some audible improvement.

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