RSA Tiny Amps: The Shadow or The Mustang

After coming out with the RSA Shadow, people started asking question if it’s worth selling their P51 Mustangs to get the newer Shadow amp. We did a short comparison to find out.

If we look at both the Shadow and the Mustang, both amps are pretty tiny, though the Shadow is still considerably smaller than the Mustang. Perhaps the thickness of the Mustang makes it less practical if you decide to stack it with a DAP and to put it inside a jeans pocket.

Feature wise, the Shadow comes with a digital volume control, where the Mustang still utilizes old fashioned analog potentiometer. On the other hand, the Mustang comes with selectable gain, definitely a big plus if you frequently alternate between headphones and IEMs. The fact that most people uses IEMs for their portable set up means that the Shadow with its digital volume control should be much more appealing than the Mustang.

What’s next? Loudness level on the Shadow is identical to the Mustang at the low gain setting. The sound of both amps is very identical. The Shadow is slightly more neutral and it has a slightly better instrument separation, which somewhat gives an impression of a faster speed from your IEM, because instruments are less mixed together. The Mustang has a little lift in the upper treble for a more airier sound, though its mids are slightly more recessed. Notice all the “little” and “slightly” words I added to the description, because both amps really sound identical for all practical purposes.

The RSA Shadow is definitely the amp to get, if you haven’t gotten one of these tiny portable amps for your IEMs. However, I’d probably wait for the next upgrade cycle if I’m already a Mustang owner.

Special thanks to nspr6 and Dayak for making this comparison possible.

System for auditioning:
Headphones: Shure SRH-840, Westone Um3X
Source: Ipod Classic 120GB
Amplifier: Ray Samuels P-51, Ray Samuels Shadow

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  • Reply November 21, 2009


    Hi, I had a few questions. I been looking for an amp. I am debating between the P-51 mustang and the Shadow. I am going to use it with the Westone Um3x and planning on getting an AKG k701.

    So far I am leaning more towards the Shadow because of the reviews and the small size. Do you think this amp will work alright with the AKG K701s? I read that the K701s are hard headphones to drive. I dont like listening to my music very loud btw. Or would I be better off with a P-51 or something else?

    • Reply November 21, 2009


      Hi Kevin, the UM3X is very easy to drive, and both the Shadow and the P-51 Mustang will do fine driving it. However, for the AKG K701, you will need the bigger amplifiers like the SR-71a, the Sharps, or the Lisa 3. Of course, desktop amplifiers are better suited for the AKG K701.

  • Reply November 28, 2009


    Can you give a few more of your opinions on how the shadow drives full size headphones that have impendence under 40 ohms. And have you ever reviewed the etymotic er-4s I am thinking about getting those to go with my shadow. But I also like to use the shadow with the fullsize mentioned above. Thanks.

    • Reply November 28, 2009


      HI Cesar,
      What full size headphone are you thinking of driving with the Shadow? The Shadow are not designed to drive full size cans, though there can be some exceptions. The Shure SRH840 (44 ohms), for instance, is fairly easy to drive and make a good match for the Shadow. Headphones with the same impedance can still differ in amplifier requirements. A lower end Grado from the SR60 to the SR225i, would be fine for the Shadow. I never really tried these combinations, but something like the GS1000 or the PS1000, while still maintaining a 32 ohms impedance, would be out of the Shadow’s capability. Generally, the bigger the size of the housing, the harder it is to drive (given a same impedance factor).

      I also haven’t tried the Shadow with the ER4S, but I don’t think the ER4S, even with 75 ohm would be a problem with the Shadow. I’m quite familiar with it, having owned it for quite a while. Generally, the Shadow are suited for IEMs and closed headphones with small to medium size housing. Anything more than that would be a stretch for the Shadow.

  • Reply December 14, 2011

    Faisal Q

    Hey mike, I was looking at some USB Dac/Amp combos and I had Emmeline’s “The Predator” in mind, I’ve got the Sennhesiser HD598’s. Do you reckon that’s a good combination?, Or are there other 300 to 400 dollar Dac/Amps you can recommend?

    Can’t seem to find a lot of Amps with DACs built in at that price range.

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