Strymon Iridium vs. Walrus Audio ACS1

Apr 05 2021
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  • strymon iridium
  • walrus audio acs1
strymon iridium
smallsound bigsound mini
walrus audio acs1
smallsound bigsound mini

The Strymon Iridium and the Walrus Audio ACS1 are the top contenders when it comes to compact amp and cab simulators for your pedalboard. In this demo, we'll not only compare all amp models, but also how they stack with overdrive and fuzz pedals.

Disclaimer: Walrus sent me the ACS1 for demo purposes. The Iridium I bought with my own money. While I tried to make both pedals sound as good as I can, I'm human and my opinions might be biased.

To me, these are the ultimate solutions for home recording. While you could definitely find cheaper alternatives, or alternatives with more features like the HX Stomp*, these sound good out of the box, are easy to use and require minimal menu diving.

In this shootout, I chose the best sounding settings to my ears for each amp model. I do know that the ACS1 Marshall-type amp (the London) is supposed to be a Bluesbreaker, while the Iridium's Punch is based on a Plexi. The Punch has way more gain than the London. In general, the Iridium amps all have considerably more gain on tap. Strymon tends to use a JFET analog frontend to create overdriven sounds. The ACS1 amps have much more subtle "sparkle".

There is one caveat that is true for both pedals: While both can take drives and sound good, they sound the best with their gain/drive set to pretty clean. My go-to reference setting for the Iridium (which you'll basically hear in all of my demos) is the Vox-style setting above, but with the drive set even cleaner to 10 o'clock.

There is also one issue I found with the ACS1: If you hit it with a brutal boost, something like the 40dB from the Jive, there is digital clipping happening, which doesn't sound good at all. The Iridium has way more headroom and handles this much boost more gracefully. I've heard rumours that Walrus might provide a firmware update for this.

The overdrive and fuzz used in the demo above are the Smallsound/Bigsound Mini Overdrive and the Animalizzer by T.X Pedals.



You will have to decide what you need in an amp/cab sim. Both have some pros and cons.

  • Size: The size argument I find negligible. Who cares about a tiny bit of space on their board?
  • Input/output: The ACS1 has 5 pole MIDI in and out, while the Iridium has a TRS input for MIDI or expression pedal. The ACS1 has separate ins and outs for stereo. For the Iridium, you need a TRS Y-splitter cable. I use this one*. Both have a headphone out. The Iridium's headphone out offers more volume and I think it does sound better.
  • Presets: The ACS1 has 3 presets available via pressing the two stompswitches. The Iridium only offers 1 preset. With MIDI, the ACS1 offers 128 presets and the Iridium 300. For dummies like me, the 3 presets on the ACS1 win. I wouldn't know what to do with more than that.
  • User interface: Both are very intuitive. Both have easy to understand interfaces for just finding a setting you like. For more advanced twiddling, both require you to look up the secret combinations in the manual. The Iridium has a few more options like disabling amp or cab sim and choosing room sizes.
  • Stereo: The main selling point for the ACS1 here is the ability to easily dial in two different amps for the left and right channel. This is very nice for recording or getting a fuller sound in a gigging scenario. With Strymon's Impulse Manager software, you can choose different cabs for the left and right channel, and adjust it with a 3-band EQ. But it's definitely not as easy as simply turning some knobs. If you are a stereo or wet/dry fanatic, I'd recommend the ACS1.
  • Boost: The ACS1 has it. The Iridium has not 🤷‍♂️


I guess this is the most important thing for most of us. It all depends on what sounds you're used to hearing and what you like.

  • Cabinets: I think the Impulse Responses that come with the Iridium are just a bit better than the stock ones from the ACS1. I configured my Iridium so that most cabs are OwnHammer IRs. These just sound fantastic. Overall, the ACS1 cabs sound a bit more boxy to me. Of course you can load your own IRs onto the ACS1.
  • Cleans: Both sound excellent. I think the ACS1 has a slight edge here. If a session just required a nice, sparkly clean with a bit of breakup, I'd go with the ACS1. I also really like the character of the London amp. It just "feels" really good under the fingers.
  • Amp Gain: If you want driven or gainy sounds straight from the amp sim, Strymon clearly wins for me. I must admit though, personally I never really use the Iridium for that. I prefer separate pedals for that, which brings me to ...
  • How do they take overdrives and fuzzes? I think both handle them well. Besides the headroom issue of the ACS1, you can find a setting on both amp sims that will work with your setup. The ACS1 sounds a bit more nasally and boxy to me. I need a bit more fiddling to get it to play nicely with my overdrives and fuzzes. It's easier with the Iridium. But that might also be because I'm so used to the Iridium sound by now.
  • Room reverb: Both have a room reverb. The Iridium has 3 different sizes, the ACS1 has only one. On the larger room settings, I'd prefer the Iridium. But for what I would use these pedals, just a tiny bit of room reverb is enough to bring some life into the sound. And for that, I can't really hear a difference.

Bottom Line

I do prefer my Iridium and will stick to that for now to record demos at home. It might just be the fact that I'm so used to it. I have that one setting which I love. I saved that as the fav setting and use it for everything. The ACS1 sounds great. It's just made for a different guitar player. I would recommend that for anyone doing ambient stereo stuff or someone that plays in a cover band and needs presets available more easily.

Signal Chain

K'mo Memphis (T-style bridge pickup) straight into the pedals, recorded with a Focusrite Scarlett 2i2 into Garageband with no post-processing.

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