Shootout: Three Amp Sim/IR Pedals

I recently did a personal shootout of three different amp simulator and impulse response pedals for my board. Here are my thoughts and what ended up staying on the team: the pedals were Line6 HX Stomp, Strymon Iridium, and Walrus ACS-1. I tried all 3 pedals with the same stereo impulse responses from ownhammer (DLX112 & VC30) as well as the stock cabs/IRs into vintage ns10s and JH Audio iems. Notes: all pedals have up-to-date software installed as of 5/25/22, I didn’t use reverb on any of the initial tests just amps and the same three IRs for the three different amp types, and after comparing fender vs fender vs fender and vox vs vox vs vox etc, I pitted all three pedals against each other with stereo amps and other features available to form my final thoughts.

1st pedal - Line6 HX Stomp

The HX Stomp should be in its own category because of all the extra effects, patching, and interface abilities. Those aside, I want the best amp sim for my board, so I judged it equally with the other two using only an amp and IR. Here’s how it ranked in the categories I was looking for:

Amp sound - 7
Amp feel - 5
Takes pedals - 5
Size - 5
Ease of use - 5
Tweakability - 10
Software - 10

I thought the amps sounded and felt good, almost more like a mastered track than an amp sitting in the tracking room next door. It takes overdrive/distortion/boost fairly well and they affect the input/gain of the amp sim, but there are some digital artifacts added that made me take away a couple points. The software is great for computer tweaking, and changes on the software can be instantly heard from the unit. However, because it does so much and there are so many parameters, editing on the pedal alone is a bit clunky and requires some time. Another downside is size and power requirements, but with a pedal that does so much I wouldn’t expect any less. This is a pedal I would be completely happy gigging with on a smaller board for a lot of different and great sounds.

2nd pedal - Walrus ACS-1

The second pedal I tried was the Walrus ACS-1. This unit attracted my attention because of the size, reviews, and ability to run stereo amps. Here’s how it performed in the same tests:

Amp sound - 5
Amp feel - 3
Takes pedals - 2
Size - 10
Ease of use - 8
Tweakability - 6
Software - 5

Honestly, I was shocked by how lackluster the amp sims sounded on this pedal! I want the best sound and feel, and although I could use this live and be fine, it doesn’t stack up to the other two competitors. The gain on all three amps sounds the same to me and doesn’t get dirty enough for even an edge of breakup sound. The gain knob sounds like a clipping compression circuit before the amp sound (cool sound like I can get with the Fairfield Accountant comp, but doesn’t sound like amp gain). The amp sound was the most “direct” sounding of the bunch, with little of the 3D-ness (air and compression around certain frequency ranges) I attribute to a great amp sound and feel. Each amp sounded more like an intense EQ than an amp sim. I thought boosting into the amp sound with the gain all the way up would get it into edge of breakup territory, but only the volume increased until some digital clipping made me bring the boost back to normal range. Other drives worked the same way, the drive from the pedal was represented of course, but the output volume wasn’t translated to more amp gain, only overall volume. The upside of this unit is the size, and ease of use. It was simple to dial in different amps in stereo and get a great wide clean sound running stereo effects before it. The tweakability is lacking mostly due to limited parameters and the lack of amp drive. The software was a bit clunky; uploading IRs took about 4x longer than the other units as each one had to be uploaded to the slot and then the pedal power cycled before you could hear what it sounded like. I was shocked by my reaction after seeing and reading other reviews because, although I could use this live, it wouldn’t be my first choice.

3rd pedal - Strymon Iridium

The last pedal I tried was the Strymon Iridium. It’s one I had been looking at for a while, but already having an HX Stomp on my board stopped me from pulling the trigger until this shootout. Here’s how it scored:

Amp sound - 8
Amp feel - 8
Takes pedals - 7
Size - 8
Ease of use - 10
Tweakability - 3
Software - 10

To my ears, this one is the closest of the three to a real amp mic’d up in the studio in terms of sound and feel. All 3 of it’s amp models are right up there with the best of digital amp solutions, which are better than an ok amp into an ok system, but not as good as a great amp into great mics and pres. Pedals did mostly what they would to a real amp, but I think there is a little too much gain and compression added to cleaner amp sounds. It has a small footprint like Strymon’s other small pedals, but I took off a couple points because trying to fit this efficiently on a pedalboard with all normal sized (taller) pedals is rough. The unit is very easy to use because of its limited tweakable parameters. I will give Strymon credit here because all three amps have different tone controls respective of the amps they model, but I wish instead of dual mono you also had the ability to use different amp sounds on the left and right sides. The software was top-notch, simple and user-friendly with a drag and drop IR uploader and instant sampling by clicking around the 9 different amp/IR sounds.


After trying all 3 of these pedals, I would be happy with the HX Stomp or Iridium, but not the ACS-1. The Iridium ended up on my personal pedalboard for now because of the instant inspiration to play I got from the sound, feel, and simplicity of the unit. We’ll see if it gets dethroned by another contender coming up! What are your thoughts? What is your current favorite amp sim pedal and why?


Thanks for reading,
- Dave Denton
Owner / Seafoam



I have not tryied yet, but trying to chose one, what about the UAFX pedals, dream 69 and Ruby?


I too have tried different pedals like the ones you tried but ended up going with the HX stomp because it really give me more options and because my pedalboard is stereo outputs
But I use it as my stereo amps only
But I do like the way you did the comparison

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