Echoing the experience of another user, the way this pedal compresses the signal when interfacing with overdrive and distortion is a little bizarre. I know there was a firmware update about a year ago to address this (just bought the pedal brand new and am using current firmware), but I don't think the sound is quite there just yet.
I'm stacking a JHS morning glory with all knobs set to noon into a Walrus Ages set to a moderate drive that I am running into the mono input of the ACS1. It's a pretty moderate "rock" distortion/drive sound, nothing particularly crazy. I'm also using appropriate gain staging, in other words, I don't think I am slamming the front end too much from the drive pedals. Even still, I am getting compression pumping and a squashed feel on the attack of certain notes, and it is apparent enough to be annoying.
Bypassing the IR block and running an IR plugin in my DAW (pulse) seems to help a little, if not completely. It's almost as if the compression is tied to the IR block and not the amp model? I am using the exact same IR's (Ownhammer 48k, 200 ms, mono) in both cases. It's worth mentioning that the compression "problem" is present with the included factory IR's, all third party IR's I've loaded into the pedal, and when using all amp models.
Like the other user's review I am referencing, I too have been an audio engineer and musician for over 20 years, and have an ear for the effects of compression and limiting. If there was a way to adjust the radio or turn off the compression altogether, I might have better results. Turning down the gain to below noon does seem to help a little, but does not completely get rid of the compression "breathing" and slight volume fluctuations on certain notes and dynamic passages when using overdrive and distortion.
This is my fourth Walrus pedal. Overall, the sound and functionality of the ACS1 is great. It was this or the Iridium, and I went with Walrus. Just wish the pedal played nicer with my drives...
Hey TR, We appreciate your review. Thank you for taking the time to share your thoughts. We would love to discuss your thoughts further. Someone will reach out soon! - Walrus Audio