Aphex Compellor - Awesome/easy mod with clips vs SSL/API

Hello, here is an awesome, easy mod for the Aphex Compellor. I've seen posts from a few folks on this website that have one of these laying around. Figured I would finally sign up and post this.



In case you're not familiar, the Aphex stock is an excellent tool as a transparent leveling device, but this mod really opens up the possibilities. What we're doing here is modifying the attack time on the Leveler side. But what's interesting is that up to 60/40 (level/comp) setting, the comp side also responds to the control, and both sides attack/release speed up radically. Now the unit can really shape transients and it adds a ton of apparent volume, without squashing the sound (compared to other units narrowing the peak to RMS gap). It has a great smack on drums as you can hear in the clips.


The mod itself is very easy. We're just strapping a 1m stereo pot (mounted on the faceplate near the power switch) across the large resistor that controls the leveling attack (it's 5.6m on most units, on the 320a, which this unit is, it's r123). I also added a switch on the back to interrupt the feed to that pot which returns the unit to stock. With the 1m pot it can go from too fast, to most of the way to the stock setting.

The second step of the mod is removing opamp 107, this disables the dynamic verification gate (it is 107 on the 320a, on other models the number might be different, but you can easily find it on the schematic as it's labeled). It makes the unit function much better as a studio comp/level/limit.


About the clips. The first thing you'll likely notice is the volume difference. Well, they are all peak matched. The Aphex just really excels at retaining transients while increasing the RMS. The API... it's a great waveshaper, and adds a lot of smack to drums, but it really struggles at times to catch peaks as well as the others. As a result, the track either ended up sounding noticeably quieter, or the attack needed to be set where it really became detrimental to the sound. In the clips, I opted for quieter over sounding bad. Anyway, back to the Aphex.


As mentioned, the Aphex excels at retaining transient signals while boosting the RMS. Drums and acoustic guitar in particular. On the acoustic sample, I went very heavy handed, regularly reaching 10db of compression. Despite that, the transients are still clear, while sounding way more up front, and with the body being filled out dramatically. On sources like vocals, let's say compared to an 1176, it's smoother, and does a better job of actually leveling the vocal, but doesn't quite have the same RMS boost of the 1176. The Aphex is an even, leveled signal, while the 1176 is aggressive, and the loud parts, appear even louder because of the increased RMS. Different tools for different jobs... Just speculating, but I suspect the difference in reaction to how it boosts RMS on transient sources, vs leveling less dynamic ones is due to the "dynamic recovery computer" and how it treats more, or less transient signals differently. Remember it's original intent was to level a loud song on the radio (or an excited radio DJ), or to bring up the volume on a quieter song, which very likely would have had more transients. It was designed to react differently to those two situations. Whatever happening, it's a very cool box.


So there you go, for 5 bucks in parts, you can turn it from a box that you can’t hear working, into something that competes with, if not beats some of the most popular buss compressors around. Sounds like a good deal to me. Enjoy!!!



PS, attached is a little sketch of the mod