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ACA Upgrade Information

Audible upgrades for all versions prior to V1.6

To use the new 24V PSU and also bring your ACA up to 1.6 specification:

  1. If you have a PCB labelled revision 1.0, add bias resistor R15 (increases power to 6W)
  2. If you have PCB 1.0 or 1.0b, adjust R12 from 68k to 39.2k
  3. If you have PCB 1.0, 1.0b or 1.1, simply plug in the 24V PSU (no DC jack change required) and adjust the DC value on the output to 12V

Aesthetic / mechanical upgrades

V1.6 to V1.8

Please see the list of differences between the two here at the top of the V1.8 build guide. List of all differences between V1.6 and V1.8:

  1. Rear switch is a 3 position DPDT instead of 2 position, necessitating a change in wiring
  2. Rear panel is printed with a connection diagram
  3. Chassis rails are improved using weld nuts and secured by bolts
  4. Blade terminals are included for the front power switch
  5. Longer wire
  6. LED resistors have been changed from 10k to 33.2k to reduce LED brightness

Please note that the PCB did not change whatsoever between 1.6 and 1.8, and so the PCB included in all 1.8 kits says "V1.6". That's the correct version of the PCB.

V1.5 to V1.6

If you want to build matching monoblocks, you can order a whole new complete kit and choose the "silver faceplate with no power switch hole" option (we added this option just for you!). It will perfectly match your existing chassis.

Then to upgrade your V1.5 to be the same as your pre-ordered V1.6:

From the store pre-order:

From Parts Express:

From Digikey:

Chassis modification:

  • Using a low speed battery operated drill and the above step drill bit, perform the following operations on the rear panel:
    • Enlarge the 8mm DC input cutout to 7/16" (11mm)
    • Enlarge the 6mm toggle switch cutout to 1/4" (6.4mm) (this step may not be required)
  • Make sure the panel is secure and you are going slow enough not to hurt yourself! A Panavise 350 is a great all rounder that did this trick for me nicely (you might want to look at this too for soldering).


The only difference between the Parts Kit V1.5 PCB (labelled V1.1) and the new Parts Kit V1.6 PCB (labelled V1.6), is that V1.6 has some extra mounting holes so it can be mounted to a 4U or 5U UMS heatsink. There are no changes to the design or sound.

If you also want an exactly matching V1.6 PCB for a perfect OCD zen state as well, I do understand. We'll have V1.6 PCBs available for separate purchase in July 2018 (they are not currently available for order). However, if that's the case, it might be better to finish your current ACA and enjoy it for the next 3 months, pre-order 2 more and build them in August, and then (a) give away your V1.5 to a worthy friend, or (b) use it as a center channel :)

If you have already built the ACA V1.0, 1b (or 1.1 that was given away at BAF 17 (not the one in the March 2018 ACA!)) and want to use the new chassis

Ok, so you've built an ACA before but want to use the fancy new chassis? Yes, you can do it, but there are some caveats as the PCB mounting has changed so you'll need to DIY...


From Parts Express:

From Digikey:

You will need to find some small nuts and bolts to mount the XLR jack, depending on your mounting preference (inside or out).