PSA and ACA power... and daisychaining power

Post Reply
User avatar
laurie
Posts: 1634
Joined: Fri Aug 17, 2018 2:07 am
Location: Canada
SBZ: Multi Platinum
Bossarea: Multi Platinum

PSA and ACA power... and daisychaining power

Post by laurie » Fri Aug 24, 2018 12:31 am

Power-supply overview:

PSA power supplies give out 9.6VDC regulated, which means the output voltage is "clamped" at 9.6VDC and does not vary. It remains at 9.6VDC or some very close voltage under all load conditions. Regulated supplies like the Boss PSA, the one-spot, and a regulated 9VDC output from something like a voodoo labs supply are a good choice to use for PSA power, however, there have been reports of added digital noise from cheaper switched-mode supplies. When the term PSA is used in the pedal power scenarios below it means a power supply with an output between 9VDC and 9.6VDC, regulated (does not vary under load). If you are in doubt, measure the output of the power supply with no load and if it is over about 9.8VDC it is not regulated and can not be considered to be "PSA power".

ACA power supplies give out 12VDC unregulated, which means the voltage can vary from perhaps 15VDC unloaded to 10V fully loaded. This is described as nominally 12VDC. While ACA pedals are not specifically designed to operate from a regulated supply, a regulated 12DC supply (remains at 12VDC or some very close voltage under all load conditions) can be considered to be ACA power.

Power supplies marked "9VDC" without also saying "regulated" must be treated with suspicion. ALWAYS measure the output voltage - often these are unregulated and will give a similar voltage to ACA power supplies. There has been some success using unregulated power supplies with a "9VDC" nameplate to power ACA pedals. Never use a power supply like this with a PSA pedal under any circumstances - it will kill it. This is the biggest destroyer of "D6" in old DD-3 pedals.

When the term ACA is used in the pedal power scenarios below it means a power supply that is nominally 12VDC, like an actual ACA supply or a 9VDC nameplate supply that has been measured to confirm the output is similar to an ACA supply.

Power supplies marked "12VDC" without also saying "regulated" must be treated with suspicion. ALWAYS measure the output voltage - often these are unregulated and will give up to 20VDC unloaded - this is too much even for an ACA pedal. Never use a power supply like this with with a Boss pedal under any circumstances - it will kill PSA pedals and may kill ACA pedals.

A note on "AC" power supplies. If the power supply is marked "AC" or has a wavy line next to the output voltage rating on the name-plate DO NOT USE IT ON A BOSS COMPACT PEDAL.

===============================

For the "PSA power" thing to work when daisy-chaining PSA and ACA pedals, there are mandatory requirements:
a) There is at least one PSA pedal in the chain.
b) The power is daisy-chained - you must power all the pedals from the one PSA power supply with a power daisy-chain cable.
c) The pedals must have audio patch leads patching them all together.

The ACA power circuitry in the ACA pedals is defeated by using the audio ground connection as the ground for power in the ACA pedals. The ground/return current for the ACA pedals runs down the audio patch leads to the PSA pedal(s).

IMPORTANT NOTE: in this context, you can substitute ANY pedal that has "normal" or "non-ACA" power circuitry for the PSA pedal. In the real world, this means almost any non-ACA pedal, Boss or non-Boss. Just ensure it is a negative ground pedal!

===============================

Various pedal power scenarios (remember the definitions of PSA power and ACA power above):

1) ACA only pedals on PSA supply, daisy chained or isolated = insufficient voltage for ACA under all circumstances. Most ACA pedals will work. PSA power will not damage an ACA pedal. However, the LED may be dim/non-existent and distortion levels may be higher.

2) ACA only pedals on ACA supply, daisy chained or isolated = appropriate voltage for ACA.

3) ACA and PSA pedals mixed on a daisy-chained ACA supply = overvoltage for both PSA and ACA pedals (the PSA pedal wants 9V and is receiving 12, and the voltage drop circuit in the ACA pedals is also defeated). Never use this arrangement under any circumstances - it will kill the PSA pedal(s) and probably damage the ACA pedals.

4) ACA and PSA pedals mixed on a daisy-chained PSA supply = appropriate voltage for ACA and PSA pedals

5) ACA and PSA pedals patched together but each pedal supplied from an isolated supply ... OK as long as you make sure PSA pedals have PSA power and ACA pedals have ACA power.

6) PSA only pedals on PSA supply, daisy chained or isolated = correct voltage for PSA

7) PSA only pedals on ACA supply, daisy chained or isolated = overvoltage for PSA. Do not do this! It is the biggest killer of Boss PSA pedals

User avatar
SteamAbacus
Posts: 9
Joined: Thu Aug 16, 2018 10:43 pm
Location: London
SBZ: Silver

Re: PSA and ACA power... and daisychaining power

Post by SteamAbacus » Sun Aug 26, 2018 2:03 pm

I've just performed my first ACA to PSA mod!

I've recently put a GigRig Isolator box on my small board (see it here viewtopic.php?f=13&t=10#p166 ) but that meant my old BF-2 was now getting an isolated 9V supply with no daisychaining. So today I did a quick mod - not the 'proper' pull the components from the board and replace with jumpers but simply by bridging between the blue and yellow cable inputs on the board (connecting to the power socket and the input socket).

I was a little anxious to attempt it as I have a gig next weekend but all seems well. :D


I'm not sure how badly affected by the low (isolated) voltage the BF-2 was. It certainly worked and the LED was reasonably bright (especially compared to my PH-1r on which the LED barely glows on an isolated 9V supply). Now that I've done the mod, the LED does glow slightly brighter. Testing at low home volume (and using distortion, which is how it's used with this gig) it may sound slightly fuller but that may just be placebo affect. I would expect it to be lower noise, though - would that be correct?

There's a good overview of the mod process (with photos) on Stinkfoot - http://stinkfoot.se/archives/1019

My experience is that, with some basic soldering skills and a steady hand (which was the hard part for me), it's not too difficult and only takes a few minutes.

Zombie
Posts: 3
Joined: Tue Aug 21, 2018 12:29 pm
SBZ: Copper

Re: PSA and ACA power... and daisychaining power

Post by Zombie » Sat May 09, 2020 1:44 pm

So should/can I run my aca boss pedals on a regulated 12vdc off my one spot pro cs12, or should I leave them on the regulated 9vdc?

User avatar
laurie
Posts: 1634
Joined: Fri Aug 17, 2018 2:07 am
Location: Canada
SBZ: Multi Platinum
Bossarea: Multi Platinum

Re: PSA and ACA power... and daisychaining power

Post by laurie » Sat May 09, 2020 2:44 pm

#5 applies. Run it off an isolated 12V regulated supply.

Zombie
Posts: 3
Joined: Tue Aug 21, 2018 12:29 pm
SBZ: Copper

Re: PSA and ACA power... and daisychaining power

Post by Zombie » Sat May 09, 2020 8:07 pm

Thank you!

User avatar
Goran
Posts: 39
Joined: Tue Oct 23, 2018 10:27 am
Location: Malmo, Sweden

Re: PSA and ACA power... and daisychaining power

Post by Goran » Sun May 10, 2020 9:01 am

Great and thanks!

Post Reply