Using a 12V AC Power Supply when 9V is required? (Arion SAD-1 & Digitech PDS...)

[scott_v]

I've read that its ok or even prefered to use an AC power supply that is rated higher than the required 9V for some older effects units, in this case i'm refering to the Arion SAD-1 and the Digitech PDS-1002.  I've read that a 12V AC power source is Ok and preferred in these pedals (and perhaps others), is this right?  and why?

I have an older, 80's Arion SAD-1 that I haven't used in a years and pulled it out of the dust box so to speak, and when i plugged it in i noticed that it sounds "weaker" than what i remember. i recently tried it with a 9V AC supply, and I'm not sure what i used years ago... I'm not sure if using a 12V AC source will make it sound better or stronger...  Also, I have a Digitech PDS-1002 and I don't hear a difference when using a 9V, 10V or a 12V so i've stuck w/ the 9V as I'm afraid the higher voltage may cause some component damage especially on an older and rarer unit like this.


Thanks!

[tiges_ tendres]

If the output is 12V AC you will likely destroy anything that requires DC voltage.

[R.G.]

I've read that its ok or even prefered to use an AC power supply that is rated higher than the required 9V for some older effects units, in this case i'm refering to the Arion SAD-1 and the Digitech PDS-1002.  I've read that a 12V AC power source is Ok and preferred in these pedals (and perhaps others), is this right?  and why?

Lies, damned lies, and the internet...

I have this quirk that I always want to have the people who wrote the stuff that people refer to when they say "I've read that..." answer the question. 

There are some very knowledgeable people on the internet. There are some normal people, and there are also some d****d fools. Fortunately you've placed yourself out of the third category by asking.

The answer is - who knows? Maybe. Could be. It depends on the units involved, and where there were multiple independent designs, any answer might be true for some or even all of them. These speculations seem to be associated with less-technically enabled folks with a bad case of BUMS (Blind Urge to Mod Syndrome). 

If and only if the original power supply was 9V*AC*, then the unit in question had to convert that to DC and probably regulate it to DC to operate. It is possible that the regulator was marginally designed and would work better if it had another 3-5V of DC to regulate from, and that's what you'd get if you gave it more AC. It's also possible that the extra voltage would pop a marginally specified cap, or overheat a marginally specified/designed regulator. Or that the design is not a regulator at all, just a filter, and that it would have better/worse effects on the circuit. Or that there would be no detectable change at all. It kind of all depends on what's inside the particular box you're talking about. It is even possible, if everything happens to line up right that there could be an increase in headroom if the circuit happens to be one that has biasing that follows power supply changes and needs more headroom. Could be, I guess.

If the box originally wanted 9V*DC* and you feed it AC, it will kill the unit dead, regardless of the polarity protection inside. The only commercial effects I know of that this is not true for is the V2 series from Visual Sound, because I included a protection circuit specifically to avoid this problem.

But there is literally no way to make any kind of blanket statement that putting 12Vac into a circuit designed for 9Vac is better without knowing what is inside and what "better" means in this context.

[scott_v]

Well in the case of the Digitech PDS-1002 it states on the bottom cover that an adapter of 9V to 12V is acceptable, I always wondered why that would be the case... Its the only effects unit of the 25 or so that i have that i've seen have this varying input power supply requirement.  R.G., Thanks for giving me some insight with you response.

[petemoore]

  Here's some more interesting interesting fodderbunk for the DDS:
  [Don't try any of this at home]
  Don't see any problems. I know you can open it up and adjust the trim pots to get upwards to 8 seconds of delay, but I never tried this, heard it on LoopersDelight.
  ..."I know blah blah blah...but I never tried it...heard about it somewhere...lol''
  Another person said it's analog, and mentioned seeing SAD chips in it, seems a~ bit more reliable info.
  Another person referred to DC input...
  And I guess the PDS makes it's own DC...interesting.
  The manual recommends the Digitech 9v adapter   AC adapter:
  http://www.loopers-delight.com/tools/digitechPDS/pds8000man-4.JPG
 

[R.G.]

Well in the case of the Digitech PDS-1002 it states on the bottom cover that an adapter of 9V to 12V is acceptable, I always wondered why that would be the case... Its the only effects unit of the 25 or so that i have that i've seen have this varying input power supply requirement.  R.G., Thanks for giving me some insight with you response.

That makes perfect sense then. The unit may well be designed to accept 9-12 inputs. It's important to find out whether its *DC* or *AC*, though. I don't know any commercial pedals that have taken the route of making their input function well with either. The best ones are just immune to damage from the wrong one.

[Cliff Schecht]

Well in the case of the Digitech PDS-1002 it states on the bottom cover that an adapter of 9V to 12V is acceptable, I always wondered why that would be the case... Its the only effects unit of the 25 or so that i have that i've seen have this varying input power supply requirement.  R.G., Thanks for giving me some insight with you response.

That makes perfect sense then. The unit may well be designed to accept 9-12 inputs. It's important to find out whether its *DC* or *AC*, though. I don't know any commercial pedals that have taken the route of making their input function well with either. The best ones are just immune to damage from the wrong one.

I'm pretty sure the Digitech pedals all run off of either 5 V or 3.3 V internally anyways.

[scott_v]

Sorry to make this confusing for anyone including myself because i was going by memory with my previous posts. now looking at my unit the bottom of the Digitech PDS 1002 specifically states that "For AC operation use a 10V DC negative ground power supply" and I have the manual that states it can accept 9V - 12V, and it accepts one 9V battery which obviously i don't use because like alot of delays they suck the life out of batteries.

As mentioned above i beg to differ on NOT adjusting the trimpots, as long as you are very comfortable about doing this and take note of where the position is before adjusting them and listening very closely for sound degradation you can satisfactorily increase delay time (slightly) and increase repeats.  However i disagree on increasing the delay from 2 sec. to 8 sec. that is way too much for it to sound anything acceptable.  I tweaked my unit and gained almost a second (going from 2 seconds to perhaps 2.8 or 3 seconds) before the delay sound was degrading in ultra lo-fi territory, not really worth the effort.  however what i liked the most is adjusting the trimpot that allowed the repeats to start the "self oscillation" just prior to the point of it getting out of hand, so it is very controllable and slowly builds in volume (stock these units are not setup to self oscillate).  Though the best way to adjust trimpots is by using a meter, something i don't have.  If you not careful with taking note of what you are doing you can easily make the unit silent and useless or noisy and nonfunctionable.

btw, i did try using a 12V adapter on my Arion SAD-1 and it sounds slightly more "lively" or having more "headroom" and also seems to have less noticable high end sqweelly hiss on the delay repeats that these units inherently have when using a 9V battery or adapter. i'm not too worried about zapping it as i prefer to use my DMM and was just doing a sound comparison.