Aristocrat working on battery but not DC

[lumpylipton]

I've got a bizarre problem that makes no sense to me.  First off, I don't generally put the battery option on my pedals, so I wire the DC jack to the 9V and ground on the board.  Doing this, the unit was horribly buzzy, fizzy and obviously not working correctly.  I checked everything, including of course the polarity of the DC and found nothing wrong.  So, grasping at straws, I wired a 9V snap to the board instead of the DC jack, and voila, it works perfectly.  This makes no sense, why would it work with a battery but not the DC jack?  I've tried it with 2 different 9VDC adaptors, which work with my other pedals (Sunking, Big Muff), so I know the adaptor is fine.  Measuring the voltage at the 9VDC to ground on the board I get about 11.5V with the adaptor (it runs a touch higher than 9) and 9.4V with a battery.  Any ideas?  This defies logic to me.

Thanks.....
Warren

[irmcdermott]

Pedals will always have less noise when you use batteries. What power supply are you using to plug into the circuit? This might sound like a dumb question, but have you tried another outlet in your house/shop? What else is plugged in around the pedal?

[cjkbug]

is it possible that your supply is putting out the proper voltage but too much/little current?

[lumpylipton]

This isn't a slight noise, it's a crazy buzz that's far louder than the actual guitar tone, totally different than when it works fine on batteries.  It sounds like a grounding problem, but everything seems right, and as I said, it works perfectly on a battery wired to the same exact points on the PCB.  I have tried several outlets and adaptors, including at a friend's house, and it does the same thing.

Still puzzled....

[cjkbug]

where did you get the dc jack. I got some faulty ones from tayda.

[lumpylipton]

Not likely a current issue, as this is a 300mA adaptor, and I also tried a Pedal power supply that my friend had, that has tons of current available.  How much should an Aristocrat draw?  Anyone have any values I can verify?

[cjkbug]

It doesn't need much current at all. 300 ma may be too much.

[stecykmi]

current supplied by a power supply is a function of demand. so if a power supply is rated for 9v/300mA, 300mA won't always be flowing but there will always be 9v supplied.

you never need to worry about the lower limit of current, only upper limit.

The aristocrat likely uses on the order of >10mA, so you'll be fine in that sense. 95% of the time, problems like this are wiring mistakes. that said, check for connectivity (use a multimeter) between the DC jack and 9v input on the board and all other related wiring.

[lumpylipton]

OK I swapped the DC jack with a known good one (from another pedal) and no difference.

I would agree that there must be a wiring issue, however, why does it work fine on battery?

I desolder the DC jack (from the 9V and G3 points on the board, then solder a 9v battery snap to those same points, it works fine.  I swap the DC jack back, ensuring the polarity is correct, and it doesn't work.  Is it possible that the circuit is so sensitive to voltage that the slightly higher DC of the adaptor is making it not work?
I also notice somewhat of an oscillation in the distortion of the pedal with DC, underneath the crazy humming of it.
Thanks for everyone's suggestions thus far, I'm still stumped and nothing like this has occured on the 10 plus other pedals I've built over the years.....

[bigmufffuzzwizz]

I've had problems with wiring the DC jack before. I found that if I didn't wire it a certain way it wouldn't work. I didn't experience these buzz issues your getting but this might help. If you have the ground connection lug, flat facing up towards you, the outside positive lug (upper one) will be 9V and the lower (middle) positive lug should be connected to the battery. I didn't used to pay attention to orientation but now I always do it this way and never experience any problems in that field.

[madbean]

I would still question the 9v adaptors in this case. If you are using standard wiring then the board gets its power at the same place, although from two different sources....battery or PS. Wall warts are finicky things and not always suitable or useable with every effect (without noise).

Here's an experiment to see if the noise goes away. It requires a breadboard. It uses some series resistance and three caps to filter the DC supply. Keep in mind that whatever the wall wart is rated for is the minimum it will supply under load. So, if it's working properly, then it should supply 9v with a 300mA load. But, if you use a DMM to actually measure the voltage supply without connecting it to anything, it will probably read closer to 13v+.



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[lumpylipton]

Brian, you're a genius!  That filtering fixed it.  I guess it's just fussy in it's DC power.  Now, to figure out how to jam this into the box will be the trick.

Thanks a lot to everyone for their quick and helpful responses.  Hope this helps someone else out as well at some point.

I'm going to try some slightly smaller electrolytics, I used 1000's (that's what I had around), but I'll try some 100s next to reduce the footprint.

Thanks again!
Warren

[madbean]

Warren,

Glad that worked out. 100uF's might be fine. You should be able to squeeze it into a small perf or vero strip. Or, if you wanna go all the way, use 1000 and put it in a separate box. But, that's probably overkill.

[lumpylipton]

Brian, now that it's working with the filtering, the question is:  why would this have been required?  I can only assume there have been many successful builds of the Aristocrat, and obviously lots of KoTs out there that didn't require this.  I used all the original parts, including the harder to find diodes. 
What in the circuit is making it so sensitive to noise on the DC in?

Thanks again,
Warren