Can I use a 15V supply?

[soren]

First of all, hi everyone, I'm new here...

I found the forum a few days ago, and I have been reading here and there. I found a simple circuit, and decided to make my first attempt at a stompbox. (Blue Clipper, because it looked simple enough, but that is really not relevant to my question)

I have two power supplies: a 15V and a 13.8V, and I want to use those for testing, in stead of a battery. Can I do that? Do I have to change the voltage divider values? Should I build a 9V voltage regulator?

Another question, now that I have your attention: I'm not entirely sure what type of capacitors I have. Some are electrolytes, I know. Some of them might be tantalum or ceramic, or something else. How important is that? A lot of them are in little blue, square, plastic packages, what type could that be?

Thanks for your help! I hope my questions are not too stupid...
/Søren

[jrem]

your power supplies may be unregulated, so when you load them up the voltage will get pulled down.  So if that's the case a voltage divider resistor network won't give you a reliable 9vdc.  You'll want a LM7809 regulator for that.  However . . .   the data sheet states +/-22vdc for that opamp, so you could run it up to 0-44vdc . . . you may be able to get by with what you have.  You may need to adjust the bias resistors (240k/20k) to get the swing right on the opamp, though.  I would think the opamp is just driving the output and the diodes are doing the clipping, but someone else can chime in here.

little blue square plastic packages . . .  sounds like polyethylene or polypropelene capacitors, go for it.  If the values are close you won't do any damage.

[jxoco]

you want the 15v supply to be used for your testing/building, correct, so you don't go through expensive batteries, right.
And when you are finished building and testing you want the effect to actually run on a 9v battery, correct.
Then you need to first build yourself a 9v regulator.
they are simple and cheap and will get you started on the skills that you need for your effect building.
There are many schematics for a regulator.

here is a good starting piont;
http://www.geofex.com/Article_Folders/pedalbdpwr/pedalbd.htm

[jxoco]

A better starting point
http://generalguitargadgets.com/index.php?option=content&task=view&id=77&Itemid=106

under effects, power supplies, ultra clean 9v

you wouldn't need the transformer and ac plug.

you could just connect the + of your 13v supply to the + of the 1000uf capacitor and connect the - of your 13v supply to the - of the 1000uf capacitor.

[soren]

Thanks a lot for your quick replies.

I took your advice, and built a 9V supply. Turns out I had a 7809 lying around, so that was almost too easy.

I had made a small mistake on the breadboard, so I'm not sure which of the two errors where the worst. Oh well, whatever, I NOW HAVE MY FIRST DIY STOMPBOX!!! I'm so exited!

It sounds like crap, though... I mean, the mid and high range is great, but the low end is a big muddy mess. Maybe I got a capacitor value wrong, or something. I think I'll solder it anyway, it is, afterall, my first...

Thanks a lot for your help! Don't go far, I'll be back shortly with more stupid questions for my next pedal... 

[jrem]

don't solder it up if it's on a breadboard!  you don't know how long I leave breadboards wired up with input/output leads and show people . . . it's almost cooler than having a finished box!

Seriously, if your lows are muddy tweak the circuit.  Input/output caps, and feedback to the op amp circuit would be my first stab at it.