Hopefully this party isnt over

So, to make a long story short, I finally built my WTPA! (Long story I know...) But sadly it is in no working order. After the big moment of plugging it in, my pink power LED turned on for a second, turned off, and that was it. I unplugged my power supply and felt the regulator which was very hot. I plugged the power supply back in, and nothing at all happened, not even a flash from my beloved pink LED. I am going through all my connections and they all seem ok so I am thinking my issue may be with the power jack itself and how I wired it. I used a 9V guitar pedal power supply (center negative, with the jack wired appropriately to the board) but realize now that it outputs 1700mA. Its one of those daisy chaining power supplies.

Did I just kill the party???

In general how durable is the WTPA against knuckle heads like me pummeling the circuit with too many amps/backwards wiring/etc/etc.

Anyone have not-turning-on issues before and successfully debug them?



  • edited October 2011
    the wtpa has some reverse polarity protection (the 1N400X diode)
    the 1700mA generally don't matter, it's just how much current the supply can provide at max.
    do you have a multimeter? (with resistance) maybe there's a short somewhere that knocked something out...
  • Good to know. I'll go thru with with a fine tooth comb today.
  • Found some simple mistakes and now it works! Joy! Noise aint to bad but I think I messed something up with the clock. When I turn either coarse or fine knob it affects the sample but I also hear a very prominent tone. Here is a link to some images:


    Here is a video of the WTPA recording silence.


    Definitely noisy. Is that more than I should expect? I still use a Tascam cassette tape 4 track so I dont have the highest standards of audio fidelity. But this video also shows the coarse/fine oscillator/clock issue. I grounded all the pots with some aluminum tape but realized there two separate grounding busses for the pots. I currently have them all on the same one. Does make a difference?
  • edited October 2011
    Hey, sorry to be slow about getting to this.
    So, there are a few different noise problems in your device.
    The first one in your video is processor/digital noise, most of which comes from inside the AVR. I fixed this in WTPA2, but there isn't a whole lot to do about it in WTPA1.
    The second is clock feedthrough. The routing of the clock and audio lines is a big noise source here -- the biggest. Don't route your clock lines anywhere near your audio lines, return the grounds from clock and audio separately, and use shielded cable if you have it. The 500k pots are especially susceptible to noise. If you feel handy with math, and want extra credit you can change the component values to lower the impedance of the audio section's pots.
    The last (the loud 60 cycle hum) has to do with the input being disconnected, I think. Ground your input or connect it to a mixer or the like, and I bet that will go away. It may help with your other noise woes a bit too.

    Oh, also -- pretty job on the enclosure! It looks great.

    Hope this helps,
  • edited October 2011

    and I like your suitcase:
    please step out of line sir and keep your hands where we can see them.

    so now you need to link the rainbow to react to the audio from the wtpa?
  • Anyway I dropped in with this Todd, is it of any interest?
  • Thanks Todd!! Im making an order today to get supplies and shielded cable, and am building my AVR to upgrade to V3. I am thinking by mid November my WTPA will be in full effect.

    @Sealion, Thanks! We luckily havent had to travel very far with that thing. If your NYC based were showing it this weekend in Bushwick.
  • @Reid -- Awesome. Let me know how it goes. And I'm in Bushwick, FWIW.
    @Sealion -- Thanks for the link. Sometimes regulating a VREF is important, but usually I end up using a proper voltage reference (LM4040 etc) when it is, or an analog circuit. You can use an MCU to switch references, but using it to make a really clean and/or precise reference is probably not something I would do unless there was a really good reason for it.

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