Sunday, 13 November 2016

Frostwave Funk-a-Duck

"The Funk-A-Duck is an envelope control filter which can be used to produce a wide range of "synthetic" analog-ish sounds. The input causes a control signal to be generated, which goes up and down as the input signal loudness contour goes up and down. This in turn sweeps the filter frequency back and forth."

  • Output Level
    Sets the output level ;)
  • Envelope (Down-None-Up)
    Controls the amount & polarity of envelope modulation.
  • Input Range
    Sets the input sensitivity, has major effect on intensity of effect as well as overall loudness. Important to set this so that when bypassing, the levels are about the same.
  • Res
    Sets resonance of the filter. Can be turned up to actually resonate, either continually or when triggered by peaks of the input signal. This is one thing that makes the unit rather unique.
  • Frequency
    Sets the filter cutoff frequency. It has a very wide range, so it is possible to have it set so NOTHING at all comes through. Also, when any of the other knobs (input, res, envelope, speed) are adjusted, the resonance freq moves, and needs retweaking.
  • Speed
    Sets attack/decay of the envelope. When fully anticlockwise, the speed is FASTEST. Recommend using in this position, at least until one is familiar with the unit.
  • LP Filter / HP Filter
    Selects the type of filter: lowpass or highpass. Unit will resonate in either mode.

  • Original FSB thread and schematic are available here.
    I've used an LM13700 instead of 2 LM3080.
    Drawing it was quite complicated and it came out quite large.
    Always double check the schematic before building an unverified layout.
    (You may be able to use an LT1054 based voltage doubler but I'm not sure about noise level)
    Special thanks go to Digi2t (Dino T.) for drawing this and many other schematics we've been using on this blog.
    Here's his video:


    25 comments:

    1. Thanks Alex! Just need to wait until my stash of jacks comes in and i'll give it a go.

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    2. digi2t here; I posted the schematic for review, BUT IT IS NOT VERIFIED YET. Until I back trace and stamp it verified, building this is risky at best. Alex, please contact me at diysb first when you layout from my traces. I'll let you know if it's verified or not.

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      1. Thanks mate! I'll put the project on hold in the mean time.

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    3. Just a tip:
      From my experience building the Frostwave Resonator clone, the resonance trimmer (TR-1) might have to be increased to 100K if you can't get the resonance to set correctly. I believe this has to do with the current capacity of the LED's used. In the original Resonator, the trimmers were 20K, but I couldn't get the resonance set up within this range when I built the Tresonator. Upping the value to 100K solved this problem. The resonance control itself is usually set that the unit will self oscillate when you set the pot past 80%. Start with the Frequency pot set to around noon (at minimum, you might not be able to hear it), and crank the resonance to maximum. Beware of the volume here, don't set your amp too high, or else you'll be sorry. If it starts oscillating, turn the trimmer until it just stops. If, like the original, you want to retain the option of self-oscillation, then back the pot off to the point where you would like it to start, and slowly up the trimmer until it does. Double check with the frequency pot now to ensure that it will go into self-oscillation throughout it's range. If it does, you're all set. If however, you set the resonance pot to max, and you have gone though the entire range of the trimmer without the unit going into oscillation, then up the trimmer to 100K. Do not use super-bright LED's, or LED's that require high current demand. The lower the current requirement of the LED's, the lower the trimmer value required.

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    4. Built this but seem to have a problem of not getting enough voltage to the input of the 7915, its getting 0.584 volts only. Is D3 the wrong way round?

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      1. Hi Gavin!
        I don't think so cause it's -15V but I wouldn't swear on it.
        Do you have 18V at the input of the 7815?

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    5. Realised looking at the Schumann Lion that D3 does look to be the correct way round. Maybe i'm missing a minute solder bridge. I'll use the trusty USB microscope and let you know.

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    6. Just missed your post. I am using a 7660s voltage doubler which is giving me just under 17v at the 7815 and i'm getting 15v on output. But the 7915 is acting weird. As i just posted i will give it another check in case i have missed something.

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    7. Just checking voltages and on the lower leg of D3 i am getting ~17v but on the upper leg i'm getting 0.584v which is whats feeding the 7915. Odd.

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      1. Can't seem to find any issues. Changed out the 7915 just in case that was the problem but still the same. Weird can't figure why it would do that unless its my choice of voltage doubler?

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      2. Do the 7915 voltages change if you remove the 7815?

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      3. I'll try that tomorrow evening. Need to rest the eyes and play some tunes. Why would you think that would change things?

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      4. It would remove the load of half the circuit on the charge pump. Just a guess but if the voltages to get better then the pump may well be the problem. If it doesn't well......

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      5. OK, i see what you mean. Could i just lift the leg of the diode going to the input so i don't have to remove the 7815? They are a bugger to desolder.

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      6. Ah..I assumed sockets sorry. Yeah, lift one leg of the diode. Purely speculative mind you but this does remind me of Savvas' nightmare with the Rust Bucket

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    8. Ok, tried that ended up with millivolts coming out of D3, weird.

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      1. Do you think it might be better to use Mark's Bipolar Voltage Converter like for the Schumann Lion?

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      2. Just had a look at the scheme and only realised...this requires an AC input. Your 7660 will put out DC only so it makes sense that only the positive regulator will get anything. D3 will block any V+ just like you see will parallel protection diodes.

        Yes a voltage converter will work (current load permitting) but you'll need to remove the diodes and wire the 2 voltages directly to the regulator inputs. Luckily there's 2 free rows on the layout to do just that! Serves me right for posting when pissed! Sorry bout that.

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      3. I only have a 12v AC power supply for my Schumann PLL, however thats probably no use, or is it?

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      4. Sorry, scrap that, misread your reply. I was thinking along similar lines after looking at the Lion. Fortunately i have a voltage doubler already built so i'll do just that. Cheers Ciaran aand sorry for any confusion.

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    9. Mark's bipolar voltage converter did the trick and its now working. Finding it hard to dial in though. It may be that i need to change that trimmer for 100k as Dino suggested.

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      1. Cool Gavin. I've chenged things on the layout to make it easier. Eliminated those 2 diodes and increased the trimmer to 100K.

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      2. What do you mean by "finding it hard to dial in"? What's the symptom? Is it just resonance that's not working? How about the filtering? The reason I ask is because if I have to go back and recheck through my trace, I'll need to know.

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      3. Hey Dino! On another subject.. looking forward to see the Guyatone PS-021! I know: I will wait to draw a layout until the schematic will be verified(although I expect it would be quite large on vero).
        Thanks again for you hard work!

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      4. No worries, it's fun finding these little gems. The Guyatone is something that should be permanently embedded on ones pedalboard. I'm not tracing it straight away though, I have an idea for a "Lion-X-esqe" type circuit, which I want to breadboard first. I give you a heads up when I get to it though. I`m a bit anxious at the moment to see if the F-a-D trace/vero can get confirmed. Gavin!! What happening man!!

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