Nurse Quacky works!

[Connoisseur of Distortion]

yep, the op-amp will kick your ass.

i built it last night (4:00 am or so   ) and when it didn't work, i turned in. Today, feeling ambitious, i checked the layout against the schemo (all seemed well) and browsed the forum for info. I replaced the TL082 with a MC4558 and now there is a wah action. I still want a LM358, though.

This thing has a very interesting tone. it doesn't seem to sweep all that far, but it sweeps well enough for my purposes. My real gripe is that i have to brutalize the string for the nurse to catch on that i want it to quack. ordinary playing will be ignored! be warned! i'm hoping that the 358 might fix this.

also, the controls seem kinda strange. i am having a hard time deciding exactly what it is that the attack pot is doing. it seems that using it heavily makes the pedal work, and backing off on it makes it not work. very strange. the range pot doesn't create a huge spectrum of sounds, but it does allow some variety. The sensitivity pot is cranked, because otherwise my signal passes through unnoticed.

some mods may be in order, but this pedal seems very promising.

[Connoisseur of Distortion]

sorry to double post, but i thought i'd mention that i used Torchy's veroboard layout. it works perfectly, BUT suggests using a TL072. That's the only issue... Thanks Torchy! your layouts are fantastic!  

[H4T]

Cool, keep us posted! I just ordered all the parts for the Nurse Quacky the other day myself, going to build it as my second ever pedal. I ordered the LM358 op-amp from Small Bear too. You should get the LM358 and try it out, I'm sure it'll make all the difference.

I'd love to see how this pedal turns out for you!

[Connoisseur of Distortion]

UPDATE

i changed out the op-amp with various types i had lying around. I have found the one i like the best! It is a BA4560 salvaged from a recent-ish Fender SS amp.

It is a ton more sensitive, and the attack is hard and fast. the range is longer, and it just sounds great! i can play as i normally do (reasonably hard) instead of my morning playing (hard as is possible) with better results.

if you don't want to order a new IC, try a different one! it can make all the difference!  

[mick]

witch layout did you use?  :roll:

[Mark Hammer]

Now that you have a working version, consider some of the following things to tinker with:

a) Increasing the value of the 470k feedback resistor in the filter stage will increase the gain of the filter and the apparent resonance.  You don't want to overdo it, though.  A 330k resistor in series with a 500k pot, or a 3-way toggle that selects between low/med/high resonance are probably enough.

b) The sweep range is adjustable via the trimpot, but the amount  of sweep and zone of sweep are strongly linked.  To shift the filter range, change the value of the .005 (.0047uf, really) caps.  Larger shifts the range downward, smaller shifts it upward.  For bass, caps between .01 and .022uf work well.  AS always, I recommend use of switched series capacitors rather than parallel, so as to minimize popping.

c)  The variable attack time is useful but may offer more subtle adjustments than some want.  As well, the decaytime is fixed.  Here is a suggested alternative to produce a fast/slow choice. http://ampage.org/hammer/files/fast-slow.png

d) Should you explore the variable resonance/gain option, you will likely want some sort of output padding to produce effect/bypass volume balance.  Stick a 100k pot (log) on the output of the pedal after the 0.1uf cap.  The design needs a terminating resistor anyways to minimize popping during switching.