TL082 = 1458 in Nurse Quacky

[strungout]

Oy, I had a TL082, so I figured I could use it for a Nurse Quacky (auto-wah from runoffgroove.com) since it says "any dual opamp". So I got a question, the pins on the TL082 are labeled:

1-offset null
2-inverting
3-non-inverting
4-Vcc -
5-non-inverting
6-inverting
7-output 2
8-Vcc +

Instead of "offset null" on pin 1, the 1458 (original in Dr. Quack, the box nursy was modded from) says "input 1", so are the two the same thing or equivalents? Should it work if I used 2 x 741's instead?

I breadboarded the Nurse Quacky and the signal gets thru but no wah-ing. I do get an effect tho, this out of tune second sound when I turn the distortion on on my amp.

Ciao.

[Johan]

on a TL082 pin 1 is output-1
the 1458 is basicly two 741 in one capsule. the 4558 is an improvment
they are buiolt up with bipolar transistors inside. the TL0xx family is built up with J-FETs. most of the time it makes little or no difference, but the loading is different and in some applications one type or the other is prefered..it shouldnt be any problems in the Nurse Quacky...

Johan

[strungout]

Ok, thnx. I had tried with UA741's instead of the TL082 but I got the same effect, thos maybe a bit noisier. I'ma keep reading up on envelope filters

Ciao.

[Mark Hammer]

In fact, any dual op-amp will work on both the Nurse Quacky and the original Dr. Q.  It will certainly work for the filter section.  The problem is that "working" and "usable" are two different things when it comes to the envelope follower.  I tried a bunch of different dual op-amps on a stick DQ, and the only one from the assortment I tried (and there were about half a dozen different types) that yielded a pleasing sweep was the 1458.  The rest were either wayyyy over the top, or else ridiculouly sluggish.  Jack's solution that appears in the Dr Quack and Nurse Quacky resulted in an acceptable sweep with essentially any dual op-amp, including the TL082.

[Transmogrifox]

I built the Dr. Quack (basically a Nurse Quacky) on my breadboard and found it to be very finickey and hard to get the effect out of it.  Some of your problem may simply be coming from the envelope follower section.  A good way to tell if you did something wrong with the filter or the envelope follower is to remove the BJT transistor that controls the frequency response and replace it with a pot (50k will do) making a variable resistance to ground and vary the resistance as you play and see if it "wahs" from that.  If it doesn't wah, you did something wrong in the filter.  If it does, you need to tweak with the envelope follower until it works.

Almost any opamp will work as long as you know the pinout. I am using a Quad TL074 and it works fine.

...but... once you get it tuned up and working right, it's a very useful effect.  I was doing some very sweet sounding leads the other night driving my Peavey Duel 212 tube distortion with it...very tight and expressive sound.