Penfold autowah

[Kipper4]

Anybody got any good ideas for a replacement ic3 in this circuit.

http://files.effectsdatabase.com/docs/diy/penfold_autowaa_article.pdf


Apparently a pmos input and CMOS output.
I've never heard of such a thing.
If no ic could replace it what options could one use please?


Thanks for any ideas and help
Rich
Edit oh I forgot to ask .
Is it suitable as a guitar stomp box or is it intended for another application.?
I haven't got all the way through the text yet.

[roseblood11]

http://www.ebay.de/itm/CA3130-CA3130E-Operationsverstarker-15MHz-1-fach-DIP8-/360282179284?pt=Bauteile&hash=item53e27dc6d4

[Kipper4]

Thanks mate they're silly price over in uk.

Anybody got any ides on updating this part of the circuit.

[armdnrdy]

http://www.taydaelectronics.com/ic-integrated-circuits/audio-amplifier-instrumentation-op-amp/ca3130ez-ca3130e-ca3130-ic-operating-amplifier.html

The original "T" designation is for the metal can.

[armdnrdy]

Here's a project with a couple of sound samples. Click on google translate.

http://www.pisotones.com/Maplin-AW/Maplin-AW.htm

[Mark Hammer]

Never built it, but had always been intrigued by it, ever since RG sent me a photocopy a decade back.  It is configured as a lowpass, and the samples at Pisotones are certain different sounding.  I suspect this may be because it seems to sweep really high (or at least is set that way), such that it seems to zip past the critical freqencies that would give it more of a wah character.  It's tolerable sounding because it IS lowpass.  If the output were tapped from the first OTA section, yielding a bandpass, I suspect it would sound atrocious and skip way up into mosquito noise range far too quickly.

Again, not having built it, it may simply be a matter of the sweep (mod depth) setting, and that with the right frequency and mod depth settings, it will sound every bit as nice as any state-variable can.  And as embarrassing as it is to admit it, I can see no point of intervention to play with the attack or decay times.  However, IC3 provides nice low pass filtering of the envelope signal to minimize ripple.

[armdnrdy]

Reading Pistones build info, he stated that he deleted the "depth" pot but didn't mention what he used in it's place.

470K resistor? Nothing? Who knows. 

Judging by those samples, this thing doesn't sound very impressive. Was it the modifications?

Probably a good idea to breadboard this one.

[Kipper4]

cool thanks guys. I might add this to the xmas build list then and bread it instead.
chips on order.

[Ice-9]

You could try a LM324N in the position for IC3, it can do rail to rail  so should work.

[duck_arse]

I had a go at the rectifier section around the ca3130, using an lmc6482. it works. hooked into the mxr noisegate to test, it shows a very short decay time.

[edit:] I used bat46 instead of Ge's.

[Mark Hammer]

Using Schottkys, instead of Ge, shouldn't impact very much on attack or decay time.  You'll note that there is no electro to ground to "hang onto" the rectified voltage, so that likely accounts for the fast time.  I gather Penfold's strategy was to ignore time constants altogether and simply use the lowpass filtering of the audio signal to do all the ripple rejection and smoothing for him it gives a particular character, which is interesting, but doesn't provide much flexibility.  It might be worth considering an electro to ground from the junction of D2 and RV3.  Figure 1uf for starters, and take it from there.  A modest-value averaging cap like that, plus the lowpass filtering, ought to yield a fairly ripple-free sweep.

[Kipper4]

Wow some advances already great work guys.

[Kipper4]

My 3130 chip arrived for this today its looking increasingly likely for the holiday build list. Yippee

[Kipper4]

Would someone please check my perfboard Layout for me
Thanks
Rich


https://www.dropbox.com/sh/7ma9n53c5jqdgsr/gMqd9X-iGc/Penfold%20AutoWah%20trial%201%20perfboard%20layout.pdf


The build doc is in my first post above

[Kipper4]

In the process of redrawing the layout.
Fresh post coming soon