Penfold Autowah

[rutabaga bob]

Hey Fredrik!  That layout is sort-of what got this started - a desire for a perf version.  Any ideas on taming the weird frequency control?

[Kipper4]

The controls are a bit fiddly to get it sounding ok. I had a play last night.
I'll have a play with some series resistors on the freq and resonance controls to try to make it more useable for guitar.

edit
I also tried swapping the bc109 for a 2n5088, sounds a bit better to my lame ears.

[Kipper4]

I stuck a 220k between the +9v rail and lug 3 of freq and it made more of the pot usable.
YMMV
Dont forget I'm using a B100k for freq pot.
So if you use the 50k freq  pot used in the schematic try a 100k series from +V rail.

[Kipper4]

I'm keeping the reso pot at low settings.
I know many people would as a matter of course anyway but, I soldered the unused lugs to the wiper lug too.
The changes have made it more useful now.
I need to do more testing though.

Thanks for the Tayda heads up by the way.
Some manufacturer must have had a bunch of new chips done then because when I bought mine there were not that many about. I ended up getting mine from Germany on ebay.
I might add a few to my shopping list next time I do Tayda shopping.

[rutabaga bob]

Okay, Rich...I'll make note of your tweaks.  Don't have the chips as yet.  I think Fredrik has a note on his about using a BC108 in place of a 109c. 

[Kipper4]

Ooops did I mention I'm using 250k B pot for Resonance.

[Kipper4]

I tried several R values between pin4 of lm13700 and the resonance pot.
The one that works best for me is a 1K series.

[rutabaga bob]

The rez pot is spec'd at 250k...

[ElectricDruid]

Don't sweat about the BC109. It's only a buffer for the envelope follower, so it doesn't affect the audio directly. Anything would work there is my guess - BC547, 2N3904, whatever - the common stuff. It's only a BC109 because of its era, in the same way the default op-amp used to be the 741 (and is now probably the TL072).

Also, looking at the schematic again - what the hell was he thinking with that S1 switch for "bypass"?! Whack the filter up to some high frequency and that's "as good as bypassed", right? I doubt anyone would agree this side of 1995. It was cheap is about the best that can be said about it...

Tom

[rutabaga bob]

Rich...any updates?  Got this all finalized?

[Kipper4]

No I've been a bit busy with other stuff.
It works but its the devils own job to get it to wah nicely as yet.
How's yours?

[rutabaga bob]

Built, but no cash for chips at present.