Help me with my Weener

[eldanko]

Ok, I'm trying to model this thing based on the changes that JakeFuzz made to his Waffle Wah (mentioned in this thread: http://www.madbeanpedals.com/forum/index.php?topic=3685.0) and I'm getting the "volume swell problem" where I lose signal where there should be bass frequencies...

Changes I've made to the circuit:
Omitted FREQ pot
Omitted C6
Changed C5 from 3n5 to 10n (didn't have a 15n lying around that moment)
Using 2n2925 trannies in Q1 and Q2
Using the stock crybaby sweep pot - it's measuring at 104k

[BraindeadAudio]

Nice use of carbon comps! I love how they look.

[JakeFuzz]

Hey Dane. Everything looks good to me. The one thing I would check first is the orientation of those transistors. Those 2N2925's have a very strange pinout, I remember I had to twist mine all kinds of weird ways before I could get them in (I think they are ECB) and adding the BC549's backwards pinout (CBE) I definitely put mine in wrong the first few times. I am not too sure that would be causing the volume swell issues though. I would say try and socket C5 and bump it up slowly and see if that changes anything.

[eldanko]

Hmm - yeah, I know what you mean about the transistors.  I'm 95% sure I've got them oriented correctly at the moment, as from 50% of the sweep on up I'm getting good sound/volume out of the wah.  I swapped in a pair of 2N3565s at one point, but had the swell problem with them as well.

I will try the socket in a few minute... I did try adding some different caps in parallel to C5 earlier (like the rotary is supposed to do) and they definitely added some throatiness to the sound, but none of them were able to eliminate the volume dropout.  I think I tried a 47n and a 100n.

Hmm.

[JakeFuzz]

Hmm indeed, sounds strange. Maybe socket the ||C2 slot and put in another cap to try and bump it up to about 10uF and see if that helps at all. I know if that spot is too low the volume dropout is more pronounced.

[eldanko]

Hmm... still nada.  This is perplexing.

[eldanko]

Should the peak control be doing anything?  It doesn't appear to change anything - is it tied to the FREQ?

[JakeFuzz]

Hmm, strange. I can take some voltages for you later tonight when I get home.

The peak controls the width of the bandpass. Lower values should be wider and higher should be sharper. To be honest mine doesn't do much either, if it does it is very subtle.

[eldanko]

I. Am. A. Moron.

Had lugs on the pot switched... forgot to double-check the config on that thing since it's not a standard-looking pot....

So... as I was backing off the wah, it was just sending the whole signal to ground.

Got it working.  This thing is frickin' cool.  Probably going to increase the value of C5 now, as the 10n in that's in there now isn't quite giving me the low end I'd like.  I'm also getting a little distortion out of it on harder pick attacks - increasing R4 would do the trick, right?

[JakeFuzz]

Sweet glad you got it working! yeah raising R4 and even R2 you should be able to dial out the distortion. I use it mostly with dirt so I just left the grit in.

[timbo_93631]

I'm glad you guys got it figured out!  The pinout on 2N2925's is ECB, I thought I included a little drawing of the pinout.  Looks really good Dane!  There are alot of nice looking weeners around here lately!   

[eldanko]

You absolutely did, sir.  Once I compared it to the 2N5457 on the board, I had them correctly oriented in a jiffy.

This thing sounds killer now.  Running a 22n in C5, but am probably going to run a switch once I get one, because higher values sounded pretty cool for certain things.  Ended up increasing R4 with another carbon comp that was measuring higher than 390R, and it cleaned it up just enough!