axis wah

clamup1 · January 13, 2011, 10:51:10 PM

anyone built this and had it work? i noticed the web site hasnt been updated in 5 years or so.

clamup1 · January 14, 2011, 10:21:50 AM

i have a few ?'s

1. the axis wah from http://fuzzcentral.ssguitar.com/axiswah/axiswahlayout.gif doesnt have a output shown, but if you look at the buffer http://fuzzcentral.ssguitar.com/mccoy/bufferlayout.gif it has a signal coming from wah 3. if i rem correctly the signal from the original cry baby came from wah 2 right. is this wrong or is it wired differently? building and output buffer http://fuzzcentral.ssguitar.com/axiswah.php says you dont have to have it but it helps when hooked up to a fuzz face. mine doesent work. im thinking the wrong wah tab is hooked up to the output signal.
2. i subbed the bc109c's with 3904's. if the above is correct then this is the prob.

any suggestions

kristopher612 · January 14, 2011, 12:32:39 PM

if you look at the schematic of the vox Clyde McCoy wah the output is coming from lug3 of the wah pot. same as the axis wah. since the opposite lug is going to ground you shouldn't get signal from it. try using the one opposite to what you're using now

clamup1 · January 14, 2011, 02:59:06 PM

you mean lug 2 right? thats what i was thinking.

kristopher612 · January 14, 2011, 06:12:34 PM

lug 2 would be the wiper, this is not the output on a wah like the axis/crybaby/vox. 3 would be the uppermost lug on the pot in the schematic. if that's the one you mean, then yes, unfortunately there's no standard numbering of the lugs on pots, which makes them harder to learn than a transistor, or IC which have names/number for pins

kristopher612 · January 14, 2011, 06:21:54 PM

hopefully having these pictures will clarify. the blue wire is the output in both diagrams, shows where output is in the scheme and how to wire the pot. that is where you need to send signal to the buffer from. if that doesn't work then you need to take voltages and make sure you have pinouts right on all of the transistors/fets. i know i recently spent way too long trying to troubleshoot a build and the problem was that i had the pinout on the fet wrong, and was getting no sound.

clamup1 · January 14, 2011, 07:04:38 PM

dang thats how i have the hot pot hooked up. so the hot pots arent numbered the same as regular pots, that sucks. i found an old post from 2006 from here that said you could sub the bc109's with 5088's. so i changed out the 3904's with those. maybe the layout is diff with the 5088's. this pedal cannot be this freakin hard.

clamup1 · January 16, 2011, 07:57:13 AM

well people liked this pedal and it worked in 2007 (though with some tweaking) ill post some pics this afternoon

clamup1 · January 20, 2011, 03:44:32 PM

sorry i had to find the cord that hooked the camera to the comp.

the wah pot ill number like a reg pot. left to right. 3 wired as output, 2 input, 1 ground. on the pc board. left to right, input, wah 2, wah 3, 9v+, ground.

hope these help

clamup1 · January 21, 2011, 08:07:10 PM

bump

kristopher612 · January 21, 2011, 08:43:27 PM

sorry, I'm a fulltime work/college guy so I'm late getting back. looking at your pics i see that you've made sure part of your board isn't grounding out on the enclosure, however your +9V wire doesn't appear to be insulated, and could be grounding out on the enclosure, which =no sound. did the circuit work outside of the enclosure? if it did then that is the type of thing i would look at. if it didn't you really need to get your voltages, check for bridges/cold solder joints, etc. if i have time tomorrow after class I'll try to get voltages from my wah which works. they may not be exactly where yours are, but if yours is working properly then they should be close. did you make the separate board for the buffer? i don't see it, and if it's in there then that may hold the answer as well. another thing is to make sure you have the proper resistor values in there, which i can't really make out from your pics. looking at the scheme this should be a really nice wah, so hopefully it's something easy to fix.

kristopher612 · January 21, 2011, 08:47:52 PM

QuoteQuote
MPSA18 (This is the one in the middle of the schematic)
C 7.69
B 1.08
E 0.69

Not too bad. I'd like to see the base and emitter be higher and the collector lower.

Quote
MPSA18
C 8.40
B 1.29
E .83
Not horribly bad. I'd like to see the emitter be higher, up at a couple of volts.

this was in another thread about a diy jh-1 build, just to give an idea. the comments on the voltages are made by RG, so i would trust that. i will still try to check min for you though to have them from a working unit.

clamup1 · January 22, 2011, 09:09:50 AM

its ok Kris. im a part time student. studying seems to about the only thing i get done lol, i havent built the buffer yet. i was waiting on parts.

i checked my trannies and i was getting 8.41 or about on the ebc of both the trannies.

i dont understand the uninsulated 9v+. ive got it hooked up like ive always dont it.

clamup1 · January 22, 2011, 10:02:33 AM

q1(closest to output wires) battery-8.89
e-8.45
b-8.39
c-8.89

q2
e-8.46
b-8.45
c-8.87

these are not neg

so ive got a prob somewhere

kristopher612 · January 22, 2011, 03:30:56 PM

yeah, with voltages that close together on all pins, i would check resistor values and for bridges around your transistors an +9V trace. give me a while to get my voltages for you, it's homework time right now...

clamup1 · January 22, 2011, 04:13:22 PM

ive scrubbed the board with hydrogen peroxide. ill check the resistors

zombiwoof · January 22, 2011, 04:13:34 PM

I would say that if you are going for the vintage sound, 5088's are going to be too high gain. According to the FuzzCentral info on the Clyde McCoy wah, transistors in the 350-400 hfe range are the best with the original circuit to get vintage sound. That's why BC109B's are usually suggested, as these are BC109's that are sorted into the medium gain range, and are most likely to be in the 350-400 hfe range that other higher gain trannies. One of the reasons that the modern production wahs (like the current CryBaby's) don't sound like the vintage ones is that they use very high gain MPSA18 transistors. If you don't care about it sounding like the vintage wahs, then 5088's will be fine. Just a thought.

Al

Gus · January 22, 2011, 05:10:59 PM

Adjust the operation points of Q1.
http://fuzzcentral.ssguitar.com/axiswah.php
see the 100K resistor by the 4.7uf cap. You can adjust that up and down in value to shift the operation point of both transistors. Measure the collector voltage of Q1 change the resistor value measure again note the sound change.

The gain is controlled more by the ratio of the collector to emitter resistor than by the transistor hfe. So if you want to tune it you can shift the operation point and gains with the 100K and/or emitter resistor and adjust the gain with the series input resistor.

The gain of Q1 circuit is a big part of the "sound" the more the gain(as long as there is enough current and the circuit is not clipping) the greater the voltage out of the wha pot wiper to sweep the filter part. The wha pot is like a volume control

clamup1 · January 22, 2011, 08:49:30 PM

i used the 5088's bc i didnt have any bc109's. i bought a multi pack that was supposed to have some in it but it didnt.

im not getting any sound. if kris is right ive got 9v+ bleeding into my signal somehow. ive scrapped the flux and scrubbed the board with peroxide. there shouldnt be anything touching but there is somewhere.

zombiwoof · January 22, 2011, 10:54:37 PM

Quote from: clamup1 on January 22, 2011, 08:49:30 PM
i used the 5088's bc i didnt have any bc109's. i bought a multi pack that was supposed to have some in it but it didnt.

im not getting any sound. if kris is right ive got 9v+ bleeding into my signal somehow. ive scrapped the flux and scrubbed the board with peroxide. there shouldnt be anything touching but there is somewhere.

If you buy unsorted BC109's, there's a big chance you'll get ones that are either too low gain or too high gain to be in the recommended gain range for a vintage wah sound. As I said, the reason BC109B's are suggested is because the "B" version is sorted into the medium gain range. So even if the package had some BC109's in it, they could be higher gain like the 5088's. It's not the type of transistor that is important, just that they are NPN in the "good" gain range. And yes, you can make up for higher gain transistors by changing other component values in the circuit, but this isn't necessarily going to get the vintage sound, as the Dunlop Crybaby's can attest to. That's what they do to adapt the circuit to the higher gain transistors they use. Just like a Fuzz Face sounds best with certain gains for the transistors, a wah sounds best (IF you're going for the vintage sound, which I don't even know if you're trying for) with medium gain transistors. I know you're having other problems with making yours work, I was just mentioning this in case you want a wah that sounds like the old Voxes. In my case, I was trying to recreate the sounds I got in the past with the Clyde McCoy wah I had when I was a kid, and I found that keeping to those guidelines for the transistors was one of the keys to getting that sound. I would never have sold that vintage wah had I known that the Crybaby's and such in the future were going to sound as bad as they do.

Good luck, I hope you iron out your problems with the wah,

Al

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