Axis Wah

[kin0]

Hay, My crybaby broke down so I decided to build an axis wah usig the shell, the pot and the inductor. I read in some topics here that this wah needs some twiking. what do you mean by that and how can I do this? Also how does this wah sounds good? and have any body tried to build it (I wanna use  pref board).


Also how can I put the board on the shell so that it'll not touch the shell, it'll stay on there and won't start moving left and right and also that I could get it out later.

I'll be thankful if anybody could help I got a gig in 2 weeks and I need the wah til' then.

[kin0]

Can anyone help?

[geertjacobs]

My crybaby broke down.

Do you know what is wrong with it?
Are you sure you can reuse the pot and the inductor?
Maybe you can try to fix it first?

Here's what google gives me on "axis wah":
http://fuzzcentral.ssguitar.com/axiswah.php

Most wah's I know hold the pcb with screws. Check your wah.
Otherwise you can use these thingies: http://www.banzaimusic.com/Adhesive-Standoffs/

[kin0]

Yeah this is the wah that I wanted to built. My I'm not sure if the pot and the inductor are okay. How can I check this? (The value of the pot is right but I'm not sure about the inductor).
I don't want to fix my wah cause I think this one just sounds better and Because I HATE debugging.
Also is anyone have a prefboard layout to this wah?

[clamup1]

hey ive built this from my old crybaby. i couldnt get it to work. the website hasnt been updated in 7 years and noone knows where the op is. unless someone can find something wrong with the pcb  or schematic i made a mistake somewhere. im gonna etch another board and give it another go.

[kin0]

I've compared the schematic to the basic wah scehmatic here: http://www.geofex.com/article_folders/wahpedl/wahped.htm and the difference is in the value of 5 resistors, in the transistors and in the output buffer.

2 of these resistors are changing the tone so I'll put 2 pots there. Another one that not make many difference. And another 2 that are used for baising so I won'y touch them.

[clamup1]

so i guess i screwed up somewhere. ill have to do another and see if it works

[kin0]

Do anyone know if I can use BC107 instead of the bc109c because in my local shop it cost much more and it takes about 2 weeks to get it to the shop.

Here is their datsheet. http://www.datasheetcatalog.org/datasheet/philips/BC109C.pdf

[Gus]

I recommend you repair  the wha first.   Then note what you like and what you want to change about it.

Sometimes all it takes is changing one part.  Say you want more bass sometimes all you need to do is move the pot in the mount or up the sweep cap value.

Question what you read on effect forums and web sites.

IMO transistors don't matter as much as you will read on the web it is more about understanding how the stages of a wha work.  Sometimes you can change two resistors to adjust the first stage gain and operation points.

Look at the Axis wha schematic you linked.  The 330 ohm emitter resistor affects the gain(lowering it the gain goes up to a point and the sweep goes up because the wha pot is a volume control) HOWEVER you need to keep in mind that changes the operating points BUT you can readjust them again with changing the 100K resistor value that has the 4.7uf cap in parallel.  Having the cap bypass removes the 100k from the circuit at the operating frequencies and lets it set the operating point (biasing) of the first and second stage.  I like to increase the 4.7uf value.

Blindly changing transistors and not understanding the circuit is not the way to go.  I think it is better to first adjust the gain and operating points of the first stage, in this circuit the first stage collector voltage sets the second stages bias.

[kin0]

I know this. I got my wah moded and I pretty liked it but there was a problem with the pots (I connected some resistors to them and the resistors always break). I used the wah for a while then I haven't touched it for a week and it started to work as a volume pedal. I left it for a month because I was very busy and now it doesn't work at all even then bypassed (true bypass). I got so angry so I decided to build a new one without so many control (just 2 trims inside).

[zombiwoof]

Do anyone know if I can use BC107 instead of the bc109c because in my local shop it cost much more and it takes about 2 weeks to get it to the shop.

Here is their datsheet. http://www.datasheetcatalog.org/datasheet/philips/BC109C.pdf

You can use just about any medium-gain NPN silicon transistor in there, as long as they measure between 350-400 hfe, to get the vintage sound, with the vintage component values.  If you get BC109's, you're more likely to get them in that gain range if you get the BC109B, because the "B" version is already sorted into medium-gain range.  I'm surprised that he got BC109C's that measured in the correct gain range, but there is some variation in the sorting of gains.  Small Bear sells some BC109 "work-alikes" (which means they are similar transistors but with the same specs) for a good price, it will make it easier to get some in the correct gain range to buy those.  That's what I put in my modded V847.

Al

[kin0]

The HFE of the BC109 is between 200-800 and in the bc107 is between 110 and 450. Isn't the BC107 better? And would I need to change anything in the circuit if I'll use the bc107?

[zombiwoof]

The HFE of the BC109 is between 200-800 and in the bc107 is between 110 and 450. Isn't the BC107 better? And would I need to change anything in the circuit if I'll use the bc107?

As I said, measure the gain of the BC107's and make sure they are somewhere between 300-400 hfe.  It might be difficult to find some that high if the range is 110-450, you might have to buy a bunch and find some in the higher range for that tranny.  That's why I suggest just buying some BC109B work-alikes from SB, they would be more likely to be in the best gain range.  If you put in lower gain trannies, you may have to change other component values in the circuit to compensate.

Al

[kin0]

Okay I read more about the wah technology. And how can I measure the gain of the transistor. If I'll but 5 BC107 are my chances to find two good ones are good?