Input buffer for a wah wah, why would you want one?

[vanessa]

I was looking over the Tonepad wah project and I noticed the input buffer on there. I can see why you might want an output buffer, say for (impedance matching) use with a fuzz face but why would you need an input buffer? Is there some other effect that makes the wah die if put before the input?

Also I've used this output buffer in the past for a wah I built for a friend. The wah effect is still dead when going direct into the fuzz face. They now use a Boss pedal as a buffer between the two, with the Boss pedal the wah works very well. Is there a better buffer to be had to do the impedance matching with a fuzz face, or maybe better values for the Tonepad version?

[Hal]

you need an input buffer if you don't use true bypass switching.

[Mike Burgundy]

http://www.geofex.com/Article_Folders/wahpedl/wahped.htm
Great stuff, and also answers that particular question.

[vanessa]

http://www.geofex.com/Article_Folders/wahpedl/wahped.htm
Great stuff, and also answers that particular question.

Mike-

So based on what I have read from the GEOFEX article (link above) your saying that when the Tonepad wah is in volume pedal mode it is tone sucking and needs an input buffer to correct this issue?

[CS Jones]

Take a look at FP's .pdf again.
Notice his switch.
Notice his first stage compared to this by Doug H.

Notice what FP calls this first stage.
Compare FP's input stage to his output stage.
Quotes from RG's article

There are two ways around this (tone suck). One is to completely disconnect the wah board from the guitar signal when the wah pedal is bypassed by changing the Single Pole Double Throw (SPDT) bypass switch that is stock in most wahs for a Double Pole Double Throw (DPDT) footswitch.

The easiest simple buffer is the JFET source follower.

The JFET is connected to ground by the 1M resistor, and it picks up the input signal from the wiring pad that the input resistor used to connect to. The JFET drain is connected to +9V through a low resistance path. The JFET source is connected to ground by a 10K resistor, which self-biases the JFET into the linear region, and the signal is taken from the source of the JFET into the old input resistor. The input blocking capacitor that used to block the 0V signal level from the guitar from reaching the several-volt bias level of the first wah transistor now blocks the volt-or-two DC level at the JFET source from reaching the first wah transistor, so all is well from a DC bias standpoint. The JFET is happy with it's gate at ground, the guitar is happy with a 1M input resistor, and no tone sucking happens.

Edit note:  Sorry about the large image. I can't edit it.

[Satch12879]

It prevents loading your guitar signal if it's the first unit you plug into.  As PC would say, you want each unit, your guitar included, to think it's connected directly to your amp's input even if realistically it's not.

[formerMember1]

It prevents loading your guitar signal if it's the first unit you plug into.  As PC would say, you want each unit, your guitar included, to think it's connected directly to your amp's input even if realistically it's not.

maybe that's why roger Mayer supposedly added a input buffer to hendrix's wah, he always plugged into it first,
Would this elimanate most of the tone suck from the curly cords?  or is this only for not using a true bypass arragement,...

alot of people talk about how a fuzzface sucks when you have a buffered pedal before it, but didn't the same thing happen to Jimi, when he put the univibe inbetween his wah and fuzz?

Hendrix plays with a germanium fuzzface and a clyde mccoy wah on the bbc sessions gig, and his wah tone is great and fuzztones, and he didn't have a univibe on that gig, so i guess Roger Mayer added an output buffer to the wah,....

Also I've used this output buffer in the past for a wah I built for a friend. The wah effect is still dead when going direct into the fuzz face. They now use a Boss pedal as a buffer between the two, with the Boss pedal the wah works very well. Is there a better buffer to be had to do the impedance matching with a fuzz face, or maybe better values for the Tonepad version?

yeah that is odd, my wah used to wah before my fuzzface, becuase i added an output buffer like Fuzzcentral, but for some reason just recently i noticed it still wahs, but it also squeals when not hitting any notes on guitar, and changes pitch with movement of the wah, as if there was no output buffer,...
It could be the fact that the fuzzface oscillates even though no wah is on, when i  don't hit any notes on guitar also,..yeah,... i guess that is my problem,...

OT:Vanessa how is the Ge fuzzface you just built compare to the Axis Face sili rev 3 you built, i was thinking about building a GE fuzzface to compare to axis face,...but was wondering how it worked out for ya,...

[vanessa]

yeah that is odd, my wah used to wah before my fuzzface, becuase i added an output buffer like Fuzzcentral, but for some reason just recently i noticed it still wahs, but it also squeals when not hitting any notes on guitar, and changes pitch with movement of the wah, as if there was no output buffer,...
It could be the fact that the fuzzface oscillates even though no wah is on, when i  don't hit any notes on guitar also,..yeah,... i guess that is my problem,...

OT:Vanessa how is the Ge fuzzface you just built compare to the Axis Face sili rev 3 you built, i was thinking about building a GE fuzzface to compare to axis face,...but was wondering how it worked out for ya,...

That’s strange. My friends wah does the same thing. It squeals and does the pitch change with the movement of the wah just like you describe. I gave them that Axis Face rev 3 pedal. This is the one that is in combo with the wah.
I don't remember but I think we tried a number of combos and there was something to it. I'll have them check it out again and see if it's only with the Axis FF.
As I said I gave the Axis FF rev. 3 away. I think it does a great job at being a fuzz face, but it is different than a real ge FF. The ge FF's seem to have more clarity and brightness over the Axis. I like the ge FF a little better than the Axis.
Did you go with the 2.2uf input cap? As I said before I think Phillip must have some pretty dark sounding amps over there.

[formerMember1]

yeah i went with a 2.2uf input cap, and also left the 8.2k stock, and used the 33k to bias the pedal, i think it sounds better biasing by the 33k resistor,..I also added a 1k resistor in series with the fuzz pot, i like it, but still am gonna build Ge fuzzface,....

Yeah i only tried the wah with output buffer with the Axis FAce, i don't know if the problem lies in the Axis Face and not other Ge fuzzfaces, but then again. that might be the problem, the silicon transistors, but that doesn't make sense, so i don't really know, if i do find out i will post up,...

[vanessa]

I don't know, Brett has had similar issues with his FF builds using that PN2369A. I know he had the noise issue without the use of the "smooth" pot. I added a resistor at about 10k to solve that issue. It really sounds like an impedance issue between the wah and the Axis. Even though the wah has an output buffer maybe it may not be enough? My friend uses a Boss tuner pedal between the two and it works but it does not stop the squeal when the guitar is not being played.

[formerMember1]

yeah, the odd thing is i swear it didn't do this before, only now,...i think it might have been after i swapped the bass resistor for a lower value(330), but not sure,...i'll experiment more tomorrow

how'd the carbon comps workout for your fuzzface,...

[Fp-www.Tonepad.com]

Similar to Doug's idea, but not quite.

It's a high input impedance booster, you set the gain using a trimpot. That's why there's a volume trimpot at the output.

It gives the wah circuit a stronger signal to work with, and you may not want to believe me, but this is the best wah I've played.

Fp

[vanessa]

Similar to Doug's idea, but not quite.

It's a high input impedance booster, you set the gain using a trimpot. That's why there's a volume trimpot at the output.

It gives the wah circuit a stronger signal to work with, and you may not want to believe me, but this is the best wah I've played.

Fp

Then you should leave the input buffer in there if you are going to use the output buffer?

[Fp-www.Tonepad.com]

if you want to use the output level control or boost the volume, yes.

It's nice to set the input boost gain just before it breaks and lower the volume at the output to maintain a balanced level between bypass and engaged. Notice that they also affect the pedal in volume operation. You can wire a true bypass to it too and use a toggle switch for the wah/volume. (That's what I did).

You must be noticing the advantages of doing that in terms of the potential harmonic richness of the signal to be processed by the wah if the guitar is strummed a little too hard  ...

That's how I like my wah

Fp

[CS Jones]

Well, I didn't mean to imply that it was like Doug's. I meant the opposite actually.
I put Doug's up as a graphic of what a true source follower buffer would look like.
It follows, to the letter, what RG explained in the text. That's why I put it up.
That is a source follower buffer.

FP's isn't even really a "buffer" at all - well, in so far as an FET has a naturally high input put impedance and "buffers", sure.
But what you have here is a simple voltage amplifier... a preamp. A pretty beefy one too, if you wanted. I was trying to bring this out without saying it outright. Sorry for the confusion.

Hal had the nut of Vanessa's answer from the beginning.

you need an input buffer if you don't use true bypass switching.

You can read his answer this way...
"If you're using a DPDT forget the buffer. You won't suffer tone suck like the original".

That's also why I referenced FP's 2 stages.
Two different animals.



So, Vanessa, if you want a buffer on the front end of your wah, model it after Doug's layout.
If you want an additional gain stage which adds a buffering benefit use FP's.
Do you need to buffer the front end of your wah?
Well, I don't know really. It can't hurt. In this case, I'd say "why not". Spend a quarter and buffer the thing.


As far as FP's output buffer -
it works perfectly. You might want to recheck your build on it.
It can drive a stack load of paralleled fuzzes if you needed it too.

[vanessa]

As far as FP's output buffer -
it works perfectly. You might want to recheck your build on it.
It can drive a stack load of paralleled fuzzes if you needed it too.

I understand that. I'm sure this circuit works with just about anything. I think this may be an issue with the Axis Fuzz rev. 3 with the wah and this type of buffer. I know it sounds off the wall but the Axis has had some strange issues with it. They seem to be centered on the use of the PN2369A for Q1. formerMember1 describes the same issue to a "T".

By the way FP I wired it up with a toggle switch for wah/vol and a true bypass switch too! Really cool.

[Fp-www.Tonepad.com]

CS, I know that's what you were talking about.

I thought I was giving a clue 

The output buffer should be able to drive any pedal. Comparing it to the buffer in a boss pedal, it even has lower output impedance... I wonder if you have the FET soldered backwards, not all fets have the same pinouts, make sure you match the Gate with the pad marked G in the layout.

Fp

[vanessa]

FP-

Have you tried your wah with an Axis Face rev. 3?

[Fp-www.Tonepad.com]

No, I haven't. Could you trace just the input stage of the Axis circuit?

Fp

[Phorhas]

my 2c:

I'm the owner of a 67' vx wha (wich I found for almost nothing at a flea market. the dude thoight it was malfunctioning so I took it and fixe it what a happy day that was)

anyways, at first I was really bumed with the tone sucking but after a while I discoverd that the "tone suckage" when plugged to a crancked amo is a very important part of the Jimi-SRV tone. so I decided to build me a looper box so I'll "on" wah, "off - ToneSucking" wha and true bypassed wah.

felt like a good advice

have fun