wah buffer at Fuzz central question

[yeeshkul]

I was thinking about the WAH output buffer on the brilliant Fuzz Central site:

http://fuzzcentral.ssguitar.com/mccoy.php

I have troubles to undestand why is the 47nF(0.05uF) cap used at the input of the buffer when the signal goes through 220nF caps right before that.
Also, how would it affect the sound if i add 1M res to bias the base current/voltage? How does DC biases the base without this 1M res from 9V to the base?

thanks
Jan

[beatstrat]

Seems to be 'standard practice' to throttle the bandwidth just prior to the JFET (in this case) - it would help to keep it from overdriving as well as over-amplifying lows.  You can experiment here for your own benefit - 0.1uF would allow just about all of your signal thru and not cause you any issues at all.

[Derringer]

funny that this wah buffer has just come up ..

I recently installed one on my GCB 95 so that it would work with my fuzz circuits

I used a J201 (socketed) because that's the only Fet that I currently have on hand ... the circuit seems to work fine, I can wah with my fuzzes. The only thing is that I had to max out the trimpot to get a good volume. Is this because of the J201?

I'm ordering some 2n5457's with my next parts order though.

Is there a benefit to using the 2n5457 over the J201 ?

[raycroft]

It is amazing to me how I can look at the recent posts and find what I've been thinking about without having to ask.  Such a great site- thanks Aron!   

I just added this output buffer to my VOX v847.  I didn't have a 2n5457- so I used a 2n5458.  I read somwhere on this site that these 2 can be interchanged with no issues; however, I have the same issue with my volume trimmer on the buffer.  It's maxed out and still needs to be louder.  Also, I replaced the 390 ohm resistor w/ a 1meg trim pot ( among other mods) - and was getting some great tone out of my wah; really loving it.  This has been an on-going process over about 6 months and I just finally got it where it sounds like I want it, then I add this output buffer in order to use it w/ my fuzzes- now it sounds like crap.  It's not supposed to color the sound of my wah, but it sure does.  It doesn't sound the same at all;  which sucks coz it took me 2 days to get this right (first time perfing and I had to do it twice).

to be sure I don't have some other issues I removed the buffer and I'm right back to great wah-ing.

[yeeshkul]

i'm using a switch to turn off the buffer, but there is almost no affect to the sound so i will most probably remove the switch . I used J201 and 100k volume trimpot. I am not sure if the bigger trimpot can really help to kick tghe volume here(the loudness was the same with or without the buffer in my case when the volume trim was fully turned up). 68k->47k helped me to get the perfect balance.

There is still one question - how do we get some DC voltage to the base without anything leading the current to the spot between the base and the 47nF cap?

[raycroft]

you mean the 'gate', right?  the 9v on the pcb runs to 2 resistors; I just hijacked it off one of them.  I read to do that in a thread somwhere. 

I was researching a Teese wah and found this vid http://www.youtube.com/watch?v=aPNF_P4LVjE(it's 2 parts); and then I started researching wah buffers from there.

Hope this helps.

[yeeshkul]

you mean the 'gate', right?  the 9v on the pcb runs to 2 resistors

yeah i mean gate. and this doesn't help hehehehe

[raycroft]

Yeah, sorry; I tried.  At least it's a good watch.

I do hope someone can chime in on the whole volume drop/tone coloration of this buffer, though.

I really need to get a 2n5457 and throw in there; just to make sure.

[yeeshkul]

and when you remove the buffer completely - does it affect the volume difference? i mean are you happy with the wah volume on/off in case there is no buffer at the output?

[raycroft]

volume is fine w/out the buffer- I know how to mod it to be higher if needed- but; it's not necessary.  with the buffer; it needs to be louder.  It just sounds dull, also.  I was loving the 1 k resistor in place of the 390 ohm - I was getting great nasally stuff.  Now it's just boring, and almost muted.  too much bass.  I modded everything I could except for the inductor  and the volume mod coz with the mods I did make, it was perfect.  The buff changed all that.