very general wah wah tips

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very general wah wah tips

Postby dai h. » Sun Mar 17, 2013 1:01 am

simple suggestions anyone would like to share would be cool. (Off the top of my head) :

-adjusting the 470 ohm seems like a generally useful mod
-use a gain selected transistor for the 1st one (seems to affect wah range in the lows and on a mass produced one, maybe less likely to be well chosen)
-small tweaks to 10nF at emitter of the 2nd transistor to adjust frequency (large changes such as to 22nF, 33nF, etc. seem way too large--but possibly not for bass??)
-some of the inductors seem not very tight in tolerance, so could be a source of relatively poorer sound if off towards low side (thinner)
-taking time to adjust the gear/pot/exact footswitch height, as well as possibly remove the felt (and maybe replace with something thinner so the treadle doesn't "clank" when switching) seems worthwhile to try to achieve max. range (if that is what you want)
-I've found using a buffer after the wah info a fuzz helps with the interaction. It made the highs too excessive so reducing them after the buffer seemed to help a lot make things sound more correct
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Re: very general wah wah tips

Postby David B » Fri Mar 22, 2013 9:45 am

I’ve heard of the higher hfe for Q1 , one example I read was a preference 500-550 for Q1 and 200-250 for Q2 thought others seemed to like a balanced approach so YMMV.. I’m going to socket the transistors on my project board to try some of these tweaks 8)
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Re: very general wah wah tips

Postby dai h. » Sat Mar 23, 2013 8:48 pm

I haven't experimented too much with gains, but it did seem like there was an effect in the wah effect at low freqs. depending on Q1 gain. (Q1 gain seems more important than finding the "vintage correct" transistor, though I suppose it isn't impossible that someone finds and plugs one in that happens to be in a "good" range.)

(another possible tip) :

-careful not to overspray a wah pot w/contact cleaner since some pots seem to be destroyed easily (had a "scratchy pot" which turned out to be a bad connection/solder joint and ruined a Fulltone wah pot in the process)

-older caps can be really loose tolerance, so for example a 20% 10nF(0.01uF) at the extreme ends could be 8nF(0.008uF) to 12nF (0.012uF). Modern film caps seem generally better (5 or 10%), but some ceramics aren't that tight (GCB-95 input cap for example).

(Guess I'm repeating myself but) when you can get a wah and fuzz to work really well together it sounds amazing. Sort of like the wah is on PCP and steroids. It's almost a little too wild and crazy you have to tell it to, "Get out of my house!", or "Get back inside your cage!". :mrgreen:

(B.Bradshaw touches a bit on their wah mod which included an output buffer from about 0:26) :

https://www.youtube.com/watch?v=dpcJ8dA4GXg
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Re: very general wah wah tips

Postby David B » Sun Mar 24, 2013 11:25 am

dai h. wrote:-careful not to overspray a wah pot w/contact cleaner since some pots seem to be destroyed easily (had a "scratchy pot" which turned out to be a bad connection/solder joint and ruined a Fulltone wah pot in the process)



Yeah cleaner can be tricky, I find (if possible) disassembling & cleaning a scratchy pot is a bit safer and works better than shooting the offending thing with contact cleaner.

Always wondered if the cleaner did damage to the carbon track ??? Guess it would depend on the material.

Haven't looked at the caps yet but that and the transistors will be on the agenda with this project wah..

Bradshaw MC404 sounds nice.

db
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Re: very general wah wah tips

Postby dai h. » Mon Mar 25, 2013 6:27 am

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Re: very general wah wah tips

Postby David B » Mon Mar 25, 2013 10:27 pm

Ah relic 8) nice split pedal Univibe, like the duct tape.

One interesting feature was that the screw- down opto shroud had been replaced with a duct tape covered RCA Vacuum tube box top which had been adhered to the PCB with white glue. Why I have no idea, but it may have increased response because it was larger than the original shroud and perhaps because it was made of white cardboard it diffused the light better.
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Re: very general wah wah tips

Postby dai h. » Tue Mar 26, 2013 5:29 am

yeah I dug that cover, lol
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Re: very general wah wah tips

Postby David B » Sat Mar 30, 2013 2:22 pm

roadie repair :lol:
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Re: very general wah wah tips

Postby dai h. » Sat Mar 30, 2013 4:44 pm

I like that it's from a tube (the box). She says "RCA" but I'm thinking GE(my nerd powers at work?).

edit:

ooh, I can see it now, "EBAY 2014...AUTHENTIC GE TUBE BOX AND GAFFER'S TAPE. AS FOUND ON HENDRIX UNIVIBE. OWN A PIECE OF GENUINE ROCK HISTORY! A STEAL AT $1000!!!" :mrgreen:
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Re: very general wah wah tips

Postby dai h. » Fri Apr 05, 2013 8:47 am

related links (thx David :) ) :

http://forum.metroamp.com/viewtopic.php ... 6&start=45

http://www.diystompboxes.com/smfforum/i ... ic=88660.0

another (small) idea: another practice some wah tweakers do is cutting the rubber stoppers to enable more mechanical travel. Pretty much self-explanatory (Be careful. Use razor blade, exacto-knife, etc.) THINK CAREFULLY (how much you want to remove) BEFORE you cut (since you can't simply replace the rubber slice after you've cut it off. Of course Dunlop does sell replacement rubber stoppers). Also, you NEED a bit of a cushioned stop before the roration of the wah pot reaches the extreme ends (the point which the shaft can't spin any futher). Obviously you don't want to place things so the rotation reaches to the stopping point and beyond since that will make it more likely to damage the pot (and maybe other pieces as well).
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Re: very general wah wah tips

Postby David B » Fri Apr 05, 2013 4:30 pm

On my project wah I removed the back bumper for more range and glued in a thin rubber washer to prevent clanking & adjusted the pot accordingly . Didn’t bother with the front one’s yet.

Per Joe’s recommendations in the thread I used low gain transistors, on hand I have BC109B Q1 hfe 300 Q2 hfe 280 & they’re in sockets so I can try some different devices but I like the results as is :D
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Re: very general wah wah tips

Postby David B » Fri Apr 12, 2013 7:35 pm

Dai,

Yep I changed the 470r to 330r that brought it closer in the bass to my favorite original as that seemed weak with the 470.

Also took a look at Stuart Castledines site DIY resources for some mod ideas and came up with the following preferences for my wah build..

Input resistor 68K to 47K, tried 56K but 47K works better for me.

I changed the midrange 1.5K to 1.9K which again matches the value my favorite wah, liked that.

I swapped transistors to slightly higher gain Q1 hfe 400 and Q2 hfe 300 and I like it…however might go in the opposite direction and try lower 200ish hfe just for some contrast..

No cap sampling yet…

db
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Re: very general wah wah tips

Postby dai h. » Sun Apr 14, 2013 1:02 am

David B wrote:Input resistor 68K to 47K, tried 56K but 47K works better for me.


(I don't recall playing with that much--oh wait, actually on my Roger Mayer 9090A kit that was variable (100k pot) but that had a transistor buffer immediately previous--but) I think that can use a bit of value tweaking when going from stock to true bypass?

I changed the midrange 1.5K to 1.9K which again matches the value my favorite wah, liked that.


Interesting. Carbon comp? (From memory) not too much range there seemed to work better than say a big value such as 5k(FWIW on RMC3 if memory serves, the value is a 2k pot).

(off topic, but stumbled on this--haven't heard NY in a long while: )

http://www.youtube.com/watch?v=SEhnFU3y8wI
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Re: very general wah wah tips

Postby David B » Sun Apr 14, 2013 10:31 am

Yep this wah is true bypass & needed more volume, still haven't looked at buffers. Actually I might want to have a separate buffer so I can switch out at will, this dude has a switch on the wah..
http://www.youtube.com/watch?v=xEGBgvPu9bI

Used all carbon film on this one, board is nice but has a small footprint fer resistors. I think the recommend tweak range to use is between 1.5K to 2.7K, yeah small range there..

I saw that BBC show a while ago,great stuff & btw there is a Niel Young documentary in Starz channel if you get it might be worth checking out.

db

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Re: very general wah wah tips

Postby dai h. » Sun Apr 14, 2013 5:30 pm

Could very well be I don't understand things enough, but not really sure how useful input buffers are for a wah (maybe w/input less loaded, allows non-true bypass that doesn't affect signal as much?). Also wonder if the GCB-95 input buffer had something to do w/a bit of perceived harshness from those (maybe along w/relatively poorer tol. input 10nF cap being lower(I think I measured about 8nF for one of mine if mem. serves). Maybe needed to have a bit of highs rolled off after the input buffer?). An output buffer (not really new since IIRC the very old Vox stereo wah fuzz had one) seems more useful to reduce the weird interaction with some inputs (not enough drive from wah output leading to resonance and oscillation, weirdness?). Oh, and there is the easy mod of adding series R at wah output to get it to behave more nicely w/fuzzes.
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