help with crybaby mods - sounds bad!

[jg24]

Hi, hope someone might be able to help.  I've just converted my dunlop crybaby to true bypass and made a few changes to try and improve the sound - but now it sounds terrible!  The changes are:  

Four trimpots in place of the resistors that affect the sound -
Gain/Bass 500R trimpot (stock resistor 390R)
Volume 100k trimpot (stock 68k)
Vocal 100k (stock 33k)
Mids 2k2 with 1k resistor in series (stock 1k5)
(I've marked out the stock values and recommended alternatives on the trimpots).
Transistor sockets - and presently BC108c transistors (measuring 370-380 according to my cheapo multimeter; stock were 570ish).
15nf 'sweep' cap for the stock 10nf one.
Metal film resistors.

Heeling the wah there's a massive drop in frequency – it suddenly goes muddy and just horrible sounding.  I think the problem might lie with the 'vocal' trimpot (the one with the pink wires running to it)??  Off the stipboard it seems fine (I desoldered it to check).  But soldered to the board I get no resistance – instead there is continuity from the outer leg I'm using to the middle leg.  Measuring the other outer leg (which I'm not using and I've isolated on the stripboard) I do get resistance.  Adjusting the pot whilst using the wah there's no affect on the sound until I pretty much shut it off (dial it to zero).

I'm guessing there could be no resistance here – and that explains the bad sound I'm getting??  The three other trimpots work fine – I can't see what I may have done wrong with this one.  (This is the first time I've used stripboard so not the neatest soldering - but I checked each strip with my meter and there are no unintentional bridges across the strips).

[GP]

Not a direct solution to your problem but have you considered putting the stock resistor back in again to see if it solves the problem?

I realise you've checked for solder bridges on the stripboard but, if you're reading continuity between the wiper (middle leg) and the outer leg of the trimmer, there's a high chance that you have a solder bridge on the main board.

It's all very well saying this now that you've made all the changes but maybe, in hindsight, you should have tested each modification one by one rather than give yourself more of a headache trying to find which mod (or mods) has caused your problem.

[R.G.]

There is a contagious disease which runs in effects fanciers. It's called BUMS - Blind Urge to Mod Syndrome.   

[jacobyjd]

There is a contagious disease which runs in effects fanciers. It's called BUMS - Blind Urge to Mod Syndrome.   

With my wah, I have something more like: Near-sighted Urge To Tear Apart and Rebuild, or NUTTAR.

[GP]

Indeed.

Many of those wah circuit mods are nice and useful - and no doubt your technology of... documents and the like have helped to get this guy in the mood for modding.

I'm not against the OP's urge to mod but I would suggest one mod at a time  

[Paul Marossy]

I have the disease called LWEAS - the Leave Well Enough Alone Syndrome. 

[jacobyjd]

I have the disease called LWEAS - the Leave Well Enough Alone Syndrome. 

Apparently you're a freak of nature then. *rummages around for his torch and pitchfork...*

[jg24]

Appreciate the replies, but I didn't pull the thing apart for the fun of it.  Nor did I suffer from any blind urge to add all kinds of bells and whistles to the wah - as you clearly all think!  I've owned the wah about a decade now and it's virtually never been used.  You may have noticed I changed the batt clip - that's cos the battery left to fester in there had leaked and stuck firm to the old one.

Ok, one mod at a time makes perfect sense.  But the changes I made are hardly major surely?  Effectively they allow me to dial in near enough the stock settings and take it from there - one change at a time.  Moreover, I would only have to work on the pcb once - surely that's good practice??  I've no idea what mods I need to make to give me a better sounding wah - and I'm sure it would be the result of 'alchemy' to a large degree.  I don't know which combination of resistor values will help - unlike yourself Paul.  You seemed pretty clear about what you were after with your dunlop wah on your website.

Granted the use of metal film resistors wasn't necessary - but whilst the pcb was out I thought why not... same for the transistor sockets (I read on that fuzz central site that the higher gain stock ones may give a harsher sound... but i can always stick them back in).  Otherwise I would have thought the changes were relatively basic and minor.  I guess all I was looking for was some advice about using the trimpots - whether I'd wired them in correctly.  Whether I should have set them out differently.  As I say, I've not used stripboard before... well back in school I did but that's further back than I've own the wah and I just had to follow diagrams.

Fair enough if this forum is for the boffins only - my mistake.

[DiscoVlad]

All of my crybabies whether modified or stock, do the same in the heel down position.

Usually, altering the EQ on the amp (less bass) fixes it.

[Talon5051]

Heeling the wah there's a massive drop in frequency

You could try adjusting the pot so that it does not go into that frequency range.  Loosen the pinion from the gear and turn the pot a couple of gears so that it sweep is a little higher in the range of the pot.  Just be careful that you get a full range of motion with the pinion so that you are able to turn the wah off.

[jacobyjd]

Johnny--

I had to look up what 'boffins' are...hah--I'm far from it  

Don't get us wrong--we're just giving you a bit of a hard time. In all reality, I like the idea of moving those mods to a separate board for trimmers. Usually I don't encourage anyone to make mods unless they have a specific direction in which they want to go or a problem they want to solve (my c-baby needs more mids, or my wah is too piercing at its highest point, etc.).

However, doing what you did here is a good way to figure out what you want, if you don't already know (i.e. I want my c-baby to sound better, but I don't really know what I'd want to change to get it there).

That said, I would definitely double-check your wiring on the pot where you're getting no resistance. That's got to be part of your problem.

(gear adjustment ninja'd by Talon...)

Additionally, for the issue of losing your sound in the muddy heel position, you may be shooting yourself in the foot a bit by raising the value of the sweep cap--this will definitely lower the range of the heel position outside your guitar's range ('specially if you're using, say, really bright single-coil pickups in your guitar).

If you are attached to the .015uF sweep cap (I can relate!), try adjusting which end of the pot's range you're using. If you're not sure what I'm referring to, take note of how much of the pot's rotation you get from the heel to the toe position. It's not the whole pot sweep. Try adjusting the gearing so that you're using the pot's range toward the higher frequencies, rather than the lower.

Also, if you adjust your amp's EQ, that will help, as DV suggested.

If none of that gets it, you might have to revert that sweep cap back to where you want it.



Oh, and most people get rid of the buffer when they mod to true bypass...it might be favorable to add that back in (or a better buffer), since you still have the enclosure space to work with. That might solve your problem too.

Let us know what you figure out!

[Paul Marossy]

I have the disease called LWEAS - the Leave Well Enough Alone Syndrome.  

Apparently you're a freak of nature then. *rummages around for his torch and pitchfork...*

I'm used to it, I'm an ogre.  

I've no idea what mods I need to make to give me a better sounding wah - and I'm sure it would be the result of 'alchemy' to a large degree.  I don't know which combination of resistor values will help - unlike yourself Paul.  You seemed pretty clear about what you were after with your dunlop wah on your website.

A "better sounding wah" is highly subjective, you know.  For one of my Dunlop wah mod pages, I used this site as a guide: http://www.wah-wah.co.uk - See the Circuit Mods part of the DIY resources section

[panterafanatic]

i found RGs page highly useful, combined a gain/distortion for Q1, created a volume drop though even with a pot for the volume, helped but didn't solve

his page
http://www.geofex.com/Article_Folders/wahpedl/wahped.htm#whatwah

[GP]

Appreciate the replies, but I didn't pull the thing apart for the fun of it.  Nor did I suffer from any blind urge to add all kinds of bells and whistles to the wah - as you clearly all think!  I've owned the wah about a decade now and it's virtually never been used.  You may have noticed I changed the batt clip - that's cos the battery left to fester in there had leaked and stuck firm to the old one.

Ok, one mod at a time makes perfect sense.  But the changes I made are hardly major surely?  Effectively they allow me to dial in near enough the stock settings and take it from there - one change at a time.  Moreover, I would only have to work on the pcb once - surely that's good practice??  I've no idea what mods I need to make to give me a better sounding wah - and I'm sure it would be the result of 'alchemy' to a large degree.  I don't know which combination of resistor values will help - unlike yourself Paul.  You seemed pretty clear about what you were after with your dunlop wah on your website.

I didn't suggest for a minute that you'd pulled it apart for the fun of it. Despite RG's suggestion (which was, I'm sure, intended as a joke) I did attempt to back up your motivations a little bit. I think RG and all the others with pages suggesting miriad mods for existing circuits should maybe consider that they are perhaps fuelling the 'blind urge to mod' they mention. I, for one, am very glad they do post all these informative articles - and long may they continue - but they can hardly be surprised when people act on them.

That said - and i certainly don't want to offend RG or anyone else for that matter with what i've just said - I did suggest you try each mod one at a time to try and isolate which of them is most responsible for your problems. Reading resistors/trimpots in circuit will often give unpredictable results and that trimpot is in parallel with the inductor so it's likely to be a low enough resistance to trigger your continuity test on your meter. As far as I can see with the pictures you've posted, your trimpot wiring is fine by me but being able to see the solder side of the main board might help us identify any other problems. Maybe you could post some more closeups of that board?

I'd also suggest that each of the mods you've made can tend to be a little interactive on the overall sound and so it will probably take quite some amount of experimentation to find a combination of trimpot settings that actually sound good to your ears.

[Paul Marossy]

I'd also suggest that each of the mods you've made can tend to be a little interactive on the overall sound and so it will probably take quite some amount of experimentation to find a combination of trimpot settings that actually sound good to your ears.

Yep. I think that is part of the problem right there. Just changing one strategic resistor value can have a sweeping effect. No pun intended. 

[jg24]

Thanks for all the replies and advice.  Only read them today as I've not had the chance to get online the past few days.

Don't get us wrong--we're just giving you a bit of a hard time... Usually I don't encourage anyone to make mods unless they have a specific direction in which they want to go or a problem they want to solve (my c-baby needs more mids, or my wah is too piercing at its highest point, etc.).

That's ok Josh - maybe it was necessary to make me think more about what I was trying to achieve!    Having thought it over I suppose I'd like - if possible with the stock crybaby - to find a warmer, smoother wah sound than what I had... with a bit more oomph or 'wah' if that makes sense.  The crybaby just sounded a bit repressed to my ears - and wasn't as 'deep' or warm (or however you try and describe it) as the famous wahs I hear on record.

Oh, and most people get rid of the buffer when they mod to true bypass...it might be favorable to add that back in (or a better buffer), since you still have the enclosure space to work with. That might solve your problem too.

Listening to Hendrix (obv) and stuff like Wishbone Ash's the king will come gets me reaching for the wah.  I presumed the old wahs had no buffers so thought I should get rid of mine.  But I didn't expect converting to true bypass and losing the buffer would make a big impact to the sound - possibly lower the volume from what I'd read.  I now think though it can make quite a difference. 

If I find I can't get a sound I'm content with from the crybaby (I'm not expecting much any longer!) perhaps I should try a buffer... or build one in a separate enclosure (it might be useful elsewhere on different occasions).  I seen a kit for one at musikding - which would simplify things for a novice at tinkering with circuits like myself.

On reflection GP - you're completely right and I should have tried each mod individually.  I'd been inspired to make all the mods I did mainly by what I'd read on Paul's website (I did hesitate about removing the buffer from what Paul says - but removed it for the reason above); http://www.wah-wah.co.uk that Paul references; and above all http://www.stinkfoot.se/andreas/diy/mods/dunlop.htm - that's where the use of trumpots in place of resistors is suggested.  I had thought using trimpots would simplify things, but really too many variables makes things too messy as you and Paul say.

So this weekend I'll be putting stock resistors back in and making any changes from there - one at a time.  I'll stick with the 15nf cap for the time being - given I'd like a warmer sound (and the Hendrix and other versions of the crybaby use 22nf).  I'll try adjusting the pot and eq (and using different amps) before I go resoldering if I don't like the sound.  Hopefully I'll find something in the pedal without too much more hassle.  I'm more than a little tempted by the replacement boards available from wah-wah.co.uk... I'm thinking perhaps I should have just gone for one of them in the first place! 

Thanks again.

[GP]

Glad to hear you've not given up!
I re-read your original post just to be sure of a couple of things and I wanted to ask the following question:

Given that you've marked all the trimmers with the original stock values, does setting everything back to stock (or at least thereabouts) cure the problem? Or at least alleviate it? I'm imagining, since you've actually been quite systematic with your modifications, you'll have tried this and it hasn't had the effect of putting things back the way they were.

By a process of elimintation, that sort of leaves the things you haven't allowed to be varied, i.e the "sweep cap" and the transistors. Have you tried subbing those back to see if it helps? The sweep cap is certainly intended to widen the frequency range so maybe this is something to consider?

I don't think you necessarily need to go back to the start here if you can reasonably guarantee that you're able to set the trimmers to stock values. There's still the ability to try one mod at a time even with the change of components if you're methodical about it.

[GP]

Oh, and one more thing... i don't really think a replacement board is going to be of much advantage. Most inductor based wah circuits are pretty much the same deal with component variations so a different board isn't really going to give you a different circuit to the one you already have.

[george]

just wondering if maybe your solder joints are making contact with the wah shell causing inadvertant grounding?

[Paul Marossy]

I had thought using trimpots would simplify things, but really too many variables makes things too messy as you and Paul say.

Using trimpots is fine. But you should start by having them at the stock values and then tweaking them one at a time, evaluate each adjustment and go on the to the next one. Do it systematically & take notes. You should be able to discern one by one how each adjustment affects the overall sound.