Modding DOD chorus and flanger pedals for bass

[LirvA]

I have a DOD FX 67 Stereo Chorus and a DOD FX 75C stereo flanger I'm wanting to mod for bass. I'm only just learning how to build pedals, I've completed one build so far, a BYOC tremolo, and am working on my second one, a BYOC modified tube screamer, and I want to mod these DOD pedals cause I have a friend who plays bass who wants to buy them. I have no idea what to do as far as what parts or components need to be changed. I'm fine soldering and desoldering and all that, I just need to know what needs to be changed out.


Here's the schematics for the FX 67 Stereo Chorus
http://experimentalistsanonymous.com/diy/Schematics/Chorus/DOD%20FX67%20Dual%20Turbo%20Chorus.gif


I haven't been able to find a schematic for the FX 75C stereo flanger, but I can probably post a decent pic if needed.

[mremic01]

Do they not sound good with bass already?

My understanding is that modulation effects aren't usually tailored for bass. They usually work fine for both bass and guitar as is.

[Mark Hammer]

the most common adaptation of modulation effects for bass is to simply apply the modulation above most of the note fundamentals.  That way, you get the swirl, but you keep the pitch sounding fairly stable.

Probably the easiest way to accomplish that on the FX67 would be to replace the 1uf caps shown just ahead of the J113 FETs, for a smaller value, like .1uf, or even .047uf.  That will trim off much of the bass from the delayed signal so that you'll hear more of the fundamental from the clean signal, and less pitch wobble.

The other thing that bass players prefer is to move the chorus effect a little further in the background.  So, in addition to the change in cap values, you can see that there is a 47k resistor just on the other side of each of those J113s?  Make those 56k or even 68k to mix the modulated signal just a little bit more in the background for more subtlety.

[LirvA]

I haven't tried either of the pedals with a bass as I play guitar instead of bass. I know the concerns bass players have with using guitar pedals for their bass is the pedal taking away low end. Are there mods that would increase the low end or allow more low end to go through?

[LirvA]

Is there any way you could show me which caps and resistors you're talking about? I still haven't learned how to read a schematic yet :/

[LirvA]

oh ok, I see 3 J113 transistors

[LirvA]

Also could someone please tell me if these are good for making pedals?
http://www.ebay.com/itm/1000-pcs-1-4W-5-ASSORTED-CARBON-FILM-RESISTORS-/250786975012?pt=LH_DefaultDomain_0&hash=item3a64118d24


I have no idea what 1/4W 5% means, I'm a newb.

[mremic01]

Modulation pedals usually won't take away low end. You just don't want the effect to sound muddy, which is what Mark is talking about. Try the pedals with bass first and see how you like the sound.

Those resistors will work fine. 1/4 watt is the most common size for use in pedals. Sometimes you'll see 1/8 watt resistors and those are fine too. Carbon film resistors will usually be 5% tolerance, while metal film will usually be 1%. A 5% tolerance means the ACTUAL value of a resistor might be +/- 5% from the marked value. So a 100 ohm resistor with a 5% tolerance could actually be anywhere between 95-105 ohms. A 1% tolerance resistor will be 99-101 ohms. The kind of resistor doesn't really matter, just that it has the right impedance. If a 5% resistor happens to be at the value you need, it's better than the 1% resistor that happens to be one or two ohms off.

I recommend getting stuff from Tayda. Their resistors are about 1 cent a piece. The metal film selection is lacking, but they have almost every value you'll need in stock in carbon film. Their capacitors are well priced too. The green mylar caps are the cheapest, but are generally considered lower quality. I like their box capacitors. It's always a good idea to buy a few more than you need when you place an order, just in case you fry a component. It also lets you build up a nice supply of parts to use on future builds.

Since you're new at this, I would recommend starting with a kit though. BYOC and General Guitar Gadgets both offer great kits. They come with everything you need but the tools, and putting them together will teach you a lot.

[Ben N]

Bass likes effects to be blended with straight signal. Build yourself something like a Buff'n'blend (essentially a parallel effects loops in a box) and you might not want to mod the pedals anymore.

[LirvA]

I was wanting to get an assorted batch of resistors and capacitors to use for production instead of buying however many I need for a pedal at a time.

I've got some of the BYOC kits, I finished the tremolo and it works and sounds really well, I'm currently working on the modified tube screamer and I need to figure out how to go about painting it, then I'm going to build one of their regular tube sceamers and sell it, and then the Ampeg Scrambler kit and sell it, then I have a divided octave kit I'm planning on keeping. After I build and sell the tube screamer and scrambler kit I want to move on to doing it all myself without using any kits and just build and sell pedals for income.

As far as these DOD pedals, I'm not too concerned about how they sound to me as I don't really like chorus or flanger pedals, but a bass player I know is looking for a chorus and a flanger bass pedal, so I'm just gonna mod them to however is advised in this thread and have him check them out and if he likes them, sell them to him.


What are the most common resistor values for pedals? What about the least common? I was looking through the values listing on those assorted resistors on ebay and it looks like they didn't have all the values ... like they didn't have 56k or 68k.

[mremic01]

Don't get an assorted batch, and don't get what you need for one pedal at a time. Pick three or four circuits you want to build at a time and make a list of parts you'll need to build them. Then buy enough to build three or four of each circuit, or more if you want to spend the money. The common parts overlap between projects and you'll wind up with a surplus to use. If you buy the parts in assorted lots, you'll wind up with a lot of values you'll never use. For one cent a piece, it's not hard or expensive to stock up on resistor values that you actually need. If you get 20 resistors of 20 different values, that's only 4$.

Beware of ebay parts. Some people have gotten carbon comp resistors painted and passed off as metal film. Others have gotten those assorted lots and they turned out fine, but had thin leads. Some sellers sort through things like transistors and, take out the good ones, and then sell you the ones they don't want.

It really sounds like you just want to mod these two pedals to do it, not because they need it. Really, try them on bass stock first. If they don't sound good, then worry about doing mods. If you just want a learning experience, try doing some simple perf builds like a Ruby or a Son of Screamer.

[LirvA]

Thanks all for the input, appreciate it very much.