MXR envelope filter

[jimbob]

I finished the envelope from Tonepad using all the mods except the filter range mod. It has been a long time since I used a auto wah but would think it would wah or quack a lot more than it does. Its like a mild version of a wah. Simply put-- Too mild. I want insane quack.

Any mods or ideas?

[oldrocker]

I haven't built this effect because of the level of difficulty and parts count etc...  That's why I'm surprised that this effect seems light.  I would've thought you'd be in wah heaven with this thing.  I have built the Dr. Quack and Nurse Quacky and they both quack pretty good IMHO.  Have you tried these two builds yet?

[jimbob]

I built the nurse quacky and was impressed with that one.

[Mark Hammer]

Then something's wrong because the Quacky will not do anything more severe than the MXR.

[jimbob]

Im not sure if this maters but instead of 200k i used 220k.

[Ardric]

Is the filter sweeping through a wide range?  If it won't sweep, you might try a bit of boost into it, or a distortion pedal with gain low/vol high.  I ended up permanently installing a Fetzer valve in the front of my build to get it to respond the way my buddy wanted.

I couldn't get it to work with TI chips either.  I did change the power supply current limiting resistor and one of the Vr divider resistors as a lot of other builders suggested, but I don't have the box now to look at. The reverse and range mods worked for me, but the wiring to the switches was picking up some interference from the rest of the circuit.  It should probably be kept short and/or shielded.  I just took them out again, since he liked the original settings best.

[Dave_B]

I had the same problem with the Bi-Filter until I messed with the cap values in the filter section.

[Mark Hammer]

Im not sure if this maters but instead of 200k i used 220k.

There's a bunch of 200k resistors in there, doing different things.

• Replacing R2 with 220k will get you a slightly louder output.
• Replacing R7 with 220k may alter the gain of the first stage a bit.
• If you've used the variable emphasis mod, replacing R19 with 220k shouldn't do a whole heckuva lot other than nudging over the range of possible Emphasis settings a wee bit.  Given the variation in pot tolerances, that extra 20k shouldn't do much.
• Replacing R12 with 220k might alter either the feedback to IC1c (if that's how it works) or feedforward to the junction of R12/C2.

I had a problem with one of mine, where the sweep was pretty sporadic and pathetic.  Improving the contact betwen the chips and sockets helped a lot.  It is not uncommon to buy brand spanking new CMOS chips and the pins have a kind of dull surface to them.  If you can do it without wearing the sweater grandma knitted, your phentex slippers, and dragging your feet across the shag rug, gently scrape any tarnish off the pins with an X-acto blade, maybe even tin those pins a bit, and make sure you have solid contact with the socket.

The EF will not do those in-your-face ultra-wide sweeps that the Mutron does, but it will certainly do anything the DQ/NQ will do.  Especially with the shorter attack time and variable emphasis.  As I noted in the "Technology of..." paper, the radicalness of the sweep sound will depend on how far the filter sweeps per unit of time.  Sweeping over a moderate range slowly will sound much LESS striking than sweeping over a wider range very quickly.  Sweeping over a wide range slowly will not sound more striking than sweeping over a narrower range very quickly.

Although the EF doesn't sweep wide, it DOES sweep fast if you let it.

[Gus]

Mark

     Is the circuit sensitive to chip suffix and brand?  I seem to remember posts here or maybe ampage years ago about something like that.

     Ardric posted above it did not work with TI chips
 

[Mark Hammer]

Yes, it appears to be.  I couldn't quote you chapter and verse about which ones "work", but digging around with the search function should identify which brands have been found to work without difficulty.  If they haven't done so already, perhaps either Francisco Pena or JD Sleep might include that chip info in their respective PDF documents at their sites.

[Pushtone]

I finished the envelope from Tonepad using all the mods except the filter range mod.
Any mods or ideas?

When you say all the mods
does that include the suggested part substitutions in the Tonepad build reports?

The part subs in the build reports can bring the effect level up to unity and add a fuller sound.
Might get you auto wahing more.

What 4069 chip are you using. The Texas Instrument one didn't work for me.
I used the Fairchild.

I recently finished the GGG MXR EF with mods,
very similar if not exact to the TP version.
I applied the TP build report subs to the GGG version.

Mine can range from very extreme filter sweeps to sweet reggae sounds.

[Gus]

Pushtone

    What are the letters after 4069?   on the fairchild and TI chips?   This might be a big help.

[jimbob]

OK- I think I have it going now. I replaced all the 220 with 200k, I found a wire in the wrong place, and replaced the 4.7k (r4) with the required 3k. It seems this one is more sensitive to the required eaxct parts. Alot of times I can put something close in without issues but not this one. Also drinking a lot of beer while doing this in the hot arizona sun cant help much either.

I have to still try out the filter range mod after I mess with it and play with it some more.

As far as the ic's go Im using fairchild cd 4069ubcn and the 4066 I got from Smallbear. I think this thing sounds the best and can get crazy when I add distortion to it. I really like it that way but on the clean channel it still isnt as extreme as I would like. Im sure theres still a few more mistakes on it or Im just picky and asking for too much. Also I found I had a 47k in r7 near the input which is supposed to be a 200k!

Live and learn

[Mark Hammer]

R4 limits the current supplied to the chips.  Gotta have your current if you're gonna get the work done!

Breakfast, whether its electrons or toast and coffee, is the most important meal of the day.

[Fp-www.Tonepad.com]

I couldn't call the mxr ef mild. Maybe there's still some part beerrors in your build.

Fp

[phxbass]

Jimbob, where do you go locally to get components? (sorry, this probably isn't the right place for this)

I've only have a few builds under my belt and still buy my components as i need them.  Every time I go to fry's electronics i can get almost everything i need except one diode or something so get frustrated, put everything back, go home, and order from small bear.  I just hate paying shipping and hate the wait even more.  Any suggestions for a good place to go here in Phoenix?

(once again, sorry if this is in the wrong place)

[Pushtone]

Pushtone

    What are the letters after 4069?   on the fairchild and TI chips?   This might be a big help.

I used CD4069UBCN_Q
http://www.mouser.com/search/productdetail.aspx?R=CD4069UBCN_Qvirtualkey51210000

When I looked at my notes it turns out it was the  NTE4069 that did not work in the MXR EF circuit.

[StephenGiles]

I repeat myself here, but it worked for me with any old 4049 I picked out of my box - using the correct pins of course, as I had no 4069s at the time.

[jimbob]

Any suggestions for a good place to go here in Phoenix?/quote]

I order from samllbear but if im in a  pinch Ill go to the local ratshack. Ill have to check out fry's though. Thanks.