Name:Miguel Angel Lamas
Date:4/17/2010
Build Report:I have done this proyect after 2 months, becasue y bougth another CD4069 instead CD4066, so i decided to leave the proyect, but when i figured out the problem about the CD4069 I run to the shop to buy the original CD4066 so check it out, I guess I'm not the only fool that make that mistake. Other thing that i cannot find out is why when I turn it on, i feel like the volume decrease a little bit, so I have to turn up the volume in the amp, and it's not cool to go check your amp everytime you turn on the stompbox, so please if you got the same problem and you solve it please let me know. thank you very much, Good Luck

Name:BobP
Date:7/1/2009
Build Report:I built this with TI chips and it didn't work... Tried it with Fairchild and it still didn't work... I adjusted R16 (The ground side of the clock voltage divider) using a 100k trimpot. I got both the Fairchild and the TI chips to work.
I have all 3 TI chips in there now with the clock voltage down to 1.62v and it works like a charm!

Great sound! This should be fun playing some Grateful Dead on!!!

peace
BobP

Name:FIlip
Date:6/21/2009
Build Report:Hi!
I finished building MXR EF about 2 weeks ago , and I have to say that it is very great sounding pedal. I used the original ICs CD4066 and CD4069 and it works as it should. I had to connect 10M +10M+2M to get the value of 22M ohm. If You want some mode to do , make the emphasis control and reverse sweep. I have also make the filter range mod but it doesn't give any strong change of sound.

Name:Aditya
Date:4/18/2009
Build Report:This is my 3rd tonepad build. worked right off the bat. built it with all 3 mods - reverse sweep, range and emphasis. this pedal OWNS on guitar or bass! i love the degree to which i can control and tweak the sound with the mods too.

if there is one mod that MUST be done, it's the reverse sweep switch. i like all the mods though, and would recommend them to anyone who isn't afraid of a bit of wiring hassles. thank you very much again francisco, and best regards from bombay!

Name:Charles Stieg
Date:3/28/2009
Build Report:Did not work at first. Used IC sockets. The Problem was that the Texas Instruments (TI) 4069UBE chips DO NOT WORK in this pedal. I switched them to Motorola, and it started to function as it should. DO NOT USE TI BASED CHIPS IN THIS BUILD

Name:fLuXx
Date:12/26/2008
Build Report:I've been building this thing for a while now, and now, when I'm finally done, I'm fairly satisfied with the result. I'm not going to put it in a box yet, however, as I plan to experiment a little before I close the deal. When I first turned it on, it wouldn't work, because I had errors on my PCB (I etched it myself), as usual. When I fixed it, it finally worked, but not quite as I expected it to work. Since I have humbuckers, the treshold level has to be maxed out so I could get some sweep. I placed a resistor in series with pot temporarily, but in future I'll either change the R5 to a bigger value, or buy another pot. I'll decide experimentally. Same goes for emphasize control. I am satisfied with attack as it is. As for filter range mod, It wouldn't work like I expected it to work. Turns out 560pF is too little for me, the sound just hissed and it was useless, so I changed C6 and C7 back to 1nF. Now it's way more acceptable. I will try to change Ca1 and Ca2 to 1nF as well to see wether it will suit me better. The mod itself is very useful and it gives a lot of different sounds, so it would be nice to put a multiple-position switch and connect all the different capacitors to improve versatility of the device. I'm not going to do that as I can barely fit this version im my hammond 1590B box, but I would recommend everyone to try out that mod if they have space. I'm not yet sure if there's a volume drop with using the effect, as I haven't assembled my bypass switch yet, but if there is, I'll try to fix it by following advices from other DIY-ers who wrote their build reports (thanks in advance).

Tweaking really paid up. When I finished it, you could barely tell it was working - there was no obvious sweeping, but with a little effort, it now quacks like a duck.

This is a true DIY project! It has sooo much space for moding and tweaking and experimentig, fairly easy to build, fairly cheap parts and a good effect as a whole. The experimentig here really is well rewarded by the results. Francisco, thanks a million, you really nailed this one.

I will report again, when I put it in a box and try it out in detail. I'll let you know what tweaks I applied.

Name:Indrek Haav
Date:4/22/2008
Build Report:I've built the MXR EF on a Tonepad PCB. No problems other than the 4069 ICs. I failed to read the build reports before assembling the pedal, so I learned the hard way that TI chips won't work. I ended up ordering both Fairchild and Philips (NXP) chips, so I figured I might as well compare all the different combinations of them. Here's what I found.

TI chip in IC2 does not work - the sound is simply cut at the beginning of the sweep.

TI chip in IC1 with a Fairchild in IC2 produces a filter sweep, but the sound is also distorted a bit. With an NXP in IC2, there's no sweep (still distortion, though).

All other combinations work fine - filter sweeps, no distortion. In my opinion the sweep was a little weak with NXP chips in both positions, but the difference was almost negligible. In the end, I went with Fairchilds in both positions. IC3 was already Fairchild.

Bottom line - don't use TI chips. I bought mine from SmallBear. I'm not sure whether they only stock TI, or other manufacturers as well, but you should definately send Steve an email and ask about this before ordering.

In the US, you can get Fairchild chips from Mouser. In Europe, Banzai Music stocks Fairchild and NXP.

Having sorted out the IC problem, I'm fairly satisfied with the pedal. I built it with the reverse sweep and filter range mods. The effect is not quite as dramatic as I'd hoped, so I might look into modding it a bit, but as it is, it's nice for some reggae or funk rhythm playing.

Name:Reeko
Date:3/9/2008
Build Report:Excellent! It was the envelope i was looking for, a lot of tweaking to achieve every kind of autowah sound, did the emphasis mod but also changed some values to obtain a proper volume and a good filter cap. Now there is no volume drop when is active.
I've changed C4 to 0,01 uF, R1 to 2,2k , R2 to 150k, and to make it better sounding with humbuckered guitar I've raised thresold pot to 1M(log).
I've used all philips HEF 4069 and HEF4066.
I've also built DR quack envelope filter, but this MXR is astonishing better!

Name:qwixzh
Date:5/26/2007
Build Report:Same problem, got to build the pedal first before knowing that the TI 4069 chip doesnt work, replaced the TI with National Semi and work fine. Have to delete C4 to fix the low output problem. So lesson, before buying the parts, read build reports first (the thing i failed to do) youll have to eventually read them later plus the frustration during first power-up! ;-)

Name:Andy
Date:2/2/2007
Build Report:I built this circuit and it had a low output and didn't wah. I changed C4 to a 0.001uF capacitor to cure low output.
I changed R14 to 100K and fitted the emphasis control mod leaving R19 as a 220K and fitting a 1meg variable resistor now it wahs very impressively.
Fitted the Filter mod which has some effect on the output tone and the reverse sweep mod which gives a different sort of wah.
By adjusting attack, threshold and empasis I can get all sorts of different wah sounds, a very nice effect.

Name:Steven
Date:6/4/2006
Build Report:soy de venezuela. este proyecto funciona perfectamente y tiene una gran gama de sonidos. si consiguen los componentes y lo arman tal cual indica el plano con todas las modificaciones, disfrutaran de un buen efecto. Gracias Frncisco Peña, Eres el hombre.

Name:Steven
Date:6/2/2006
Build Report:Esto esta del carajo tipo echenle cojones.

Name:John
Date:10/23/2005
Build Report:Excellent filter effect! mine could benefit from using a boost pedal. I had problems with the TI Ic's as well, had to switch out the 4069's and replace with Fairchilds. Works great!

Name:Bill Mathewson
Date:9/9/2005
Build Report:Built this baby up, had some trouble getting the ICs to work, couldn't use the TI ics, replaced with Fairchild. No problems. Very tweakable, good range. Crunches with hot pickups though, so you have to keep the volume a little bit lower. I'd like to get it to work with a bass by lowering the overall filter frequency. But not sure how to get that to work. If anyone has done this, please tell me how. Thanks tonepad for the great projects and build reports which helped me get this to work.

Name:Hammer
Date:11/1/2004
Build Report:Hi!!! once again from Argentina enjoying an amazing project!!! It was very friendly to build for me. The IC's (both 4069 and 4066) were obtained disassembling a crashed-old wireless telephone Sanyo and the others discrete components easy to ackire too, even in my country.
Nice envelope filter with several capabilities to modify the sound changing or adding a few components. The MXR Env Filter sounds with a special personality, remembering some early '80s bands.
Good taste, Tonepad and very well developed project !!!

Name:Johan
Date:4/8/2004
Build Report:Hi, Just finished or should I say got it working. Used FPs great layout (as always) but it didn't work. The 4069s ordered from SmallBear (TI) did not do it as mentioned in other reports. But switching only IC2 did not help either. It was not until I also switched IC1 to a Fairchild alternative that it started to work! Built the emphasis and reverse mod.
Changed components:
R1-1k
R2-100k
R16-62k
C2-1uF
C4-0.01uF
It is a great inspiring effect!
Thanks FP for THE best DIY effects site.

Regards from Sweden,

Johan

Name:Gringo
Date:2/15/2004
Build Report:I built it stock, except for the 62k from Vr, changed to 100k as sugested. Used a log threshold pot for increased sensibility in this control.

At first it didn't wha, but cut the sound at the beggining of the sweep. Turned out that this build won't accept a TI chip at IC2 (thanks to Bill_F for pointing that out), changed that one for ANY other brand and worked ok. TI chips at IC1 and IC3 worked fine.

Now the sound: This is a temperamental one, not the fire-and-forget kind of fx. When it says pick-attack sensitive, it means it. Hit softly and will sound bassy, hit hard and you get more sweep (my favourite part), hit harder and you'll sweep up to the treble side of a wha (quite harsh). You regulate this with the threshold pot, to some extent.

The only problem with this build is the volume drop. I just went with the brute force approach and stuck an lpb1 at the end of it, with a trimmer to set it just above unity.

Mods: tried the reverse sweep but no cigar, i wonder if the TI chips are messing with it again.

As noted before, if you are going to do 1 mod, do the emphasis pot. As its name indicates, it'll accentuate/soften the sweep to your liking. This is specially useful if you have hot pickups (like me) to stay away from the "clipping zone" (along with careful strumming), or to get more tight sweeps with average pu's/single coils or at the low e string.

Very nice wha/quack, hard to tame, i like challenges :)

Name:Nano
Date:9/22/2003
Build Report:This is my second project from the Tonepad site (the other one is a PEZ 45)and sound really good for me.
I included all the mods and change some values:
C2: 1 µF
C4: 0.01µf
R16: 68K

This is the best site for DIY.

Thanks Francisco.

Name:Dade
Date:6/13/2003
Build Report:Built it in a couple of days without any trouble except for some components which are very difficult to find here in Italy!I etched pcb using UV process and H2O2 + HCl. It sounded great even after the first test and without any mod. Next days i'll fool around with any possible modification!

Name:Steve
Date:5/26/2003
Build Report:I have fooled around with the mods and got a great sound out of the reverse filter! sounds great for reggae lead lines! I changed the values of a few things though. R1 is now 1k (100 Ohm as mentioned by another person made my unit go crazy!). R2 is now 100k. C4 is .05uF. C2 is 1uF. I have wired all the mods and they sound great! I am a beginner to building my own circuts, but with a little help this one came off perfect!

Name:Steve
Date:5/23/2003
Build Report:Just finished wiring this up on my breadboard. Wouldn't do anything other than cut the high frequencies when I first tried it. Changed out some older 1M resistors that I had for new metal film ones with spot on accuracy! Now the pedal works fine. The Emphasis control is great. Don't have the caps on hand to try the Filter Range Mod. The reverse mod did nothing for me at first. I am going to have another go at it though. I do get some crazy high freq sounds when I turn the Threshold know all the way one way. Not sure if this is normal. Any ideas.. email me. I'll repost more as I fool around with the mods and such.

Name:tomboy
Date:4/5/2003
Build Report:I made it last month after I did a redraw of the layout.
It work within the first test.
I included all the mods which are really cool. Except the reverse sweep which is a bit difficult to get a good sound out of it. I did change the output cap value for less bass response - I believe it's absolutely important.

Finaly I think it is a good env.filter and easy to build for a medium experienced builder (as I am;o). I'm also very happy with its sound.

Name:John Egerton
Date:3/30/2003
Build Report:Well this is my first project from the Tonepad site and may I say it was well worth it. very nice clean wah sound, performs especially well on the lower strings for a chunky, slappy wah effect. I'm going to attempt all the modifications now so I'll get back to you all to tell you how its gone.

I lost the 10k resistor for R10 and so temporarily substituted it for a direct wire link.. I don't know if this made a differece but it does sound really good.. I'll see what happens when I buy a replacement.

Name:Tim
Date:3/12/2003
Build Report:Here is my 2 cents on the low-pass made by R1 and C4: The original design has frequencies start getting cut at "A" 440Hz. If you short out R1 and give the strings a whack, it is high frequency mahem. I solved both the frequency issue and volume drop by installing an LBP-1 booster in the R1 spot.
I still have one issue: with a humbucker, when I attack the string with the force of your average strum there is distortion (happened before the LBP-1 addition, I just hear it better now)that sounds clearly like a clipping (nasty) op amp. Any helps on this one? Since these are inverter amps, I don't know how to calculate gain (IC1c and IC1e, I assume set the gain level).
All other functions (all mods included) work as they should.

Name:Erick Cohn
Date:3/5/2003
Build Report:When I first completed this circuit, it didn't sound all that impressive. It didn't wah + output was fairly low. I did some tweeking with the caps and resistors near the output jack, which constitute a bandpass filter. It sounds really good now and I really like this effect. I don't recommend taking out C4 because even though that will allow higher frequencies to pass on the guitar, it doesn't attenuate much, if any high frequencies going way into the MHz range. This makes it possible for radio interference.

Name:Brett
Date:3/2/2003
Build Report:One more build report. I tested some more mods and also found C4 should be < 0.01uF (I settled on 0.001). Output cap of 1uF (monolythic or MKT) also helped.
But neither of my MXR EFs auto-wah unless I feed them through a high-output pedal! (I use an Orange Tonebooster; dead simple 1 transistor circuit). Why? High output impedance from the guitar or low output signal or both? In any case, with a pedal in front, it works great. I love that funky sound! Makes some of that wild Jimi Hendrix wahing a little bit easier.

Name:Peter Lund
Date:2/28/2003
Build Report:I have solved the problems with tonesuck and defeat in volume:

Leave C4 out. Change C2 to 1 uf. Use a filmcap I you can. Change R1 to 100 ohm. Change R2 to 100K.

This mod makes a huge differens. I'm 100% satisfied with the effect now.

Name:Brett
Date:12/30/2002
Build Report:A follow-up to my earlier report and comments. The tone problem will be worst when this pedal drives something with high-impedance because there will be a cut in treble. This was probably designed for input to a low-impedance transistor amp where the output stage would have cut plenty of bass, too (ie. two wrongs making a right). But driving anything with high impedance will correct the bass cut, while the treble will be very weak. To help correct the treble cut, decrease R4 from 0.1uF to 0.01uF. Because virtually nobody will be driving a low impedance device, the bass cut isn't really an issue, but increasing the output capacitor to 1uF would be good insurance (but use an MKT metal film capacitor. Always avoid passing the signal through an electrolytic, or if you must, use tantalum not aluminium, which have terrible dielectric properties).

Name:Peter
Date:12/28/2002
Build Report:Just made this unit, but not without trouble.

Sounds great though.

You have to check the parts very carefully before you begin.

Like others have reported, your should try to change R16 down to 62K. 47K is too small a value IMO.

I think that the bass is cut a little to high. If anybody can figure out which cap to change to get a more flat responce, please mail me.

Could also benefit from a gain opamp at output, since output is faily low.

The reverse-mode does not work. I have double-checkked everything, with no change.

Any idea whats wrong?

BTW: I'm using Phillips HEF4066 & HEF4069.




Name:Tim
Date:10/25/2002
Build Report:Built with all mods. I have used this pedal at a gig to mimic the keyboard part on "Won't Get Fooled Again" and it does a great job due to its sensitivity to picking dynamics. Volume drop when turned on that varies depending on settings. Could just be frequency related.

Name:Brett
Date:5/19/2002
Build Report:This was ok to build. (I think blew up one of the CMOSs, which took a while to work out). I used press-n-peel for the PCB, cos it is awful otherwise. Emphasis control is essential, reverse sweep doesn't work on mine, and attack control is fairly weak. Like other reporter, I took R16 down (to 47 k). Has anybody else noticed the weak top end (top 'e' string at 12th fret and up is almost non-existant). Might need a treble booster pre-input. Could also benefit from a gain control at output, cos output is faily low. In spite of these gripes, it's a pretty cool unit. PS.
I'm an average ability gtr player and FX builder.

Name:Jason Doughty
Date:5/3/2002
Build Report:Just finished wiring this bad boy up, and getting ready to put her in a big hammond C-size box with funky colors. After some debugging (make sure you check your 22M resistors!) this thing is running. I went for both the emphasis and reverse mod's. I now have one of the funkiest envelope filters I have ever heard. I love the reverse mode! Thanks

Name:Frank Clarke
Date:4/15/2002
Build Report:It's not hard to build, since the transistors are on discrete chips. It does autowah well. The 2 knobs aren't quite enough, but the reverse filter mod works and goes "toyt toyt" like on John Martyn records. So you can make it more flexible.
I used 4069UB, but NTE4069 also works.
22Meg resistors are strange, remember to order some.

Name:Gino
Date:3/8/2002
Build Report:I built the thign with all mods. At first the reverse did nothing, and the normal setting wanst sweeping. I modified it by changing r16 to around 62k. That helped a lot. Some chips may react differently, so tweaking this resistor may need to change dependant on chips used etc. Just a heads up! Otherwise a VERY cool unit! Great for the '70s "Jerry Garcia" thing!!!

BTW. Great site, Francisco! I plan on doing a Phase90 SOON!

Name:Matt Burnside
Date:3/5/2002
Build Report:I put this one together using all of the mods available, and it sounds great. If you are only going to do one mod, do the emphasis pot. The reverse sweep is nice; the filter goes from high to low when you pick.

The range mod is fairly nonessential, but it does increase the flexibility of the circuit.

The whole thing can fit into a Hammond 1590BB; I mounted it with the 3 pots along the top, then a second row of toggle switch -- LED -- toggle switch. I'll post a pic as soon as I get the knobs put on.