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Thanks to Spin for solving my first problem with this build, now I'm officially humbled. I'm having issues as I'm dialing it in. When in filter mode, I only get sound when the sensitivity knob is turned all the way up. I seem to have an innate ability to make 1 mistake that renders the pedal useless. I'm hoping someone can help me find my mistake on this one.

Also, I get a loud pop when I toggle between env/man, don't know if that is normal. Thanks in advance for any and all help.

I went back and re-soldered all the joints, double checked everything and now I have no sound at all when in filter mode (regardless of sensitivity setting). The fixed wah is "weak" doesn't really deliver the wah it can.

Does anybody have any insight or direction? Thanks.

Some of your leads on the underside of the board look a tad long--clip them back and make sure nothing is shorting out against the bottom of either the attack or sensitivity pots.

_________________
--erin (Irish; not female)

Thanks for the reply. I have clipped anything long but I had wrapped the pots in electrical tape so I don't know if that is my problem. I'll reconnect and give it a go.

Alas no luck. When sensitivity is turned all the way up, it's almost like a delay. I'll strum a couple of times there is a short delay and only one strum comes through. The manual setting sounds like it is being played through a tin can. This is my 5th build and the only one that doesn't work, it's now a matter of pride to get it working. Any comments or suggestions are appreciated.

Sorry to hear you are having problems, this is a fabulous pedal when it is working. I have checked your pics against my build and nothing obvious leaps out. You will get a pop when you throw the auto/manual switch and the manual wah may sound weak if you don't use it in conjunction with the Q control (what BYOC refers to as Range).

Just one thing - from the pics I can't see the jack wiring. You do have those wired correctly? Are the ICs properly bedded in to the sockets? Sometimes a leg can get bent and curl under the IC rather than into the socket.

When you get it working you will find that, unless BYOC have made a recent change, the manual filter control does nothing until rotated half way and the Wah frequency then shoots up rather rapidly to about 3kHz. It acts more like an on off control than a manual sweep. If you find like me that this is rather useless I have worked out a mod that will give you a much smoother and usable sweep from this control. See my post on Improving the envelope filter manual control characteristics

Best of luck in getting this pedal working.

Oh wait - just saw your new post - the delay effect you describe sounds like the envelope follower portion of the circuit is where your problem lies. Either the time constant capacitor is faulty or the wrong value or you have a faulty transistor or diode or a short or bad joint there. It may be something around that half of the dual op-amp too. See my comments above for what you hear in the manual positon.

Tark-

Thank you, I was beginning to feel like a man on an island. While you clearly know what you're doing I am a complete noob. The Jacks are wired properly and both ICs are seated into their respective sockets. How would I go about troubleshooting the envelope follower of the circuit (in laymans terms)?

I noticed the issue with the manual setting you referred to but I assume it was part of my dead pedal. If I can get this working then I will attempt your mod. Even though I didn't notice much of a difference when adjusting the range knob. Thank you for your help.

You can at least use the manual knob and its setting to check that the filter portion of the circuit is probably working. Turn the 'Range' knob to maximum (the 'Range' or Q knob adjusts the width or resonance of the filter peak, so turning the 'Range' knob to max makes the filter effect more noticeable). Run some audio through the pedal and with the switch in the manual position (to the right) slowly sweep the Manual knob from 0 to max. You should find (as I pointed out before) that the manual knob does very little until half way through its rotation, then if you turn it slowly you should hear an obvious wah effect between half way and maximum. Then at least you know the filter portion is working.

I haven't traced it through on the PCB but a quick look seems to show that unfortunately the envelope follower portion of the circuit is rather spread out, rather than having all its components grouped together in one area. On the circuit diagram (in the instructions) it is all the bits between the 250K pot and the switch. I don't know if you have any test equipment, but first of all, with an audio input to the pedal, you should get a strong audio signal at the output of the op-amp, which should vary in level depending on the setting of the 250K pot. As far as I can see this output will be pin 7 on the 4558 (unfortunately BYOC hasn't put pin numbers or component numbering on the circuit diagram and the only view shown of the back of the PCB in the instructions is in fact the back of the Phase Royal PCB, so I cannot trace the tracks to see how the circuit is arranged by looking at that picture).

If you have a strong signal at the output of the op-amp then check that it gets to the junction of D1 and D2. At this point it will probably be distorted. If the signal gets this far set the attack pot to about 1/3rd of its rotation and switch your audio input on and off (Sensitivity at perhaps 2/3rds). If the op-amp and the diodes and the 4.7uF cap are OK you should see a varying DC voltage of a few volts at the base of the transistor and also at the emitter (you should be able to use an ordinary multimeter to check this). Check that the collector of that transistor really is connected to +9.

BE VERY CAREFUL when probing around the circuit to make these measurements. It is usually necessary to apply some pressure to make a probe connect properly. It is all too easy to slip with the probe point and short something out which may cause permanent damage. I suppose another thing you could try is, with the pedal un-powered (remove the battery) just check around the envelope follower part of the circuit with a meter set to low current continuity check just to see if the point to point circuit connections are being made (and/or a really close up examination of the envelope follower part of the circuit using a magnifying glass and a bright light - in fact perhaps you should start with that). You might want to used a blunt pointed probe to carefully chip away the flux residue between some of the tracks and pads. Oh and the junction of the 150K and 22K should be biased at around 1.3 volts with no audio in ... I think.

Since you are getting something happening with the env follower every few strums that might indicate that either the op-amp is not amplifying the signal properly or the rectified version is not charging the 4.7uF cap properly - might be a bad cap or transistor.

The envelope follower works by that half of the dual op-amp amplifying the input signal and feeding it to the two diodes. The diodes rectify the AC signal and the rectified signal is then used to charge the 4.7uF cap through the Attack pot. This produces a rising and falling DC voltage at the base of the transistor that roughly follows the amplitude of the input signal. This envelope voltage causes the transistor to pass current into the current control input of the two transconductance amplifiers in the LM13600 and as a result sweeps the filter peak frequency.

I've had another thought about what might be wrong. It's at least worth checking and is easily done with a multimeter.

Check all your VRef points.

The two 22K resistors, shown at bottom left of the circuit diagram, form an equal divider across the battery voltage, decoupled for AC purposes, to ground from their junction by a 4.7uF electrolytic capacitor. VRef should therefore be close to 4.5 Volts (9Volts /2). Check that when the pedal is powered everything labelled VRef on the circuit diagram really is at VRef. In addition, without any audio input (but of course with a jack inserted into the input so the pedal is powered) the output pins of the two halves of the dual op-amp (pin 1 for the input buffer and pin 7 for the envelope follower amp) should also sit at VRef.

If the op-amp that drives the envelope follower is not correctly biased from Vref that might explain your symptoms. That half of the op-amp gets its bias through a 150K to pin 6.

Tark-

Checked all the values & continuity points along the path and everything checked out OK. So I reassembled the pedal and low-and-behold it works. However, the sensitivity pot is not consistent, sometimeswhen turned completely clockwise I get the same dead air as before. But if I slowly work it clockwise it works throughout the entire rotation.

I think there is still something off however. When I play full chords I get sound but when I play individual notes there is a delay between when I hit the note and when I hear it through the amp. If I play a succession of notes "quickly" (nowhere near Steve Vai speed) it's as though the note doesn't have time to "come out" before the next note is played. Also, the tone is not spectacular (tinny) but I will hold off until I can play through my main amp as opposed to my little practice one (it's a bit late and the wife & kids wouldn't find the troubleshooting assuming).

I agree about the manual pot and will hit you up in a bit with questions on how to go about that. Thanks again for all your help.

Glad to hear you are making progress.

The response of the pedal may take some getting used to. It is of course touch sensitive and depending on the control settings it can either be very touch sensitive or very insensitive. You need to set the controls carefully and adjust your playing technique (in a good way) to get the best from the pedal.

In this particular design, in auto mode when there is no note input, the filter sweeps off well into the bass, so it acts like a gate. As far as I can tell it sweeps down well below the 300Hz or so you get on a normal Wah Wah, which still passes some signal even when the treadle is heel down. On the other hand when driven with a strong signal it sweeps up perhaps higher than a normal wah. If you drive it hard all the time and set the Q control (Range) to maximum you will have your signal passing through a narrow width filter sitting at a few kHz, so yes this will produce a very thin, tinny sound. Back off the Q to about half way, Attack to 9 or 10 o'clock and Sensitivity to around 1 or 2 o'clock (guitar vol and tone at max) and play defined separate notes and you should hear something like a standard wah sound sweeping up and down on every note (providing you apply some damping between notes rather than letting them ring on).

Most envelope followers, and this one is no exception, can only approximate following the true envelopes of each and every note. Every time you play a note the signal starts charging the 4.7uF, building a voltage on it. As this voltage rises the filter should sweep open and you should hear a wah effect on the note, just as if you had rocked your foot forward on a standard wah starting just as you pick the note. In this respect, because the voltage takes time to build on the cap, you will hear what you describe as a 'delay', just as you could say there is a 'delay' between you picking the note and rocking a standard wah fully forwards. Once that voltage has built up on the 4.7uF cap it will take a certain length of time to fall again. If you keep playing a series of notes without damping in between notes the repeated signal will simply continue to add to the voltage on the cap and the filter will open further and further. Or if you set the Sensitivity to a low setting it may take several successive notes being played before the voltage is high enough to open the filter to the point where you can hear anything. In this situation, if you are playing quietly through a very small amp with no bass response then the filter may never open far enough for the signal to be audible.

I don't think I have ever turned my Sensitivity control to maximum (leans down and tries it - nope I still get a usable sound) but the fact that yours cuts out indicates either a faulty pot (cracked track, dirt and de-soldering debris inside or poorly connecting wiper perhaps) an intermittent solder joint or short somewhere. With the pot at full clockwise the 1K feedback resistor connected to pin 6 of the op-amp should be effectively grounded for AC and the gain of the op-amp stage will be set by the ratio of the 1K to the 1M at 1,000. If anywhere on the 1K leg of the feedback path goes open circuit the gain of that op-amp drops to 1, so you will have the minimum of signal driving the rest of the envelope follower. I suppose another possibility is that the 0.1 cap is shorted inside and turning the Sensitivity control to max is affecting the bias of the op-amp, forcing the output to swing up hard to the +9 supply voltage. This is easily diagnosed by connecting a multimeter set to the 20 Volt range to the output of the op-amp and turning the Sensitivity pot back and forth. The output bias point of the op-amp should remain steady at 4.5V (assuming there is no input signal or hum pickup to disturb the DC readings).

Actually this brings up another possibility for modification. Below a certain point the gain of the envelope follower input op-amp may be too low to be useful, so the range of the Sensitivity control could perhaps be offset a little by inserting a resistor in parallel with the pot.

The simplest way to fix the manual sweep is to replace the pot with an ANTI-LOG version. As far as I can see this would be Mammoth Electronics - C100K : RV16AF-41-15R1-C100K at $1.09. If you feel that on your particular pedal the upper point of the sweep is too high (you can hear this with the old pot before you make any mods, just turn it to maximum) you can shift the entire sweep range down a bit by increasing the series resistor from 10K (R16 - one of only 2 resistors on the BYOC diagram to have a number). I went for a 27K on my pedal.

The other way to go about it I have already described in my previously posted link in this thread. Upside - you use the pot you have ... Downside - some messing around to make the mod and the control works in reverse with the lowest filter frequency at full clockwise.

There are various opinions floating around on the internet as to whether or not reversing the connections of an audio taper / log pot produces an anti-log characteristic. Most authoritative opinions are that it does not. I can assure anyone with the view that it doesn't that it does, but with the obvious proviso that the direction of operation is reversed.

Tark- OK, so this pedal continues to baffle me. I hooked it up to my pedal board and I had the same problem, manual worked but nothing on envelope. After much cursing and huffing a puffing, I gave the nut maybe a 1/2 a turn on the sensitivity knob and it started working. When trying to dial it in, I still get no sound when sensitivity is turned completely to the left. I have to go about half way before I get something and even then it doesn't sound real good. When adjusting the attack knob I experienced the same issue as with the manual knob in manual mode. A slight turn produces significant changes. Then with sensitivity turned all the way to the right and attack all the way to the left, I get no sound. Instead there is a strange electronic sounding crackle. Plus there is a significant loss in volume when compared to the clean signal. I should mention that all the troubleshooting was done "off the board" with no other effects in the chain.

When checking the 4558 here are the settings I get starting at top left:

4.68 9.3
4.67 4.63
4.24 4.67
0 4.58

None of the values change when turning the 250k pot. I'm at my wits end with this one but will not give up! Thanks in advance for your help, again.

When you say you turned the nut on the Sensitivity pot do you mean the fixing nut? If so that means that your turning the nut has put some mechanical stress on the circuit and made something connect that previously was not connecting. There is a dry joint somewhere or the pot is faulty. There are several techniques to use to locate a dry joint - under a bright light use a fairly high power magnifying glass and examine each joint slowly and carefully. The solder on a joint should appear smooth and shiny and should obviously have alloyed with the surface of the two conductors it is supposed to join. Sometimes a layer of oxidation or dirt on say a resistor lead may have stop the solder bonding. Another thing to do is with everything plugged in and switched on and a signal running through the pedal just poke around the suspect area with a non-conducting probe, such as a tooth pick. You can normally prod a bad joint and get the pedal to burst briefly to life.

It sounds to me that it is the Sensitivity pot itself that is the problem. First just re-solder the pot connections on the PCB. Look carefully at and tap on the cap and two resistors and their joints near that pot on the circuit diag. You could try just soldering in a temporary shorting link around that pot and see what happens. That is equivalent to having the Sensitivity pot on maximum and you should get a strong signal through the pedal.
The Attack control is reasonable sensitive and affords a wide range of control although it is not as on/off as the Manual control. The Attack and Sensitivity control do interact to a degree. With the Attack turned up even a little you will find the Sensitivity will need to be about half way up or further. With Attack at minimum the filter opens up very quickly and you do get some very snappy synth type tones. The volume loss is worrying, this should not happen.

You could try just briefly connecting a 100K resistor across the 150K that connects to D2. This will change the DC bias feeding the 4.7uF and should cause the filter to open up every time you make contact with the resistor. If the filter opens up then that eliminates everything on the circuit to the right of that point. Careful not to short anything out if you try this.

The voltages you give for the op amp all seem about right.

Other than that it starts to get to the point where you need to go through the circuit point by point with an oscilloscope.

OK- I'm going to swap out the 250k pot (I assume it is a reverse taper, the instructions say reverse audio) as well as the manual pot (with another reverse taper). While I have it apart, I will recheck all the solder joints. This is my 5th pedal and haven't had any issues yet with my soldering so I'm hoping it's a faulty pot.

Any suggestions on the loss of overall volume? Thanks again for all the help.

Well a large overall loss in volume would indicate there is something wrong with the main signal path through the other half of the op-amp input buffer and through the filter. Is this loss in volume present when you run the pedal in manual. If so this dose indicate a problem with the main signal path. If not then not.

In auto mode with the filter shut down (as it is when there is no input signal driving it, if your envelope follower is not working the filter wont open) it is normal for there to be almost no signal. The filter sweeps down to a very low frequency and acts as a signal gate.

If there is a problem with the main signal path you can narrow down to where the problem occurs using an AC coupled probe (a series cap in front of the amp input - some amps already have an input cap but some don't) connected to a small audio amp (a small battery powered practice amp will do). BYOC provide such a probe as their Signal Tester Kit, although you can make one yourself. Follow their instructions to build and use. With a signal source running into the pedal and the switch to manual so the filter is in theory partly open, just move the probe through the circuit, starting with the input jack and touching on significant points such as the output of the op-amp buffer and pin 8 of the OTA.