Build Your Own Clone Message Board

Hi all, great forum! First off, please bare with me as this is my very first build (beyond simple ABY or relay boxes). Also, yay for me, this effect fired up on the first try! I love it when there isn't any trouble shooting.

Also, I have read every single thread I can find here about this filter, even the old ones from 2007 (which don't really apply, but I read em anyway). The 440 filter I assembled works fine (I think, see below), ie, led lights, sound goes through, effect 'effects' the signal... it acts like an envelope filter and all knobs respond to adjustment. I'm using a Warwick Thumb Bass 5 string into a Mesa M9/PH210.

So far, I've made only one modification to the effect: I switched the Manual pot from a A100K to a C100K.... Hard to tell which I like better so far. Seemed to switch the sweep control from the last %50 of clockwise turn to the first %50 of clockwise turn. Guess I shouldn't be surprised going from log to anti-log...

My questions are:
Is there anyway to broaden the range of the Manual knob (beyond what I've done already)? ie, so that the entire range of rotation effects the signal.

Does this filter ship with the 'bass mods'? ie, the caps to use for a bass? There were no 'extra' caps in the kit. I did notice there were no .022 caps, so I'm guessing this kit has been updated for bass use. I just need a confirmation as this effect kills most of the frequencies below about 600Hz.

I'm getting a high pitched squeal (high frequency) through the signal whenever I turn the knobs to their extreme positions. Is there a way to fix this? Most notable is Attack turned all the way down and/or Sensitivity turned all the way up, and/or Manual turned all the way up (this occurred with the A100K Manual pot as well).

Is there a way to improve the gain or response of the filter with distortion effects? Or, like, at all? Though the low-end is mostly killed running bass > filter > amp, I find all but the highest frequencies remain when I run a distortion (such as fuzz) into the effect. This didn't happen nearly as much with the Boomstick Bottom Feeder I used to own, which is also a 440 clone. That is, am I possibly getting phase issues, or is it just the nature of this effect?

Most of the mods I've seen for this filter are for the first version, and thus the component locations are different, so changing R8 on the first version may or may not translate to R8 on this newest version. As such, please reference any modifications to this effect for the new board, version 1.1.

Thanks in advance. Any help you all have to offer to make this louder, more sensitive, more bass friendly and less squealy is greatly appreciated by me (and others I'm sure).

If you find that the manual pot has switched from doing nothing from 0 to 5 to doing nothing from 5 to 10 by switching from a log pot to an anti-log pot I am extremely surprised. I think you may have a dodgy or mis-labelled pot.

The control characteristic of the filter itself is logarithmic. Driving the control input from a log pot exaggerates this characteristic and turns the control into a hard L (well backwards) nothing along the bottom of the L curve and then it just shoots up. fitting an anti log pot should cancel out the filter control characteristic and render the control smooth and almost linear. That is what happened when I modified my pedal and I have plotted all of the curves to prove it. I also increased the series 10K to 27K to bring the top end down to around 2,000Hz instead of over 3,000. With a 27K and a 100K anti-log pot I get a smooth manual control over the range of a standard foot treadle wah (300Hz to 1700Hz).

I find the range of the filter in auto mode is so wide that when the filter is closed it effectively does not pass anything. It also opens quite a long way and gets pretty high when driven hard.

When you say it kills most of the frequencies below about 600Hz do you mean it never sweeps that low and those frequencies are never passed? Because if so there is something wrong with your build.

Thanks for reply Tark, most appreciated!

I did see your chart and found it helpful, and it convinced me to do the Manual pot mod in the first place.

I won't say that the new pot totally reverses the characteristic of the sweep (to my ears), more like the range is now weighted more towards 1-5 as compared to the A100K pot (5-10). I did not, as you mentioned 'increase[d] the series 10K to 27K to bring the top end down to around 2,000Hz instead of over 3,000.'

Which 10K, um, thingy did you change to widen the sweep? (please, forgive my ignorance here). I think, based on your description of the effects of this mod, and in conjunction with the C100K pot already installed, it would make the Manual knob do exactly what I want it to do.

As far as 600Hz frequency death goes... There is a noticeable difference in bass response from clean, to 'effect engaged'. More so than with the Bottom Feeder, which I only compare to the 440 clone since it too is a 440 clone. The loss of lowend seems to begin around 600Hz, I have not scientifically measured this, so take it as an estimate only. I understand that with filters, the lowend response may be temporary depending on settings. It just seems that this effect cuts a lot of the lower frequencies associated with bass guitar signals.

All that said, I understand this effect was designed for skinny string guitar. I was just wondering if there is anything else I can do to 'fatten it up', as it were, and perhaps add some gain to the circuit as well, to 'louden' it up.

The (somewhat subtle but definitely noticeable) squelchy high pitched noise at the extreme ends of the knobs still has me scratching my head too....

Again, thanks for the help!

The 10K is in series with the manual pot, I believe it is the horizontal resistor immediately below the manual pot solder pads. Making it bigger wont widen the range it will actually make it a bit less but it moves the whole thing down in frequency to put it in a more normal area for a wah.

600Hz is a pretty high frequency even for a guitar. The two things you get with guitar pedals when used with a bass are the inter stage coupling caps (input, output and any caps between stages) are not big enough and roll off to early for bass and secondly if the pedal is any kind of filter or tone control the filtering is centred an octave too high for bass.

You might also want to increase the envelope filter cap itself (4.7uF connected to the Attack pot) otherwise the sweep signal might be too rough.

However it is not unusual to find that guitar pedals use stage coupling caps that are plenty big enough for bass and as far as the envelope filter is concerned I haven't tried it for bass but as I said my filter sweep shuts right down to sub-sonic - there is no signal getting through. You can hear it sweep right down way past the bottom E (80Hz).

I suppose a rule of thumb for pedal bass conversions might be to say - well just double the value of all the caps, but it isn't always necessary.

I'll have to try it with a bass.

Thanks Tark.

That helps me understand it a bit more. And I see the resister you're talking about, under the Manual pot. I'll change that out to make it more wah like too.

Well just tried my envelope filter with my bass and it seems to work just fine to me. Sweeps down past the low E. It seems a little less sensitive than it does with guitar, I have to turn the Sensitivity control up a bit further, but my bass isn't particularly high output. I think you have to consider that a Wah Wah is essentially a moving band pass filter, so it accentuates the frequencies near the centre of its tuned frequency and cuts those above and below.

You said your pedal squeals with the knobs maxed? That is not normal at lowish amp settings. You might get feedback squeals with high gain amp settings just as you might with a distortion pedal or any pedal that adds gain at the front end.

I'm not an habitual bass player nor do I have a bass oriented rig, so I can see that a bass player might be looking for something a little bit more than I would. I suppose it is always possible that fine tuning the values in the envelope filter might provide a better bass sound, but mine does exactly what I would expect it to do for bass.

Thanks again Tark.

Would you know of a way to add a clean blend to this effect? Maybe that's what I need...

I'm not entirely certain it's placement in my pedal chain isn't a cause of my whoas either. More experimenting is definitely in order.

I was thinking the same thing - that maybe you need to mix he effect with the clean signal. Of course that will diminish the prominence of the wah effect somewhat.
I cannot see an easy way to do that within the Envelope Filter circuit because the output feeds straight out of the state variable current controlled filter itself. There is no output stage as such where you might mix some clean signal back in.

It might be good to try the EF without any of the rest of your rig. Bass - EF - amp, and see how that sounds. I have calculated the capacitive reactance of the 0.047uf the 4.7uf and the 100nf capacitors in the audio path and as far as I can see they are more than big enough to pass bass guitar frequencies, so I don't think you are losing any low end because of the coupling caps being too small and rolling off the bottom end.

I suppose you could try doubling the two filter caps to shift the centre of the filter down 1 octave - 0.01uf (10nF) connected to pin 5 and pin 12 of the LM13600. Just carefully tack another two 0.01uf in parallel with the original caps, on the back of the PCB.

The filter does sound better: bass > filter > amp
Than it does: bass > dirt effects > filter > amp

I'm wondering if its a phase issue or not. I do blend the signal with a parallel blender, but flipping the phase switches (180 only) does nothing to improve things. Maybe it's the buffer within the blender messing with things. Still, I'd like the filter more pronounced, regardless of its location in the chain.

This idea you offered intrigues me.
'I suppose you could try doubling the two filter caps to shift the centre of the filter down 1 octave - 0.01uf (10nF) connected to pin 5 and pin 12 of the LM13600. Just carefully tack another two 0.01uf in parallel with the original caps, on the back of the PCB."

I might give that a try... Would replacing the 0.01 uf caps with 0.02 uf caps do the same thing? And would doubling the other caps, like C1 and C3 next to the 455580 IC do anything?

I'm starting to look at this board in sections, and its starting to make sense to me logically, somewhat.

Thanks again for all your help with this. Its an education.

Odd - maybe your distortion pedals are driving the filter input too hard. Mine sounds amazing preceded by a BYOC OD2. I know some people run things the other way round with a wah pedal into distortion, but that seems wrong to me.

If anything buffers should help, not make things worse.

Yes ... replacing the caps with 0.02uf would do the same thing. Except the standard value series would make it 0.022uf. I suggested tacking in two 0.01uf in parallel because it is a little easier to do than removing the caps and cleaning out the holes. And it is fairly easy to reverse.

I did check the other values and as far as I can see all the coupling caps are more than big enough for bass. The only other cap is the time constant cap in the envelope follower, a 4.7uf - the size of this cap determines how quickly the filter responds to an input note and how smoothly. A small value ends up with the note itself modulating the filter frequency rather than the filter following the shape of the note.

There are three sections to this circuit - the input buffer, the envelope follower and the current controlled filter.

Thanks Tark. I'll do as you suggest.

I have a ton of stuff to do over the next several days, so won't be able to attend to this until next week, unfortunately. Despite all the head scratching, I'd rather be tinkering with this effect than doing most of all the other things on my 'to do' list. I hate it when life gets in the way of my fun.

Till then...

I did as you suggested Tark, and adding the 0.01uf caps in parallel works great. I haven't tested it with fuzz/distortion yet, but it is much deeper sounding than it was before.

I still can't figure out the high pitched squelchiness occurring when the knobs are at maximum though. I shortened wires a bit though.

Thanks again for all your help Tark.

With all its quirks, this is a cool filter effect.

Interesting, glad the extra caps helped.

>> I'm getting a high pitched squeal (high frequency) through the signal whenever I turn the knobs to their extreme positions. Is there a way to fix this? Most notable is Attack turned all the way down and/or Sensitivity turned all the way up, and/or Manual turned all the way up (this occurred with the A100K Manual pot as well). <<

When you say - with the Manual pot all the way up - you do mean with the toggle flipped to manual? Because if the Manual pot has an effect on the circuit when the toggle is switched to Auto something is wrong.

Otherwise this seems like the pedal is going unstable and oscillating. I would expect this to be most sensitive to the so-called Range control since this controls the feedback around the filter.
This pedal should be stable and the wire lengths you had on there should not be a problem. It may be a chip fault and you could try replacing those.

Thanks again Tark.

Yeah, the squealing/squelching occurs with the Manual knob only when the switch is engaged. It also occurs at the extremes of both attack and sensitivity knobs. It does sound like a 'digital' glitch, like too much power (or not enough) is going into the circuit, though I'm running on a standard power adapter.

I'll send a note to BYOC about it. Maybe they can send replacements.