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PostPosted: Thu Jun 11, 2009 7:48 am 
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I just realized that the thread that had a lot of the mods for the Filter is gone/lost/missing...

...SO, if you have done a mod that works for any version of the BYOC Envelope Filter, please post it here.

THANKS!

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PostPosted: Sat Jul 18, 2009 2:45 am 
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Hi, so i looked all around the forum for the backwards sweep mod on the envelope filter/ fixed wax pedal. I was wondering if anyone could post it for me. I would gladly appreciate it. Preferable a diagram because im not so savvy at reading schematics. Please and thank you.
Kaleb-


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PostPosted: Sat Jul 18, 2009 2:52 am 
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o nvm i just found it.


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PostPosted: Fri Sep 25, 2009 8:48 am 
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kaleb wrote:
o nvm i just found it.


linky?

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PostPosted: Tue Jan 10, 2012 7:04 am 
As far as I am concerned, replacing the Envelope Filter Manual pot with an Anti-log (C) is absolutely mandatory. As shipped with log control the Manual control just exaggerates the natural exponential control characteristics of the state variable filter and the Manual control operates more like an on / off control for filter = 400Hz to filter = 3000Hz. Left like that an otherwise great feature is just not usable.

I have already documented the pedal responses and the mod in detail here - http://www.buildyourownclone.com/board/viewtopic.php?f=12&t=34270


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PostPosted: Thu Mar 01, 2012 12:57 pm 
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There's a mod for a switch that will reverse the attack/decay, right? Does anyone have the wiring for that?

Considering a tone knob, too for to get teh phatness. :) Edit: I don't suppose I can use a pot instead of a rotary switch for the tone? I'm not sure what the pot value would have to be.

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PostPosted: Thu Mar 01, 2012 2:04 pm 
A tone knob??

Do you mean a switch to change the two filter caps? There isn't much point because the filter swings a long way in auto.

Off hand I can't see an easy mod to reverse the auto sweep direction. i guess you could move the filter tap from the output of the first OTA to the output of the second (the emitter of the second darlington).


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PostPosted: Thu Mar 01, 2012 2:38 pm 
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Tark wrote:
A tone knob??

Do you mean a switch to change the two filter caps? There isn't much point because the filter swings a long way in auto.


I'm not totally sold on the need for it, but wouldn't it shift the total response darker or brighter, just like in a wah with a switch?

viewtopic.php?f=21&t=12109&p=95314&hilit=rotary#p95314

I see now I can't use a pot, because it would have to change cap values simultaneously.

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PostPosted: Thu Mar 01, 2012 10:08 pm 
Yes changing those filter cap values would shift the entire response. But my point was that the swing of the circuit as it stands is quite extreme. In auto mode when there is no input signal the filter sweeps to a very low frequency. In fact I'm not sure if it doesn't close down completely all the way to DC. Then when you do have an input signal and you increase the sensitivity the filter opens up to a relatively high frequency.

In comparison the range of a standard Wah is much smaller and you can benefit there by switching in a different cap for bass guitar, although I don't see the point of a range switch with several caps for use with a standard electric guitar. The Crybaby design is pretty much fine tuned to suit an electric guitar in normal tuning.

This does mean that the Envelope Filter does have a very distinctive sound, but when you turn the sensitivity down for the more subtle effects where you want to limit the upper point of the sweep you have to be very careful with your picking strength otherwise some notes don't open the filter at all. I have found you can help this by using a compressor in front of the Envelope Filter, although this leads to another range of interesting effects and sounds because the compressor alters the shape of the note envelope.

What might be more useful is an offset control which allows you to set the bottom rest frequency of the filter. So like a pedal wah which is rocked back you still get some low frequencies which are audible. This would then allow you to set the lower frequency to pass quite a bit of the guitar signal and use just a small amount of sweep for a subtle and less violent effect. I'm thinking about working on a mod that would switch the manual control to become an offset control.

However even as it is I love this pedal. combined with an OD2 and maybe a compressor there is an absolutely huge palette of tones available. You can get everything from almost a normal wah pedal sound, to swell pedal effects, to very synth like sounds with fast poppy attacks. And once you fix the manual pot sweep it makes a great parametric tone control for distortion.


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PostPosted: Fri Mar 02, 2012 4:10 pm 
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Quote:
What might be more useful is an offset control which allows you to set the bottom rest frequency of the filter.

Word. That would indeed be interesting :)


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PostPosted: Sun Mar 04, 2012 3:58 pm 
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Now that it's assembled and I've spent a day messing with it, it does seem to be a much more violently wide range than I expected and the 'tone' mod would have been pointless. (I had messed around with some other E filters like the Malekko that didn't have nearly so big a sweep or fine control.)

I really like this one. It interacts with other effects boxes in very unexpected ways. The most interesting I've found so far is with my delay pedal - it generates controllable feedback on a lot of notes without much extra volume. It really seems to like a compressor in front. Gets along fabulously with darker dirt boxes.

I've spent a day finding all sorts of filter sounds that aren't just funk, like synth stuff. Very inspiring effect.

I don't find the fixed wah mode very useful at all and it would free up some space for a switch. The offset control sounds interesting, but I don't see fitting it in the BYOC box since the switch is board mounted.

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PostPosted: Sun Mar 04, 2012 11:57 pm 
Well if the manual control has not been changed by BYOC since my pedal the manual control will essentially be almost useless. My pedal shipped with a log pot for that position when what it needs is an ANTI-log pot. With the log pot the Manual control does nothing until past the half way mark. From that point on the filter frequency just shoots up, there is little fine control. The knob operates more like an on off control - filter low filter high.

With an anti-log pot the manual sweep is much smoother. You can use the manual settings as you would a 'half-cocked' wah pedal for a certain tone. It works great as a powerful tone control for a distortion pedal placed before the Envelope Filter.

As you say there are a lot of sounds available and it only takes a small tweak of the knobs to get a completely different sound. The offset mod I was thinking of would either use the existing switch or an extra off board switch. I'm thinking to try and arrange it so that the Manual control is switched either to Manual as it is now or in auto mode the manual control is still active and simply sets the bottom frequency. But I have yet to work on the details to see if this is practical.


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PostPosted: Fri May 25, 2012 10:00 am 
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Tark wrote:
Yes changing those filter cap values would shift the entire response. But my point was that the swing of the circuit as it stands is quite extreme. In auto mode when there is no input signal the filter sweeps to a very low frequency. In fact I'm not sure if it doesn't close down completely all the way to DC. Then when you do have an input signal and you increase the sensitivity the filter opens up to a relatively high frequency.

What might be more useful is an offset control which allows you to set the bottom rest frequency of the filter.


I just build my Envelope Filter last night... it took me an hour or so to build and 5 to tweak hehehe. I have found that I definitely want the concept you describe above Tark. I did make changes to all of the film cap values (thankfully I knew I was going to want this and socketed them all during the build). Here's what I ended up with (caviat - I'm doing it all from memory at the moment, and I changed these so many times last night I'm not 100% certain but I believe these to be correct)

Attachment:
Env Filter Cap changes.jpg


This gave me a smoother filter tone (most especially the .01uF at the top) so that the effect is much more subtle (less in-your-face, considerably less tinny at the top of the sweep). Another change that I made was to swap out the 4558 OpAmp for the Burr Brown Hi-Fi one (I have a habit of this change in most of my pedals) and the tone of the effect seems cleaner, more crystalline (Hi-Fi, in truth). After swapping, re-swapping, un-swapping, and finally settling on the caps listed in the picture (90% certain - I'll verify when I get a chance) I still foudn that the bottom end of the sweep essentially functions as a gate effect, which is a fun effect in its own right, but as I tend to use my Envelope Filter somewhat regularly (currently have a Riddle: Q-balls - which I intend to replace with the BYOC Env Filter, for a lot of reasons:standard power source, footprint, and the fact that the Q-balls adds a huge signal boost when active) I need for some signal to pass through even at a lower volume. The compressor helps certainly, but it also pushes the attack of the filter, and thereby the sweep ranges above where I want it.

Ideally, I want that gate effect to allow pass through of even low volumes, and the the hardest strikes to remain in the range of a pleasant tone, rather than pushing the signal up into the brash tweet range. I got the high end dialed in with the changes above, but still have the low end gate to tackle.

Needless to say, like all of my BYOC pedals, I love this one and will probably continue to futz with it forever hehehe.

Anyone have an idea what part of the signal path is pushing the low end so far down that it effectively becomes a gate? I'll find it eventually (hopefully with wrecking anything), but if someone can point me at a component to swap, I'd appreciate it.

Also finished my Pickled Beaver, and Octave Fuzz this week, and needless to say, I have lots and lots of new tone to play with for a while.

CEW


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PostPosted: Fri May 25, 2012 10:32 am 
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On a side note, has anyone tried the CA3280AE or LM13700 chip in the Envelope Filter?

The CA3280 apparently has some status as a favorite (but obsolete) chip. I just picked a couple up from ebay and will give it a whirl. According to TI, the LM13700 might be a small improvement over the 13600, but I have nothing other than this quote to base that on:

Quote:
The output buffers of the LM13700 differ from those of the LM13600 in that their input bias currents (and hence their output DC levels) are independent of IABC. This may result in performance superior to that of the LM13600 in audio applications.


By the way, in case it's not obvious, I'm no electronics engineer. Generally speaking my technical vocabulary extends as far as words like "thingy", "doohicky" and "whatsis". I am a sound engineer and thanks to BYOC a tone snob regarding pedals for my guitar sickness. I am technically inclined, but bandwidth challenged.

That is precisely why I love BYOC. I get a killer-sounding effect that I can dig into and modify myself to go after the tone in my head, rather than spending huge amounts on a boutique pedal and ultimately finding that it doesn't quite meet my needs.

CEW


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PostPosted: Fri May 25, 2012 12:34 pm 
I looked in to it a little and if I remember right the LM13700 is the replacement for the LM13600. What bothers me a little is that I believe the spec sheet for the LM13700 gives 10V as its MINIMUM operating voltage.

As far as I can see the reason that the filter shuts off is that the signal from the envelope follower into the control inputs to the filter OTAs drops so low when there is no input.
What is needed is a variable bias current into the OTAs control inputs.

This way with no input signal you could set the filter frequency to a suitable point and then the input signal would sweep the filter up from that frequency. You might even be able to get away with shorting out the manual switch to do this, but I suspect a more elegant approach is to add another current drive transistor like the one buffering the 4.7uF time constant cap, but drive its base with a variable voltage from a resistor connected to the wiper of a pot across the supply.


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