"Funky MF (Multimode Filter)" - LM13700 Multimode Envelope Filter

[slacker]

I think you need rail to rail opamps for that envelope follower to work. The second stage has the + input referenced to ground and "normal" opamps often only work to within a few volts of the rails.

[frequencycentral]

I think you need rail to rail opamps for that envelope follower to work. The second stage has the + input referenced to ground and "normal" opamps often only work to within a few volts of the rails.

Thanks Ian, so what would have to change (and how) in that envelope follower to make it work with a 4558?

[frequencycentral]

I think I might have found the bug in this design. I just breadboarded the envelope follower for another circuit I'm working on. I used a 4558 for the two opamps that make up the envelope generator - and it didn't work. As soon as I changed to an LM324 for those two opamps it worked. Is that it? I hope so. Strange, I would have thought it would work the same with 4558s.

I think you need rail to rail opamps for that envelope follower to work. The second stage has the + input referenced to ground and "normal" opamps often only work to within a few volts of the rails.

Thanks Ian, so what would have to change (and how) in that envelope follower to make it work with a 4558?

I did get my breadboard circuit using the 4558 to work by switching the 220K and 100K resistors (after the Range control) from ground to vref. This may affect the range of the output of the unity gain buffer after the detector, so the biasing of the resistors at pin 1 and 16 of the 13700 may need tweaking.

[chicago_mike]

Mine are being built off the pcb pdf. I think I should be fine.

I just need to get off my butt and order the lm13700's I need about 10 anyways.

[orangetones]

Do let us know if you get it working off that PCB.  Others have not had any luck.

[chicago_mike]

UH OH!!!!!!

Well once i get the lm13700's ill be bale to find out.

What seems to be the biggest issue? And when you say not working off the pcb, is not working in any way shae or form or does it kinda sorta work?

Damn!

[orangetones]

My suggestion would be to go back and read through this entire thread.  If I am correct there was much discussion about the functionality of this project.

[chicago_mike]

Oh god...the read the thread answer....

Thats never good.

[frequencycentral]

My suggestion would be to go back and read through this entire thread.  If I am correct there was much discussion about the functionality of this project.

$h!t, am I going to have to build myself another to salvage my tarnished reputation? It's hardly rocket science - but a more complex build than a Fuzz Face!

[chicago_mike]

I just need some of those ota's to give mine a run through.

I have the ca3280's and if I knew how to do it, I would make some kind of converter board and just use those.

perhpas you should build another...but really for the purpose of having another filter. you can never have too many. And us bass players need cool diy pedals..NOt another ff or tonebender, or derivative.

[chicago_mike]

Well I orderd my LM13700's and I have the LM324's and the tlo72 / 062's.

I was wondering if theres any progress on this project from others.   I have the schematic for another ef that uses the 13700 but I would like to get this going first.

[T1bbles]

Has anyone anywhere got this circuit to work yet? Other than the mighty Rick of course I've sat for about an hour now switching between the schem and the PCB layout and it all seems to be right, unless I've overlooked something, which isn't unlikely!

It'd be a shame to have to give up, cuz this baby looks and sounds a beast!

[frequencycentral]

Development thread for a future version 2 with more features and less issues here: http://circuitworkshop.com/forum/index.php?topic=235.0

[svstee]

Anything new with version 2? Should I wait for it or build V1?

[frequencycentral]

Anything new with version 2? Should I wait for it or build V1?

Wait.............................

[svstee]

Awesome! Looking forward too it. 

[Altitude]

Greetings all. I've been lurking around here looking for a worthy filter for a expanded 8 bit sampler I am working on and this thing sounds like exactly what I am looking for.. In lieu of the issues with the envelope follower could it just be dropped and the filter run wide open permanently? For my needs, that would be fine. Frequency Central, you mentioned that someone else got this working with a different env design, can you elaborate?

[frequencycentral]

Greetings all. I've been lurking around here looking for a worthy filter for a expanded 8 bit sampler I am working on and this thing sounds like exactly what I am looking for.. In lieu of the issues with the envelope follower could it just be dropped and the filter run wide open permanently? For my needs, that would be fine. Frequency Central, you mentioned that someone else got this working with a different env design, can you elaborate?

Boogdish made three posts on page 2, including a vero layout for the filter section: http://www.diystompboxes.com/smfforum/index.php?topic=73021.msg593387#msg593387

[Altitude]

Gotcha, thanks.

So just tie pin 1 and 16 and it will be "open"?

[frequencycentral]

Gotcha, thanks.

So just tie pin 1 and 16 and it will be "open"?

Yeah, you can use other stuff to modulate the filter then. Don.t forget a resistor between your modulator and pins 1/16.