Enveloped stereo ping pong Panning pedal. Please help :)

[Haynesarama]

Hi everyone

I've got an idea for a pedal I'm trying to put together but I'm having difficulties
Figuring it out and I was hoping someone with more experience/knowledge
Could help or point me in the right direction....fingers crossed.

So what I'm trying to do is to create a pedal that Has one input
And two outputs. The pedal sends the signal to either output 1 or 2
Depending on the strength of the note played.
So if you played soft notes it would go to one output with notes played harder
Going to the other output. Also notes played at the same level will
Make the signal ping pong between the two.

I've been looking at this informative article

http://www.geofex.com/Article_Folders/VCA%20Applications.pdf

And I'm thinking that application 4a is roughly what I'm after.
I'll need to add a sensitivity/threshold control to set at which point the output changes
With your playing dynamics. I'd also like to add a sweep control
To change the sweep of the output from smooth to stuttered.

I hope this is making sense?
Is anybody able to give me some advice or point me in the right direction please?
I've looked around and have found nothing similar. DIY or commercial.

Thanks in advance everyone
Michael

[frequencycentral]

LM13700 data sheet figure 4 'stereo volume control' as a starting point. Feed the same signal into Vin1 and Vin2, as well as into an envelope follower. Feed the output of the envelope follower into the Iabc input of OTA 1, feed the envelope follower via in inverter into the Iabc input of OTA 2.

http://www.ti.com/lit/ds/symlink/lm13700.pdf

[Haynesarama]

Hi Rick.

That's a great help. Thank you do much
It seems easy when you know how. Lol

So are you saying the output of the envelope follower goes
To OTA 1 Amp bias input?
Also the output of the envelope follower is inverted then goes to OTA2 amp bias input?

I pressume the input will need to be buffered
Then going to the OTA and envelope follower as well as some additional buffering/gainstage
At the output?
I'll have a look at an appropriate envelope follower circuit to use then. And get my breadboard
Out

Any further help regarding the sensitivity and sweeping controls would be hugely appreciated.
Im thinking the sensitivity pot would be at the input of the OTA and the sweep control at the output?

Many thanks again Rick.
Cheers
Michael

[Haynesarama]

Hello everyone

Thank you for your help so far on this project.

I've had a few days to mull over this idea and i think I'm getting there.
I have a few more questions if anybody can help.

I mentioned previously that there would be one input being sent to two different outputs depending on the playing dynamics and set threshold.
Seeing as the diagram 4 on the LM13700 datasheet is a good starting point and it also has two inputs, My quesions is could i add a second switched input for stereo
setups?
The idea is if there is only one input being used it would preform as previously mentioned.
Then if the stereo input is used it would pingpong input A & B with Output A & B.

Also i guess that the threshold and sweep controls will come from the envelope follower part of the circuit?

I noticed this one from MFOS mentioned in this forum.
Would his be a good starting point?

http://www.diystompboxes.com/smfforum/index.php?topic=78325.0

As you can see there's three parts to the schematic. Can anybody clarify which section is the envelope follower section?
I'm thinking it's the top or bottom section.

Thanks again for all your help with this.
Once I've got a fair idea of how it's going to be done i can work on a schematic to post
and look at parts to order to start breadboarding it

Thanks again
Michael

[Gurner]

U1A thru U1D make up the envelope follower.

U1A amplifies & feeds half of the full wave rectification diodes, U1B has a gain of 1, inverts the signal & feeds the other half of the full wave rectification diode circuit, U1C amplifies the (now) full wave rectified signal (to restore signal level lost attributed to the full wave rectification), the output of U1C is low pass filtered to yield a DC-esque voltage level, and U1D buffers this voltage so it doesn't get loaded down by the circuit that uses this voltage.

[Haynesarama]

Hello again.

I hope everyone has enjoyed the festive period

Right then. I've had some time drafting up a schematic for this dynamic stereo panning switching device which you can see here

https://dl-web.dropbox.com/get/DYNAMIC%20STEREO%20PANNING%20SCHEMATIC.png?w=e454a51e

IC1 is TL072
IC2 is TL074
IC3 is LM13700

This schematic is basically the StereoStereo volume control (figure 4) found here
http://www.ti.com/lit/ds/symlink/lm13700.pdf

being fed into a MFOS Envelope follower which you can find here
http://www.diystompboxes.com/smfforum/index.php?topic=78325.0

Then being fed from the envelope follower into a standard dual opamp TL072 buffer circuit with one side inverting the signal and the other side non-inverting the signal.
Then the inverted and non-inverted signal are being fed into the LM13700 OTA & OTA2.

This is all as Frequencycentral kindly suggested Many Thanks!

Could anybody please check this schematic for errors?
Also If it all looks fine i want to start looking into how to change the sensitivity and sweep controls as previously mentioned.
If anybody could help further i would greatly appreciate it

I'll post a PCB layout for the circuit once the breadboarding side of things are complete.

Thanks again for all your help
Michael







It is basically

[frequencycentral]

https://dl-web.dropbox.com/get/DYNAMIC%20STEREO%20PANNING%20SCHEMATIC.png?w=e454a51e

Link not working. You need to right click the file in dropbox and click 'copy public link', then paste the public link here. If you have a problem, email it to me and I'll host it (like last time!).

[Haynesarama]

Thanks for the tip Rick

Here's the schematic again

http://dl.dropbox.com/u/30126212/DYNAMIC%20STEREO%20PANNING%20SCHEMATIC.png

Thanks again.
Michael

[Taylor]

I'm pretty sure that there's a full project for an envelope-controlled panner in the "envelope" issue of Stomp-box-ology. I can't remember whether it's prohibited here to link this or not - if so, sorry mods.

Pretty sure it's ratchet-o-matic, page 12.

http://moosapotamus.net/IDEAS/stompboxology/EnvelopeEffects.htm

[Haynesarama]

That's fantastic!!!!!
Thanks Taylor

that does pretty much exactly what I'm looking for. I've just looked at the other pages in the link too.
What I'm trying to do is to be able to use mono or stereo inputs.
So while using the mono input i want the circuit to switch this to output A and output B on everyother note, With the ability to change the sensitivity of the switching threshold as well as control over the sweep of the switching, from smooth to choppy.
So pretty much what the circuit above does.

Now I also want to use stereo inputs so Input A & B will switch between output A & B with your playing dynamics on every other note
I've noticed that some of the other pages in the link look to do something similar. can anybody confirm if one of the circuits in the link work like this.

Thanks so much
Michael

[Haynesarama]

Right then.

I've done some more reading and it appears to be do able by
using the Raceht-o-matic schematic but replacing the input with a stereo input and the NE570 part of the circuit with Diagram 3 on page 3 of the above link.
What do people think?

Would one of the buffered inputs need to be inverted?
Also when using the stereo version i presume only one input needs to feed the envelope follower part of the circuit as its the same signal.

I'll post the completed schematic for the circuit shortly

Thanks
Michael

[Haynesarama]

Hi People

Ok So I've drawn up a schematic for the panning stereo device which you can see here
http://dl.dropbox.com/u/30126212/DSP%20SCHEMATIC.png

So It is put together from the Ratchet-o-matic schematic found here
http://moosapotamus.net/IDEAS/stompboxology/Vol13No4/Page_12.gif

but replacing the input and the NE570 and output for the example found here figure 3
http://moosapotamus.net/IDEAS/stompboxology/Vol13No4/Page_03.gif

I've drawn the schematic up in eagle.
I've triple check it however when i run the ERC it is showing up with 7 errors all saying
OUTPUT AND SUPPLY PINS MIXED ON NET VR (SUP)
these are all showing up on the points where I've added VR which I've used for the B symbol in the above schematics which is half supply voltage.
I guess i could just join them together myself but the schematic is all over the place. Lol

It's the same as the linked schematics so there shouldn't really be any errors.

Can anybody see why this wouldn't work or if there's any additional things I'll need to add?
It would be greatly appreciated

Also when you look at the Ratchect-o-matic schematic it mentions that
R15 & R16 DETERMIN PANNING SPEED. INCREASING THE VALUE OF C4 & C16 FOR GENTLER PANNING.
These are R12 & R13 On my schematic.

Would I be able to replace the 2 resistors for a stereo pot to achieve the sweep control I'm wanting for the panning?
If not would I need to use a rotary switch to change the value of the R15 & R16 and C4 & C16 Together?

Now that I've done the schematic I've got a parts list to order so that i can start breadboarding to test it.
If anybody knows of anything I'll need to add it'll be a great help and I can add it to my order

Cheers
Michael