WaveWiper 2.0 (improved version)

PHOBoS · Last edited by PHOBoS on Thu Jan 14, 2016 9:21 am; edited 1 time in total

continuing from this thread in which the orginal wavewiper was conceived.

In short: the WaveWiper is a circuit that merges two waveforms together. It's based on Jim Patchell's Control Voltage Splitter
and it splits two input signals in a positive and negative part. The positive halve of one signal is then added to the negative
halve of the other signal and vice versa. The level where the signals are split can be controlled with a potentiometer and/or
an external Control Voltage.

Because I am working on a PCB design I thought it might be a good idea to test the circuit again first before sending out
the designs to have it fabricated. I am glad I did Very Happy

One thing I wanted to test again was to see what happens when the CV is outside of the 10Vpp range. I remembered something
about one halve of the signal being cut off and indeed that's what it does. So I had a look at the schematic and what I noticed
was that the signal was actually being clipped. With the CV being 5V and the signal being 5V using a 12V supply voltage it is
already close. So with a higher CV voltage the opamp just couldn't go any further while there was still being more offset voltage
being added at the end.

I solved this by changing some of the resistors so that in the first (splitting) stage the signal gets amplified by 0.5 and at the output
stage (merger) it gets amplified by 2. Now the signal doesn't get cut off anymore, although that could be considered a feature,
it did produce some interesting sounds.

I added a attenuator to the CV input, put the 1K current limiting resistors (on the outputs) in the feedback loop to prevent a
voltage drop and replaced the LM324 with a TL074. I also reversed the diodes again as I had them originally. So with a -5V CV
the outputs follow the inputs and with +5V they are swapped. So now it goes from pass through to swapped by turning the wipe
pot clockwise.

As I was experimenting with it I wanted to understand the circuit completely, see if the math adds up. I pretty much knew how it
operates but not what the actual voltage levels are throughout the circuit. So I did some tests with parts of the circuit mainly
focusing on the voltage splitter section and drew some graphs. I still had the last opamp removed from the circuit (U1b in the
original schematic) which adds an offset voltage and shifts the levels after splitting. I did some calculation and as it turns out the
offset voltage it needs was actually the same as what is coming out of the first CV mixing stage. So instead of attenuating + inverting
that signal and adding it to the non-inverting inputs of the merge opamps I hooked it up directly to the inverting inputs and that
works perfect. Razz

So WaveWiper 2.0 does no longer need any calibration!
banana

I still used a TL072 instead of a TL071 because that was already on the PCB design and I like the pinout better. And you get an
extra opamp which might come in handy for something else in the future. The price is pretty much (if not exactly) the same and
it takes up just as much board space.

You could actually leave it out altogether. Connect the CV in directly (or with attenuater) instead of opamp U1a and add 4x 130K*
resistors to the inverting inputs of opamps U2a..U2d, which are than connected to the Wipe pot. Downside is that the impedance
on the CV input drops and with the opamp it is much easier to change the CV response. So I decided to leave it in.

*not tested

here's the schematic of WaveWiper 2.0 and some more graphs to show how it works. I used 50K resistors as an example to get
nice round voltage levels. The actual circuit uses 47K ones but because I used 100K/47K pairs the end result is the same. Cool

WaveWiper 2.0.gif

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WaveWiper 2.0 schematic

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WaveWiper 2.0 graphs

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PHOBoS - Wave Wiper.gif

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original WaveWiper for reference

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piedwagtail · Posted: Wed Dec 30, 2015 5:27 pm Post subject:

Exemplary stuff!

You could use the other half of the '72 as an attenuverter on the CV input either as replacement or complement to the 100k attenuator.

R

PHOBoS · Posted: Thu Dec 31, 2015 3:28 pm Post subject:

good idea. Very Happy

And I will be able to fit that on the board, which I am going to make a little bit larger anyway.
I do have a bit of mixed feeling about attenuverters though. It's great to attenuate and invert a signal with one knob,
but it's not as easy to set to 0 as a simple attenuater. I've only tried a very simple version though, don't know
if the one with the trimpot makes any difference. So let me try that one too Cool

piedwagtail · Posted: Thu Dec 31, 2015 4:00 pm Post subject:

Ok stick a switch in to.....er switch it out when you need a dead null! Very Happy

Looking forward to what you do in 2016!

R

PHOBoS · Posted: Thu Dec 31, 2015 5:11 pm Post subject:

best wishes for 2016!

I just tried the one with the trimpot and as I was somewhat suspecting it is to zero the center of the pot.
That would work great with one of those pots with a center click.

I am thinking of indeed making 2 CV inputs, one with an attenuator and the other one with an attenuverter.
If I then add a positive voltage using the switch contact of the jack I could replace the wipe pot with it.
At the moment I designed it so that the wipe pot can add so much offset voltage that in the most outward
positions it will "override" the CV in. The nice thing with the attenuverter is that by changing the resistor that supplies
the positive voltage (when no CV connected) I can still set a larger range than when using a CV.

So the circuit would function exactly the same as it does now but with the added bonus of having an extra CV input
and for that one the wipe pot acts as an attenuverter. Also if I add the trimpot I can zero the center of the wipe pot.
It doesn't have that option now but I guess that would be nice.

PHOBoS · Posted: Thu Dec 31, 2015 6:08 pm Post subject:

so that would look like this Cool

WaveWiper 2.1.gif

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WaveWiper 2.1 schematic

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piedwagtail · Posted: Thu Dec 31, 2015 9:29 pm Post subject:

Yep, Happy New Year!
On Moonbase, you appear to be working hard at the synth diy couture detailing!

In the atelier, I've just received the VCO motherboards from Shenzhen which feature, amongst a few things, two attenuverter inputs and an attenuator input with a log pot Smile

.

R

PHOBoS · Posted: Sat Jan 09, 2016 7:33 am Post subject:

I just received an order update: boards are ready and being shipped.
banana

They also included a photo of the PCBs and it looks good, but it seems that all the holes are filled with solder.
Maybe it's just glare from the plastic since they seem to be vacuum packed, it would be a rather odd thing
to do and I didn't select any extra options. So we'll see how that turns out.

WaveWiper PCBs.jpg

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WaveWiper PCBs

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piedwagtail · Posted: Sat Jan 09, 2016 12:17 pm Post subject:

panic!
yes it's addictive.

R

Paradigm X · Posted: Tue Jan 12, 2016 5:22 am Post subject:

interesting, great work

Cool

ill be up for a pcb if youre selling any...

PHOBoS · Posted: Tue Jan 12, 2016 8:14 am Post subject:

great

yes I will sell them, I don't need 10 boards myself but I will probably keep 2. 1 to build and test and 1 just to keep
because it's the first time I am having boards made, maybe I'll frame it Wink

First run will be the set of both boards for a special price and if there is enough interest I'll have more made which
will be sold seperately. I also made part kits for it if you are interested. I'll probably make a seperate thread for it once
I have the boards and all the parts and can calculate all the costs. And I am now looking into frontpanels as well.

And yes it is addictive Laughing

I definitely want to make more designs, but let me stick to this one for now.

Paradigm X · Posted: Tue Jan 12, 2016 10:01 am Post subject:

cool!

whats the 'set of two boards' tho? does it need 2 pcbs?

I got a few pcbs made (someone else did the layout, i just paid!) and they arrived looking like that, they (almost certainly) aren't pre-soldered! just eh shrunken plastic looks metallic due to the warping

seeed etc are so cheap these days. like you i have spares of everything.

cheers

PHOBoS · Posted: Tue Jan 12, 2016 10:49 am Post subject:

One board has the actual WaveWiper circuit, the other board is for pots and connectors for a euro-rack module
(the boards are sandwiched together with some printheaders in between). And yeah if I look at the 3,5mm connectors at
the top I can see that they are indeed not filled with solder, but it does look like it. I hope they arrive this week Razz

.

Paradigm X · Posted: Thu Jan 14, 2016 7:31 am Post subject:

ah ok cool.

euro pot/jack boards are all the rage at the mo.

i build in 5u so prob not required but these no wiring projects are really popular. are there pads etc for easier/easy wiring of pots etc

cheers

PHOBoS · Posted: Thu Jan 14, 2016 9:01 am Post subject:

yeah, you wouldn't need it for 5U but it should make wiring easier since the holes/pads are larger and it is easier to see
how to wire everything up. Besides that you can wire it up and still take the circuit board off if needed for whatever reason.

Or you can use it as a keychain, christmas ornament, ice scraper, coaster or whatever you come up with Laughing

Paradigm X · Posted: Thu Jan 14, 2016 9:37 am Post subject:

ha

looking at the picture a bit more makes it painfully obvious what youve done. doh! Laughing

Shame theres no MOTM power connector, if youre doing a second run it might be worth adding one maybe? (4 pin 0.156 molex).

You can cleverly incorporate the two with very little extra board space -

eg;

Posted Image, might have been reduced in size. Click Image to view fullscreen.

Posted Image, might have been reduced in size. Click Image to view fullscreen.

PHOBoS · Posted: Thu Jan 14, 2016 1:47 pm Post subject:

yes! a double power connector was something I had in mind for a second run. I don't think I have something existing in one
of the eagle libraries so might have to draw it myself. But maybe i can find one that has been tested somewhere.

It shoudn't be very hard to power it with the connector it has now though. you could either solder wires to the double pin header
or solder a piece of perf to it and either add wires directly or a MOTM connector to it. I actually thought about making a little
converter board you could just stick on top of it.

If you have any other suggestions please let me know. Very Happy

hmm, looks like the one in the photo you posted can actually support 3 different kinds that's really neat.

PHOBoS · Posted: Wed Jan 20, 2016 8:03 am Post subject: I haz WaveWiper PCBs!

WaveWiper PCB (cc).jpg

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piedwagtail · Posted: Wed Jan 20, 2016 8:33 am Post subject:

PHOBoporn! Rolling Eyes

PHOBoS · Posted: Wed Jan 20, 2016 9:04 am Post subject:

They are beautiful and everything looks purrrrfect. And seperating the boards
by snapping works great! That was a bit scary to try though.

Of course I don't know yet if they will actual work.

here's another photo Cool

(color corrected the photos a bit so they looks closer to the actual color)

WaveWiper PCB set - first run (cc).jpg

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piedwagtail · Posted: Wed Jan 20, 2016 9:51 am Post subject:

I can see from your neat parts placements how this is an extension of your enjoyment of drawing schematics.
Did you use auto-routing? I never do puzzles, but I really enjoy the 'puzzle' of routing a pcb.

R

PHOBoS · Posted: Wed Jan 20, 2016 3:41 pm Post subject:

Dave breadboarded the WaveWiper v2.1 to do some tests but he had some problems with the attenuverter part.
I breadboarded it too and got the same results he did while I knew it should work. As it turns out I made an error
in the schematic, so I just uploaded the corrected version. Luckily the Eagle schematic I used to design the PCB is correct.

piedwagtail · Posted: Wed Jan 20, 2016 4:09 pm Post subject:

I've always used the Ian Fritz version with 220k signal to - terminal and 220k feedback resistor.100k pot. With 15/0/-15 I found it worked as advertised with CV signals until -13V then it wasn't happy; which is pretty extreme.

R

PHOBoS · Posted: Thu Jan 21, 2016 7:33 pm Post subject:

it works!

here is some more pr0n

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AlanP · Posted: Thu Jan 21, 2016 9:36 pm Post subject:

I'm still not sure what these do, but could I buy a set off you? Any panel plans? Smile