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 Forum index » DIY Hardware and Software » Les Hall's Projects including eChucK
emSynth
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Inventor
Stream Operator


Joined: Oct 13, 2007
Posts: 6219
Location: near Austin, Tx, USA
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PostPosted: Mon Dec 19, 2016 4:40 pm    Post subject:  emSynth
Subject description: open source and 3D printed
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Hi all,

*edit* Changed title to better name for this synth: emSynth, a name that I reserved long ago for the synth (not the url).

I received a Christmas gift from CFish (we exchanged items yay \o/) and it turns out to be sort of a minimalist's starter-synth! I am very excited about it and plan to make a modular synth beginning with this module and a power supply.

This will be my first modular synth. So I plan to create something really wild, something fun and interesting and unusual and joyful. A synth that will warm the hearts of elders and newbies alike, a synth that we can all enjoy regardless of our level of experience.

Here in this thread I will imagineer some ideas for the potential structure of the synth and hopefully some of our more experienced synth designers and builders as well as folks of any experience can chime in as we go skipping along from start to finish!

Les

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Last edited by Inventor on Mon Dec 26, 2016 3:51 am; edited 8 times in total
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Inventor
Stream Operator


Joined: Oct 13, 2007
Posts: 6219
Location: near Austin, Tx, USA
Audio files: 267

PostPosted: Mon Dec 19, 2016 5:29 pm    Post subject: Physical Structure Reply with quote  Mark this post and the followings unread

First, the physical structure: it's a cylinder!

Second, the manufacturing: it's 3D printed!

Third, the interconnection method: it's mechanical with no soldering!

Fourth, the jumpers: to be determined!

Dozens of ideas are running through my head, trying to lasso the best ones!

Les

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Stream Operator


Joined: Oct 13, 2007
Posts: 6219
Location: near Austin, Tx, USA
Audio files: 267

PostPosted: Tue Dec 20, 2016 1:04 am    Post subject: Reply with quote  Mark this post and the followings unread

For reasons of safety, I am opting not to DIY the slip ring, which will act as a 360 degree power and signal connection between the synth itself and the base connected to the outside world. Using a slip ring enables full rotation of the synth to any angle and any number of rotations. The slip ring shown here has 12 contacts certified for 240V and 2A, so this thing more than does the job!

Slip Ring, 12 connections
$19.95
https://www.adafruit.com/products/1196

12 conductors allows the following pin assignments:

    Power Ground
    Vcc +15V
    Vdd -15V
    Signal Ground
    Mic in
    Stereo out Left
    Stereo out Right
    USB Ground
    USB +5V
    USB Data+
    USB Data-
    USB Unknown Pin


And all of the connections are used.

Les

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Stream Operator


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PostPosted: Tue Dec 20, 2016 7:24 am    Post subject: Reply with quote  Mark this post and the followings unread

A word about grounding: star! i'll be using a star ground configuration because it is the best way (to my knowledge) to avoid ground loops. It's called a star because there is one single point which is the center of the star and all the other grounds connect to that point like the points of a star.

In this case I feel that the best place to locate the star is above the turntable.

Les

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PostPosted: Thu Dec 22, 2016 12:21 pm    Post subject: Reply with quote  Mark this post and the followings unread

In the attached image you will see the planetary gear system that comprises my latest gear toy for my Neice AVA. A modification of it will serve as the project's base.

Les


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AVA's Gear Toy 2b
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PostPosted: Thu Dec 22, 2016 12:40 pm    Post subject: Reply with quote  Mark this post and the followings unread

In the chat, my good friend wofl posted this as prior art reference:

Les


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Cfish



Joined: Feb 24, 2016
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PostPosted: Thu Dec 22, 2016 2:46 pm    Post subject: Reply with quote  Mark this post and the followings unread

I love the concept Les.

Looking forward to seeing your take on it materialize.
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Cfish



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PostPosted: Fri Dec 23, 2016 9:24 am    Post subject: Reply with quote  Mark this post and the followings unread

Edit. Switched back to 2 9v battery supply and scrapped this. Biasing the FET output buffer was tedious and affected the UJT core to much.

I spent some time yesterday on a project using the little EFM VCO.

I adjusted it to see how it worked on 9v. Wanted to use it with a battery.

I added the 2 150 ohm resistors as a divider, and adjusted the capicitor value to bring it back in range.

It worked really well.

Even ran it on a 9v battery. Though I'm sure it would drain it fast.

☀️Edit. Error. The top 2 PNPs should reference 1/2v not ground.

I built 2 of these. On the third one I built it like I drew it and couldn't figure out why it wouldn't work.


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Last edited by Cfish on Wed Dec 28, 2016 5:21 am; edited 2 times in total
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Cfish



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PostPosted: Fri Dec 23, 2016 9:42 am    Post subject: Reply with quote  Mark this post and the followings unread

Then I added an extra 2n 3904 amplifier, so you can hear it on a small speaker.

I love trimmers to bias transistors. Sweep it till it works good. Saves a lot of time.

Edit ( I just realized I made a mistake drawing the schematic) the top 2 PNP transistors reference 1/2 v not ground.

Last edited by Cfish on Fri Dec 23, 2016 8:36 pm; edited 1 time in total
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Stream Operator


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Audio files: 267

PostPosted: Fri Dec 23, 2016 12:03 pm    Post subject: Reply with quote  Mark this post and the followings unread

Great work CFish! I see you are no cat fish at all, lol! in fact you are a circuit fish! It would make a nice credit-card synth module.

This brings to mind a project that I designed but never constructed - the credit card Karpov Strong circuit. In fact, if the emphasis is on super simple circuits that run on 9V batteries then the whole synth could be composed of credit card sized boards! Wouldn't that be cool? Let me find the link for the credit card KS board...

Les

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Stream Operator


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PostPosted: Fri Dec 23, 2016 12:08 pm    Post subject: Reply with quote  Mark this post and the followings unread

here it is:

http://electro-music.com/forum/topic-41976-25.html&postdays=0&postorder=asc&highlight=credit+card

It has both a boolean sequencer of minimal complexity and a Karplus Strong of minimal complexity. maybe we could separate those, make each a card, and make those be two of the designs.

CFish, your work is making this project take shape in a very imaginative way - thanks!

Les

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Cfish



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PostPosted: Fri Dec 23, 2016 12:33 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi Les

I like the credit size modules concept.

What I'm working on right now is a desktop type synth, and I decided to use no integrated circuits. I love working with independent transistors.

Using 2 of the little VCOs, a switch that can direct the first VCO to drive the second, or each down there own signal path.

Am including the simple transistor flip flop below as a 2 channel sequencer to ping pong between the VCOs

Just got done testing the values in it on the breadboard.

( the parallel resistors on the stereo speed pot, are because I want to use only things I have on hand)


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PostPosted: Fri Dec 23, 2016 1:00 pm    Post subject: Reply with quote  Mark this post and the followings unread

CFish, I like your idea of transistors only. I kinda had that thought when inspired by your transistor-only VCO and the credit card synth pushed me in another direction.

Personally I'm in a situation where I cannot really solder. I mean, I can technically but there are oxygen tanks nearby which do not ignite from the soldering but there is the danger of igniting paper which could then ignite the oxygen. So I don't solder at this point in time.

There is, however, the modern invention of the "Cold" soldering iron. The Weller unit is only $30 and I have budget for it. It does not solder any lower temp, actually it just gives you enough heat for one solder joint and then it shuts itself off. Even if you keep the button pressed it shuts off and stays off. so it all but infinitely eliminates the possibility of igniting paper with it, so it is very safe compared to ordinary soldering irons.

If I get a cold soldering iron then i can solder again.

Les

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PostPosted: Fri Dec 23, 2016 1:10 pm    Post subject: Reply with quote  Mark this post and the followings unread

CFish, Also I have wanted for a long time to make music circuits by designing 3D printable "forms" around which one could wrap the leads of discrete components and then either twist, solder, or both to make the connections. We have prior art on this site in the Lunetta sub-forum. I'll try to find it. This would be different from the prior art but similar in concept.

Les

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Cfish



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PostPosted: Fri Dec 23, 2016 1:14 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi Les

I believe Radio Shack sells a conductive glue to do electronics without heat.

As long as it does not give off fumes that might cause problems.

I know I have seen it somewhere, but I have never tried it.
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PostPosted: Fri Dec 23, 2016 1:22 pm    Post subject: Reply with quote  Mark this post and the followings unread

Google provides the following images:

https://s-media-cache-ak0.pinimg.com/originals/60/df/01/60df01376913762aca054bf9d0871315.jpg

https://s-media-cache-ak0.pinimg.com/236x/8c/73/15/8c7315e4762b091d15ecc7dd2ece5121.jpg

and others. These are free-form circuits, my concept would be to use a plastic (insulating) form.

comments? suggestions?

Les

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PostPosted: Fri Dec 23, 2016 1:26 pm    Post subject: Reply with quote  Mark this post and the followings unread

Cfish wrote:
Hi Les

I believe Radio Shack sells a conductive glue to do electronics without heat.

As long as it does not give off fumes that might cause problems.

I know I have seen it somewhere, but I have never tried it.


Hi CFish,

I have a conductive ink pen that a friend sent me, plus I have conductive 3D printer filament. I can work with that and/or just wrap and/or twist the leads around forms. I'm going to work with your oscillator (since you sent me the parts). I'll get a cold soldering iron next month probably. Anyway, for beginners having some way to build circuits without a soldering iron is primo!

Les

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Stream Operator


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PostPosted: Fri Dec 23, 2016 1:31 pm    Post subject: Reply with quote  Mark this post and the followings unread

Just looked up the credit card size:

84 mm x 54 mm with 3.18mm radius corner rounds

Posting here for reference.

Les

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PostPosted: Fri Dec 23, 2016 1:38 pm    Post subject: Reply with quote  Mark this post and the followings unread

Not to go off track on your thread, but I thought you would appriciate these.

Open air wired VCOs, dipped in fiberglass resin.


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PostPosted: Fri Dec 23, 2016 1:47 pm    Post subject: Reply with quote  Mark this post and the followings unread

Forms would have been a big time saver when I made those.
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PostPosted: Fri Dec 23, 2016 2:30 pm    Post subject: Reply with quote  Mark this post and the followings unread

Here is an image of the card I am preparing to print. Print time is 24 minutes plus setup and cool down. So basically well under an hour each on a 3D printer.

Les


Credit Card Synth Blank 1.png
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Here is a blank card that I will soon put on the printer just to see how it works. 6mm (1/4 inch) keep out distance on both x and y.
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PostPosted: Fri Dec 23, 2016 2:32 pm    Post subject: Reply with quote  Mark this post and the followings unread

Cfish wrote:
Forms would have been a big time saver when I made those.


Dang CFish, you've been around the block a few times! Takes experience to create a wonder like that...

Les

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PostPosted: Fri Dec 23, 2016 3:54 pm    Post subject: Reply with quote  Mark this post and the followings unread

The Karplus Strong module could be implemented in transistor-only plus also simple and easy to build form. The key to that would be a discrete delay line so that the bucket brigade chip could be replaced. If we fix the delay to a single value, perhaps with taps and/or a replaceable gizmo, then the circuit will only need one transistor gain buffer to work.

A lot of very cool sounds could then be produced. The key question then is: how the heck do you replace a delay line with one discrete part? The answer is: a distributed RC circuit. I learned in grad school that an RCRCRCRC etc. model is a good approximation to a delay line and it's used in computer modeling of metal interconnect in processor chips. Spice models and their kin. Also I recently learned that depositing a trace made of conductive 3D printer filament can produce a distributed RC delay (or so I believe by observation).

The way that works is when you print with the filament, it naturally oozes into a layered structure. This layered structure varies in resistivity, so that several layers makes a sandwich of low and high resistivity. Also if that does not work there are two types of filament and one is 30 times more conductive than the other, so a sandwich is certainly possible.

It would be efficient and worth the trouble of swapping filament (which takes time and effort) if small modules or perhaps direct deposits on the PCB could be made in batch form.

Well, a lot of thinking out loud here. I can't try it until tonight or later because of issues with rest and recuperation and such. Long story. Save it for later, or better yet never, TMI lol!

Les

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PostPosted: Fri Dec 23, 2016 4:46 pm    Post subject: Reply with quote  Mark this post and the followings unread

Les. I like the delay line idea, and the form looks great.

I worked today on layout for front panels, and went ahead and did up a VCO module.

Will try to Finish up the front panel for it tomorrow.


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PostPosted: Fri Dec 23, 2016 6:57 pm    Post subject: Reply with quote  Mark this post and the followings unread

In 2007 my birthday present was electro-music.com;
in 2016 my Christmas present was the credit card synth.

Thanks CFish.

Les

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