Hi, a keyboardist friend has set me a task to build him a synth!

Can I build a function generator and use that as a basis for a synth?

I have a schematic for a sine/sq/tri using an 8038 IC. What other chips should I look at please?

 

While today's synthesizers are mostly digital boxes calculating stuff and playing sampled waveforms, the term synthesizer comes from the way these things started out. They synthesized the sound of a musical instrument or voice with basic waveforms, noise sources, and envelope shapers, not a microprocessor in sight. If you want to go that route, search the innergoogle for old documents and plans from PAIA. They were small kits that could be combined to basically emulate a Moog, the gold standard of the day.

God I miss Popular Electronics.

ak

 

Thanks AK. Will do, he wants modular old skool which is lucky for me!

 

While not a simple chip, have a look at this one:

http://musicfromouterspace.com/index.php?MAINTAB=SYNTHDIY&VPW=1390&VPH=783

It's based around a saw wave generator, which it converts to triangle and pulse, and uses a shaper to approximate a sine from the triangle.

 

What a great site Vera with stripboard layouts too!

 

Treeman
There is something important you have to understand about analog synthesizers. The music VCOs are not linear, they are logarithmic.
An example
A 8038 IC VCO voltage verses frequency
1V = 100Hz
2v = 200Hz
3V = 300Hz
4V = 400Hz
etc.
a music VCO works this way
1V = 100Hz
2V = 200Hz
3V = 400Hz
4V = 800Hz

Look at the schematic of the "VCO 1V/octave" in the Music from outer space link. There is a matched transistor set that is thermally coupled to a Palladium film compensation resistor. This is the heart of a precision log amp. You must get those parts or you have no hope of making it work. It will not be an easy task to tune this thing unless you have a precision volt meter and a musical tuner.

It is not a simple task you have signed up for.

Mark

 

Having spent ages looking at the schematics on music from OS I heartily agree lestraveled. I obviously have a big mouth but am still unable to masticate properly!
Thanks very much for your input - I was wondering if I should start off with a kit - I need building experience and a week off the kids to start the AAC worksheets for any of it to make sense. I have no hope of planning the layout of something so complex but feel its cheating to buy a pcb - i'll have to drop that attitude to continue methinks.
Nevertheless there is much on the website that helps/inspires and I have already built a useful companion from the website which i'll blog in a few days.
At least I understand the log/linear issue from an ear perspective even if my mnemonics for pot markings were wrong. Decided yesterday to start GCSE Electronics in September at night school. Poor teachers.....
Thanks again I don't want to build something that works well but is useless. Like some of my 'projects' this one may take a few years to become reality but I need some lofty goals. Its interesting how electronics is changing my gung ho character-planning and organisation are everything.

 

It is not cheating to buy a PCB when you are inexperienced at laying one out and building it.

I suggest the following: Download the PCBExpress software (free). Using the picture of the VCO PCB and the schematic, lay out a copy of it (both schematic and PCB.) Doing this with teach you the software. (Its a very simple program.) Now improve it. Learn to link your PCB design to the schematic. You will be surprised at how quickly you can become proficient by doing this.

Mark

 

Honestly an exponential converter is not that difficult until you get into precise calibration and temperature compensation. The designs on MFOS are a bit overkill for a starting step, he likes to provide a lot of external control options because his designs are based on a modular concept. Tou could easily start with a simple design and get a roughly correct control voltage/octave response, then play around from there.

I found this useful to explain the exponential converter:

http://electronotes.netfirms.com/s019.pdf

 

Synthesizer.
Meeting the Korg MS-20 Kit Synthesizer.
Korg Releases Monotron Synth Schematic.
Basic synth.

 

The average musician can tune their instrument to within .5 Hz of true pitch. The average musician can pick out an out of tune instrument in a band while playing a song when that instrument is just a few hertz high or low.
The reason the music industry went to computer based synthesizers is that open loop VCOs could not hold true pitch over 4 octaves.

Mark

 

And I thought I was just an average musician Lestraveled.......!

 

Hi Les travelled - can I just make sure is it PCB Express or Express PCB? Found link below.
http://www.expresspcb.com/expresspcbhtm/download.htm

 

Oops, I mixed that one up, but that is the right one. I use it all the time.

Mark