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DIY Synths General Discussion
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Macaba



Joined: Jul 13, 2005
Posts: 160
Location: UK

PostPosted: Mon Mar 13, 2006 11:25 am    Post subject: DIY Synths General Discussion
Subject description: For the small things
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It just seemed to make sense to me to have a thread that we can talk about anything related to DIY Synths, but not important enough to warrant a new thread about it. A true discussion, and a place to ask small questions and get answers.

Mosc- sorry if I've overstepped my bounds.

--------------------------------------------------

In the not too distant future I might be doing a run of Step sequencer boards. These will be surface mount technology and have normal SIL headers for the LEDs/Pots/Reset-on-step/etc. Is anyone interested in obtaining one of these? It'll be the cost of parts, shipping and a bit extra.

Mac
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mosc
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PostPosted: Mon Mar 13, 2006 12:25 pm    Post subject: Re: DIY Synths General Discussion
Subject description: For the small things
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Macaba wrote:
It just seemed to make sense to me to have a thread that we can talk about anything related to DIY Synths, but not important enough to warrant a new thread about it. A true discussion, and a place to ask small questions and get answers.

Mosc- sorry if I've overstepped my bounds.


Well, we have the Schmooze forum for general discussion on topics not related to anything else. . You can talk about anything there, but if you want to start a topic in the DIY forum, that's OK.

Your offer to provide boards for your step sequence seems anything but not important though. Shocked

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v-un-v
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PostPosted: Tue Mar 14, 2006 4:56 am    Post subject: Re: DIY Synths General Discussion
Subject description: For the small things
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Macaba wrote:
It just seemed to make sense to me to have a thread that we can talk about anything related to DIY Synths, but not important enough to warrant a new thread about it. A true discussion, and a place to ask small questions and get answers.


Mac, if you want to start a new thread discussing DIY- just go ahead- that's what the DIY forums are there for. Don't feel like you are overstepping the mark- you are not. Very Happy
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Mikmo



Joined: Dec 01, 2005
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PostPosted: Tue Mar 14, 2006 11:27 am    Post subject: Reply with quote  Mark this post and the followings unread

It's a nice initiativ.

I would be interested in one or maybe a couple of these boards. Depending of course on price and functinality.

Mikael

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Macaba



Joined: Jul 13, 2005
Posts: 160
Location: UK

PostPosted: Wed Mar 15, 2006 11:15 am    Post subject: Reply with quote  Mark this post and the followings unread

I just hand soldered my first SMT part! Very Happy
I used a blunt gas soldering iron, thats not great to be honest. Still managed to solder all the joints and have no bridges.

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

I'll be getting a better soldering iron with fine tip, finer gauge solder, and some fine soldering braid. I should get nice joints then. Its rather good this SMT stuff! Laughing
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Macaba



Joined: Jul 13, 2005
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PostPosted: Sun Apr 09, 2006 4:19 am    Post subject: Reply with quote  Mark this post and the followings unread

Oh, just to show off my latest SMT board:

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

Anyways... QUESTION:

How do you convert a Linear CV(v/hz) to a LOG(v/octave) CV?
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dnny



Joined: Mar 12, 2005
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PostPosted: Sun Apr 09, 2006 5:13 am    Post subject: Reply with quote  Mark this post and the followings unread

cute SMT´s i think we all have to learn that someday. soon there will be only surface mount´s...

but i still like more this kind of surface mounts
Posted Image, might have been reduced in size. Click Image to view fullscreen.
sorry for cross posting

d

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rylos



Joined: Sep 06, 2004
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PostPosted: Sun Apr 09, 2006 8:54 pm    Post subject: Reply with quote  Mark this post and the followings unread

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

Doing this one with press-n-peel was pretty tedious!
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dnny



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PostPosted: Sun Apr 09, 2006 10:18 pm    Post subject: Reply with quote  Mark this post and the followings unread

rylos wrote:

Doing this one with press-n-peel was pretty tedious!


what is it? what does it do?

you must have good nerves and non shaking hands Shocked

thing i like on "through hole" IC´s that you can heat the socket and then press the IC on its place. whit no worries about overheating.

there are some sockets for PLCC and SOJ type
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.


by the way what is the difference between SMT and SMD ?


d

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Macaba



Joined: Jul 13, 2005
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PostPosted: Mon Apr 10, 2006 2:47 am    Post subject: Reply with quote  Mark this post and the followings unread

'SMT and SMD'

Surface Mount Technology and Surface Mount Devices.

I wish there was a socket for 6x6mm 16 pad QFN! Its interesting trying to solder these.

Anyways... QUESTION:

How do you convert a Linear CV(v/hz) to a LOG(v/octave) CV?
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mosc
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PostPosted: Mon Apr 10, 2006 5:57 am    Post subject: Reply with quote  Mark this post and the followings unread

http://www.play-hookey.com/analog/logarithmic_amplifier.html

(this are inverting amps, BTW)

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

or

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

http://www.peg.si/electro/logamp.html

Consider getting the IC Opamp Cookbook http://www.amazon.com/gp/product/0138896011/104-1861336-3611114?v=glance&n=283155

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Macaba



Joined: Jul 13, 2005
Posts: 160
Location: UK

PostPosted: Mon Apr 10, 2006 10:01 am    Post subject: Reply with quote  Mark this post and the followings unread

Just tried simulating the diode circuit. It doesn't really work out too well.

So I tried the CV expo converter off the VCO of the soundlab. That works nicely. I dunno why it didn't occur to me before to try this.

I've always wanted to get the OP-AMP cookbook, just never the money. Is there a free downloadable version, or is it still copyrighted?

EDIT:

Ahh, that last link. Most interesting, its very similar to the soundlab version.
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zipzap



Joined: Nov 22, 2005
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PostPosted: Wed Apr 12, 2006 1:19 pm    Post subject: Reply with quote  Mark this post and the followings unread

isn´t logarithmic the opposite of expotential?
I thought you use an log-amp to convert v/oct to v/hz (why would you do that?)
Vactrols are best driven by a log-amp, right?
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Macaba



Joined: Jul 13, 2005
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PostPosted: Thu Apr 13, 2006 8:31 am    Post subject: Reply with quote  Mark this post and the followings unread

An exponential is a logarithmic to the base E (approx 2.71828183).
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bigtex



Joined: Mar 30, 2006
Posts: 321
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PostPosted: Thu Apr 13, 2006 11:36 am    Post subject: Reply with quote  Mark this post and the followings unread

Look here:

http://www.themathpage.com/aPreCalc/logarithmic-exponential-functions.htm

An exponential equation using e as the mantissa (y = e^x) would be symmetrical, about y, to the natural log, or logarithm with e as the base (y = ln x)

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

The natural log, which uses e as the base, is just one specific logarithm.

y = log x would usually be assumed to have 10 as the base.

You stated that "An exponential is a logarithmic to the base E (approx 2.71828183)" which doesn't really make sense. An exponential equation can have any mantissa (base) or exponent (what base is raised to).

Sorry to get all math nerd on you... but I am a nerd at heart and I just can't help myself sometimes Smile
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Macaba



Joined: Jul 13, 2005
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PostPosted: Thu Apr 13, 2006 11:45 am    Post subject: Reply with quote  Mark this post and the followings unread

Hey, what can I say, my ass was kicked by superior knowledge!
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bigtex



Joined: Mar 30, 2006
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PostPosted: Thu Apr 13, 2006 1:11 pm    Post subject: Reply with quote  Mark this post and the followings unread

Well.... I understand the math of linear versus logarithmic, but I'm still figuring out how to get a circuit to do it right. I just need to read more schematics.

So, to be clear, in the logarithmic scaling used for audio audio, "e" never comes into play (e = 2.718281828) because we use base 10 for audio frequencies and amplitudes. That way, on a frequency graph, octaves will be equally spaced.

So... I get the math part, but I'm still learning the electronics part. I think this is kind of funny, since I've taken as many electronics classes as math classes Rolling Eyes ....oh well....
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v-un-v
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PostPosted: Fri Apr 14, 2006 3:01 am    Post subject: Reply with quote  Mark this post and the followings unread

Macaba wrote:
Hey, what can I say, my ass was kicked by superior knowledge!


me too Shocked

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Scott Stites
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PostPosted: Fri Apr 14, 2006 7:25 am    Post subject: Reply with quote  Mark this post and the followings unread

Hey BigTex,

The Korg MS-02 contains both a log amp and an antilog amp. I've got the original schemo around somewhere, but this guy has thrown a lot of work into re-drawing the schemo:

http://www.cykong.com/Synths/Korg%20MS-02/Images/Korg-MS-02-Schematics-Coloured.gif

Cheers,
Scott
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jksuperstar



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PostPosted: Fri Apr 14, 2006 9:16 am    Post subject: Reply with quote  Mark this post and the followings unread

Wow, those *are* pretty schematics!

OT -- I wish I knew what programs people used to make these, and if the software can keep up as fast as pencil/napkin. I'd like to move my urge of drawing into using a PC more, since it's soooo much more organized and repeatable. And it's hard to store napkins around. I did get a tablet to try & do this, but it's slow going, mostly due to the lack of software support.
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zipzap



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PostPosted: Fri Apr 14, 2006 10:48 am    Post subject: Reply with quote  Mark this post and the followings unread

That interests me too. very much. Especially when it comes to making a pcb layout. I´m working on this sequencer-master section right now. Where all the signals come together, are mixed, gatelength, lag and so on.
Its 9 ICs and some resistors, cabs. Well, right now, when i´m doing this i draw each ic with the related parts around it seperetly, numbering the places that have to go to other places in the shematic. Then i try to figure out how to get it all onto the board. Of course it works, but its kind of annoying sometimes, and you really have to concentrate. The larger the circuit gets, to harder it is not to need too much space, not to have too many wires going from one part of the board to another. Also the connections to the outside are spread all over the place.
I´ve tried Eagle, but the freeware version doesn´t include the autorouter. I´ve heard it´s making rather strange layouts anyhow.
But you can use it to draw nice shematics. Problem is, i guess, that you have to spend some time learning the program, to get a good workflow. For me the napkin is much faster. As long as there is a note on the napkin saying what it is its even possible to remain some kind of orginasation.
I never write notes
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toppobrillo



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PostPosted: Fri Apr 14, 2006 1:58 pm    Post subject: Reply with quote  Mark this post and the followings unread

heya i havent been on here much lately, it is starting to warm up finally outside i really can't wait for summer...

as far as auto-routing things, i have never used it. some software has this option that show you what connections have yet to be made point for point and allow you to rotate things around until none of them are crossing paths. this is all done off the schematic you have drawn. i never really liked that though. the program i use is very very simple but i like it because it is easy to keep track of what's going on visually. it does require alot of concentration for the more complex layouts. i have literally started over from scratch halfway thru if something isn't working. probably because i am obsessed with efficiency! i.e. using all space available to the maximum potential. but i only do single-sided boards [for now] .

oh, the software i use [and there are a bazillion out there] is called PCB Designer from Niche Software. Check it out it's cool and there is a demo for free.

josh
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zipzap



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PostPosted: Fri Apr 14, 2006 2:50 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
heya i havent been on here much lately, it is starting to warm up finally outside i really can't wait for summer...

true!
i´ll check that prog
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Macaba



Joined: Jul 13, 2005
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PostPosted: Sun Apr 16, 2006 6:56 am    Post subject: Reply with quote  Mark this post and the followings unread

Hey guys, might as well show you what I knocked up this morning:

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

This takes acceleration data from all three axis (X,Y,Z) and sends it down a serial data link to my computer.

My first program was a mouse program. When you tilt the board in the direction you want the mouse to move, the mouse moves that way. (Tilt because of acceleration due to gravity).

Obviously it has musical applications. Later on, I will make the data translate into MIDI signals, and see how intuitive it seems!

I will buy the 3-axis all in one accelerometer in a QFN package to experiment with, this will basically eliminate the top board in that picture because its only 6x6mm. Which makes soldering it a master feat in itself. But its doable, i'm quietly confident.

QFN package = Tiny and LEADLESS. Shocked Gotta try though. Laughing

This surface mount stuff is addictive. The surface mount parts you see in the picture are pretty much the large end of the SMT scale. The IC's are SOIC package, and the resistors and caps are 0805. I find it lots quicker to solder these compared to their through-hole counterparts. Whats more, i just do it with a pair of normal eyebrow tweezers and a $5 rat-shack soldering iron. I encourage people to try it!

Now its just occured to me that the only thing thats more expensive in transferring to SMT is the equipment to make decent PCB's. You'll probably want a UV exposure box and laserjet transparencies. But some people have this equipment for through-hole PCB making, so its a simple change really.
The board in the picture was made with a CNC engraver, simply because the PCB etching equipment at college was not then functional.

Hope this gives you all a nice insight.
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Uncle Krunkus
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PostPosted: Sun Apr 16, 2006 7:00 am    Post subject: Reply with quote  Mark this post and the followings unread

Very cool little board Mac
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