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 Forum index » DIY Hardware and Software » MusicFromOuterSpace.com designs by Ray Wilson
Patching out the sound lab...
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nerd of nerds



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PostPosted: Mon Aug 29, 2005 3:12 pm    Post subject: Patching out the sound lab... Reply with quote  Mark this post and the followings unread

Hi!

I've been thinking about starting a modular synthesizer after my sound lab is complete...seeing as modulars can be complex beasts i'd like to get a grasp of using patch cables to make sounds instead of having it rouded for me...

but it seems there isn't really a definitive howto for doing this to the soundlab...

can somebody give me some guidelines for doing this?

Thanks!
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elektro80
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PostPosted: Mon Aug 29, 2005 3:14 pm    Post subject: Reply with quote  Mark this post and the followings unread

Why not try out the G2 demo? This is a piece of software that emulates the G2.

You might of course also consider the Arturia MMV.

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nerd of nerds



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PostPosted: Mon Aug 29, 2005 3:51 pm    Post subject: Reply with quote  Mark this post and the followings unread

elektro80 wrote:
Why not try out the G2 demo? This is a piece of software that emulates the G2.

You might of course also consider the Arturia MMV.


i guess that'd work...
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elektro80
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PostPosted: Mon Aug 29, 2005 3:59 pm    Post subject: Reply with quote  Mark this post and the followings unread

You can get the G2 demo from the Clavia site. It is free.

I guess you wil have more clear ideas about what modules you want after you haveplayed around with that one a bit. The MMV is "expensive" but it is damned good. Personally I would suggest you look into the G2 demo. You probably won´t be building a Moog modular clone anyway.

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mosc
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PostPosted: Mon Aug 29, 2005 5:47 pm    Post subject: Reply with quote  Mark this post and the followings unread

Still, if you are going to build a real patchable analog modular system, this is something to consider very well.

I suggest look at every patchable analog synth you can. Check out sites like synthesizer.com and read about every module. See how they do patching - what inputs and outputs are available. Imagine how you would patch such a machine. As you do this for several different designs, you'll get a feel for it and what you want will jump out at you.

Playing with the G2 demo is fantastic, but the connection with those patch cords and real ones not congruent.

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nerd of nerds



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PostPosted: Mon Aug 29, 2005 8:40 pm    Post subject: Reply with quote  Mark this post and the followings unread

mosc wrote:
Still, if you are going to build a real patchable analog modular system, this is something to consider very well.

I suggest look at every patchable analog synth you can. Check out sites like synthesizer.com and read about every module. See how they do patching - what inputs and outputs are available. Imagine how you would patch such a machine. As you do this for several different designs, you'll get a feel for it and what you want will jump out at you.

Playing with the G2 demo is fantastic, but the connection with those patch cords and real ones not congruent.


Edit: actually, if i built the sound lab into a rackmount case (similar to the moog one) and made it patchable could i use it with other modules?

yeah, its something that i've considered in the past but never really realized how much nicer it would be than just buying something like a poly evolver...

if i get bored with the sounds (highly unlikely) i can just add another module, wheras something like a poly evolver i'd just get bored and end up getting another super expensive synth...
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PostPosted: Tue Aug 30, 2005 3:46 am    Post subject: Reply with quote  Mark this post and the followings unread

My SL is rack-mountable for exactly that reason. I put the original layout in the middle of a 19" box so later on I have space on the left for some extra add on mods, and space on the right for front access patching sockets. Everything I make now is going to be a variation on the same theme, so in the end I mount them one on top of the other, and it will all act as a mega/DIY/patchable/modular/SL/sequencer (How much is this thing gonna cost I hear you say!!) The next step is a good +/- 15V power supply (also rack mounted)
If some module doesn't patch directly into any of the others then we get out the mallet and persuade it a little!!

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Wild Zebra



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PostPosted: Tue Aug 30, 2005 6:19 am    Post subject: Reply with quote  Mark this post and the followings unread

Why don't you patch out the Sound LAb like you said. I did and its very cool you can hook it up to other synths , run stuff through the filters , etc.
It really wasn't as hard as I thought it would be. Especially with all the help around here.

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nerd of nerds



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PostPosted: Tue Aug 30, 2005 3:02 pm    Post subject: Reply with quote  Mark this post and the followings unread

Wild Zebra wrote:
Why don't you patch out the Sound LAb like you said. I did and its very cool you can hook it up to other synths , run stuff through the filters , etc.
It really wasn't as hard as I thought it would be. Especially with all the help around here.


yeah, i'm gonna patch it out, but you speak of help around here?

so far all i've gotten is people telling me wether i should or not Rolling Eyes

since you have done this before would you be willing to (be the most wonderful person in the world and) take some time and write a few paragraphs detailing how you patched it out?

Thanks!
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PostPosted: Tue Aug 30, 2005 10:41 pm    Post subject: Reply with quote  Mark this post and the followings unread

Okay,
here's an example.
At the moment you can't vary the PWM with the AR output.
So I suggest adding two patch points:-
a)PWM in
&
b)AR out
a) Find the connection which feeds the PWM voltage from the pot to the oscillator, connect a wire from this to the tip terminal of a skt. (and label it PWM IN)
b) Find the connection from the AR generator which goes to all the points on the front panel that need AR. Connect this to the tip terminal of a skt. (and label it AR OUT)
Now mount the sockets on the front panel, and when a patch lead is plugged from one into the other,.... The AR voltage will control the PWM!!
NOTE: As I've described it you've made a parallel patch point. Normally patch points are "normalised" that just means that the signal goes to the tip terminal and then through a set of contacts which are disconnected when a plug is in the skt. The other contact is connected to the point in the circuit where the signal would have gone if there was no patch point. This way when you plug in a patch lead you disconnect the circuit and force the signal to go down the lead only. The reason this is the standard with audio signals is because just hanging an extra input or output off a circuit point can cause problems with impedance matching and de-coupling of DC voltages. In a synth you can usually get away with just all inputs (or all outputs) being normalised. Sometimes you don't need to normalise at all, but assuming you don't in every case will eventually lead to the odd smoking chip!!!!

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dnny



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PostPosted: Tue Aug 30, 2005 11:25 pm    Post subject: Reply with quote  Mark this post and the followings unread

nerd of nerds wrote:

since you have done this before would you be willing to (be the most wonderful person in the world and) take some time and write a few paragraphs detailing how you patched it out?

Thanks!


if you wan´t technical info on SL. read this:How do I patch out the Sound Lab instead of building it with switches?

and if you want to learn to make patches. read this: Advanced Programming Techniques for Modular Synthesizers

it´s for Nord Modular, but
the techniques described in the document can be applied to any modular synthesizer

and you can test your patches in the Nord Modular G2 Free Software

hope this helps

daniel

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Wild Zebra



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PostPosted: Wed Aug 31, 2005 6:27 am    Post subject: Reply with quote  Mark this post and the followings unread

Let us know when you are getting real close. As Dnny pointed out the SL page has very good instructions. Thats what I followed and when I came across somerhing I couldn't figure out I ask here. Like I know there is a thread on fine tuners mod. And I'm sure I made a thread called Anybody PAtched It OUt? Just me asking some questions.

Do you have any specific questions?

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nerd of nerds



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PostPosted: Wed Aug 31, 2005 12:56 pm    Post subject: Re: Patching out the sound lab... Reply with quote  Mark this post and the followings unread

nerd of nerds wrote:
Hi!

I've been thinking about starting a modular synthesizer after my sound lab is complete...seeing as modulars can be complex beasts i'd like to get a grasp of using patch cables to make sounds instead of having it rouded for me...

but it seems there isn't really a definitive howto for doing this to the soundlab...

can somebody give me some guidelines for doing this?

Thanks!


do i just replace certain switches with bananna jacks?

EDIT: and can i power the soundlab with 12 volts? i'd like to make it the same size as a MOTM module so i can just put it in a big cabinet...then i can build a few of the simple 8 step sequencers and i'll be in business...
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Wild Zebra



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PostPosted: Fri Sep 02, 2005 6:38 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
do i just replace certain switches with bananna jacks?

Yep

Quote:
and can i power the soundlab with 12 volts?


not sure about that one

on this page http://www.musicfromouterspace.com/analogsynth/SOUNDLABMINISYNTH/SoundLabMods.html for instance with the VCA in the top right the switches are replace with 'green' dots which are now your input jacks

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ladislaobiro



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PostPosted: Fri Sep 02, 2005 7:38 am    Post subject: Re: Patching out the sound lab... Reply with quote  Mark this post and the followings unread

nerd of nerds wrote:
can i power the soundlab with 12 volts?


yes, you can... there is a good +/- 12V power supply here...
Ray suggested me to use this one for my Sound Lab, and he also told me that the higher voltages it provides will not damage the SL at all...
ladislao
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Etaoin



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PostPosted: Fri Sep 02, 2005 1:14 pm    Post subject: Reply with quote  Mark this post and the followings unread

By the way, I just took that very same diagram, replaced the transformer by an 18V one and exchanged the 7x12's bij 7x09's to make a +/-9V adapter for my SL. There's a little hum in the power lines though, so you might want to get a slightly more elaborate design to get clean power.
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Blue Hell
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PostPosted: Fri Sep 02, 2005 6:16 pm    Post subject: Reply with quote  Mark this post and the followings unread

2000 uF of elco & regulators & the thing draws almost no current at al & still hum, hmm it's probaly getting in through some other way then.

Might be loops in the ground wiring or a not so optimal routing of wires, or the transformer or the mains wires being too close to sensitive audio lines, stuff like that.

Or maybe the transformer output voltage is not high enough, when you have an oscilloscope you should check that the lowest voltage over the elcos does not go too much below 9 V + about 3 Volt for the regulators = 12 V).

You could calculate this as well, but that needs some assumptions and quite some work.

A rough estimate would suggest a > 13 V transformer to be needed, allowing for some reasonable variations in mains supply voltage, some regulation of the transformer, some drop over diodes, some ripple over the elcos and some regulation headroom for the regulators.

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Macaba



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PostPosted: Sat Sep 03, 2005 3:37 am    Post subject: Reply with quote  Mark this post and the followings unread

If you want the end product to be 12v, then you start with about 18v. You also use quite a bit more capacitance (Think 10000uf at least), and always use regulators.
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PostPosted: Wed Sep 14, 2005 10:33 pm    Post subject: Reply with quote  Mark this post and the followings unread

there is now a .pch2 file that emulates Sound Lab!
whit this and G2 demo you can explore SL posibilities.

Emulation of the SoundLab analog synth. Basic building blocks, knobs, and MIDI only.

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PostPosted: Sun Sep 18, 2005 10:09 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
Or maybe the transformer output voltage is not high enough, when you have an oscilloscope you should check that the lowest voltage over the elcos does not go too much below 9 V + about 3 Volt for the regulators = 12 V).


I'm not sure why I should measure the voltage with an oscilloscope instead of a volt meter? Anyway, the voltage across the capacitors is 14.35 V, which is more than enough.

Quote:
A rough estimate would suggest a > 13 V transformer to be needed


This would imply the whole design on musicfromouterspace is faulty as well, since that uses 2x12.5V to get 2x12V. I think you're missing the increase in voltage here you get from the rectifier.

By the way, my power supply is seperate (physically) from the SL and about two metres away. The only wires leading from the power supply to the SL are the -9V, ground and +9V lines.
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Macaba



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PostPosted: Mon Sep 19, 2005 12:16 am    Post subject: Reply with quote  Mark this post and the followings unread

You don't get an increase of voltage from the rectifier, no, this is what is actually happening:

The transformer says its rated at 12v RMS, which is a good measurement for AC. When you rectify into DC, you have to un-RMS it which is about 15v DC.
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PostPosted: Mon Sep 19, 2005 12:42 pm    Post subject: Reply with quote  Mark this post and the followings unread

Let me try to explain. I might go wrong somewhere as it's been quite a while since I did any electronics - if so please correct me, anyone.

After the rectifier you have peaks and vallies in the signal that you try to smooth out by using a capacitor. When the vallies go below the input voltage needed for the regulator to be able to regulate, some of the fluctuations will ripple through to your output votage which will result in hum to be produced on your circuit's outputs.

Using a voltmeter this is sort of hard to judge as the measurement will be "smeared out" over time, the voltage is averaged. A scope would allow you to see the actual lowest (and highest) values of the voltage.

Some example calculations.

When you measure the AC voltage of a transformer the peak voltage will be about 1.4 times as high. So when you have a 12 Volt transformer your peaks will be just below 17 volt. You'll have to subtract about 1.4 V for the diode drop, which gives you peaks of about 15.5 volt.

When you want 12 volt output from this the valies can't be lower than 15 volts (as the regulaters need 3 V to be able to regulate), allowing for a ripple of 0.5 Volt, which is not very much especially as the transformer's output voltage will drop when you start to draw current from it - especially cheap transformers will act bad in this respect (unless you greatly overrated the transformer for the current you want to draw from it).

And I didn't allow for any fluctuations in the mains voltage yet, which could be as high as 10 or even 15%. The 0.5 Volt above would allow for a mains voltage to be about 5% low, that is when no current is drawn from the supply.

To be able to judge how much ripple you can expect, or need rather, over your smoothing capacitor you'd want to know how large the capacitor is and how much current is drawn from it. Then with some aproximations this can be calculated, but it's far easier to see what actually happens on a scope.

When you do want to calculate it, 1 mA drawn from a 1 mF (or 1000 uF) capacitor will give a voltage drop of about 1 Volt after one second. Doubling the capacitor halves the voltage drop, doubling the current doubles it. For a 50 Hz mains and assuming double rectification the discharge time will be a bit less than 10 ms. This is not exact, but a reasonable first order aproximation.

So let's say you have 1.000 uF and want to draw 50 mA in 10 ms : as C = Q / V or C = I * t / V or V = I * t / C you'll get V = 0.5 V - just to get an idea about orders of magnitude.

That's the sort of reasoning I had in mind, and so, to answer your question:

Yes a 12.5 V transformer to make a 12 V regulated supply is kind of lousy I think, although when you draw almost no current from it and your mains supply is good you might get away with it.

And the other point. measuring 14.35 V over your capacitor. This means your lowest value will be somewhat lower than this value, how much lower can be estimated when knowing the value of the capacitor and the current drawn (just like I did in the example above).

Now the assumption I made earlier for the regulators to need 3 V was an estimation for the 7812 type regulator, you'd have to look up actual values in a data sheet (but these are not "nice figures" so you'll have to interpret the data sheets carefully - manufacturers for sure know how to hide the bad behaviour), but IMO 14.35 V is lowish indeed for hum free operatiion, I'd like to see something like 16 V rather. But, as said before, it depends on how much current is actually drawn and on how large your capacitor is.

You could try to do an AC measurement on the DC output of your supply to get a rough indication of how bad things are. When you see just a few mV you'll be alright probably, but 10's of mVolts could mean trouble.

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Etaoin



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PostPosted: Mon Sep 19, 2005 1:48 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
Now the assumption I made earlier for the regulators to need 3 V was an estimation for the 7812 type regulator, (...) but IMO 14.35 V is lowish indeed for hum free operatiion, I'd like to see something like 16 V rather.


Point is, I'm using NOT using the 7812, but the 7809. I have a 9V power supply as the SL needs 9V, not 12V. So I'm 5.35V over what I need. Should be enough shouldn't it? Too much and it will just end up as heat anyway.
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PostPosted: Mon Sep 19, 2005 2:36 pm    Post subject: Reply with quote  Mark this post and the followings unread

Oh, I 'm sorry, I thought you wanted to make 12 V, thought I'd read that somewhere. As I said before somewhere I tend to read over the obvious, sorry again.
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