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 Forum index » DIY Hardware and Software » MusicFromOuterSpace.com designs by Ray Wilson
sound lab mini VCO
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synthesist



Joined: Feb 17, 2011
Posts: 79
Location: austria
Audio files: 2

PostPosted: Sat Mar 26, 2011 1:06 pm    Post subject: sound lab mini VCO
Subject description: doesnt make beep- beep
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hey!

I started to build a soundlab mini synth on stripboard.
The noisegenerator and the LFO is working so far.
Now that I finished the first VCO, I thought I would test it before I go on with VCO No. 2.
I hooked up my earphones to the oscillator but I dont hear a sound. Only when I touch the cables where I hook up the earphones there is a scratchy short sound. I changed the phones with a LED and it is glowing. So there is some current coming out.
Is it possible that you can hear the VCO only after it went through the filter and the VCA?
I mean it's stripboard and that makes it complicated to control the connections and everything. But I do search and cannot find a bug.

I am lost.. . ..
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jordroid



Joined: Jan 17, 2010
Posts: 193
Location: ithaca, new york

PostPosted: Mon Mar 28, 2011 7:01 am    Post subject: Reply with quote  Mark this post and the followings unread

Hello,

A little more information would be helpful,

you wrote-

"I hooked up my earphones to the oscillator but I dont hear a sound."

Where exactly are you hooking them up to (IC pin? switch? jack?), and are you probing the circuit directly with a wire from the headphones?

Opamp outputs may not be happy directly driving headphones, and you may not get reliable information from them. Ray shows a simple audio probe on the MFOS site under "synth DIY" then "hot tips" then "guitar amp signal tracer" that can be helpful if you don't have access to a scope.

VCO1 can be seen or heard at IC5-D pin 14. VCO2 ramp can be heard at IC6-D pin 14, and VCO2 pulse can be heard at IC2-A pin 1. These will be fairly hot signals so be cautious when first listening. Also, if the coarse tuners are turned down the oscillators will be running at a subaudio frequency and you won't hear them.

Regards Smile

jordan
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synthesist



Joined: Feb 17, 2011
Posts: 79
Location: austria
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PostPosted: Mon Mar 28, 2011 1:23 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thanks a lot for answering.

I hooked the earphones up to a breadboard- through a phone jack. Pin No. 8 already has a cable soldered on the stripboard, so I only have to stick it into the breadboard. I do the same with the ground connection.
But there is no capacitor or resistor between the signal from pin no. 8 and my earphones. Maybe there is the problem?
I checked the guitar amp signal tracer tip from ray wilson. A pity I dont even have a guitar amp. I may try it anyway with using my cassette player's input instead.

You wrote:

Also, if the coarse tuners are turned down the oscillators will be running at a subaudio frequency and you won't hear them.

I turned them all the way - no there is no sound.
I tested the sound of the noise generator circuit the same way. And it works well, I can hear the windy noise.
To be honest, I thought I could always just pick up an audible oscillator signal directly with my earphones... Shocked
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jordroid



Joined: Jan 17, 2010
Posts: 193
Location: ithaca, new york

PostPosted: Wed Mar 30, 2011 6:00 pm    Post subject: Reply with quote  Mark this post and the followings unread

I'm really not sure if one can reliably hook a pair of headphones straight to an opamp output, it seems like most common phones have a pretty low impedance, and wondered if an opamp would comfortably drive such a low impedance, maybe someone more knowledgeable will chime in about it. If it's working for you with the noise output maybe it's ok.

Other than that i'm not sure what to suggest beyond standard troubleshooting tactics, visually check for shorts/ missed or cold solders/ wrong component/ missing jumper/ verify connections with a multimeter set to beep mode/ print a couple copies of the schematic and highlight each connection as you verify it with your meter.

Ray has some good troubleshooting tips on the MFOS site as well.

If you can find a friend with a scope it would be the ideal tool for the job, but if that is not possible you can still get it with some perseverance.

You can focus your efforts on the VCO page of the schematics Since it is a proven circuit and you are building it on stripboard the solution is probably just a simple error that you have not spotted yet.

You could check the operation of the VCOs with just a multimeter by dialing the coarse tuner way down and measuring the DC voltage at pin 14 of IC5-D (for VCO 1), the voltage should slowly ramp up and then abruptly drop down, and then start ramping again, always ramping to the same level before jumping down again, at a rate controlled by the coarse tuner. Or that could be backwards, but either way if it's operating properly the frequency should get low enough for that to work.

Good luck Smile
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jordroid



Joined: Jan 17, 2010
Posts: 193
Location: ithaca, new york

PostPosted: Thu Mar 31, 2011 3:19 pm    Post subject: Reply with quote  Mark this post and the followings unread

I remembered the thread dealing with headphone/opamp problems, it's here http://electro-music.com/forum/topic-41765.html

maybe worth a read.

Smile
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synthesist



Joined: Feb 17, 2011
Posts: 79
Location: austria
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PostPosted: Wed Apr 06, 2011 11:33 am    Post subject: Reply with quote  Mark this post and the followings unread

He!
Biggest thanks jordroid. You are right.

First I tried it by plugging the oscillator into the cassette-player - still no sound.

Today I have found there was a 10 k resistor missing in one spot of the circuit. But after fixing this, the phones still didnt make a sound.
Finally I plugged the osc. into my diy amplifier and... well I can here it oscillate. Very Happy

In German we call this shit-thing "Impedanz". An AC-depended resistance or something thats way too complicated for my small crackhead brain to understand and which makes my life even more worse and so I have to suffer...
But now it makes beeps.
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Ojd



Joined: Feb 22, 2008
Posts: 65
Location: Ua
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PostPosted: Wed May 04, 2011 3:12 am    Post subject: Reply with quote  Mark this post and the followings unread

could you post your stripboard layouts for VCO 1 and 2? It would be very helpful for other who build the thing.
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synthesist



Joined: Feb 17, 2011
Posts: 79
Location: austria
Audio files: 2

PostPosted: Wed May 04, 2011 6:15 am    Post subject: Reply with quote  Mark this post and the followings unread

@Ojd
I draw the stripboard layouts always on squared paper cause I dont have a program. I know there is a program called "lochmaster" for veroboards. But I dont wanna pay for it.
Do you know an apropriate shareware I could use?
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Ojd



Joined: Feb 22, 2008
Posts: 65
Location: Ua
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PostPosted: Fri May 06, 2011 1:55 am    Post subject: Reply with quote  Mark this post and the followings unread

http://www.google.com.ua/search?hl=ru&source=hp&biw=1280&bih=686&q=diy+layout+creator&oq=diy+layou&aq=0&aqi=g3&aql=&gs_sm=e&gs_upl=369l2273l0l9l8l0l2l2l0l161l583l2.4
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synthesist



Joined: Feb 17, 2011
Posts: 79
Location: austria
Audio files: 2

PostPosted: Sun May 08, 2011 1:10 am    Post subject: Reply with quote  Mark this post and the followings unread

this link sucks. There are many sites where I could download the layout creator, but after the second try I gave up. The program doesnt work and I dont wanna get an infection.
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inlifeindeath



Joined: Apr 02, 2010
Posts: 315
Location: Albuquerque, NM

PostPosted: Mon May 09, 2011 6:34 am    Post subject: Reply with quote  Mark this post and the followings unread

synthesist wrote:
this link sucks.


Well, don't expect that dude's help again. If aren't competent enough to find a program on your own, don't be a d*ck when someone tries to help you out.

_________________
http://www.youtube.com/user/borisandfef
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synthesist



Joined: Feb 17, 2011
Posts: 79
Location: austria
Audio files: 2

PostPosted: Mon May 09, 2011 2:08 pm    Post subject: Reply with quote  Mark this post and the followings unread

@Ojd
Sorry for that. Embarassed
I'd better think before writing the next time.
Thanks for the link anyway.
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inlifeindeath



Joined: Apr 02, 2010
Posts: 315
Location: Albuquerque, NM

PostPosted: Mon May 09, 2011 6:04 pm    Post subject: Reply with quote  Mark this post and the followings unread

good man, here's a link that will work
http://diy-fever.com/software/

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