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 Forum index » DIY Hardware and Software » MusicFromOuterSpace.com designs by Ray Wilson
Troubles with my Sound Lab...
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ladislaobiro



Joined: Mar 24, 2005
Posts: 105
Location: Italy

PostPosted: Fri Oct 12, 2007 12:39 am    Post subject: Troubles with my Sound Lab... Reply with quote  Mark this post and the followings unread

Hi all,
I've sent the same questions to Ray, but maybe someone here is able to help me as well...
finally I have finished my Sound Lab... it looks really good, but it's not working like is supposed to do.
So, I’ve got some questions for you guys in order to understand where is the problem(s) and how it could be fixed...
(Please, forgive my lame english... I will try to ask questions and explain the problems as best as I can...)

VCO1:
Looks like everything’s fine here.
VCO2:
Is the PW-Modulation controlled by the LFO when switched on?
How does the PW% pot work? Should it be also working with PW-Modulation switched on?
How does the sync switch work? I’ve seen that, with sync on, the two VCOs are producing the same note only if the two frequency pots are almost in the same position (or a little shifted – meaning that the two VCOs are producing a similar note already, with sync off); otherwise, if the frequency pots are shifted a lot more, the sound produced feels a bit weird... like the addition of the two frequencies, or something like that... is it normal?
VCF:
Looks like everything’s fine here.
A.D. GEN.:
Looks like everything’s fine here.
VCA:
Is the INITIAL pot supposed to work like a volume pot when the two switches are off?
When I want to modulate the VCA with the A.D.GEN., if I want to hear it working I have to turn the initial pot CCW a lot (around minimum position area)... in this condition I can hear the output signal fading in and out, but the total amount of volume is lower compared to the volume I hear when switches are off and the pot is fully turned CW.
Is it all normal?
NOISE:
It makes some noise but not the usual “blowing wind” sound I was expecting... it makes a weird randomly “modulated” and randomly interrupted grainy and dirty sound... I don’t think it is normal...
LFO:
It works, but its behaviour is pretty weird... when setted to LOW it seems to be working fine, but if you choose a square wave modulation, you have to make sure that the ramps switch is in center position, otherwise no modulation happens and a high or low note (depending on the position of the ramps switch), is produced.
Furthermore, when LFO is setted to HIGH, the frequency feels pretty unstable... if you turn the freq pot CCW you can hear the modulation freq going down, and then it suddently goes up again with no control even if the pot is at its minimum position...
Differet settings of switches and pots give different weird results... none of them feels like a proper result... pretty unstable and un-repeatable behaviour...
An obvious consequence of this misfunctioning is that the LFO modulation activated on other modules works really weird/bad...

So, given the fact that the two main problems seem to be the NOISE and the LFO, I thought it could be connected to a faulty LF444 (IC7)... I’ve replaced this part, but nothing changed...

Any suggestion?
Is there a procedure to troubleshoot the unit?
I thank you guys in advance for your precious help...
Cheers,
ladislao
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Pehr



Joined: Aug 14, 2005
Posts: 1307
Location: Björkvik, Sweden
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PostPosted: Fri Oct 12, 2007 1:53 am    Post subject: Re: Troubles with my Sound Lab... Reply with quote  Mark this post and the followings unread

ladislaobiro wrote:
VCO2:
Is the PW-Modulation controlled by the LFO when switched on?


Yes that's wat that swith does. Smile

ladislaobiro wrote:
How does the PW% pot work? Should it be also working with PW-Modulation switched on?


It always work, switch on or off.

ladislaobiro wrote:
How does the sync switch work? I’ve seen that, with sync on, the two VCOs are producing the same note only if the two frequency pots are almost in the same position (or a little shifted – meaning that the two VCOs are producing a similar note already, with sync off); otherwise, if the frequency pots are shifted a lot more, the sound produced feels a bit weird... like the addition of the two frequencies, or something like that... is it normal?


That sounds normal. The sync effect makes the slave VCO to restart its cycly in the same frequency as the master VCO. If they're tuned right, you can get a filter-like effect. Set VCO2 to square, I think the effect is more noticeable then.

ladislaobiro wrote:
VCA:
Is the INITIAL pot supposed to work like a volume pot when the two switches are off?
When I want to modulate the VCA with the A.D.GEN., if I want to hear it working I have to turn the initial pot CCW a lot (around minimum position area)... in this condition I can hear the output signal fading in and out, but the total amount of volume is lower compared to the volume I hear when switches are off and the pot is fully turned CW.
Is it all normal?


Yes when the switches are off then it's just a volume pot. If you want it to behave like a normal synth. Set the AR switch on and turn the AR output high, you should get higher volume when fading. Cool

ladislaobiro wrote:
NOISE:
It makes some noise but not the usual “blowing wind” sound I was expecting... it makes a weird randomly “modulated” and randomly interrupted grainy and dirty sound... I don’t think it is normal...


Sounds weird... it should be pure white noise. To get that "blowing wind"-sound you have to have a llittle more resonance on the filter, and then modulate the filter with a TRI-wave from the LFO.

ladislaobiro wrote:
LFO:
It works, but its behaviour is pretty weird... when setted to LOW it seems to be working fine, but if you choose a square wave modulation, you have to make sure that the ramps switch is in center position, otherwise no modulation happens and a high or low note (depending on the position of the ramps switch), is produced.
Furthermore, when LFO is setted to HIGH, the frequency feels pretty unstable... if you turn the freq pot CCW you can hear the modulation freq going down, and then it suddently goes up again with no control even if the pot is at its minimum position...
Differet settings of switches and pots give different weird results... none of them feels like a proper result... pretty unstable and un-repeatable behaviour...
An obvious consequence of this misfunctioning is that the LFO modulation activated on other modules works really weird/bad...


When using the square you should have the other switch to TRI, that's right. But I'm not sure about the unstable frequency...

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ladislaobiro



Joined: Mar 24, 2005
Posts: 105
Location: Italy

PostPosted: Fri Oct 12, 2007 2:35 am    Post subject: Re: Troubles with my Sound Lab... Reply with quote  Mark this post and the followings unread

Pehr wrote:
Yes that's wat that swith does. Smile

ok...
Pehr wrote:
It always work, switch on or off.

ok...
Pehr wrote:
That sounds normal. The sync effect makes the slave VCO to restart its cycly in the same frequency as the master VCO. If they're tuned right, you can get a filter-like effect. Set VCO2 to square, I think the effect is more noticeable then.

nice, I got it...
Pehr wrote:
Yes when the switches are off then it's just a volume pot. If you want it to behave like a normal synth. Set the AR switch on and turn the AR output high, you should get higher volume when fading. Cool

ok...
Pehr wrote:
Sounds weird... it should be pure white noise. To get that "blowing wind"-sound you have to have a llittle more resonance on the filter, and then modulate the filter with a TRI-wave from the LFO.

nothing happens... always the same grainy interrupted sound...
maybe I can try to replace the noise transistor?
since the 2N3904 is a bit hard to find (the guy at the shop says it's a very old tranny), any suggestion for a common and easy-to-be-found sobstitute?
Pehr wrote:
When using the square you should have the other switch to TRI, that's right. But I'm not sure about the unstable frequency...

after replacing IC7, opposite to what I've said before, it looks like the LFO is working fine now...
so, except for the noise section, all the rest seems to be working fine...
in the end, it was just a matter of understanding how the unit works...
the longer you twick knobs and hit switches, the better you understand how to get sounds out of it...
thank you Pehr, very kind, fast and helpful with your reply... Smile
ladislao
P.S.: by the way, here's a pic of my unit...


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Pehr



Joined: Aug 14, 2005
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PostPosted: Fri Oct 12, 2007 4:10 am    Post subject: Re: Troubles with my Sound Lab... Reply with quote  Mark this post and the followings unread

ladislaobiro wrote:
nothing happens... always the same grainy interrupted sound...
maybe I can try to replace the noise transistor?
since the 2N3904 is a bit hard to find (the guy at the shop says it's a very old tranny), any suggestion for a common and easy-to-be-found sobstitute?

P.S.: by the way, here's a pic of my unit...


Great looking sound lab you got there! Very Happy
Nice work! Cool

I guess BC547 or BC550 would be a good replacement... perhaps BC547 is the best since BC550 is low noise Rolling Eyes
Those transistors is easier to find here in Europe, I think.

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crazeydazey



Joined: Feb 15, 2007
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PostPosted: Fri Oct 12, 2007 4:25 am    Post subject: Reply with quote  Mark this post and the followings unread

loads of 2N3904's

Oh and cool looking soundlab... nice one.. Very Happy
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ladislaobiro



Joined: Mar 24, 2005
Posts: 105
Location: Italy

PostPosted: Fri Oct 12, 2007 5:50 am    Post subject: Reply with quote  Mark this post and the followings unread

thanks Pehr and crazeydazey for your nice comments...
and thanks for the suggestion to buy the transistors on ebay, but I want to try to find them 'round here as I don't want to wait for them to come from germany... there are a couple of shops of electronic stuff around my homeplace, so it might be easier and faster to get a sobstitute...
cheers... Smile
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Pehr



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PostPosted: Sat Dec 22, 2007 7:52 am    Post subject: Re: Troubles with my Sound Lab... Reply with quote  Mark this post and the followings unread

Pehr wrote:
I guess BC547 or BC550 would be a good replacement... perhaps BC547 is the best since BC550 is low noise Rolling Eyes
Those transistors is easier to find here in Europe, I think.


Beware! the BC547 should be rotated 180 degrees in order to replace the 2N3904. The C, B and E pins are 'mirrored' on the BC547. Shocked

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fluxmonkey



Joined: Jun 24, 2005
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PostPosted: Sat Dec 22, 2007 12:26 pm    Post subject: Reply with quote  Mark this post and the followings unread

transistors will vary widely when using them as a noise source... i went thru a couple dozen 2n3904s when i built my last noize cornucopia, low output on them all. evenutally went with an older (metal can) 2n2222.

filter setting can also affect the noise pretty drasticlly. you might want to tap direct into the noise out (where r101/102 connect to noise volume pot r44) when troubleshooting, to help isolate the problem

b
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Wild Zebra



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PostPosted: Fri Dec 28, 2007 8:57 am    Post subject: Reply with quote  Mark this post and the followings unread

Wow looks great. As bobb said, I went through quite a few trannies til I found one I liked, some had very different sounds.
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Clack



Joined: Aug 08, 2005
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PostPosted: Sat Dec 29, 2007 5:36 am    Post subject: Reply with quote  Mark this post and the followings unread

Yes the noise part of the soundlab is always pretty poor, I guess the 2n3904's you get theese days are too good!
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tommi



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PostPosted: Sat Dec 29, 2007 10:47 am    Post subject: Reply with quote  Mark this post and the followings unread

Have anyone tried the LM349 or SSM2210 NPN pairs in place of Q1-3 and Q2-4 for the oscillators?
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Clack



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PostPosted: Sat Dec 29, 2007 11:53 am    Post subject: Reply with quote  Mark this post and the followings unread

yup! lm349 and a 2k tempco on the top, I built a little adaptor out of stripboard. I'll show pictures when I get back home. I havnt tested how good it is yet, I dont have my MIDI/CV up and running yet. I did test the tempco though - I put them in tune for a few 10-15 mins they didnt go out then touched my finger on one chip till they went out of tune then when I let go they went back in tune fairly quick so I guess that means the tempco works fairly well?
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tommi



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PostPosted: Sat Dec 29, 2007 12:55 pm    Post subject: Reply with quote  Mark this post and the followings unread

Stripboard? So it's impossible to mount them on Ray's board the same way as Ray's oscillator module?
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Clack



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PostPosted: Sat Dec 29, 2007 1:21 pm    Post subject: Reply with quote  Mark this post and the followings unread

there isnt much room, I did it so I could use a socket - I guess you could buy a long pinned wirewrap socket instead
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tommi



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PostPosted: Sat Dec 29, 2007 2:52 pm    Post subject: Reply with quote  Mark this post and the followings unread

I didn't knew about long pinned sockets. I wish to see a picture of your solution Mr. Clack!
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PostPosted: Sat Dec 29, 2007 2:56 pm    Post subject: Reply with quote  Mark this post and the followings unread

There is a proto area on the SL PCB for these kind of mods but I'm not sure if it is big enough. Confused
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tommi



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PostPosted: Sat Dec 29, 2007 5:34 pm    Post subject: Reply with quote  Mark this post and the followings unread

I hope that LM349's legs are long enough to permit to leave room for the tempco under!
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Clack



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PostPosted: Fri Jan 18, 2008 9:40 am    Post subject: Reply with quote  Mark this post and the followings unread

tommi wrote:
I didn't knew about long pinned sockets. I wish to see a picture of your solution Mr. Clack!



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tommi



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PostPosted: Fri Jan 18, 2008 10:08 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks mr. Clack for the picture! The matched trannies are ssm2210 isn't it? Have you tried with 3904 to hear the difference? Just less tracking or different sound?
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Clack



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PostPosted: Fri Jan 18, 2008 10:45 am    Post subject: Reply with quote  Mark this post and the followings unread

they are 394's - LM394CN
wouldn't bother putting an ssm2010 in the soundlab

I don't think it affects the sound that noticeably - the reason to use them is for tracking more than anything - im not even sure if the tempo's do anything anyway! ( they are thermally bonded they just arnt in the photo )

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