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 Forum index » DIY Hardware and Software » MusicFromOuterSpace.com designs by Ray Wilson
My Soundlab is up and running! - now the troubleshooting
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Lemmy



Joined: Apr 12, 2007
Posts: 106
Location: London
Audio files: 1

PostPosted: Sat Nov 17, 2007 8:48 am    Post subject: My Soundlab is up and running! - now the troubleshooting Reply with quote  Mark this post and the followings unread

Well, it makes sounds and it's very very cool!
I have a couple of problems though.

- Say I only have osc 1 turned up in the mixer.
If I switch in the envelope for osc 1, it's like turning on a low pass filter. The freq of the sound drops right down low. If I have the env on gate, I can use the manual gate to trigger sounds. But, there is always the low freq sound coming through, even when not triggering sounds. When I press the manual gate, the pitch soars up, then comes back down when I release the button. I can modify the low freq sound using the filter.
Is that expected behaviour?

- BP mode on the filter is quiet

- I have the fine tuners mod, and they don't do anything at all. They seem very simple, so I can't see what's wrong here... I've connected the midle pot pins to AA and BB on the panel - is that right?

LFO behaviour also seems a bit quirky, but I'll worry about that later.

Other info -
I haven't hooked up the osc 1 & 2 CV ins to the board yet, I've just got the earth wires running to them.
I have the "OSC 1 mod" mod.
I'm using quite a few bits of terminal strip on the panel to connect resistors and diodes to wires. Connections seem OK though.
I've got S&H on the panel but haven't wired it in yet.

Any suggestions?

EDIT: low pass, not high pass...
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creekree



Joined: Mar 30, 2006
Posts: 192
Location: Morgenland Neukölln
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PostPosted: Sun Nov 18, 2007 12:30 am    Post subject: Re: My Soundlab is up and running! - now the troubleshooting Reply with quote  Mark this post and the followings unread

lemmy wrote:

- I have the fine tuners mod, and they don't do anything at all. They seem very simple, so I can't see what's wrong here... I've connected the midle pot pins to AA and BB on the panel - is that right?


nope, you mixed something up here.
you've got to hook them up to points AA and BB on - and this is important - the schematics, not the ones on the panel wiring guide.

look here
point AA is pin 6 of IC5... just where you'd hook up additional CV inputs. this point is labelled X1 on the pcb. (BB is X2).
i admit, it is a bit confusing, but ray makes it perfectly clear that rectangular panel designators and circular inter-schematic dsignators are not the same.


also, the BP filter is quieter than the LP - this is a quirk of the design. yours is not the only one that does that.
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Lemmy



Joined: Apr 12, 2007
Posts: 106
Location: London
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PostPosted: Sun Nov 18, 2007 11:16 am    Post subject: Reply with quote  Mark this post and the followings unread

Excellent, thanks for pointing that out - got them working now.
I'm going to go through all my connections. If I'm still having problems I'll put out another SOS with more details.

PS. X1 and X2 aren't quite at AA and BB - they have a resistor inbetween.
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Lemmy



Joined: Apr 12, 2007
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PostPosted: Sun Nov 18, 2007 2:56 pm    Post subject: Reply with quote  Mark this post and the followings unread

OK, I think it's working fine. Very Happy

I'm pretty sure I'm getting the expected behaviour when sending the AR outputs to the oscillators. And now I've got all the always-on noise sorted by just sending the AR outs to the initial amp and setting the amp level. Duh!

This is such a cool synth! And I haven't even hooked up the S&H yet! Fun fun fun.

Thanks to everyone who has helped me with my questions so far.

OK - I have another question.
Will trying different transistors in the white noise generator, at Q7, affect the quality of the noise, or just the volume? My noise doesn't sound as consistent as it could be.
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Adam-V



Joined: Jan 29, 2007
Posts: 300
Location: Australia
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PostPosted: Sun Nov 18, 2007 3:27 pm    Post subject: Reply with quote  Mark this post and the followings unread

Yep, you need to select the transistor which gives you the best noise.

Good work on getting your SL up and running.

Cheers,
Adam-V

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Digitalis Effect | Fractured Symmetry (www.spiralsect.com)
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Lemmy



Joined: Apr 12, 2007
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PostPosted: Thu Nov 22, 2007 2:26 pm    Post subject: Reply with quote  Mark this post and the followings unread

I notice I'm not getting much out of the filter resonance except when it's turned up really high.
Would it be worth changing the value of one of connected resistors - maybe R47? (I'm guessing.)

By the way I notice my R47 is 0.6W, not 0.25W - that won't make any difference will it?
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Randaleem



Joined: May 17, 2007
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PostPosted: Fri Nov 23, 2007 12:59 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi Lemmy,

I don't have the circuit in front of me, so I don't know which resistor might be changed, but yes, you can often affect the resonance with a simple resistor change.

And the .6W rating won't make any difference in the sound. It's a power rating, the resistance in ohms remains the same for different wattage resistors of the same Ω value.

Kind regards, Randal
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Lemmy



Joined: Apr 12, 2007
Posts: 106
Location: London
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PostPosted: Fri Nov 23, 2007 11:57 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks Randaleem.
I tried reducing the resistance values going in and out of the resonance pot. I got some interesting stuff going on at the top end, extra self-oscillation I suppose, but the rest wasn't too affected. So I'll leave it unless someone else has any suggestions. (It was easier to put some resistors in parallel to reduce resistance - I didn't desolder the resistors to try higher values, but my guess is that wouldn't help?)

I have another question Very Happy Twisted Evil (Quite enjoying this fine tuning phase with the soundlab.)

When triggering sounds with the manual gate, I can't choose certain AR values without getting "always on" sound, even though my VCA pot is turned all the way down.

Example: Fairly short attack and short release - this triggers OK. But if I turn up the release value, the sound is "always on". So I can't trigger percussion type sounds with short attack and long release from the manual gate button. (Long release works OK if the attack is set to a longer value too.)

Example2: Fairly short attack and short release, OK as above. I turn down the attack to 0, and I hear low freq sounds coming through from the oscillators.

I've tried fixing the above by playing with the AR out levels and the VCA levels, but that doesn't help.

Do you think it's a bug or a feature?
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Lemmy



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PostPosted: Fri Nov 23, 2007 12:46 pm    Post subject: Reply with quote  Mark this post and the followings unread

Aha - I fixed the AR problem by disconnecting my new LFO led. I was sure it was working before and I was right. I wonder why that gave me problems? I'll have a play with it.
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Lemmy



Joined: Apr 12, 2007
Posts: 106
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PostPosted: Fri Nov 23, 2007 3:09 pm    Post subject: Reply with quote  Mark this post and the followings unread

Oops, misdiagnosis. When disconnecting the LED lfo I also disconnected the S&H. It was the S&H which was giving strange behaviour at the AR envelope.
Even when S&H input is switched to none, turning the rate above 0 results in the "always on" behaviour I described above.

By the way, the LFO led was "pulling down" the oscillators when I was using batteries, but it's fine now that I've hooked up my PSU instead. I like the way it fades in and out differently according to the wave shape selected... Cool
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