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 Forum index » DIY Hardware and Software
2 vco's phase issue
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AndyR1960



Joined: Feb 16, 2007
Posts: 284
Location: Manchester UK
Audio files: 5

PostPosted: Sun Sep 15, 2013 4:23 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi Isak,

Everything looks ok at first glance...

But I'm intrigued that you're using the sawtooth output as a source for the sub-osc.

It's common practice to use square waves to drive a 4013 divider, and the Oddy VCO has the dedicated Ring Mod output which is ideal for this without the need for buffering (it's a clean square/pulse @ 0-10v).

I can't help thinking that this has a bearing on things - Is the 4013 well de-coupled (100n cap as close as possible across pins 7 & 14 of the 4013).

Beautiful looking synth by the way.
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isak



Joined: Dec 13, 2009
Posts: 703
Location: Israel
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PostPosted: Sun Sep 15, 2013 6:05 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi Andy.

yes, i know about the pulse out, but as i understand most of us do it with saw wave, dont know why though..
i'll try to change the source input of the subosc from the ody pulse if you think its a problem.

about the subosc this is the scheme and my layout, if you have any suggestions about my layout i'll be happy to hear Smile

thanks again man.

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Quote:
Beautiful looking synth by the way.

thank you for your kind words, i think its nothing compare to your amazing project that blow my mind to space Wink

Last edited by isak on Sun Sep 15, 2013 6:42 am; edited 1 time in total
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PHOBoS



Joined: Jan 14, 2010
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Location: Moon Base
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PostPosted: Sun Sep 15, 2013 6:31 am    Post subject: Reply with quote  Mark this post and the followings unread

I think you have Q2 reversed on the layout (if you're using a 2N3904). And as AndyR1960 mentioned I'd use a square/pulse wave not a saw. CMOS chips
can act a bit unpredictable with analog voltages.

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isak



Joined: Dec 13, 2009
Posts: 703
Location: Israel
Audio files: 18

PostPosted: Sun Sep 15, 2013 6:42 am    Post subject: Reply with quote  Mark this post and the followings unread

PHOBoS wrote:
I think you have Q2 reversed on the layout (if you're using a 2N3904). And as AndyR1960 mentioned I'd use a square/pulse wave not a saw. CMOS chips
can act a bit unpredictable with analog voltages.

yes iv'e noticed that and forgot to change it in my layout, on the pcb its ok Smile
thank you for letting me know.

i think the question should be, does the 4013 circuit should influence the vco's while in the mixer his vol is down?
or the maybe its the buffering circuit that influence on the vco's?

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isak



Joined: Dec 13, 2009
Posts: 703
Location: Israel
Audio files: 18

PostPosted: Wed Sep 18, 2013 11:57 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi guys.

the synth just came back to me and i can run some tests.
quick test question...
assuming the subosc or the buffering making the phase problem, if i disconnect the subosc and the buffering board from power, will it be the right way to test this matter?

now the situation is...does not matter which waveshape i use in the VCO's, they phasing no matter what.
if i'll disconnect the buffer board and the subosc it will leave me only with the square wave from VCO 2, i think its enough for test, dont you?

cheers.

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