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 Forum index » DIY Hardware and Software » MusicFromOuterSpace.com designs by Ray Wilson
Noise Cornucopia question
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otcx



Joined: Jan 14, 2006
Posts: 71
Location: Finland
Audio files: 4

PostPosted: Tue Dec 20, 2011 7:53 am    Post subject: Noise Cornucopia question Reply with quote  Mark this post and the followings unread

I am building Noise Cornucopia Revision 0 (Original) and i am missing caps C4, C16 10pF. How essential those caps are, and is it safe to test circuit without them. I have hard time to finding them in a moment, and i would like start testing.
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Mongo1



Joined: Aug 11, 2011
Posts: 411
Location: Raleigh NC

PostPosted: Tue Dec 20, 2011 11:14 am    Post subject: Reply with quote  Mark this post and the followings unread

It looks to me like C4 is providing some high-frequency rolloff as part of the feedback loop of U1-A. The circuit will probably still work, but the frequency content may not be quite right.

The C16 cap is a bit more mysterious to me. I'm not sure what the intent is of that one.

In either case I think running without these caps is 'safe' - but you'll definitely want to get those caps.

Gary
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jordroid



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

PostPosted: Tue Dec 20, 2011 11:18 am    Post subject: Reply with quote  Mark this post and the followings unread

It will work for sure without C4, and probably C16 as well, it won't hurt anything to try it without them. If you have a stash of 20pF or 22pF caps you could get 10pF by putting two of them in parallel.

I say go for it and install them later.

regards,

jordan

:edit: simultaneous post with Mongo1, hi mongo
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Mongo1



Joined: Aug 11, 2011
Posts: 411
Location: Raleigh NC

PostPosted: Tue Dec 20, 2011 11:23 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
If you have a stash of 20pF or 22pF caps you could get 10pF by putting two of them in parallel.


Oops - that's not correct.

Caps work differently than resistors. If you put 2 caps in parallel they add together.

Put the caps in series to reduce the value. Here's a handy webpage....
http://farside.ph.utexas.edu/teaching/302l/lectures/node46.html

Gary
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jordroid



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

PostPosted: Tue Dec 20, 2011 11:29 am    Post subject: Reply with quote  Mark this post and the followings unread

Doink, of course you are right, thanks for the correction. I meant series, really i did Embarassed

jordan
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Mongo1



Joined: Aug 11, 2011
Posts: 411
Location: Raleigh NC

PostPosted: Tue Dec 20, 2011 11:47 am    Post subject: Reply with quote  Mark this post and the followings unread

Yep - you were probably just distracted by octx's little avatar picture. I know I sure am....

Gary
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