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 Forum index » DIY Hardware and Software » MusicFromOuterSpace.com designs by Ray Wilson
noise cornucopia picking up signals
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roborobert



Joined: Jan 15, 2013
Posts: 24
Location: austria

PostPosted: Sun Oct 13, 2013 1:14 pm    Post subject: noise cornucopia picking up signals
Subject description: oscillators (and others) show up in noise output
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hey there,

as far as i searched this subforum i couldn't find much helpful information on this subject.
my noise cornucopia module is picking up the signals of other vcos, lfos and envelopes.
it does it so intense that the module becomes useless. e.g. random gates not random at all anymore...

is it likely that my noise transistor is just not noisy enough?
i tried many (3904, bc550, 2n2222s, 2sc945), but even with the best scratch (...whatever) metal can 2n2222, i still had to crank up the trimmer quite a bit to get the desired aproximated +/- 5V.
is it likely that all my transistors are supersilent?
i clipped off the collector lead.

i already added ferrite beads on the power rails at the module.
also (as suggested in an older thread) i tried to add capacitance on my power bus and on the module itself ( i ended up with two 1000uF Caps showing no sign of improvement).

i do know that i have quite some party going on on my power rails, envelopes, vcos and lfos are visible there when i check the power bus on my scope in ac mode (they are also audible on the vcos themselves). if i can read my scope right the intensity is about 5-10mV for the negative rail and a bit more for the positive.
i would love to get rid of this uninvited lot but ferrite beads on each and every module as well as shielded cables all over did not do the job.

i hope someone can help,
best, rob
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rumblin_cynth_rampo



Joined: Nov 15, 2012
Posts: 33
Location: Cardiff, Caerdydd, UK

PostPosted: Fri Oct 18, 2013 7:32 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi Rob

I have only bread boarded this module.

I found that 2n3904 were OK for the noise level I went through about 20 of them and about 5 were good. Ray recommends the 2n5172 and I tried a couple of those and they were all good with little twiddling of the pots to get a nice level. Didnt have much luck with 2n2222s


Have you tired to power the module of a separate power supply (bench supply) to see if it still picking up junk.

_________________
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"Like Brahms but violent."
https://soundcloud.com/rumblin_cynth_rampo
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