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crazeydazey
Joined: Feb 15, 2007 Posts: 303 Location: England
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PHOBoS
Joined: Jan 14, 2010 Posts: 5581 Location: Moon Base
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Posted: Wed Sep 19, 2012 8:09 am Post subject:
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hmm, the circuit looks fine to me. I have noticed that some of those transistor noise circuits need a
supply voltage higher then 9V to function correctly (might also depend on the transistor used). I don't
know what you're using, but since your white noise is ok; that's not the problem.
As far as I know pink noise is filtered white noise which looks to be what's happening in the circuit.
this would make it a bit softer but I see the opamp used for the filter adds extra gain,. so that takes
care of that. The only thing I can think of right now is that you might have used a capacitor that's
too big (C7), thereby filtering out too much. You could test how it sounds without the cap, it should
be the same white noise but louder. If not you might have used a wrong resistor (R7/R8 ) ? _________________ "My perf, it's full of holes!"
http://phobos.000space.com/
SoundCloud BandCamp MixCloud Stickney Synthyards Captain Collider Twitch YouTube |
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crazeydazey
Joined: Feb 15, 2007 Posts: 303 Location: England
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Dave Kendall
Joined: May 26, 2007 Posts: 421 Location: England
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Posted: Wed Sep 19, 2012 3:51 pm Post subject:
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Hi.
You can have a lot of fun with varying the resistor and cap values at the pink noise section (where PHOBos said)
If you feel adventurous, you could try subbing R7 with a fixed 10K resistor and a 100K pot in series, and R8 with, say a 47K fixed and a 470K pot. Before powering up the circuit, set both new "pairs" to read the original values (68K and 220K). Then slowly change one or the other, and check the effect. The character and/or the gain of the noise will change. Try adding caps in parallel to C7, or subbing different value caps, and it will change even more.
A combination of pots and a multipole switch for sets of resistors and caps could give you an interesting range of variable noise sources.....
The pots on the outputs can be safely omitted. It might be better to take care of attenuation with an attenuator on the next module after, and leave the output impedance of the two noise sources at a "standard" 1K.
Lastly, there is a faint hum at the "A" below middle C on both Noise outputs in the .WAV. Not necessarily a problem though. It might be from all sorts of places, but could easily be from the 2N3904, as AFAIK, in this sort of circuit they will all sound different to some degree (but you probably know that already) .....
cheers,
Dave _________________ "Everything in moderation, including moderation" |
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crazeydazey
Joined: Feb 15, 2007 Posts: 303 Location: England
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Posted: Thu Sep 20, 2012 1:43 am Post subject:
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Hi Dave,
Thanks for reply I will certainly be giving that a try later on a bit of breadboard cheers
but I've knocked this together now on veroboard and don't want to be hacking away unsoldering and resoldering components, so I think I'll leave this one as is and start again ... always fun
2 things though.. 1 didn't really understand your comment about faint hum at the "A" below middle C.. you have a better ear than me , I can't hear any hum, or it is something you've seen on a scope???
and about getting rid of the pots.. I do quite like the idea of been able to control the level of the noise, I quite like the look of this, but I see what your saying.. is there anywhere else I could maybe add the pot somewhere else so we still have the 1K output imp but can also control the level.. maybe even like the synth dotcom Q110 so can control both white and pink together?? (I could even stick another simple filter on the end and have a low freq out ... nah, again would mean hacking around at my circuit.. leave that one.. maybe add it on the next one _________________ Nothing is impossible, unless you can't do it!!! |
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crazeydazey
Joined: Feb 15, 2007 Posts: 303 Location: England
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Posted: Thu Sep 20, 2012 2:27 am Post subject:
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could I cut the circuit on the -ve side of C6 and stick a big pot it?? _________________ Nothing is impossible, unless you can't do it!!! |
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JingleJoe
Joined: Nov 10, 2011 Posts: 878 Location: Lancashire, England
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Posted: Thu Sep 20, 2012 2:29 am Post subject:
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I think pink noise is low pass filtered white noise, isn't it?
To solve your original problem I'd add more gain to the filter op amp (U3B). _________________ As a mad scientist I am ruled by the dictum of science: "I could be wrong about this but lets find out"
Green Dungeon Alchemist Laboratories |
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crazeydazey
Joined: Feb 15, 2007 Posts: 303 Location: England
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Posted: Thu Sep 20, 2012 2:37 am Post subject:
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cheers jinglejoe.. is that in response to my wav file I posted.. do you still think it's too quiet??
Quote: | I think pink noise is low pass filtered white noise, isn't it? |
yeah I think so.. is this because I said about having a low freq out on it???
I think looking the the dot com Q110 that I pinched that idea from it's just an even more filtered pink noise??? (prob not much point then really ) _________________ Nothing is impossible, unless you can't do it!!! |
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blue hell
Site Admin
Joined: Apr 03, 2004 Posts: 24075 Location: The Netherlands, Enschede
Audio files: 277
G2 patch files: 320
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JingleJoe
Joined: Nov 10, 2011 Posts: 878 Location: Lancashire, England
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Posted: Thu Sep 20, 2012 5:10 am Post subject:
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crazeydazey wrote: | cheers jinglejoe.. is that in response to my wav file I posted.. do you still think it's too quiet??
Quote: | I think pink noise is low pass filtered white noise, isn't it? |
yeah I think so.. is this because I said about having a low freq out on it???
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Yes, sorry, bit of a half asleep, just-woke-up post
It would turn it into red noise or brown noise ... let me check blue hell's link before I make any certain statements though _________________ As a mad scientist I am ruled by the dictum of science: "I could be wrong about this but lets find out"
Green Dungeon Alchemist Laboratories |
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crazeydazey
Joined: Feb 15, 2007 Posts: 303 Location: England
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Posted: Thu Sep 20, 2012 5:26 am Post subject:
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no worries ..
yeah checked that link out myself cheers blue hell, wow lots of noises
didn't read much of it, as it started going over my head a little but looks like they are just all white noise with various filters applied.. I imagine that wouldn't be to hard to build, maybe my next project _________________ Nothing is impossible, unless you can't do it!!! |
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JingleJoe
Joined: Nov 10, 2011 Posts: 878 Location: Lancashire, England
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Posted: Thu Sep 20, 2012 6:46 am Post subject:
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As you filter it the amnplitude will likely decrease unless you use an active filter with gain, or add an amplifier stage with appropriate gain to the end of a simple old passive filter. _________________ As a mad scientist I am ruled by the dictum of science: "I could be wrong about this but lets find out"
Green Dungeon Alchemist Laboratories |
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blue hell
Site Admin
Joined: Apr 03, 2004 Posts: 24075 Location: The Netherlands, Enschede
Audio files: 277
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Posted: Thu Sep 20, 2012 6:55 am Post subject:
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My fav is "drunkard's walk" noise, or brown(ian) noise which is nice for melody generation (with a S&H (and a quantizer if you want 'well defined notes')).
Pink noise would require a 3 dB roll off fillter, but you could also use a 6 or 12 dB roll off and mix some of the (possibly inverted) white in I guess. _________________ Jan
also .. could someone please turn down the thermostat a bit.
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