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 Forum index » DIY Hardware and Software
make some noise!!!
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crazeydazey



Joined: Feb 15, 2007
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PostPosted: Wed Sep 19, 2012 4:25 am    Post subject: make some noise!!! Reply with quote  Mark this post and the followings unread

hi chaps..

I recently made this circuit.

the white noise seems good and noisy and white (what ever white sounds like Smile)

but the pink is very very quiet... I assume the should both be the same volume just sound slightly different???

has anyone else made this and got same result??? if so does anybody know how to fix?? or is it me?? I have checked double checked triple and quadruple checked my circuit and it looks fine, everything goes where it should.. tried lots of different 2n3904s.

cheers all

daz


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PHOBoS



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PostPosted: Wed Sep 19, 2012 8:09 am    Post subject: Reply with quote  Mark this post and the followings unread

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. Wink

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 ) ?

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crazeydazey



Joined: Feb 15, 2007
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PostPosted: Wed Sep 19, 2012 8:58 am    Post subject: Reply with quote  Mark this post and the followings unread

yep I think that's the problem, I had a 0.1uf instead of a 0.01uf

it's now a bit louder.. still not 100% sure it's right volume, but I guess if pink noise is just filtered white noise, then it will be quieter..

does it sound about right???

oh and thank you my friend, you are a genius Smile

(btw 1st one is white, 2nd is pink, but I'm sure 99.999% of you already knew that Smile - I wouldn't Sad)


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Dave Kendall



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PostPosted: Wed Sep 19, 2012 3:51 pm    Post subject: Reply with quote  Mark this post and the followings unread

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) ..... Smile

cheers,
Dave

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crazeydazey



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PostPosted: Thu Sep 20, 2012 1:43 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi Dave,

Thanks for reply I will certainly be giving that a try later on a bit of breadboard cheers Smile

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 Smile

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 Smile, 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 Smile

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crazeydazey



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PostPosted: Thu Sep 20, 2012 2:27 am    Post subject: Reply with quote  Mark this post and the followings unread

could I cut the circuit on the -ve side of C6 and stick a big pot it??
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JingleJoe



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PostPosted: Thu Sep 20, 2012 2:29 am    Post subject: Reply with quote  Mark this post and the followings unread

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).

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crazeydazey



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PostPosted: Thu Sep 20, 2012 2:37 am    Post subject: Reply with quote  Mark this post and the followings unread

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 Smile)

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Blue Hell
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PostPosted: Thu Sep 20, 2012 2:59 am    Post subject: Reply with quote  Mark this post and the followings unread

About the colors of noise : http://en.wikipedia.org/wiki/Colors_of_noise
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JingleJoe



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PostPosted: Thu Sep 20, 2012 5:10 am    Post subject: Reply with quote  Mark this post and the followings unread

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???

Yes, sorry, bit of a half asleep, just-woke-up post Laughing
It would turn it into red noise or brown noise ... let me check blue hell's link before I make any certain statements though Wink

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crazeydazey



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PostPosted: Thu Sep 20, 2012 5:26 am    Post subject: Reply with quote  Mark this post and the followings unread

Smile no worries ..

yeah checked that link out myself cheers blue hell, wow lots of noises Smile

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 Smile

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PostPosted: Thu Sep 20, 2012 6:46 am    Post subject: Reply with quote  Mark this post and the followings unread

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.
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PostPosted: Thu Sep 20, 2012 6:55 am    Post subject: Reply with quote  Mark this post and the followings unread

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.

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