[sdiy] Noise Transistor

[Ian Fritz]

At 12:47 PM 3/18/2005, raywilson at comcast.net wrote:
>Hi All
>
>What suggestions do people have for a reverse biased NPN e-b junction 
>noise generator. I am using 2N3904s with decent success but I would like 
>to know if there is a guaranteed noisiest reverse biased NPN e-b junction 
>transistor that is readily available. Does anyone ever use PNPs for this?
>
>Just curious.
>
>Thanks
>
>Ray
>
>

Well, I obviously have an extreme minority view here, but I disagree 
*completely* that you want to use the noisiest device possible.  The 
reason, as I have posted many times, is that the noisy devices always have 
a large amount of 1/f noise, which gives a gritty sound.  The only way to 
get a good, smooth-sounding noise source is to find devices with flat 
spectra at low frequency.  I once went through about 50 3904's and only 
found three with suitably flat spectra.  The best device was actually the 
one with the *lowest* output level.

   Ian