[sdiy] When building a White Noise module has anyone ......

[Oren Leavitt]

What type of amplifier are you using?
Sounds like the rail-rail clipping of the amplifier is producing (or 
transmitting) RF harmonics though the 2ft patch cord (antenna).
You might try a slower op-amp in the stage that is clipping.
- Oren

Rykhaard D.A.M.I.A.N. wrote:
> On 1/9/06, *harrybissell* <harrybissell at prodigy.net 
> <mailto:harrybissell at prodigy.net>> wrote:
> 
>     One idea...
> 
>     Power the noise module, alone... from a couple of batteries.
> 
>     Remove it entierly from the modular, and hook it up with only
>     two wires... a ground and a signal.  One shielded cable should
>     be sufficient.
> 
>     If your problems go away... you have power supply or grounding
>     issues.
> 
>     If they don't go away... you have something VERY strange in your
>     noise module.
> 
> 
> K.  Thanks Harry. :)  I never thought of that.  :) 
> With the progress that I'd made, after I'd writ the original message, I 
> don't think that it's too severe. :)  But, I'm still going to try your 
> suggestion, anyways. :)
> 
>     You migth try the noise module with only ONE wire... the ground.
> 
>     You can try your noise module with NO wires.
> 
> 
> This was close to how it was, when I first powered up.  It was hooked up 
> (outside of power) only to the scope, to verify it's operation, or not.  )
> 1st - 2N3904 (100 times + 100 times amplification) - almost rail to rail 
> noise on the scope
> 2nd - 2N2712 (same amplification) - noise on the scope was about 60mV 
> peak to peak
> 3rd - different 2N3904 (same as 1st)
> 
> As I'd said in my last message - changing the 2nd amp to a pot, helped 
> greatly. :)
> 
> I'm still going to check into extra filtering as well, though.  With the 
> full amplification and the 2 foot banana cord, just moving the cable 
> away from any other patch cables, greatly helped reduce the amplitude of 
> the noise, through the system. :O
> 
>     (I once showed a manufacturer that I could noise hit their solid
>     state relay modules through the air... but totally floating their
>     module and making a noise spike nearby.  They had been blaming EVERYONE
>     else for the problem for months. After that, they went home quietly
>     and fixed their sh!t !!!)
> 
>     Where can you see the noise on the scope ???
> 
>     H^) harry
> 
> 
> Harry!  You have ALL of the fun in life, with electrical things!  :D :D
> Blaming every1 else, for months. :O  hahahahaha. :D  Cool experience. :O :)
> 
> The noise on the scope, through all above mentionings, is properly 
> centered about ground, as well.  No offsets.  It's good looking, 
> anyways. :)
> 
> I figured at worst case - if I couldn't get this 'repaired' properly, I 
> would just keep a lower amplitude version of it running, as a switch on 
> / off source for the on board Sample & Hold only. :)  Shall see what 
> happens tomorrow. :)
> 
> I came up with a new VCO idea tonight at work.  I'm off to the Design 
> section of my webpage, to post it at. :)
> 
> Thank you both, greatly, for your help and suggestions! :O :O
> 
> Funny in a way - I come back to building modular gear, after almost 10 
> years - forgetting a lot of stuff - and run in to completely NEW 
> problems. :O  Hahaha.  All part of learning.  And the help is far 
> beyond, appreciated, from everyone. :O 
> Someday - I hope to be able to do the same, for others. :)
> 
> -- 
> Take care,
> Warmth and Peace,
> Ryk
> 
> http://deathlehem.bravehost.com/damian.html - D.A.M.I.A.N.;s webpage - 
> Jan. 0406 update