White noise generator

[John Larkin]

Noise across the audio spectrum of a small speaker. The speaker will be
some metres away from the signal generating part of the device. The noise
level must be controllable nearly upto the limit of the speaker.

I have just about come around to the idea of a 12 volt Zener diode driving
two LM741s followed by a LM368N to drive the speaker. The op-amps would
have a 12 volt unbalanced supply with the + inputs of the LM741s biassed to
6 volts. The parts are all available and cheap. I have the speaker. Would
this work in your view?

R

You can't really zener a 12-volt zener from a 12-volt supply.

And 741's are notoriously noisy themselves, which can cut both ways.

John

 

[Roger Dewhurst]

You can't really zener a 12-volt zener from a 12-volt supply.

And 741's are notoriously noisy themselves, which can cut both ways.

John

Thanks. Should I use a lower voltage zener diode then? The extra noise
will not matter.

Roger

 

[John Larkin]

Thanks. Should I use a lower voltage zener diode then? The extra noise
will not matter.

Roger

If you use a 6-ish volt zener, it can be the supply splitter, too!

John

 

[Roger Dewhurst]

If you use a 6-ish volt zener, it can be the supply splitter, too!

John

Connect the + input directly to ground and feed the signal through a (?)100
nF capacitor and a resistor into the - input?

Roger

 

[John Larkin]

Connect the + input directly to ground and feed the signal through a (?)100
nF capacitor and a resistor into the - input?

Roger

See my sketch in a.b.s.e.

John

 

[Jasen Betts]

Thanks. Would a 741op-amp drive a small speaker?

if your small speaker has an impedance of 50 or more ohms and ypu
don't need it very loud it could work.

an LM386 is a better choice for a small 4 or 8 ohm speaker.

Bye.
Jasen

 

[James Beck]

I would be grateful for suggestions on constructing a simple random noise
generator. Most of the noise should be within the audio spectrum.

R

Record one of Howard Deans' speeches/rants.
That's some pretty good white noise.

 

[John Larkin]

Record one of Howard Deans' speeches/rants.
That's some pretty good white noise.

Pink noise, actually.

John

 

[Roger Dewhurst]

See my sketch in a.b.s.e.

My ISP does not provide a.b.s.e which I presume is a binary ng covering
electronics. I would be very grateful if you could manage to email me the
drawing as a .jpg file.

Roger

 

[Roger Dewhurst]

Record one of Howard Deans' speeches/rants.
That's some pretty good white noise.

That fellow, whoever he may be, is of so little interest to anyone in this
country (NZ) that his rants are unavailable and unrecorded.

R

 

[James Beck]

Pink noise, actually.

John

LOL, yeah, you're right.
Maybe even a bit red.

 

[Jasen Betts]

My ISP does not provide a.b.s.e which I presume is a binary ng covering
electronics.

it is. "alt.binaries.schematics.electronics". (note to self:"Avoid IHUG")
fwiw Clear and compass/freenet carry it. compass/freenet's server
is half-arsed. AFAIK there's me and maybe two other people who actually
use it.