Anyone care to discuss...
 

Anyone want to comment on this circuit?
http://www.cbcintl.com/images/DSPSCHEM.GIF


Professor
www.telstar-electronics.com

On 14 Apr 2005 18:06:58 -0700, "Professor"
wrote in
.com:

Anyone want to comment on this circuit?
http://www.cbcintl.com/images/DSPSCHEM.GIF


DSP? Looks like an analog clipper to me.....

For starters, set the voltage of your center rail (your "6.2 VDC bus")
with a voltage divider because the zener can make the op-amps lock up
on power-up, and any noise on the power supply is going to get
amplified like mad. For the same reason, don't isolate your inverting
inputs from DC -- tie them to the center rail with a high value
resistor (except for A2, more on that later). 1 Meg is fine and
shouldn't degrade the operation of the circuit. Add another 1 Meg to
ground on the mic side of C2 to prevent static noise when using a
crystal or ceramic mic (or any other mic that is DC isolated, such as
some power mics). Back to A2: ground the NC end of VR1 and feed A2
from the wiper (through R3) to keep the input impedance high, then
replace the electrolytic C3 with whatever you are using for C4 so you
can avoid polarity issues and prevent loading the output of A1 (which
will screw with your frequency response). You might also want to try
1N4148 diodes in the clipper because they tend to behave better than
1N914 switchers. This will also allow you to scale up the value of the
resistors in the clipper, and thus prevent overloading A3 (1K is a
pretty heavy load for the LM324).

I probably missed a couple things. I'll look at it more closely later.

Oh yeah -- get yourself an audio signal generator so you don't look
like an idiot by noting test voltages obtained from "loud whistling".
An old Heathkit or Eico shouldn't cost you more than $20 plus shipping
on ebay. If you can't find one there, drop me an email and I'll sell
you one of mine.





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On Fri, 15 Apr 2005 03:28:01 -0700, Frank Gilliland
wrote in
:

snip
....... ground the NC end of VR1....


Correction: tie the NC end of VR1 to the center rail.








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Yes... this circuit is a real piece of work. The distortion from this
circuit must be tremendous.

Professor
www.telstar-electronics.com



Frank Gilliland wrote:
On 14 Apr 2005 18:06:58 -0700, "Professor"
wrote in
.com:

Anyone want to comment on this circuit?
http://www.cbcintl.com/images/DSPSCHEM.GIF


DSP? Looks like an analog clipper to me.....

For starters, set the voltage of your center rail (your "6.2 VDC
bus")
with a voltage divider because the zener can make the op-amps lock up
on power-up, and any noise on the power supply is going to get
amplified like mad. For the same reason, don't isolate your inverting
inputs from DC -- tie them to the center rail with a high value
resistor (except for A2, more on that later). 1 Meg is fine and
shouldn't degrade the operation of the circuit. Add another 1 Meg to
ground on the mic side of C2 to prevent static noise when using a
crystal or ceramic mic (or any other mic that is DC isolated, such as
some power mics). Back to A2: ground the NC end of VR1 and feed A2
from the wiper (through R3) to keep the input impedance high, then
replace the electrolytic C3 with whatever you are using for C4 so you
can avoid polarity issues and prevent loading the output of A1 (which
will screw with your frequency response). You might also want to try
1N4148 diodes in the clipper because they tend to behave better than
1N914 switchers. This will also allow you to scale up the value of
the
resistors in the clipper, and thus prevent overloading A3 (1K is a
pretty heavy load for the LM324).

I probably missed a couple things. I'll look at it more closely
later.

Oh yeah -- get yourself an audio signal generator so you don't look
like an idiot by noting test voltages obtained from "loud whistling".
An old Heathkit or Eico shouldn't cost you more than $20 plus
shipping
on ebay. If you can't find one there, drop me an email and I'll sell
you one of mine.





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Yes... this circuit is a real piece of work. The distortion from this
circuit must be tremendous.

Professor
www.telstar-electronics.com

this is the a CB mod that lou franklin and his pals
dreamed up. Lou and radioactive are both in phoenix,
check out the wackpak and superwackpak and read
their BS explanation of it.

http://www.radioactiveradios.com/FAQ.html

On 15 Apr 2005 10:49:22 -0700, "Professor"
wrote in
. com:

Yes... this circuit is a real piece of work. The distortion from this
circuit must be tremendous.


A4 is a low-pass filter so it shouldn't be too noisy if the clipper is
used in moderation. But I can say, just by looking at the schematic,
that the frequency response sucks and it will have some major problems
in a number of practical installations. The overall design looks like
it was pasted together from a circuit scrapbook.

One more thing I noticed: The clipper circuit would be better located
between A2 and A3. That way A3 can serve as a buffer between the
clipper and the filter.







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clipper

"after years of research we designed a way to make your radio do just that. We redesign the
audio/wattage section of your radio (and other stuff too!) to make your radio do max watts, max audio,
and swing. But operate at much cooler temps, helping your finals last ALOT longer!! Its like watching tv,
and you hear a tv commerical tons louder than the show you were watching. They do that by audio, thats
what we do to our radios! You'll love a WackPacked radio!"

On Fri, 15 Apr 2005 12:06:03 GMT, Lancer wrote in
g4fv515va9hcfooqrnoqd3gfdpm6jvv2te@2355323778:

On Fri, 15 Apr 2005 03:32:29 -0700, Frank Gilliland
wrote:

On Fri, 15 Apr 2005 03:28:01 -0700, Frank Gilliland
wrote in
:

snip
....... ground the NC end of VR1....


Correction: tie the NC end of VR1 to the center rail.




Why would you want the inverting input of A2 tied to DC potential?

When you adjust VR1 won't you be setting the DC output level of A2?


The center rail (the "6.2 VDC bus") is a virtual ground. Fixing the
inverting input of A2 to this level prevents DC drift and/or lockup of
A2. For the other op-amps, the addition of a 1 Meg resistor from the
inverting input to this virtual ground provides the same protection.

I may not have explained that very well......





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I think your evaluation is quite accurate. I was just wondering if
anybody out there had to the sense to know that this circuit is a
terrible attempt at a speech processing. The fact that the principal of
this circuit is to severely clip an audio waveshape... has distortion
written all over it!

Professor
www.telstar-electronics.com



Frank Gilliland wrote:
On 15 Apr 2005 10:49:22 -0700, "Professor"
wrote in
. com:

Yes... this circuit is a real piece of work. The distortion from
this
circuit must be tremendous.


A4 is a low-pass filter so it shouldn't be too noisy if the clipper
is
used in moderation. But I can say, just by looking at the schematic,
that the frequency response sucks and it will have some major
problems
in a number of practical installations. The overall design looks like
it was pasted together from a circuit scrapbook.

One more thing I noticed: The clipper circuit would be better located
between A2 and A3. That way A3 can serve as a buffer between the
clipper and the filter.







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News==----
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120,000+ Newsgroups
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I think your evaluation is quite accurate. I was just wondering if
anybody out there had to the sense to know that this circuit is a
terrible attempt at a speech processing. The fact that the principle of
this circuit is to severely clip an audio waveshape... has distortion
written all over it!

Professor
www.telstar-electronics.com



Frank Gilliland wrote:
On 15 Apr 2005 10:49:22 -0700, "Professor"
wrote in
. com:

Yes... this circuit is a real piece of work. The distortion from
this
circuit must be tremendous.


A4 is a low-pass filter so it shouldn't be too noisy if the clipper
is
used in moderation. But I can say, just by looking at the schematic,
that the frequency response sucks and it will have some major
problems
in a number of practical installations. The overall design looks like
it was pasted together from a circuit scrapbook.

One more thing I noticed: The clipper circuit would be better located
between A2 and A3. That way A3 can serve as a buffer between the
clipper and the filter.







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