555 does Class D Audio?

M

Michael

Guest
http://personal.inet.fi/surf/rushi/555d.html
http://personal.inet.fi/surf/rushi/pics/555d.png
 
On Tue, 29 Sep 2009, Michael wrote:

http://personal.inet.fi/surf/rushi/555d.html
http://personal.inet.fi/surf/rushi/pics/555d.png

So?
Click to expand...

You ask a question in the subject header, but then don't elaborate on
what you might be asking.

In the early seventies, there was a class-D amplifier in Elementary
Electronics that used a 555. It was the class-d equivalent of a cheap
and dirty amplifier, not intended for hifi but there are lots of times
one needs nothing more than a loud amplifier. It was a useful learning
tool, since the circuit was simple, and simple circuits help to convey
basics.

Michael
 
On Sep 29, 8:37 pm, Michael Black <et...@ncf.ca> wrote:
On Tue, 29 Sep 2009, Michael wrote:
http://personal.inet.fi/surf/rushi/555d.html
http://personal.inet.fi/surf/rushi/pics/555d.png

So?

You ask a question in the subject header, but then don't elaborate on
what you might be asking.

In the early seventies, there was a class-D amplifier in Elementary
Electronics that used a 555.  It was the class-d equivalent of a cheap
and dirty amplifier, not intended for hifi but there are lots of times
one needs nothing more than a loud amplifier. It was a useful learning
tool, since the circuit was simple, and simple circuits help to convey
basics.

    Michael
Click to expand...

I guess I was just expressing shock that such a beast could exist.

Is even the 555 necessary? Can a simple class D amplifier be built
with discretes? Like you said I'm just looking for the basics, to
learn. Even 1 W would be plenty.

Thanks,

Michael
 
None sense . Class D audio uses junk box parts ..

and very few .

Class D , if its not close to 20khz , can be done with any

simple ckt that has a low output Z .



Simple op amps with cheap NPN ( emmiter follower) in VCC+

lead ,, another PNP in VCC- , as the LH0002 is .

As the op amp draws from supply , it also pulls current thru

the discrete NPN or PNP , cause its in series with Supply leads .






Its merely the voltage gain from an op amp , then current gain from

low cost bipolars in the Vcc inputs .

to filter out the square wave , make total inductance of the load
and its resistance , a time constant of about

50 to 100 microseconds .

A buck regulator is a
switch then an
inductor then output power supply
cap . Pick inductor to filter out above 10khz ,
pick transistor to have high drive .

now oscilate it with a LM431 .

Now add music .

two of these , one for plus side , one for minus side .

BW is so high , and the filter allows no ripple , noise is low .

When BW is 100 times higher than the output freq , you can
do it many ways ,, cheap .



--------------------------------

BTW Dont buy welders from

www.longevity-inc.com

I paid $650 , transistors broke off cause heavy heat sink is
hooked to transistor legs , breaks them off .

Heat sink is NOT secured to PCB !!!

Then the 2 outs are switched in series for Plasma , in parallel
for welding ... 90 amps thru relays , contacts will not last .
Hi quality welders have a front panel switch , with hvy contacts .

JUNK ..
 
On Tue, 29 Sep 2009 21:09:03 -0700 (PDT), Michael
<mrdarrett@gmail.com> wrote:

On Sep 29, 8:37=A0pm, Michael Black <et...@ncf.ca> wrote:
On Tue, 29 Sep 2009, Michael wrote:
http://personal.inet.fi/surf/rushi/555d.html
http://personal.inet.fi/surf/rushi/pics/555d.png

So?

You ask a question in the subject header, but then don't elaborate on
what you might be asking.

In the early seventies, there was a class-D amplifier in Elementary
Electronics that used a 555. =A0It was the class-d equivalent of a cheap
and dirty amplifier, not intended for hifi but there are lots of times
one needs nothing more than a loud amplifier. It was a useful learning
tool, since the circuit was simple, and simple circuits help to convey
basics.

=A0 =A0 Michael


I guess I was just expressing shock that such a beast could exist.

Is even the 555 necessary? Can a simple class D amplifier be built
with discretes? Like you said I'm just looking for the basics, to
learn. Even 1 W would be plenty.
Click to expand...
A conceptual class D amp can use a triangle
generator and comparator to drive on/off output
switches. The triangle sets the threshold of the
comparator. When the audio exceeds this
threshold, the output is high, otherwise low.
The triangle frequency is higher than the audio
range, so you don't hear the switching.

If you draw the triangle and a
much-lower-frequency sine wave out on paper and
look at where they cross, you can see that the
comparator will end up with a duty cycle
proportional to the instantaneous signal
amplitude. That's class D!

Best regards,


Bob Masta

DAQARTA v4.51
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Sound Level Meter
FREE Signal Generator
Science with your sound card!
 
Bob Masta Inscribed thus:

On Tue, 29 Sep 2009 21:09:03 -0700 (PDT), Michael
mrdarrett@gmail.com> wrote:

On Sep 29, 8:37=A0pm, Michael Black <et...@ncf.ca> wrote:
On Tue, 29 Sep 2009, Michael wrote:
http://personal.inet.fi/surf/rushi/555d.html
http://personal.inet.fi/surf/rushi/pics/555d.png

So?

You ask a question in the subject header, but then don't elaborate
on what you might be asking.

In the early seventies, there was a class-D amplifier in Elementary
Electronics that used a 555. =A0It was the class-d equivalent of a
cheap and dirty amplifier, not intended for hifi but there are lots
of times one needs nothing more than a loud amplifier. It was a
useful learning tool, since the circuit was simple, and simple
circuits help to convey basics.

=A0 =A0 Michael


I guess I was just expressing shock that such a beast could exist.

Is even the 555 necessary? Can a simple class D amplifier be built
with discretes? Like you said I'm just looking for the basics, to
learn. Even 1 W would be plenty.

A conceptual class D amp can use a triangle
generator and comparator to drive on/off output
switches. The triangle sets the threshold of the
comparator. When the audio exceeds this
threshold, the output is high, otherwise low.
The triangle frequency is higher than the audio
range, so you don't hear the switching.

If you draw the triangle and a
much-lower-frequency sine wave out on paper and
look at where they cross, you can see that the
comparator will end up with a duty cycle
proportional to the instantaneous signal
amplitude. That's class D!

Best regards,
Click to expand...
Nice concise description of class D !

Bob Masta

DAQARTA v4.51
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Sound Level Meter
FREE Signal Generator
Science with your sound card!
Click to expand...
--
Best Regards:
Baron.
 
In article
<1bba5278-f298-4ac8-b3b8-670418c4d8ac@f18g2000prf.googlegroups.com>,
Michael <mrdarrett@gmail.com> wrote:
I guess I was just expressing shock that such a beast could exist.

Is even the 555 necessary? Can a simple class D amplifier be built
with discretes? Like you said I'm just looking for the basics, to
learn. Even 1 W would be plenty.
Click to expand...
In practise, there's no fundamental duffernce betwen a class D audio and a
pwm motor controller.

See 4QDTEC.com ... I was with Clive Sinclair when he marketed a couple of
class D audio amps.

--
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Richard Torrens. News email address is valid - for a limited time only.
http://www.Torrens.org.uk for genealogy, natural history, wild food, walks, cats
and more!
 
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