Building a class A audio amplifier - no audio out

[Baron]

stratus46@yahoo.com wrote:

Well then perhaps this 'golden oldie' might be of interest.

http://www.swtpc.com/mholley/PopularElectronics/Dec1967/PE_Dec1967.htm

G²

I remember building that ! If it didn't get lost when we moved it will
still be kicking around in a box in the garage ! I might even still
have the original magazine.

Just Lurking

--
Best Regards:
Baron.

 

On May 11, 8:30 am, mrdarr...@gmail.com wrote:

On May 11, 8:16 am, stratu...@yahoo.com wrote:
snip
Lots of good stuff here

http://sound.westhost.com/

G˛

Ah, thank you for the reply.

One thing I noticed is, the larger amps on westhost.com (10W+) need
split power supplies (+/-).  I'd like to start with something
needing
just 0V-6V or 0V-12V.

Thanks again,

Michael

Well then perhaps this 'golden oldie' might be of interest.

http://www.swtpc.com/mholley/PopularElectronics/Dec1967/PE_Dec1967.htm

G˛

 

On May 11, 1:32 pm, Eeyore <rabbitsfriendsandrelati...@hotmail.com>
wrote:

mrdarr...@gmail.com wrote:
"pimpom" <pim...@invalid.invalid> wrote:
mrdarr...@gmail.com wrote:

Ah.  I'd neglected to say that a 1W amp would be fine for learning
purposes.

If I just wanted power I'd go for an LM3886 or just buy an Onkyo
system.  I'd like to understand how the amps work.

Any comments on this circuit as a beginner project?
http://www.redcircuits.com/Page33.htm

Looks ok to me. You have to pay heed to the instructions, especially about
adjusting the quiescent (no-signal) current.

I'd recommend mounting the two output transistors Q3 and Q4 on a small
heatsink, making sure that they are electrically isolated from each other
and from ground and other components. The two transistors can theoretically
dissipate nearly 1W each with a 4-ohm load. That may seem small, but it's
enough to get a bare TO220 transistor quite hot.

One 0.47-ohm 1/2-watt resistor in series with the emitter of each output
transistor will aid stability.

Q2 dissipates about 0.25W which will also cause the small transistor to run
quite hot to the touch. I suggest using a BD135-16 or a BD137-16

You'll have trouble getting any BD135 or 137 IME these days at least at a sensible
price. They're 30 year old devices in an little used package these days.

30 cents is unreasonable to you? Available at mouser.com

Half the trouble is the most half-assed DIY websites use exclusively obsolete
parts. Thinks 2N2222 for example. Metal can, expensive and outperformed now by a
2c TO-92 device.

I bought a mixed bag of NPNs at the local Radio Shack, and they were
all plastic TO-92s, not metal cans.

BC337s are 6 cents at mouser... what TO-92 NPNs go for 2 cents?

instead of
the BC337. Choosing a sub-type with the -16 suffix ensures that it will have
about the same gain level as the BC337.

Hahahahaha ! Just try getting suffixed types. LMAO.

Ah, thank you very much.  I'll heatsink the transistors, and thanks
for the tip about emitter resistors.

Sinclair ( of Sir Clive Sinclair fame ) made audio modules for DIYers in the 70's.
Their Z30 and Z50 power amps neglected to use emitter resistors and subsequently
failed regularly.

Thanks for the warning.

I even wrote to the company pointing out the design error. FINALLY after God knows
how many returns they found PCB space to fit some. Problem fixed.

What you need to understand is WHY they were important. That comment is to you Mr
Darrett or you'll never be a designer.

Exactly. The "why" is what makes for slow going... else I'd just buy
an Onkyo or an LM3886, as I mentioned earlier.

Graham

Michael

 

On May 11, 1:31 pm, stratu...@yahoo.com wrote:

On May 11, 8:30 am, mrdarr...@gmail.com wrote:> On May 11, 8:16 am, stratu...@yahoo.com wrote:

snip
 > > Lots of good stuff here
 
 > >http://sound.westhost.com/
 
 > > G˛
 
 > Ah, thank you for the reply.
 
 > One thing I noticed is, the larger amps on westhost.com (10W+) need
 > split power supplies (+/-).  I'd like to start with something
needing
 > just 0V-6V or 0V-12V.
 
 > Thanks again,
 
 > Michael

Well then perhaps this 'golden oldie' might be of interest.

http://www.swtpc.com/mholley/PopularElectronics/Dec1967/PE_Dec1967.htm

G˛

Thanks a bunch!

Michael

 

On May 11, 1:44 pm, Eeyore <rabbitsfriendsandrelati...@hotmail.com>
wrote:

.....

I'd have known that was crap by my mid
teens. It's about as simple as it gets. I was building stuff more complex at
age 12.

Ah, good for you.  I wasted my teen years teaching myself C
programming, assembly language programming, and modifying Michael
Abrash's VGA Mode X graphics routines.  Then Windows 95 came out and
made my experience worthless.  Eh.  That's life.

I was offered a job programming in C back around 1984. I took one look at the
bizarre syntax and ran away. My career would have been surely very different and
probably wealthier had I taken the offer but I might have missed a lot of
interesting challenges.

How could you be offered a job in C programming if you didn't know C
programming? (thoroughly confused) That would never fly over here.

On that note... I took a biochemistry lab class where I had to
calculate the A, C, G and T fractions from DNA analysis of a
bacterium. It involved *a lot* of punching numbers into a
calculator. I thought, "screw this" and wrote a Pascal program to do
it. I turned in the source code with my lab report. The grader wrote
"Mabey (sic) you're in the wrong major" on the top of my report.
Mabey he was right. ;D

.....

BUT ! Before anything else. Do you know how to bias a single transistor small
signal amplifier. Don't touch anything else until you've mastered that together
with all its variants and effects.

Nope. Will start there. Thanks.

Even better ... start with an emitter follower and ask yourself why they're used
and then do the same with the complementary version ( may not be instinctively
obvious but every audio power amp of any note uses one ).

You mean a Sziklai?
http://en.wikipedia.org/wiki/Sziklai_pair

I noticed that a lot of power amps use the Sziklai pair vs. the
Darlington. Is the Sziklai demonstrably superior?

Actually, I nearly forgot. UK magazine Wireless World had a 3 or so part monthly
article on discrete design by a practical college lecturer as opposed to an Ivory
Towers University type. I learnt more from that, faster than anything else. I must
see if I still have it. It dropped all the ultra-theoretical bunk and got on with
how to make circuits that work and why.

Graham

 

On May 11, 1:53 pm, Eeyore <rabbitsfriendsandrelati...@hotmail.com>
wrote:

mrdarr...@gmail.com wrote:
Been there, borrowed Self's book from the library, still a bit over my
head.

Buy this. It's ANCIENT and refers to a lot of obsolete op-amps which with
intelligence you can substitute with better modern parts but it covers some good
ground like noise calculations for example. It helps you get the feel.

I have an original print copy of course. Finally it''s been reprinted.

http://www.amazon.com/National-Semiconductor-Audio-Radio-Handbook/dp/...

TI have some super and huge IC mainly handbooks too that you should have. I'll
need to recheck their filenames.

Graham

Ah, thanks. You know, the title sounds similar to some texts my dad
has. I'll have to examine his library.

Michael

 

[Michael A. Terrell]

Eeyore wrote:

mrdarrett@gmail.com wrote:

"pimpom" <pim...@invalid.invalid> wrote:
mrdarr...@gmail.com wrote:

Ah. I'd neglected to say that a 1W amp would be fine for learning
purposes.

If I just wanted power I'd go for an LM3886 or just buy an Onkyo
system. I'd like to understand how the amps work.

Any comments on this circuit as a beginner project?
http://www.redcircuits.com/Page33.htm

Looks ok to me. You have to pay heed to the instructions, especially about
adjusting the quiescent (no-signal) current.

I'd recommend mounting the two output transistors Q3 and Q4 on a small
heatsink, making sure that they are electrically isolated from each other
and from ground and other components. The two transistors can theoretically
dissipate nearly 1W each with a 4-ohm load. That may seem small, but it's
enough to get a bare TO220 transistor quite hot.

One 0.47-ohm 1/2-watt resistor in series with the emitter of each output
transistor will aid stability.

Q2 dissipates about 0.25W which will also cause the small transistor to run
quite hot to the touch. I suggest using a BD135-16 or a BD137-16

You'll have trouble getting any BD135 or 137 IME these days at least at a sensible
price. They're 30 year old devices in an little used package these days.

Half the trouble is the most half-assed DIY websites use exclusively obsolete
parts. Thinks 2N2222 for example. Metal can, expensive and outperformed now by a
2c TO-92 device.

Idiot! The PN2222 is the same die in a TO-92 package, and the
MMBT2222 is the same die in a SOT-23 package it isn't obsolete, just
repackaged for modern designs. 2N2222 is considered the generic name
for the family, since it was first. Both the 2N2222 & the 2N32222A are
in stock at Digikey, which means the metal cased TO-18 package isn't
obsolete for all designs.

instead of
the BC337. Choosing a sub-type with the -16 suffix ensures that it will have
about the same gain level as the BC337.

Hahahahaha ! Just try getting suffixed types. LMAO.

Ah, thank you very much. I'll heatsink the transistors, and thanks
for the tip about emitter resistors.

Sinclair ( of Sir Clive Sinclair fame ) made audio modules for DIYers in the 70's.
Their Z30 and Z50 power amps neglected to use emitter resistors and subsequently
failed regularly.

Typical British design quality.

I even wrote to the company pointing out the design error. FINALLY after God knows
how many returns they found PCB space to fit some. Problem fixed.

What you need to understand is WHY they were important. That comment is to you Mr
Darrett or you'll never be a designer.

Graham

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

http://www.flickr.com/photos/materrell/

 

[Nobody]

On Mon, 11 May 2009 12:01:07 -0700, mrdarrett wrote:

Ah, good for you. I wasted my teen years teaching myself C
programming, assembly language programming, and modifying Michael
Abrash's VGA Mode X graphics routines. Then Windows 95 came out and
made my experience worthless. Eh. That's life.

C programming is still very useful. Apart from C itself, C++,
Objective-C, Java and C# are all heavily based upon it.

Assembler isn't so useful in application programming, but
it's still useful if you're programming microcontrollers, or writing
system code (OS kernels, compilers, interpreters), or performance-critical
applications (e.g. games). Although most of the above is written in C
or C++ rather than assembler, being able to mentally translate into
assembler will result in much better code than that written by someone who
only understands the language as a theoretical abstraction.

 

[Jon Kirwan]

On Mon, 11 May 2009 13:31:51 -0700 (PDT), stratus46@yahoo.com wrote:

Well then perhaps this 'golden oldie' might be of interest.

http://www.swtpc.com/mholley/PopularElectronics/Dec1967/PE_Dec1967.htm

I remember it! There was a follow-up article with another version, as
I recall.

Jon

 

[Nobody]

On May 11, 1:44 pm, Eeyore <rabbitsfriendsandrelati...@hotmail.com
wrote:

I was offered a job programming in C back around 1984. I took one look
at the bizarre syntax and ran away.

That "bizarre" syntax is pretty much the industry standard nowadays. C++,
C#, Java, and JavaScript all look very similar. Any deviation from C
syntax (e.g. Python) is considered bizarre.

On Mon, 11 May 2009 13:57:28 -0700, mrdarrett wrote:

How could you be offered a job in C programming if you didn't know C
programming? (thoroughly confused) That would never fly over here.

In 1984, C was still a fairly uncommon language. It wouldn't be
unreasonable to prefer someone with a reasonable amount of overall
programming experience (particularly if it's experience in the relevant
domain) who would need to learn C over someone with less overall
experience (or less relevant experience) with some C. Learning a new
language is easier than learning programming.

Of course, that doesn't hold if hiring is done by HR types with no
knowledge of the field (and no willingness to consult). A classic example
was when Java took off, companies were advertising for programmers with 2
or 3 years' Java experience when Java's existence had been public
knowledge for less than a year.

 

[Jon Kirwan]

On Mon, 11 May 2009 20:00:06 -0700, Jon Kirwan
<jonk@infinitefactors.org> wrote:

On Mon, 11 May 2009 13:31:51 -0700 (PDT), stratus46@yahoo.com wrote:

Well then perhaps this 'golden oldie' might be of interest.

http://www.swtpc.com/mholley/PopularElectronics/Dec1967/PE_Dec1967.htm

I remember it! There was a follow-up article with another version, as
I recall.

Ah. Found them!


http://www.swtpc.com/mholley/PopularElectronics/Jul1969/PE_Jul1969.htm

http://www.swtpc.com/mholley/PopularElectronics/Oct1970/PE_Oct1970.htm

http://www.swtpc.com/mholley/PopularElectronics/Oct1971/PE_Oct1971.htm

Jon

 

On May 11, 8:00 pm, Jon Kirwan <j...@infinitefactors.org> wrote:

On Mon, 11 May 2009 13:31:51 -0700 (PDT), stratu...@yahoo.com wrote:
Well then perhaps this 'golden oldie' might be of interest.

http://www.swtpc.com/mholley/PopularElectronics/Dec1967/PE_Dec1967.htm

I remember it!  There was a follow-up article with another version, as
I recall.

Jon

You probably mean this

http://www.swtpc.com/mholley/PopularElectronics/Jul1969/PE_Jul1969.htm

which I built in high school. It had an annoying tendency to blow the
outputs. And this

http://www.swtpc.com/mholley/PopularElectronics/Oct1970/PE_Oct1970.htm

and another family member

http://www.swtpc.com/mholley/PopularElectronics/Oct1971/PE_Oct_1971_Pg28.jpg

Enough of memory lane for now.

G˛

 

[Eeyore]

mrdarrett@gmail.com wrote:

On May 11, 1:32 pm, Eeyore <rabbitsfriendsandrelati...@hotmail.com
wrote:
mrdarr...@gmail.com wrote:
"pimpom" <pim...@invalid.invalid> wrote:
mrdarr...@gmail.com wrote:

Ah. I'd neglected to say that a 1W amp would be fine for learning
purposes.

If I just wanted power I'd go for an LM3886 or just buy an Onkyo
system. I'd like to understand how the amps work.

Any comments on this circuit as a beginner project?
http://www.redcircuits.com/Page33.htm

Looks ok to me. You have to pay heed to the instructions, especially about
adjusting the quiescent (no-signal) current.

I'd recommend mounting the two output transistors Q3 and Q4 on a small
heatsink, making sure that they are electrically isolated from each other
and from ground and other components. The two transistors can theoretically
dissipate nearly 1W each with a 4-ohm load. That may seem small, but it's
enough to get a bare TO220 transistor quite hot.

One 0.47-ohm 1/2-watt resistor in series with the emitter of each output
transistor will aid stability.

Q2 dissipates about 0.25W which will also cause the small transistor to run
quite hot to the touch. I suggest using a BD135-16 or a BD137-16

You'll have trouble getting any BD135 or 137 IME these days at least at a sensible
price. They're 30 year old devices in an little used package these days.

30 cents is unreasonable to you? Available at mouser.com

Half the trouble is the most half-assed DIY websites use exclusively obsolete
parts. Thinks 2N2222 for example. Metal can, expensive and outperformed now by a
2c TO-92 device.

I bought a mixed bag of NPNs at the local Radio Shack, and they were
all plastic TO-92s, not metal cans.

BC337s are 6 cents at mouser... what TO-92 NPNs go for 2 cents?

instead of
the BC337. Choosing a sub-type with the -16 suffix ensures that it will have
about the same gain level as the BC337.

Hahahahaha ! Just try getting suffixed types. LMAO.

Ah, thank you very much. I'll heatsink the transistors, and thanks
for the tip about emitter resistors.

Sinclair ( of Sir Clive Sinclair fame ) made audio modules for DIYers in the 70's.
Their Z30 and Z50 power amps neglected to use emitter resistors and subsequently
failed regularly.

Thanks for the warning.

I even wrote to the company pointing out the design error. FINALLY after God knows
how many returns they found PCB space to fit some. Problem fixed.

What you need to understand is WHY they were important. That comment is to you Mr
Darrett or you'll never be a designer.

Exactly. The "why" is what makes for slow going... else I'd just buy
an Onkyo or an LM3886, as I mentioned earlier.


Graham

Michael

 

[Eeyore]

mrdarrett@gmail.com wrote:

Eeyore <rabbitsfriendsandrelati...@hotmail.com> wrote:

You'll have trouble getting any BD135 or 137 IME these days at least at a sensible
price. They're 30 year old devices in an little used package these days.

30 cents is unreasonable to you? Available at mouser.com

I'm stunned, especially as it's a European device. They must have a customer who's been
using them for years and never changed. Most people moved to using TO-220 devices
instead of TO-126 like the TIPs.

Graham

 

[Eeyore]

"Michael A. Terrell" wrote:

Eeyore wrote:

Sinclair ( of Sir Clive Sinclair fame ) made audio modules for DIYers in the 70's.
Their Z30 and Z50 power amps neglected to use emitter resistors and subsequently
failed regularly.

Typical British design quality.

Typical SINCLAIR design quality.

Graham

 

[Eeyore]

"Michael A. Terrell" wrote:

Eeyore wrote:

Half the trouble is the most half-assed DIY websites use exclusively obsolete
parts. Thinks 2N2222 for example. Metal can, expensive and outperformed now by a
2c TO-92 device.

Idiot! The PN2222 is the same die in a TO-92 package, and the
MMBT2222 is the same die in a SOT-23 package it isn't obsolete, just
repackaged for modern designs.

I know. Its parameters are still inferior to later similar devices though.

2N2222 is considered the generic name for the family, since it was first.

Do you have a problem with using the correct prefix ?

Graham

 

On May 12, 12:34 am, stratu...@yahoo.com wrote:

On May 11, 8:00 pm, Jon Kirwan <j...@infinitefactors.org> wrote:

On Mon, 11 May 2009 13:31:51 -0700 (PDT), stratu...@yahoo.com wrote:
Well then perhaps this 'golden oldie' might be of interest.

http://www.swtpc.com/mholley/PopularElectronics/Dec1967/PE_Dec1967.htm

I remember it!  There was a follow-up article with another version, as
I recall.

Jon

You probably mean this

http://www.swtpc.com/mholley/PopularElectronics/Jul1969/PE_Jul1969.htm

which I built in high school. It had an annoying tendency to blow the
outputs. And this

http://www.swtpc.com/mholley/PopularElectronics/Oct1970/PE_Oct1970.htm

and another family member

http://www.swtpc.com/mholley/PopularElectronics/Oct1971/PE_Oct_1971_P...

Enough of memory lane for now.

G˛

All of those tended to fry your speakers?

Michael

 

On May 11, 8:03 pm, Nobody <nob...@nowhere.com> wrote:

On May 11, 1:44 pm, Eeyore <rabbitsfriendsandrelati...@hotmail.com
wrote:
I was offered a job programming in C back around 1984. I took one look
at the bizarre syntax and ran away.

That "bizarre" syntax is pretty much the industry standard nowadays. C++,
C#, Java, and JavaScript all look very similar. Any deviation from C
syntax (e.g. Python) is considered bizarre.

On Mon, 11 May 2009 13:57:28 -0700, mrdarrett wrote:
How could you be offered a job in C programming if you didn't know C
programming?  (thoroughly confused)  That would never fly over here..

In 1984, C was still a fairly uncommon language. It wouldn't be
unreasonable to prefer someone with a reasonable amount of overall
programming experience (particularly if it's experience in the relevant
domain) who would need to learn C over someone with less overall
experience (or less relevant experience) with some C. Learning a new
language is easier than learning programming.

Of course, that doesn't hold if hiring is done by HR types with no
knowledge of the field (and no willingness to consult). A classic example
was when Java took off, companies were advertising for programmers with 2
or 3 years' Java experience when Java's existence had been public
knowledge for less than a year.

Yes, I remember when Java was new. Makes sense from that
perspective. But I'm surprised why a seasoned programmer would run
away screaming from C.

I liked C as a less verbose version of Pascal.

Procedure Execute;
Var i:array[1..10] of integer;
Begin
End;

becomes

void Execute()
{
int i[10];
}

What's not to like?

Michael

 

[Eeyore]

stratus46@yahoo.com wrote:

Well then perhaps this 'golden oldie' might be of interest.

http://www.swtpc.com/mholley/PopularElectronics/Dec1967/PE_Dec1967.htm

Starting to look a fraction more modern ! Diodes proerly coupled to the
heatsink too for prevent thermal runaway. ;~)

Still no emitter Rs on the 'power' devices though.

Graham

 

[Eeyore]

mrdarrett@gmail.com wrote:

On May 11, 1:31 pm, stratu...@yahoo.com wrote:

Well then perhaps this 'golden oldie' might be of interest.

http://www.swtpc.com/mholley/PopularElectronics/Dec1967/PE_Dec1967.htm

Thanks a bunch!

The fact it's old and uses circuit techniques that are well-dated now means that you're more likely
to learn bad practice than good though.

Graham