Building a class A audio amplifier - no audio out

[Eeyore]

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.



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?

VOID !

It drives me nuts. Also things like = and ==

Graham

 

[[email protected]]

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?  

VOID !

It drives me nuts. Also things like = and ==

Graham

It's lowercase void, by the way.

Ah yes. I took a Fortran class (was required for all engineering
majors at the time: 1998 or so) and I couldn't figure out why my code
wouldn't work.

I had > instead of .gt.
I had < instead of .lt.

IF a .lt. b, etc.

Oh joy.

In C, the open parentheses took some getting used to, also.

I guess C *could* have made void the default type, and then if you
*wanted* a function to return an int, declare it as int... oh well.

Regarding = and ==, Pascal forced := to assign something, which I
thought was weird too... but yes, I made many mistakes with = and ==
too...

Michael

 

[Nobody]

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?

The type syntax can be a bit confusing if you are mixing prefix and
postfix operators, particularly in conjunction with function pointers (but
most people would just use a typedef), or if you want to specify the type
without naming a variable (e.g. for a cast).

VOID !

Huh? What's wrong with "void"? Would you have preferred "()" (a
zero-element tuple) like in functional languages?

It drives me nuts. Also things like = and ==

Are you advocating for ":="? Using "=" for both assignment and comparison
isn't an option in languages where boolean expressions aren't relegated to
the tests of if/while instructions.

 

[Nobody]

Typical HR nonsense. Ask for the impossible. Then wonder why either (a) you
get no responses or (b) those who do respond haven't a clue.

or (c) those who respond are very experienced; very experience bullshit
artists, that is.

But the most common form of "typical HR nonsense" is to specify very high
levels of knowledge and experience but offer McJob salary levels.

"The position requires X, Y and Z, and will pay W" should be "The position
requires that you are willing to work for W; having any of X, Y and Z
would be an advantage".

 

[[email protected]]

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.

G²

Ah, I see now.

http://users.ece.gatech.edu/~mleach/lowtim/output.html

"Back in the days when audio kits were popular, there was a line of
amplifiers called Tiger Amps sold by a company named Southwest
Technical Products Corporation (SWTPC). Some of these amps used common-
emitter output stages which had local feedback around the output stage
to cause it to operate at a voltage gain of 4. This was achieved by
adding resistors from the emitters of Q14 and Q15 to ground so that
only a fraction of the output voltage is fed back to the emitters.
These amplifiers were very unstable, causing them to oscillate,
overheat, and blow tweeters. Walter Jung tested one of the SWTPC
Tigersaurus Amps for the Audio Amateur. His concluding comment in his
review was, "Dan Meyer, where are you?" Dan Meyer was the founder of
SWTPC. His original company name was Demco, but the General Motors
Delco Radio Division brought a lawsuit against him to force him to
change the company name. The company went out of business after
getting into the home computer market."

Michael

 

[Eeyore]

On May 11, 1:44 pm, Eeyore <[email protected]>
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?

VOID !

It drives me nuts. Also things like = and ==

Graham

It's lowercase void, by the way.

Even WORSE. A language that's case sensitive ! God preserve us.

Ah yes. I took a Fortran class (was required for all engineering
majors at the time: 1998 or so) and I couldn't figure out why my code
wouldn't work.

I had > instead of .gt.
I had < instead of .lt.

IF a .lt. b, etc.

Oh joy.

In C, the open parentheses took some getting used to, also.

I guess C *could* have made void the default type, and then if you
*wanted* a function to return an int, declare it as int... oh well.

I would say so.

Regarding = and ==, Pascal forced := to assign something, which I
thought was weird too... but yes, I made many mistakes with = and ==
too...

You don't make those mistakes with PL/M because they don't exist.

Graham

 

[Eeyore]

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?

The type syntax can be a bit confusing if you are mixing prefix and
postfix operators, particularly in conjunction with function pointers (but
most people would just use a typedef), or if you want to specify the type
without naming a variable (e.g. for a cast).

I don't need that shit for simple embedded programming.

Huh? What's wrong with "void"? Would you have preferred "()" (a
zero-element tuple) like in functional languages?

I'd prefer PL/M's "return value".

Are you advocating for ":="? Using "=" for both assignment and comparison
isn't an option in languages where boolean expressions aren't relegated to
the tests of if/while instructions.

You'd be amazed how unneccesary it is.

Graham

 

[[email protected]]

All of those tended to fry your speakers?

Michael

The only units I built were the 2 Tiger amps running right at 60 volts
power supply - I don't remember how far the supply drooped under load,
it was 37 years ago. The finals would blow and take out the power
supply fuse. The output cap (would never run a single supply amp
again) kept any DC from the speakers. No speakers ever failed. I later
worked in a stere repair shop and a customer brought in a Universal
Tiger pair but I could never get it running properly for him as it had
a nasty tendency to oscillate. I had some friends with Super Tiger
amps and AFAIK they worked properly. My antique stuff now is a Hafler
preamp, Technics parametric equalizer, Adcom power amp and an HK
Citation 15 tuner

G²

 

[Jasen Betts]

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.



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];
}

can't do this in C

Procedure wrapper(x:integer)
procedure recursive(y:integer)
begin
if something(y,x) then recursive(y+1)
end;
begin
recursive(0)
end;

 

[[email protected]]

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];
}

can't do this in C

 Procedure wrapper(x:integer)
 procedure recursive(y:integer)
 begin
   if something(y,x) then recursive(y+1)
 end;
 begin
   recursive(0)
 end;

Probably not as written, but couldn't you move recursive() to outside
of wrapper() ?

If it needs variables local to wrapper(), pass the addresses of the
variables to recursive()...?

Michael

 

[[email protected]]

   "The Brute 70" I built this one in high school.  I made my firstPC
boards for it.  They took the circuit from the RCA Data book and drew up
plans around them.  I saw a lot of early commercial solid state PA amps
built from the same basic circuit.  Some had been ion daily use for 20
years before they needed repairs.  The big change was the addition of a
output transformer to match them to either a 25 or 70 volt line speaker
system.

http://www.swtpc.com/mholley/PopularElectronics/Feb1967/PE_Feb1967.htm

Interesting. Are Q6 and Q7 both supposed to be NPN?

And what is this RCA Data Book?

Thanks,

Michael

 

[pimpom]

Interesting. Are Q6 and Q7 both supposed to be NPN?

Yes. Those were times when high-power silicon PNP transistors were not
easily available. The arrangement was sometimes called a quasi-complementary
circuit because it's not a true symmetrical NPN-PNP complementary circuit. I
don't know if RCA invented the circuit, but it was they who made it popular.
The circuit was presented in the 1968 edition of RCA Transistor Manual, one
of the first reference books I owned.

And what is this RCA Data Book?

Mike is probably talking about the same book.

 

[Eeyore]

Interesting. Are Q6 and Q7 both supposed to be NPN?

Yes, it's commonly called a 'quasi complementary pair' output. One side is a Darlington, the other is a
Sz... pair ( never can remember how to spell it ) or 'compound transistor'.

This was done long ago because it was difficult at the time to make high power Si PNP power devices.
It's not a problem now and no-one uses it any more because of the inherent gm mismatch.

And what is this RCA Data Book?

The same as the one I've got by the looks of it ! '69 I think.

Graham

 

[Eeyore]

Yes. Those were times when high-power silicon PNP transistors were not
easily available. The arrangement was sometimes called a quasi-complementary
circuit because it's not a true symmetrical NPN-PNP complementary circuit. I
don't know if RCA invented the circuit, but it was they who made it popular.
The circuit was presented in the 1968 edition of RCA Transistor Manual, one
of the first reference books I owned.


Mike is probably talking about the same book.

I have it too. It was a poor transitional phase to pure complmentary output
stages. The method lasted some time though.

Graham

 

[Eeyore]

The only units I built were the 2 Tiger amps running right at 60 volts
power supply - I don't remember how far the supply drooped under load,
it was 37 years ago. The finals would blow and take out the power
supply fuse.

Did the output devices have inverse parallel diodes ?

Graham

 

[[email protected]]

   RCA published a series of transistor dta books throungh the '60s &
'70s.  The basic circuit was published right after RCA released the
40411 output transistors used in that circuit.  If you take a look, they
run in consecutive type numbers, which indicates they were chosen for
that application.  Amps built with the RCA parts were good, for their
time, but the clones often used other transistors and had problems.  The
40411 was rated to 100 volts, which was a lot higher than most power
transistors of that time.

Well in lieu of having that nice data book, the free online patent
literature gives this, among others:

http://www.google.com/patents?id=yus8AAAAEBAJ

from
http://www.google.com/patents?lr=&q=audio+and+amplifier+inassignee:rca&scoring=2&sa=N&start=30

Thanks,

Michael

 

[[email protected]]

   All of those are dated in the '70s, and are newer that the data I was
looking for, for you.



   I couldn't find any of my oldest RCA books, or I would have scanned
the ap note for you.

   I see a copy of SC11 for sale near here on ABE Books, but it is too
old.  It first appeared in SC12 or SC13.

   It is about a half hour drive from here, and near a flea market i
haven't been to in almost 10 years.  The store wants $5 for it, plus
local tax.

Ah ok, I appreciate the efforts you are going to, to locate the
article. Thank you. But please don't trouble yourself driving to
search for the book on my behalf. I wouldn't want to inconvenience
you.

I was hoping to find something online by searching the Google patent
literature with "RCA" as the assignee. And it may even be possible
that my dad may have the data book, or a similar one. It's just not
very often that I get to see him.

Thanks,

Michael

 

[Eeyore]

RCA published a series of transistor dta books throungh the '60s &
'70s. The basic circuit was published right after RCA released the
40411 output transistors used in that circuit. If you take a look, they
run in consecutive type numbers, which indicates they were chosen for
that application. Amps built with the RCA parts were good, for their
time, but the clones often used other transistors and had problems. The
40411 was rated to 100 volts, which was a lot higher than most power
transistors of that time.

True but shortly therafter RCA offered the 140V 2N3773 which with 4 devices could deliver ~ 200W into 8
ohms with a decently regulated supply.

That device ruled the roost for a long time.

Modern Toshiba ( and other ) audio output semis got to 230V or so. I well recall designing my first amp
with +/- 100V main rails.

Graham

 

[Eeyore]

Well in lieu of having that nice data book, the free online patent
literature gives this, among others:

http://www.google.com/patents?id=yus8AAAAEBAJ

from
http://www.google.com/patents?lr=&q=audio+and+amplifier+inassignee:rca&scoring=2&sa=N&start=30

Not terribly helpful I'm afraid.

Had I read Win's book ( The Art of Electronics ) I might recommend it. I have no idea if it has a specialist
audio section though ( hint Win ).

Graham

 

[Eeyore]

Ah ok, I appreciate the efforts you are going to, to locate the
article. Thank you. But please don't trouble yourself driving to
search for the book on my behalf. I wouldn't want to inconvenience
you.

I was hoping to find something online by searching the Google patent
literature with "RCA" as the assignee. And it may even be possible
that my dad may have the data book, or a similar one. It's just not
very often that I get to see him.

Mulling over old designs has its interest in some ways but you'd do far beter to concentrate on newer technology
that's not impaired by old limitations of device fabrication issues etc.

Go to the Doug Self site for example.

Graham