Building a class A audio amplifier - no audio out

[Eeyore]

Jon Kirwan wrote:

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

Much more up to date. A proper differential input and a complementary
Sziklai pair output. I've used that in one range of power amps I designed
but tend to use those pairs more for for low noise discrete input stages
like direct coupled low-Z mic input stages.
http://en.wikipedia.org/wiki/Sziklai_pair

I don't know how to say "Sziklai" so I use the alternative of "compound
transistor".

Graham

 

[Eeyore]

mrdarrett@gmail.com wrote:

All of those tended to fry your speakers?

There's 101 ways to do it. Designing power amps isn't quite so simple
especially when you want 1600W @ 0.02% THD.

Graham

 

[Eeyore]

mrdarrett@gmail.com wrote:

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.

Back then, few people knew C. A lot was done in PL/M which was Intel's own development
language.

The job was offered on the basis of my programming skill on a 'BBC Micro' for computer
animation. I recall one Xmas party at the film company I was working at then and I was
explaining how it worked to some tech. He said "you can't do that". I responded "watch
this then". He didn't quite fall over backwards. The company was part of a group, word
got round that I knew how to program, hence the offer.

And to be honest, later I did a job in embedded Pascal ! How obscure is that ? I said I
wasn't familiar with Pascal and one of the Directors said he'd loan me his book. Shortly
after I was programming in Pascal. I ended up liking it because of its stong data types.

That's when I realised that if you can intuitively program, it doesn't really matter
what the language is. I've even done some DSP assembler for audio effects.

I still hate C's syntax though. All those (void) s drives me nuts.

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

Possibly so !

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.

That's the basic voltage gain stage. Then learn about emitter resistor degeneration ( a
form of feedback ) and how bypassing it with a cap removes the feedback but still helps
with DC stability.

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

No, start with the basic one. Then move on to Darlingtons ( and possibly triples ) and
only then the Sziklai pair and compare their differences.

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

I thought it might be but in practice I haven't seen any real advantage in an output
stage. It went through a phase of popularity but I ended up going back a quite different
design where the main output device(s) is actually OFF in quiescent mode and the output
comes from some beefy drivers. It's all to do with trying to make the mutual conductance
as linear as possible.

And don't let the load impedance reflect into the final gain stage or instability is
likely to result, i.e. use LOTS of current gain.

Graham

 

[Eeyore]

Nobody wrote:

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.

I consider my PL/M to be nearly as readable as English to anyone with a
programming mind especially with decent use of literals. I once 'converted'
someone from assembler to PL/M. At the end of the project he said he
understood why I'd insisted and he's quite a high flyer. Mind you he made
loads of silly mistakes but his code was so easy to read because it was PL/M,
it was easy to find the errors as they got reported. It ended up as V 2.4
though.

My later re-write for an enhanced version was issued as a 'beta' i.e V 0.9,
thinking *someone* MUST find a flaw. Then we forgot about it and a year later
the product was still shipping with V 0.9 software and it seemed pointless to
change ! ;~)

And also with PL/M you can drop in 'assembler like' lines to to set registers
directly. IMHO it combines the best of medium and low-level programming.
http://en.wikipedia.org/wiki/PL/M

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.

Yes, I totally agree. I think they were quite upset I didn't take the bait.

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.

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.

Graham

 

[Eeyore]

mrdarrett@gmail.com wrote:

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?

VOID !

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

Graham

 

[Nobody]

On Tue, 12 May 2009 19:12:23 +0100, Eeyore wrote:

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]

On Tue, 12 May 2009 19:10:43 +0100, Eeyore wrote:

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".

 

On May 12, 11:12 am, Eeyore <rabbitsfriendsandrelati...@hotmail.com>
wrote:

mrdarr...@gmail.com wrote:
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?  

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

 

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˛

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]

mrdarrett@gmail.com wrote:

On May 12, 11:12 am, Eeyore <rabbitsfriendsandrelati...@hotmail.com
wrote:
mrdarr...@gmail.com wrote:
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?

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.

Those characters <> didn't exist on keyboards of the time.

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]

Nobody wrote:

On Tue, 12 May 2009 19:12:23 +0100, Eeyore wrote:

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.

VOID !

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".

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.

You'd be amazed how unneccesary it is.

Graham

 

[Michael A. Terrell]

Eeyore wrote:

"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.

Bullshit. It is what it is: a jelly bean, general purpose
transistor. The reason you don't like it, is that it is a JEDEC
registered part, instead of your lame European numbering system. It was
never designated as a low noise audiofool part.

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

Do you have a problem with using the correct prefix ?

Apparently, you do. Since it is available in multiple packages and
mounting styles, the original number is the appropriate one. The people
posting simple designs online have no idea which package will be used,
and by whom.. If they want metal, they use the original. If they can
use TO-92, they use the PN, and if they want surface mount, they use the
MMBT. The online designs aren't expected to be exotic performers. They
are simple circuits, to be built with easy to find parts. If you plane
top build 10,000 of something, you can comb the world for whatever you
want, but if you are building a single item and have no local source of
parts, then the recommended parts are fine.

You can't get it through your thick skull that beginners need things
to be simple enough to learn from. No matter how highly you think of
yourself, you were not born knowing how to do anything other than
breathe, and fill your diapers.


--
You can't have a sense of humor, if you have no sense!

 

[Michael A. Terrell]

mrdarrett@gmail.com wrote:

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

"The Brute 70" I built this one in high school. I made my first PC
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
--
You can't have a sense of humor, if you have no sense!

 

On May 12, 8:27 am, mrdarr...@gmail.com wrote:

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

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

G˛

 

[Jasen Betts]

On 2009-05-12, mrdarrett@gmail.com <mrdarrett@gmail.com> wrote:

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];
}

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;

 

On May 13, 4:16 am, Jasen Betts <ja...@xnet.co.nz> wrote:

On 2009-05-12, mrdarr...@gmail.com <mrdarr...@gmail.com> wrote:



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];
}

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

 

On May 12, 9:43 pm, "Michael A. Terrell" <mike.terr...@earthlink.net>
wrote:

mrdarr...@gmail.com wrote:

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

   "The Brute 70" I built this one in high school.  I made my first PC
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
--
You can't have a sense of humor, if you have no sense!

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

And what is this RCA Data Book?

Thanks,

Michael

 

[Eeyore]

mrdarrett@gmail.com wrote:

"Michael A. Terrell" <mike.terr...@earthlink.net> wrote:

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

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

 

[pimpom]

mrdarrett@gmail.com wrote:

On May 12, 9:43 pm, "Michael A. Terrell" <mike.terr...@earthlink.net
wrote:
mrdarr...@gmail.com wrote:

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

"The Brute 70" I built this one in high school. I made my first PC
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
--
You can't have a sense of humor, if you have no sense!


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]

pimpom wrote:

mrdarrett@gmail.com wrote:

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.

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

Graham