Building a class A audio amplifier - no audio out

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=A0pm, 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! =A0There 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.jp=
g

Enough of memory lane for now.

G=B2

On May 12, 12:34=A0am, stratu...@yahoo.com wrote:
> On May 11, 8:00=A0pm, 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! =A0There was a follow-up article with another version, a=
s
> > 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=B2


All of those tended to fry your speakers?

Michael

On May 11, 8:03=A0pm, Nobody <nob...@nowhere.com> wrote:
> > On May 11, 1:44=A0pm, 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? =A0(thoroughly confused) =A0That 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?  :D

Michael

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

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

"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

"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

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

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