Distortion from audio power amp

[Terry Pinnell]

Yes, but what is the reason for R11 (in collector bottom 2N3055).
That transistor has high Z collector out, why add .5 Ohm? It would do
nothing?

Agreed. That's down to my misinterpreting advice over where to place
R11. I aim to move it to Q6 emitter.

 

[Rich Grise]

to check this, I think the actual previous stage (dog bark synthesised
sound), would have Rs > 50.


So - you don't like this circuit too much then? <g>

What it is, is, the circuit the way it's laid out is probably a pretty
good dog bark generator - what do those waveforms from a few posts back
_sound_ like? Maybe that's the way it's _supposed_ to be. Remember, there
are people who say Toobz give a "better" sound, right?

Cheers!
Rich

 

[legg]

Interesting stuff, but couldn't find any close similarity in any of
those circuits to this one.

The second link offers an article, labeled QuasiComp.zip, in addition
to Lin's.

I picked up the ETI'76 reference from hand-written notes in the
margins of your own scanned reference, and assumed they refered to the
article.

The Babani series was pretty bad, but judging from the price of all
technical publications, in England in those days, it had it's place.
Hope the situation has improved.

The relevant pages from the '83 issue of the RCA power transistor
application manual are scanned and posted on abse.

RL

 

[Don Pearce]

Yes, but what is the reason for R11 (in collector bottom 2N3055).
That transistor has high Z collector out, why add .5 Ohm? It would do
nothing?
JP

Judging by the quality of the design generally, I would say the
designer had seen another amp (PNP/NPN push pull) that had a resistor
there, and thought he had better put one in too.

d

 

[Fred Bartoli]

What it is, is, the circuit the way it's laid out is probably a pretty
good dog bark generator - what do those waveforms from a few posts back
_sound_ like? Maybe that's the way it's _supposed_ to be.

No that's a good trick. Please Terry, don't fix it :
Distorsion is probably the part that'll scare the most whoever enter your
home.


Thanks,
Fred.

 

[Terry Pinnell]

Judging by the quality of the design generally, I would say the
designer had seen another amp (PNP/NPN push pull) that had a resistor
there, and thought he had better put one in too.

No, see my reply last night to Jan.

 

[Terry Pinnell]

"Fred Bartoli"

"Rich Grise" <[email protected]> a écrit dans le message

No that's a good trick. Please Terry, don't fix it :
Distorsion is probably the part that'll scare the most whoever enter your
home.

Non! The burglars around here are very discriminating; a mere hint of
harmonic or cross-over distortion and they'd not hesitate to press on
with their nefarious activities <g>.

 

[Terry Pinnell]

The second link offers an article, labeled QuasiComp.zip, in addition
to Lin's.

Yes, thanks, I had looked at all 3 others (Bax, Shaw and QuadTriple),
albeit very briefly. Will study more thoroughly later.

I picked up the ETI'76 reference from hand-written notes in the
margins of your own scanned reference, and assumed they refered to the
article.

Correct. I thought maybe you still had that!

The Babani series was pretty bad, but judging from the price of all
technical publications, in England in those days, it had it's place.
Hope the situation has improved.

Now checked, and author was Richard Torrens. ('A well experienced
electronics development engineer, and has designed, developed, built
and tested the many useful and interesting circuits included in this
book.') The book, ISBN 0 900162 63 S, was first published in 1976.

The relevant pages from the '83 issue of the RCA power transistor
application manual are scanned and posted on abse.

Thanks, that does look very relevant. May have to edit the scans a
bit! Do you have original source please?

BTW, is this configuration related in any way to to the Sziklai Pair?

 

[Glenn Gundlach]

As mentioned earlier in

Subject: Re: Trouble shooting push-pull amp
Date: Thu, 13 May 2004 09:21:04 +0100

it's about 30 years old. Comes from Babani Press series, Book #221,
"28 Tested Transistor Projects", page 21. I'll check author's name
(book is still in shed/workshop) and let you know tomorrow.

Try older than that.

http://www.swtpc.com/mholley/LittleTiger/PE_DEC_1967_P30.jpg

OK, its complementary. It worked.

Even older versions in the 1964 GE transistor manual.

GG

 

[Winfield Hill]

Glenn Gundlach wrote...

Terry Pinnell wrote ...

Try older than that.
http://www.swtpc.com/mholley/LittleTiger/PE_DEC_1967_P30.jpg

That circuit has a number of improvements over Terry's poor circuit.

Even older versions in the 1964 GE transistor manual.

And even before that in a 1955 paper by H C Lin, using Ge trannies.
http://groups.google.com/[email protected]
http://groups.google.com/[email protected]

I have a copy of Lin's 1955 paper around here someplace. Lin also got
patent # 2,896,029 dated 1959. His design was advanced for its time,
but some folks have learned a lot about audio amplifier design in the
last 50 years, even for simple circuits. :>)

Thanks,
- Win

(email: use hill_at_rowland-dot-org for now)

 

[legg]

Thanks, that does look very relevant. May have to edit the scans a
bit! Do you have original source please?

pages 166/167 and 174/175 of RCA PTA-400 "Power Transistor
Applications", '83. This was chosen because of it's references to
temperature and biasing, in the latter pages.

You will find similar references in

GE "Transistor Manual" 5th Ed, '60.
RCA SC-14 "Transistor Thyristor & Diode Manual", '69.
GE Electronic Data Library 400-6 "Transistors-Diodes", '82.

In fact, it shows up in most standard texts since the mid 60's,
including the more recent AofE (in ch2).

BTW, is this configuration related in any way to to the Sziklai Pair?

'Sziklai Pair' would refer only to the configuration of the two
transistors Q4 and Q6 in your drawing, also known as a complementary
darlington pair or complementary feedback pair.

The quasi-complimentary output refers to the combination of
darlington and complementary darlington structures used in the entire
totem-pole. It becomes fully complementary when complementary
darlingtons are used for both.

As to the term 'Sziklai' - I am unaware of it's use prior to 1980. I
assume it refers to the work of G.C.Sziklai at RCA. I have only read
anecdotal references to this man's work, but doubt he personally
called this anything other than a 'compementary' configuration. I note
his recent passing.

RL

 

[Stefan Heinzmann]

Agreed. That's down to my misinterpreting advice over where to place
R11. I aim to move it to Q6 emitter.

Don't you think it would be better to leave it where it was and move
Q4's emitter to Q6's collector?

 

[petrus bitbyter]

Agreed. That's down to my misinterpreting advice over where to place
R11. I aim to move it to Q6 emitter.

Terry,

IMHO R11 is at the rihgt place, but the emiiter of Q4 has to be connected to
the collector of Q6. Found this and some other tips in an (old? 1973?) book,
on the subject. This type of amplifiers were never known for their
stability. I posted a schematic on alt.binaries.schematics.electronic that
contains eight clues to stabilise an amplifier like this. I consider the
author a specialist as I did a lot of amplifier (re)building using this book
and never failed.

petrus bitbyter

 

[Rich Grise]

"Fred Bartoli"


Non! The burglars around here are very discriminating; a mere hint of
harmonic or cross-over distortion and they'd not hesitate to press on
with their nefarious activities <g>.

Well, then you'd better hang out at your local broadcast station and
pick up a couple of 813 drivers for your output stage, and get the
finest ultrapure anisotropically phase-adjusted silver speaker cables,
and be sure the low-level connectors are gold plated over platinum,
to preserve all the nuances of the original sound, while contributing
that virtually indescribable audiophile mellowness, while not interfering
with the full, rich fullness of t0obZ.

And, of course, the speaker simply has to be a woofer.

:-|
Rich

 

[Rich Grise]

Glenn Gundlach wrote...

That circuit has a number of improvements over Terry's poor circuit.


And even before that in a 1955 paper by H C Lin, using Ge trannies.
http://groups.google.com/[email protected]
http://groups.google.com/[email protected]

I have a copy of Lin's 1955 paper around here someplace. Lin also got
patent # 2,896,029 dated 1959. His design was advanced for its time,
but some folks have learned a lot about audio amplifier design in the
last 50 years, even for simple circuits. :>)

Ah, I remember the days when the transistors were just showing up. I
guess people were pretty excited about them at the time. Maybe that's
what prodded so many of us around our age to get into electronics?

Cheers!
Rich

 

[Winfield Hill]

Rich Grise wrote...

Winfield Hill wrote ...

Ah, I remember the days when the transistors were just showing up. I
guess people were pretty excited about them at the time. Maybe that's
what prodded so many of us around our age to get into electronics?

I envy you your memories. Mine were a bit later. Although I spent my
youth on tubes, switching to transistors only in 1963, I still missed
the excitement of the 50s, when Ge succumbed to Si, and serious bipolar
transistor circuitry first got underway. However I was around when the
first affordable ICs appeared. Like the old Fairchild RTL chips, with
their 8-pin packages and the elegant round black-plastic tops.

Thanks,
- Win

(email: use hill_at_rowland-dot-org for now)

 

[Jan Panteltje]

Ah, I remember the days when the transistors were just showing up. I
guess people were pretty excited about them at the time. Maybe that's
what prodded so many of us around our age to get into electronics?

Cheers!
Rich

I was prodded in a time when the AZ1 rectifier tube came.
Also build a transmitter with a DL92 ? 1.5V battery tube.
Transistors came later.
xtal detector with a whisker you had to move....
Later oa79 ge diode..
Soem Europeans wil perhaps remember the 402 coil
That was a medium wave coil with powder iron core (adjustable),
and a secondairy.. used in many amateur projects...
Then TV with tubes came, was facinated, pl81?
Transistors in TVs came much later, mmm Sony had the first all transistor
portable Tv around 1966? (not sure), but they cheated (as Sony usually does
it seems), they used a HV cascade with TUBES.
3 oclock at night, memory is offline...

 

[Rich Grise]

I envy you your memories. Mine were a bit later. Although I spent my
youth on tubes, switching to transistors only in 1963, I still missed
the excitement of the 50s, when Ge succumbed to Si, and serious bipolar
transistor circuitry first got underway. However I was around when the
first affordable ICs appeared. Like the old Fairchild RTL chips, with
their 8-pin packages and the elegant round black-plastic tops.

Oh, heck, Win, I really just remember the hoopla - I was about 7, after
all.

Cheers!
Rich

 

[Terry Pinnell]

And, of course, the speaker simply has to be a woofer.

Indeed! ;-)

 

[Terry Pinnell]

Try older than that.

http://www.swtpc.com/mholley/LittleTiger/PE_DEC_1967_P30.jpg

OK, its complementary. It worked.

Even older versions in the 1964 GE transistor manual.

GG

Thanks, interesting circuit. But it uses the commoner configuration of
a complementary pair for the power stage. This circuit of mine from
Torrens uses what seems to be the far less common dual NPN approach.