questions about quasi complementary audio output stages

[Michael]

What are the drawbacks with quasi complementary audio output stages,
like, say, this one:

http://sound.westhost.com/project12a.htm

Do they give more distortion than the usual Sziklai output stages?

I understand that 40 years ago good PNP transistors didn't exist, but
why are quasi complementary output stages not seen so often in designs
nowadays?

Michael

 

[Rich Grise]

On Sat, 02 Oct 2010 09:15:36 -0700, Michael wrote:

What are the drawbacks with quasi complementary audio output stages, like,
say, this one:

http://sound.westhost.com/project12a.htm

It uses 2N3055s? ;-)

Do they give more distortion than the usual Sziklai output stages?

Probably not - if you note the connection from the junction of the
bottom of R12 and the collector of Q6 back to the junction of the top
of VR1 and the bottom of C4, the gain is "strapped", linearizing out
all the foibles of crossover distortion and what-not.

I understand that 40 years ago good PNP transistors didn't exist, but why
are quasi complementary output stages not seen so often in designs
nowadays?

Just follow the money. ;-)

Cheers!
Rich

 

[Phil Allison]

"Rich Grise"

Do they give more distortion than the usual Sziklai output stages?

** Sziklai output stages are not the most common seen in audio amps.

Probably not - if you note the connection from the junction of the
bottom of R12 and the collector of Q6 back to the junction of the top
of VR1 and the bottom of C4, the gain is "strapped", linearizing out
all the foibles of crossover distortion and what-not.

** Absolute horse shit.

The technique is called " bootstrapping " and simply has no effect on
crossover distortion.



.... Phil

 

[Rich Grise]

On Sun, 03 Oct 2010 20:19:12 -0700, Michael wrote:

On Oct 2, 4:32 pm, "Phil Allison" <phi...@tpg.com.au> wrote:
"Rich Grise"

Do they give more distortion than the usual Sziklai output stages?

** Sziklai output stages are not the most common seen in audio amps.

Probably not - if you note the connection from the junction of the
bottom of R12 and the collector of Q6 back to the junction of the top
of VR1 and the bottom of C4, the gain is "strapped", linearizing out
all the foibles of crossover distortion and what-not.

** Absolute horse shit.

The technique is called " bootstrapping " and simply has no effect on
crossover distortion.

This quasi complementary Darlington arrangement seems to operate without
the need for a center-tapped secondary transformer. What are the audio
ramifications of not using a center-tapped secondary?

You hae to use a great big huge capacitor to keep the DC off the speaker.

Hope This Helps!
Rich

 

[Rich Grise]

On Sun, 03 Oct 2010 20:16:06 -0700, Michael wrote:

Ohn Oct 2, 11:17 am, Rich Grise <richgr...@example.net> wrote:
On Sat, 02 Oct 2010 09:15:36 -0700, Michael wrote:
What are the drawbacks with quasi complementary audio output stages,
like, say, this one:

http://sound.westhost.com/project12a.htm

It uses 2N3055s? ;-)

Sure they're not the most up-to-date, but what's wrong with those? :- D

Well, other than having a beta of five, they're just fine. In fact, I

once had a job in a Rat Shack repair department, and when we'd get an
amp or receiver with blown output TO3s, we'd just routinely slap a couple
of 3055s in there.

And you don't need that quasi-circuit since they invented the MG2955. ;-)

Cheers!
Rich

 

[Michael]

Ohn Oct 2, 11:17 am, Rich Grise <richgr...@example.net> wrote:

On Sat, 02 Oct 2010 09:15:36 -0700, Michael wrote:
What are the drawbacks with quasi complementary audio output stages, like,
say, this one:

http://sound.westhost.com/project12a.htm

It uses 2N3055s? ;-)

Sure they're not the most up-to-date, but what's wrong with those? :-
D

M

 

[Michael]

On Oct 2, 4:32 pm, "Phil Allison" <phi...@tpg.com.au> wrote:

"Rich Grise"



Do they give more distortion than the usual Sziklai output stages?

** Sziklai output stages are not the most common seen in audio amps.



Probably not - if you note the connection from the junction of the
bottom of R12 and the collector of Q6 back to the junction of the top
of VR1 and the bottom of C4, the gain is "strapped", linearizing out
all the foibles of crossover distortion and what-not.

** Absolute horse shit.

The technique is called " bootstrapping " and simply has no effect on
crossover distortion.

...  Phil

This quasi complementary Darlington arrangement seems to operate
without the need for a center-tapped secondary transformer. What are
the audio ramifications of not using a center-tapped secondary?

M

 

[Rich Grise]

On Sun, 03 Oct 2010 20:58:51 -0700, Rich Grise wrote:

On Sun, 03 Oct 2010 20:16:06 -0700, Michael wrote:
Ohn Oct 2, 11:17 am, Rich Grise <richgr...@example.net> wrote:
On Sat, 02 Oct 2010 09:15:36 -0700, Michael wrote:
What are the drawbacks with quasi complementary audio output stages,
like, say, this one:

http://sound.westhost.com/project12a.htm

It uses 2N3055s? ;-)

Sure they're not the most up-to-date, but what's wrong with those? :- D

Well, other than having a beta of five, they're just fine. In fact, I once
had a job in a Rat Shack repair department, and when we'd get an amp or
receiver with blown output TO3s, we'd just routinely slap a couple of
3055s in there.

And you don't need that quasi-circuit since they invented the MG2955. ;-)
OOps: MJ2955.

Cheers!
Rich

 

[Phil Allison]

"Michael"
"Phil Allison"

"Rich Grise"



Do they give more distortion than the usual Sziklai output stages?

** Sziklai output stages are not the most common seen in audio amps.



Probably not - if you note the connection from the junction of the
bottom of R12 and the collector of Q6 back to the junction of the top
of VR1 and the bottom of C4, the gain is "strapped", linearizing out
all the foibles of crossover distortion and what-not.

** Absolute horse shit.

The technique is called " bootstrapping " and simply has no effect on
crossover distortion.

This quasi complementary Darlington arrangement seems to operate
without the need for a center-tapped secondary transformer. What are
the audio ramifications of not using a center-tapped secondary?


** What a fucking absurd troll.




..... Phil

 

[Phil Allison]

"Rich Grise"

It uses 2N3055s? ;-)

Sure they're not the most up-to-date, but what's wrong with those? :- D

Well, other than having a beta of five, they're just fine.

** More absolute bollocks !!!!

Go look up a data sheet sometime - fuckhead.


...... Phil

 

[Rich Grise]

On Tue, 05 Oct 2010 13:57:16 +1100, Phil Allison wrote:

"Rich Grise"

It uses 2N3055s? ;-)

Sure they're not the most up-to-date, but what's wrong with those? :- D

Well, other than having a beta of five, they're just fine.

** More absolute bollocks !!!!

Go look up a data sheet sometime - fuckhead.

Where did you think I found the data?

Phil, go take your meds and don't act like a nincompoop.

Trust me - people will like you better.

Good Luck!
Rich

 

[Phil Allison]

"Rich Grise Criminal LIAR"

It uses 2N3055s? ;-)

Sure they're not the most up-to-date, but what's wrong with those? :-
D

Well, other than having a beta of five, they're just fine.

** More absolute bollocks !!!!

Go look up a data sheet sometime - fuckhead.

Where did you think I found the data?

** You plucked it out you stinking, fat arse - as bloody usual.

My god you are one truly pathetic fucking LIAR !!



.... Phil

 

[default]

On Sun, 03 Oct 2010 20:54:37 -0700, Rich Grise <richgrise@example.net>
wrote:

This quasi complementary Darlington arrangement seems to operate without
the need for a center-tapped secondary transformer. What are the audio
ramifications of not using a center-tapped secondary?

You hae to use a great big huge capacitor to keep the DC off the speaker.

And you get great big thumps in the speaker when the thing charges the
cap to ~1/2 VCC unless you put a relay or switch in.

I had an old heathkit that used that output stage (more or less). It
had an annoying hiss that would eventually die out. Some time later I
added a switch and relay so it would default to no speakers when
turned on (to prevent my girlfriend from waking me when she powered it
up) that got rid of the hissing too. Changing the output cap finally
cured it - the hiss would be gone before I could troubleshoot it.
--

 

[Michael A. Terrell]

default wrote:

On Sun, 03 Oct 2010 20:54:37 -0700, Rich Grise <richgrise@example.net
wrote:


This quasi complementary Darlington arrangement seems to operate without
the need for a center-tapped secondary transformer. What are the audio
ramifications of not using a center-tapped secondary?

You hae to use a great big huge capacitor to keep the DC off the speaker.

And you get great big thumps in the speaker when the thing charges the
cap to ~1/2 VCC unless you put a relay or switch in.

I had an old heathkit that used that output stage (more or less). It
had an annoying hiss that would eventually die out. Some time later I
added a switch and relay so it would default to no speakers when
turned on (to prevent my girlfriend from waking me when she powered it
up) that got rid of the hissing too. Changing the output cap finally
cured it - the hiss would be gone before I could troubleshoot it.

The ones I saw had a split power supply so there was very little DC
offset. I built some and repaired a lot of others.


--
Politicians should only get paid if the budget is balanced, and there is
enough left over to pay them.

 

[default]

On Tue, 05 Oct 2010 10:58:28 -0400, "Michael A. Terrell"
<mike.terrell@earthlink.net> wrote:

default wrote:

On Sun, 03 Oct 2010 20:54:37 -0700, Rich Grise <richgrise@example.net
wrote:


This quasi complementary Darlington arrangement seems to operate without
the need for a center-tapped secondary transformer. What are the audio
ramifications of not using a center-tapped secondary?

You hae to use a great big huge capacitor to keep the DC off the speaker.

And you get great big thumps in the speaker when the thing charges the
cap to ~1/2 VCC unless you put a relay or switch in.

I had an old heathkit that used that output stage (more or less). It
had an annoying hiss that would eventually die out. Some time later I
added a switch and relay so it would default to no speakers when
turned on (to prevent my girlfriend from waking me when she powered it
up) that got rid of the hissing too. Changing the output cap finally
cured it - the hiss would be gone before I could troubleshoot it.



The ones I saw had a split power supply so there was very little DC
offset. I built some and repaired a lot of others.

I think mine was the AR15 and I think the AR1500 was the first split
supply receiver with DC coupled output stage.

I had a part time job repairing consumer electronics and kept a big
bipolar cap on my test speaker to avoid blowing it whilst
troubleshooting. That and a variac to raise the voltage slowly, saved
a lot of grief.
--

 

[Michael A. Terrell]

default wrote:

On Tue, 05 Oct 2010 10:58:28 -0400, "Michael A. Terrell"
mike.terrell@earthlink.net> wrote:


default wrote:

On Sun, 03 Oct 2010 20:54:37 -0700, Rich Grise <richgrise@example.net
wrote:


This quasi complementary Darlington arrangement seems to operate without
the need for a center-tapped secondary transformer. What are the audio
ramifications of not using a center-tapped secondary?

You hae to use a great big huge capacitor to keep the DC off the speaker.

And you get great big thumps in the speaker when the thing charges the
cap to ~1/2 VCC unless you put a relay or switch in.

I had an old heathkit that used that output stage (more or less). It
had an annoying hiss that would eventually die out. Some time later I
added a switch and relay so it would default to no speakers when
turned on (to prevent my girlfriend from waking me when she powered it
up) that got rid of the hissing too. Changing the output cap finally
cured it - the hiss would be gone before I could troubleshoot it.



The ones I saw had a split power supply so there was very little DC
offset. I built some and repaired a lot of others.

I think mine was the AR15 and I think the AR1500 was the first split
supply receiver with DC coupled output stage.

I had a part time job repairing consumer electronics and kept a big
bipolar cap on my test speaker to avoid blowing it whilst
troubleshooting. That and a variac to raise the voltage slowly, saved
a lot of grief.

I had two sets of three 24 Ohm 300W non-inductive resistors in
parallel for an eight ohm loads, with small speakers and dropping
resistors so I could test amps at or near full power without breaking
the windows. It was very handy for testing guitar amps for rock bands.

--
Politicians should only get paid if the budget is balanced, and there is
enough left over to pay them.

 

[default]

On Tue, 05 Oct 2010 13:46:44 -0400, "Michael A. Terrell"
<mike.terrell@earthlink.net> wrote:

I had two sets of three 24 Ohm 300W non-inductive resistors in
parallel for an eight ohm loads, with small speakers and dropping
resistors so I could test amps at or near full power without breaking
the windows. It was very handy for testing guitar amps for rock bands.

Me too. I had three 2 ohm 75 watt resistors bolted to a chunk of
aluminum, and switches so I could short the series cap and/or switch
in the dummy load resistors.

Them were the good old days...

Now days they use a lot of modules. I fixed an old (late 80's) X
brand receiver for a friend recently with four high power Darlington
output modules. If I didn't find the silly (discontinued) things on a
surplus web site ($15 ea), it probably would be too expensive to fix.
I doubt one could make a living fixing what they turn out today (if it
ever breaks)

I keep my homebrew discrete mosfet alive and it is damn near
indestructible. I had several hot strikes from the Tesla coil hit the
speakers and the only damage was a 100K 1/4W resistor opened that was
supposed to provide a ground reference to the input of the output
stages. I think the TC did it...
--

 

[Michael A. Terrell]

default wrote:

On Tue, 05 Oct 2010 13:46:44 -0400, "Michael A. Terrell"
mike.terrell@earthlink.net> wrote:

I had two sets of three 24 Ohm 300W non-inductive resistors in
parallel for an eight ohm loads, with small speakers and dropping
resistors so I could test amps at or near full power without breaking
the windows. It was very handy for testing guitar amps for rock bands.

Me too. I had three 2 ohm 75 watt resistors bolted to a chunk of
aluminum, and switches so I could short the series cap and/or switch
in the dummy load resistors.

Them were the good old days...

Now days they use a lot of modules. I fixed an old (late 80's) X
brand receiver for a friend recently with four high power Darlington
output modules. If I didn't find the silly (discontinued) things on a
surplus web site ($15 ea), it probably would be too expensive to fix.
I doubt one could make a living fixing what they turn out today (if it
ever breaks)

I keep my homebrew discrete mosfet alive and it is damn near
indestructible. I had several hot strikes from the Tesla coil hit the
speakers and the only damage was a 100K 1/4W resistor opened that was
supposed to provide a ground reference to the input of the output
stages. I think the TC did it...

I've seen a 4' Tesla Coil make a football player scream like a little
girl, so what chance did that tiny resistor have? ;-)


Another handy item was a good 4" speaker mounted in an old Alliance
U100 rotor control case with a line transformer, a couple switches and a
pair of banana jacks. The front of the case had a piece of perforated
metal between the speaker and the case. It let the sound out, but
protected the cone. The bottom metal plate was installed with contact
cement so it didn't rattle.

One switch selected either 25V / 4 Ohm or 70V / 8 Ohm and the other
selected high or low impedance. It was quite handy looking for the
right pair of wires on school intercoms, paging systems and other
speaker systems.


--
Politicians should only get paid if the budget is balanced, and there is
enough left over to pay them.

 

[Michael]

On Oct 5, 12:50 pm, default <defa...@defaulter.net> wrote:

On Tue, 05 Oct 2010 13:46:44 -0400, "Michael A. Terrell"

mike.terr...@earthlink.net> wrote:
  I had two sets of three 24 Ohm 300W non-inductive resistors in
parallel for an eight ohm loads, with small speakers and dropping
resistors so I could test amps at or near full power without breaking
the windows.  It was very handy for testing guitar amps for rock bands..

Me too.  I had three 2 ohm 75 watt resistors bolted to a chunk of
aluminum,  and switches so I could short the series cap and/or switch
in the dummy load resistors.

Them were the good old days...

Now days they use a lot of modules.  I fixed an old (late 80's) X
brand receiver for a friend recently with four high power Darlington
output modules.  If I didn't find the silly (discontinued) things on a
surplus web site ($15 ea), it probably would be too expensive to fix.
I doubt one could make a living fixing what they turn out today (if it
ever breaks)

I keep my homebrew discrete mosfet alive and it is damn near
indestructible.  I had several hot strikes from the Tesla coil hit the
speakers and the only damage was a 100K 1/4W resistor opened that was
supposed to provide a ground reference to the input of the output
stages.  I think the TC did it...
--

Homebrew discrete mosfet? 2sk1058?

 

[default]

On Tue, 5 Oct 2010 20:22:41 -0700 (PDT), Michael <mrdarrett@gmail.com>
wrote:

On Oct 5, 12:50 pm, default <defa...@defaulter.net> wrote:
On Tue, 05 Oct 2010 13:46:44 -0400, "Michael A. Terrell"

mike.terr...@earthlink.net> wrote:
  I had two sets of three 24 Ohm 300W non-inductive resistors in
parallel for an eight ohm loads, with small speakers and dropping
resistors so I could test amps at or near full power without breaking
the windows.  It was very handy for testing guitar amps for rock bands.

Me too.  I had three 2 ohm 75 watt resistors bolted to a chunk of
aluminum,  and switches so I could short the series cap and/or switch
in the dummy load resistors.

Them were the good old days...

Now days they use a lot of modules.  I fixed an old (late 80's) X
brand receiver for a friend recently with four high power Darlington
output modules.  If I didn't find the silly (discontinued) things on a
surplus web site ($15 ea), it probably would be too expensive to fix.
I doubt one could make a living fixing what they turn out today (if it
ever breaks)

I keep my homebrew discrete mosfet alive and it is damn near
indestructible.  I had several hot strikes from the Tesla coil hit the
speakers and the only damage was a 100K 1/4W resistor opened that was
supposed to provide a ground reference to the input of the output
stages.  I think the TC did it...
--


Homebrew discrete mosfet? 2sk1058?

20 years old I'd have to look up a schematic.. Some complimentary
Hitachi parts for the bass amplifiers and ordinary bipolar for the
treble amps. I got a pair of surplus Crown amps (500 watts into 8
ohms and 1,000 into 2-5 ohms) intending to tri-amp but never got
around to it. Too many interesting things to do and never enough
time.

The Crown amps were a steal for ~$150 each - never used and intended
to go into an MRI for hospitals as "gradient" drive amplifiers, but
they are stock Crown audio amps, weighing in at >100 lbs each. No
meters on the front.
--