[DNG] [OT] Modification of audio power amplifier.

[Edward Bartolo]

The attached amplifier circuit is the result of many hours of study
and development. It is an audio amplifier that can deliver a
continuous power of 250W at 8 Ohms or 450W at 4 Ohms. The resultant
distortion figure is around 0.1% for the higher power and about 0
.09% for the lower power.

I arrived at this, and I am a dull person! The bully who smeared my
reputation on this mailing list must be capable of creating an
amplifier with exactly 0% distortion and with an output that is always
in exact phase with the input. A person with that unmatched mental
ability is wasted here. It is better for them to involve themselves
trying to convert mass directly into energy. Why waste yourself here
when you can earn billions?!

Don't post Douglas Self's famous Blameless amplifier. Every person
serious enough into amplifier design knows about that.

Yes, I studied from books contrary  to what some self inflated jealous
bastards claimed about me.
Version 4
SHEET 1 2264 680
WIRE 880 -784 816 -784
WIRE 1008 -784 960 -784
WIRE 1168 -784 1088 -784
WIRE 1296 -784 1248 -784
WIRE 720 -736 96 -736
WIRE 16 -704 -944 -704
WIRE 1440 -704 16 -704
WIRE -944 -656 -944 -704
WIRE -112 -640 -496 -640
WIRE 96 -640 96 -736
WIRE 96 -640 -112 -640
WIRE 128 -640 96 -640
WIRE 208 -640 128 -640
WIRE 256 -640 208 -640
WIRE 384 -640 336 -640
WIRE 528 -640 384 -640
WIRE 816 -640 816 -784
WIRE 816 -640 528 -640
WIRE 864 -640 816 -640
WIRE 1056 -640 864 -640
WIRE 1296 -640 1056 -640
WIRE 1616 -640 1296 -640
WIRE 1856 -640 1616 -640
WIRE 384 -624 384 -640
WIRE 528 -624 528 -640
WIRE 128 -576 128 -640
WIRE 208 -576 208 -640
WIRE -944 -544 -944 -576
WIRE -864 -544 -944 -544
WIRE -704 -544 -864 -544
WIRE 1232 -528 992 -528
WIRE 1552 -528 1232 -528
WIRE 1792 -528 1552 -528
WIRE -944 -512 -944 -544
WIRE -864 -512 -864 -544
WIRE -704 -512 -704 -544
WIRE -192 -512 -432 -512
WIRE -176 -512 -192 -512
WIRE 384 -512 384 -544
WIRE 720 -512 720 -736
WIRE 1056 -496 1056 -560
WIRE 1296 -496 1296 -560
WIRE 1616 -496 1616 -560
WIRE 1856 -496 1856 -560
WIRE 128 -480 128 -512
WIRE 208 -480 208 -512
WIRE 208 -480 128 -480
WIRE 208 -464 208 -480
WIRE 528 -464 528 -544
WIRE 528 -464 448 -464
WIRE 864 -448 864 -560
WIRE 992 -448 992 -528
WIRE 992 -448 864 -448
WIRE 1232 -448 1232 -528
WIRE 1440 -448 1440 -704
WIRE 1488 -448 1440 -448
WIRE 1552 -448 1552 -528
WIRE 1792 -448 1792 -528
WIRE -192 -432 -192 -512
WIRE -192 -432 -304 -432
WIRE -112 -432 -112 -464
WIRE -112 -432 -192 -432
WIRE -944 -416 -944 -448
WIRE -864 -416 -864 -448
WIRE -864 -416 -944 -416
WIRE -704 -416 -704 -448
WIRE -704 -416 -864 -416
WIRE 864 -400 864 -448
WIRE 1488 -400 1488 -448
WIRE -304 -384 -304 -432
WIRE 528 -384 528 -464
WIRE -944 -368 -944 -416
WIRE 720 -352 720 -432
WIRE 720 -352 656 -352
WIRE 784 -352 720 -352
WIRE 800 -352 784 -352
WIRE -1152 -336 -1232 -336
WIRE -1088 -336 -1152 -336
WIRE 384 -336 384 -416
WIRE 384 -336 176 -336
WIRE 464 -336 384 -336
WIRE -496 -320 -496 -464
WIRE -352 -320 -496 -320
WIRE 176 -320 176 -336
WIRE 176 -320 -256 -320
WIRE -1088 -304 -1088 -336
WIRE -496 -288 -496 -320
WIRE -112 -288 -112 -432
WIRE 560 -288 528 -288
WIRE 624 -288 560 -288
WIRE 656 -288 656 -352
WIRE 656 -288 624 -288
WIRE 1440 -288 1440 -448
WIRE 176 -272 176 -320
WIRE 288 -272 176 -272
WIRE 448 -272 448 -464
WIRE 448 -272 352 -272
WIRE 624 -272 624 -288
WIRE 1488 -272 1488 -320
WIRE -560 -240 -608 -240
WIRE 16 -240 16 -704
WIRE 16 -240 -48 -240
WIRE 784 -208 784 -352
WIRE 864 -208 864 -224
WIRE 944 -208 864 -208
WIRE 528 -192 528 -288
WIRE 176 -176 176 -272
WIRE 272 -176 176 -176
WIRE 448 -176 448 -272
WIRE 448 -176 352 -176
WIRE 944 -176 944 -208
WIRE 1040 -176 944 -176
WIRE -1088 -160 -1088 -224
WIRE -1072 -160 -1088 -160
WIRE -912 -160 -992 -160
WIRE -848 -160 -912 -160
WIRE -720 -160 -848 -160
WIRE -608 -160 -608 -240
WIRE -608 -160 -656 -160
WIRE 624 -144 624 -192
WIRE 624 -144 592 -144
WIRE 1040 -144 1040 -176
WIRE 1056 -144 1056 -400
WIRE 1056 -144 1040 -144
WIRE 1168 -144 1168 -160
WIRE 1168 -144 1056 -144
WIRE 1248 -144 1168 -144
WIRE 1296 -144 1296 -400
WIRE 1296 -144 1248 -144
WIRE 1440 -144 1440 -208
WIRE 1440 -144 1296 -144
WIRE 1488 -144 1488 -208
WIRE 1488 -144 1440 -144
WIRE 1616 -144 1616 -400
WIRE 1616 -144 1488 -144
WIRE 1856 -144 1856 -400
WIRE 1856 -144 1616 -144
WIRE 624 -128 624 -144
WIRE -1088 -96 -1088 -160
WIRE -912 -96 -912 -160
WIRE -848 -96 -848 -160
WIRE -608 -96 -608 -160
WIRE 1440 -96 1440 -144
WIRE -1232 -64 -1232 -336
WIRE 864 -48 864 -128
WIRE -496 -32 -496 -192
WIRE -400 -32 -496 -32
WIRE -112 -32 -112 -192
WIRE -112 -32 -400 -32
WIRE 528 -32 528 -96
WIRE 560 -32 528 -32
WIRE 624 -32 624 -48
WIRE 624 -32 560 -32
WIRE 656 -32 624 -32
WIRE 528 -16 528 -32
WIRE 656 0 656 -32
WIRE 736 0 656 0
WIRE 784 0 784 -144
WIRE 784 0 736 0
WIRE 800 0 784 0
WIRE -400 16 -400 -32
WIRE 1056 16 1056 -144
WIRE 1056 16 1040 16
WIRE 1296 16 1296 -144
WIRE 1296 16 1280 16
WIRE 1616 16 1616 -144
WIRE 1616 16 1600 16
WIRE 1856 16 1856 -144
WIRE 1856 16 1840 16
WIRE -1088 32 -1088 

Re: [DNG] [OT] Modification of audio power amplifier.

[Steve Litt]

On Tue, 29 May 2018 14:16:02 +0200
Edward Bartolo  wrote:

> On 28/05/2018, dan pridgeon  wrote:
> > I hope you will publish your circuit and its description soon.  I'd
> > like to study it.  (a .png would work if you have a sketch of it.)
> > Thanks. Dan.
> >  
> 
> I am afraid there is nothing new to study. The input is fed to a
> differential pair powered by a constant current source using two
> resistors in series with a Zener diode connected from the midpoint
> between the resistors and ground (0 volt terminal). 

Schematic please?

English is great for novels, but schematics are the way we communicate
about electronics.


SteveT

Steve Litt 
June 2018 featured book: Twenty Eight Tales of Troubleshooting
http://www.troubleshooters.com/28


___
Dng mailing list
Dng@lists.dyne.org
https://mailinglists.dyne.org/cgi-bin/mailman/listinfo/dng

[DNG] [OT] Modification of audio power amplifier.

[Edward Bartolo]

The circuit I sent you is not finished yet. Yesterday, I connected it
to the output stage to test how it behaves. At first, it oscillated at
a frequency of 660kHz. I realised this because the heatsink started
getting steadily hotter. To decouple high ultrasonic frequencies I
used a decoupling capacitor betweent the base and collector of the
transistor taking the output from the differential pair. After
energizing again the circuit, the high frequency was gone, but I am
still getting the first and second harmonics of the power supply's
ripple. This means, the power supply's ripple is being injected into
the amplifier's signal. The most obvious cause for this to happen, is
a bias voltage that is slightly dependent on the instantaneous supply
voltage. I think, I will soon have that also resolved. I will connect
a resistance and an electrolytic capacitor across the current source's
bias diodes. Since current sources have extremely high impedances,
while allowing appreciable current to pass, a slight variation in
biasing them, can result in getting harmonics from the supply's
ripple.
___
Dng mailing list
Dng@lists.dyne.org
https://mailinglists.dyne.org/cgi-bin/mailman/listinfo/dng

[DNG] [OT] Modification of audio power amplifier.

[Edward Bartolo]

On 28/05/2018, dan pridgeon  wrote:
> I hope you will publish your circuit and its description soon.  I'd like to
> study it.  (a .png would work if you have a sketch of it.)
> Thanks. Dan.
>

I am afraid there is nothing new to study. The input is fed to a
differential pair powered by a constant current source using two
resistors in series with a Zener diode connected from the midpoint
between the resistors and ground (0 volt terminal).  The output of the
differential pair is from a resistor and the + terminal of the power
supply. The output drives a PNP transistor with its collector
connected to  constant current source with the latter's current set at
13mA. This provides a very high impendance while at the same time it
improves the circuit's behaviour when the output voltage approaches
clamping voltages. A resistor as ouput would limit the ouput driver's
current to voltage_difference / R. Since we are almost at clamping
voltages, the voltage difference is small, so also the drive current.
This condition is highly undesirable if distortion is to be minimized.
The current passes through two diodes in series and an adjustible
resistor which should provide the necessary driver stage bias voltages
to minimize crossover distortion.
___
Dng mailing list
Dng@lists.dyne.org
https://mailinglists.dyne.org/cgi-bin/mailman/listinfo/dng

[DNG] [OT] Modification of audio power amplifier.

[Edward Bartolo]

On 27/05/2018, Bruce Perens  wrote:
> I salute your amplifier for its freedom from the evil emitter-follower
> created by Professor Leonard Puttering. :-)
>

Had that been the truth, the Professor would have been a very
successful electronics engineer. Nevertheless, he has a very
attractive salary.
___
Dng mailing list
Dng@lists.dyne.org
https://mailinglists.dyne.org/cgi-bin/mailman/listinfo/dng

[DNG] [OT] Modification of audio power amplifier.

[Edward Bartolo]

Thanks for all replies.

My first prototype test circuit seems to work as expected although I
haven't yet connected the output stage. Connecting a resistor, 10K
Ohm, from the inverting input to output, that is, the point between
the biasing diodes, resulted in an ouput voltage of 0 Volts. This
clearly shows the circuit is working. Also connecting a very high
resistance from the non-inverting input to the positive and negative
sides of the split power supply resulted in the output voltage
shifting accordingly. Voltages across all components followed
calculated values quite accurately.

After this test, I will connect the ouput stage when I finish all
modifications so that everything is compatible with the earth terminal
connected to the 0V terminal of the split power supply.
___
Dng mailing list
Dng@lists.dyne.org
https://mailinglists.dyne.org/cgi-bin/mailman/listinfo/dng

Re: [DNG] [OT] Modification of audio power amplifier.

[karl]

Edward:
> Warning: Out of Topic. No relation to Devuan but to technology and 
> electronics.
> 
> Since, I know some have knowledge of electronics and I am replacing an
> amplifier's pre-driver stages I am posting here.
...

If you post your question on

 geda-u...@delorie.com
 http://wiki.geda-project.org/geda:mailinglists

and/or

 linux-audio-u...@lists.linuxaudio.org
 https://lists.linuxaudio.org/

you will be more on target.

Regards,
/Karl Hammar

---
Aspö Data
Lilla Aspö 148
S-742 94 Östhammar
Sweden
+46 173 140 57


___
Dng mailing list
Dng@lists.dyne.org
https://mailinglists.dyne.org/cgi-bin/mailman/listinfo/dng

[DNG] [OT] Modification of audio power amplifier.

[Edward Bartolo]

Warning: Out of Topic. No relation to Devuan but to technology and electronics.

Since, I know some have knowledge of electronics and I am replacing an
amplifier's pre-driver stages I am posting here.

At present, I am opting to use a simple circuit for testing purposes.
This circuit uses a differential pair and the input stage. The
differential pair is supplied a pseudo-constant current (2.5mA) from a
two resistor chain with a Zener diode connected to ground. This
results in a fairly constant voltage that develops across one resistor
and the base-emittor junction. Therefore, the bias current can be
taken as constant. The output from the differential pair drives the
pre-pre-driver stage which has its collector resistor replaced by a
constant current source. This both provides a high impedance output
resistance for this stage and solves issue of using greater drive
current for the same output power.

My little hesitation at the this stage, is the biasing to remove
crossover distortion. I know a that two diodes are connected in series
but I want more control on the quiescent current in the output stages
as this can cause overheating and unnecessarily uses energy for no
output. Together with two series connected diodes I found some
amplifiers use also a preset resistor in series with the biasing
diodes to have more control. In my case, I think the choice may be an
amplified diode which is a transistor biased in such a way to behave
like a diodes but with modifiable characteristic. The latter
arrangement have the ability of presenting a voltage that ranges from
0.7V upwards whereas the former two start from 0.7 x 2 volts.

Excuse me for my intrusion. Someone might have met or read about a
biasing arrangement I have not heard of yet.

Thanks.
___
Dng mailing list
Dng@lists.dyne.org
https://mailinglists.dyne.org/cgi-bin/mailman/listinfo/dng