Simple, powerful (100W-200W into 8ohm) amplifier schematic needed

[ddog]

Hi, i need to do simple, but powerful amp for our "ghetto-blaster" "PA" sound system, sound quality is not so important, but volume is. It will be used in our bmx/mtb track to play music, and it's quite large area. I will make like four on six mono channels, so we can put speakers in many places. Source will be portable minidisc or cd and music punkrock and so, so it won't need to be extremely hifi, just cheap and rugged, short-circuit proof etc. It will be powered by SMPS and 60Ah/12V car battery.

Sorry, i'm not so good at writing english :|

And chip-amps are not good option, they cost too much (LM3886 is like almost 10euros one piece, and hose would be needed like 12 to make 6 bridged channels). It needs to be really cheap, like 10e or less / channel for semiconductors (i have lots of caps, transistors, all parts needed to smps etc. already)

I don't necesarily need PCB layout, i can make that by myself if there's not one.

Thanks!

[metha]

- Parallel TDA7293 as demo in the datasheet

- ESP's Project 3A 60-100W Hi-Fi Power Amp
( http://sound.westhost.com/project3a.htm )

[ChocoHolic]

Hi Dog!

Well the schematic which is proposed by metha requires
+/35V. You would need a DC/DC converter to derive this if you are
getting your energy from a car battery.
If you want to work without DC/DC converter there might be another
suitful way:

Make a bridged amplifier, so you can get about +/- 10V peak (if you are lucky) from your 12V supply. To get 100W from this you will need
quite a low speakers impedance (around 0.5 Ohms), I would propose multiple 4 Ohms chassis. Of course the amp would have to drive very high currents. I do not have a schematic, but a OP amp followed by a high current output stage might serve it. May be you could use a NPN/PNP combination for the positive half wave and complementary a PNP/NPN combination for the neg. This would allow about 2x 0.7V more output swing than a standard darlington configuration.
If sound is not the major focus then you could skip the bias of the
output stage and go for a current dumping design (less power consumption).

Or more sophisticated and more expensive, but much more
up to date lighter in weight:
Use a DC/DC converter and combine this with a switch mode
amp! This will save a lot of power consumption and you could easily
use a battery of half of your current plans.


Bye
Markus

[destroyer X]

This is not exactly you need....but can match your need with small efforts.

You have to find an automobile radio receiver....mono or stereo, the way you want.... that can put something alike 1 to 2 watts RMS output in 4 ohms...... 4 volts off audio is perfect...... 2 volts can be helpfull too.

So, with the advantage that you already has tone controls and volume controls.... and also a good sensitivity using the volume radio's volume control as your input.

The output goes to the amplifier largely used world wide..... the first transformer is used to invert and give positive and negative cicles into two PNP darlington transistor (can use the one you have.....better than 10 amps each one is better).

This transformer is a 110 volts AC to 8+8 volts
110 volts AC to 9+9 volts
110 volts AC to 10 + 10 volts
110 volts AC to 12 + 12 volts

Or, if easier to you 220 volts AC input to 16 +16 volts output
220 volts AC input to 18 +18 volts output
220 volts AC input to 20 + 20 volts output
220 volts AC input to 24 + 24 volts output

all them minimun capacity is 200 miliamperes secondary current... if more it's ok, but transformer will be bigger.

the other one, is an AC small transformer that you dismount and put 48 turns of cooper wire (the one used in transformers, isolated, painted and protected against shorts)..... first cut the 1 or half milimeters diameter wire in two pieces of around 3 meters.... it depends the transformer size.... those wires are shorted in the beginning of the turns, soldered together and those parallell wires will be the coil.... 48 turns....... and three points.... one shorted and two others open.... so, you have three points....if you prefere.....may be easier and better... i do not know.... you can make 48 turns.... extract a small loop and them more 48 turns on it...... the E form laminated material will form 2 to the inches long...... 2 inches high and the metal part will make 1 inch large...... so....... seeing up side down you will discover that the letter E center leg measure around one square inches....my english is awfull..... stay stand by.... not sitted and look to the assembled transformer upside a table...... thickness off metal looking this way will be around an inch.... a small transformer.... 100 miliamperes or something alike.

This transformer is used to make the colector charge resistance to output..... and also to invert to amplify both positive and negative cicles of the signal.... i am sorry if you understand a lot and i may be "teaching old doctor how to measure temperature in termometer"..... sorry, i will see if you PHD or doctor in eletronics latter.

This amp is used since seventies.... small changes...... in the past no darlington exists.....now, people here is using darlingtons.... and with two of this circuit you will make a lot of good sound!....yes!...... Ein Gutten machinen!...... people put 2 units in their automobile and bigg speakers and bass and drum shack our apartment windows when they passed in the near street..... 20 stages down....more than 50 meters distant..... shacking glasses!

Can be a surprise...... can beat some Ueristêingsfarenhouser Tecnicsonic unt Marantz machinen......

Specifications are around that:

Voltage to work: from 12 to 15 volts DC, 10 ampéres each unit
Power output: can reach 70 Watts RMS ..... i believe in 50 Watts.... and completely clean around 35 RMS in 2 ohms.
Distortion when reach 70 Watts RMS under 2 ohms is 5%
Iddle current must be adjust by the trimpot to 80 miliamps
Normal consumption with 12 volts is 8 amperes
Power consumption to low distortion is around 96 watts... can goes into 150 watts range
Eficiency of the system....... 74 percent!..... 24 percent is lost!
1500 Squared centimeters heat sink..... something alike the normal 8 fins heat sink... the old ones used to 2N3055..... but with 12 centimeters each fin side.

Use two speaker .... better to use 50 watts, 4 ohms units parallelled....minimum 25 centímeter paper diameter.... long excursion and box tuned in 40 hertz..... speaker with a flexible suspension..... called here acoustic suspension... the speaker to use, normally in sealled enclosures.
The bias trimpot, to polarized tip140 darlingtons is adjusted to 80 mA and their value is 10 K ohms

If someone do not agree, please tell Destroyer X.... if something wrong tell Mr Ddog and also E Mail to Destroyer X.... if someone simulate and encounter another values..... please.... let me know

I will put a scratch..... made it fast...... is not my design..... is public ...... everybody is doing this same circuit.

Sorry scratch quality...... but the audio will surprise you!

Carlos Eugênio Mergulhão..... is the Destroyer X..... destroyer because i am old an changing transistor leads i am always putting fire on them..... X is extra, special, plus ..... very special destructor!

Regards,

[destroyer X]

Thats a picture..... they make competitions!

Destroyer X

[5th element]

If you have slones high power amplifier contruction manual the 200watt design of 11.8 is a good one. Its simple and robust.

However it can be a little unstable, this is easy to sort out though with an alteration of a few resistors.

[millwood]

Originally posted by 5th element
If you have slones high power amplifier contruction manual the 200watt design of 11.8 is a good one. Its simple and robust.

you think it can be done in ~$10 per channel in silicon?

sounds like the guy wants to have decibles not hi-fi. maybe some sorts of digital amp would do that?

[ChocoHolic]

hi destroyer!

...car spl competition guys were always as crazy as their designs....

You tell PNP, but your schematics show NPN .
From circuitry NPN looks suitful for me.

Just to understand the circuitry:
The 220V winding (or 110V) will be connected to the
speakers? ..... not shown in the schematic....

Last but not least. Are you sure about your given
circuitry for the bias control?

Bye Markus

[5th element]

Originally posted by millwood



you think it can be done in ~$10 per channel in silicon?

sounds like the guy wants to have decibles not hi-fi. maybe some sorts of digital amp would do that?

ahh didnt c the limit price limit no deffo not done with $10.

[destroyer X]

The image is bad....but you can check some off the connections.... you will like..... it produces from 12 to 15 volts.

Power is voltage multiplied again but the same value (squared) and divided by the impedance off the speaker.... so you can have something between 70 to 112 Watts (distorted)....but you can have around 50 to 80 clean audio.

A lot off people uses and is considered good....not wonderfull....but good enough!

regards Markus.....Her chocoholic.... i cannot......140 Kg, 180 centimetres high..... very fat!

Carlos is the destroyer X