I'm ashamed 🙁 But it's nothing, I will read smart books and I will soon understand electronics.
I thought that for increasing the output power I can simply add the emitter follower at the output.
Is everything so bad and it will not work?
I thinkp robably nothing new can be invented with TDA2030. Everything has already invented. And it's easier to assemble a simple and reliable transistor amplifier instead of torture with fake chips.
For example, this is on sale under the guise of LM1875 where I live.
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i was curious about that schematic (post1) and built a prototype with old spareparts .
15V single supply psu , tda2040, res 1ohm in the supply lines, bd243c/bd244c as booster transistors.........now it has worked for a week without problems.
15V single supply psu , tda2040, res 1ohm in the supply lines, bd243c/bd244c as booster transistors.........now it has worked for a week without problems.
......yes,only 15Vdc, because i used what i had on hand.
made a sim - at 4Vpp output with a 4ohm load(res) the transistors begin to conduct...
the sound quality was good, so i decided to go on......
now i have a psu with 28Vdc and listen to it.
if it works i will change resistors ( lower values) and booster transistors (switching types ,higher currents), because i saw a schematic in an old book for "electronic practice" where 0,68ohms and tip2955/tip3055 are used.
perhaps i will buy some bd9xx transistors.......
made a sim - at 4Vpp output with a 4ohm load(res) the transistors begin to conduct...
the sound quality was good, so i decided to go on......
now i have a psu with 28Vdc and listen to it.
if it works i will change resistors ( lower values) and booster transistors (switching types ,higher currents), because i saw a schematic in an old book for "electronic practice" where 0,68ohms and tip2955/tip3055 are used.
perhaps i will buy some bd9xx transistors.......
........so it worked with the 28Vdc supply (25VA transformer, 20Vac ; 8A bridge rectifier, 6800uF elcap) without problems.
with a 4 ohm load the psu volts go down to 24,5Vdc and the amp begins clipping (distorting) at 20Vpp output........
there are no crossover distortions on the o'scope or in the sim to see.........
i think the next step is to decrease the 1 ohm resistors to 0,47ohms (0,5ohm) -
this should give less losses and a better damping factor.
with a 4 ohm load the psu volts go down to 24,5Vdc and the amp begins clipping (distorting) at 20Vpp output........
there are no crossover distortions on the o'scope or in the sim to see.........
i think the next step is to decrease the 1 ohm resistors to 0,47ohms (0,5ohm) -
this should give less losses and a better damping factor.
Interesting 🙂 20 v pk/pk sounds quite respectable given a 24 volt rail. Good to know the sound quality was good enough to pursue the technique.
I used to love playing around with circuits like these once upon a time.
I used to love playing around with circuits like these once upon a time.
I also made a temporary test facility for verification, but I can not listen to this scheme at high volume yet. I can certainly use a resistor as a load, but that is not entirely correct.
mjf, how do you think, should I lower resistance of the resistors in power rails? After all the meaning of the scheme will be lost, we will more and more load the chip.
mjf, how do you think, should I lower resistance of the resistors in power rails? After all the meaning of the scheme will be lost, we will more and more load the chip.
.......at high levels the tiny power opamp will have some "stress at work" (e.g. with low impedance speakers) and the booster transistors can deliver some extra current.
at lower levels (a few watt) the opamp doesnot need these helper transistors....
Now I see, it's my falt. You use TDA2040, and this chip more powerful than TDA2030.
More detais please. Which characteristics of transistors are important?
......i think there is no big difference between tda2030/tda2040.
(aside this , tda2030/2040/2050 and lm1875 have the same pin layout)
(aside this , tda2030/2040/2050 and lm1875 have the same pin layout)
I've made this amplifier from the trash in order to hear whether this circuit sounds normal 🙂 It's temporary. Soon I'll solder the second channel and find a suitable case.
The sound surprisingly is pretty nice. I can hear all the intonations of the singer's voice. Electric guitars that I especially like sound great. No hum, noise etc. The sound power is quite enough for a small room.
I don't have any equipment to check those aluminium caps, but I think they are dead. Then I plug off the amp from the electric system the sound immediately disappears. They are very old and the worst caps in the world- legendary Soviet K50-6 series 😀 So huge and only 2200 uF, 50 V. I'll replace them then.
And I will also reduce the resistance of the resistors from 1.5 to 1.2-1.0. Let at low volume only TDA sounds.
Now my amp's Gv is 12. Should I increase it?
The sound surprisingly is pretty nice. I can hear all the intonations of the singer's voice. Electric guitars that I especially like sound great. No hum, noise etc. The sound power is quite enough for a small room.
I don't have any equipment to check those aluminium caps, but I think they are dead. Then I plug off the amp from the electric system the sound immediately disappears. They are very old and the worst caps in the world- legendary Soviet K50-6 series 😀 So huge and only 2200 uF, 50 V. I'll replace them then.
And I will also reduce the resistance of the resistors from 1.5 to 1.2-1.0. Let at low volume only TDA sounds.
Now my amp's Gv is 12. Should I increase it?
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With transistors you have to look after their Hfe (gain) and the Vbe (usually 0.6-0.7V)
The resistor values I recommended (0,82 - 1 Ohm) will let the chip-amp "take" (very roughly) approx 0,7-0,9A of the output current, and transistors will take of the rest.
With 8 Ohm speakers, this means that the chip-amp will work "by itself" to roughly approx 4-6W peak power; and with 4 Ohm spkrs this would be 2-3W peak output power.
That should be "good enough" and somewhere in the ballpark for the "first Watt" imho.
The resistor values I recommended (0,82 - 1 Ohm) will let the chip-amp "take" (very roughly) approx 0,7-0,9A of the output current, and transistors will take of the rest.
With 8 Ohm speakers, this means that the chip-amp will work "by itself" to roughly approx 4-6W peak power; and with 4 Ohm spkrs this would be 2-3W peak output power.
That should be "good enough" and somewhere in the ballpark for the "first Watt" imho.
I wonder how these would respond (sonically) to adding a small current sink into the output such that the chip runs in Class A at very low power. Something puling around 60 or 70ma and tied to the negative rail (or ground for single rail) could be worth trying.
i increased the psu elcap to 22000uF...........
the res in the psu - opamp line is now 0,5 ohm (1//1)......
listend to it with 6ohm and 3ohm speakers (6//6) a week long.......
showed no problems.
the res in the psu - opamp line is now 0,5 ohm (1//1)......
listend to it with 6ohm and 3ohm speakers (6//6) a week long.......
showed no problems.
excellent work, and its good to know the basic design seems sound.
