problem with amplifier built around ic tda 7294

ic 7294

Hi!

got a problem with a amplifier I built.

the amplifier is the kit from kitsrus nr 106 :https://kitsrus.com/pdf/k106.pdf consisting mainly of the IC: tda 7294


I get sound out of the circuit. BUT after a short while the sound deteriorate and gets very poor and distorted. if I disconnect the power and immediately connect again the sound gets clear but again distorted after a short while.

if I turn up the volume on the input pins it also clears for a short while. why?

anyone got any clues what this might depend on?

I power it from 3st 12v batteries because its used in a portable soundsystem. I use the 2 pins called +34v and -34v but leaves out the middle 0v. I gues 0v is used for some kind of stabilising if using unfiltered DC current?

Would be great with some support! my knowleadge of audio amplifiers are very limited.

thanks! //L

tda amplifier

Linusswe said:

... I use the 2 pins called +34v and -34v but leave out the middle 0v.

Click to expand...

So you didn't connect IC1-pin4 (& R2, C2) to Gnd ? Could be dangerous for your elkos and (output) transistors!

Linusswe said:

I gues 0v is used for some kind of stabilising if using unfiltered DC current? //L

Click to expand...

No; it's absolutely necessary to connect Gnd. Failing this is likely the reason for your pb. Don't forget to insulate the IC from the heatsink (s. p. 2)!

tda ic amplifier

Hi erikl!

thanks for your response!

yes IC1 pin4 is connected to ground and also r2 and c2
I didnt mean the pin on the IC but the power pins on the PCB! sorry about the confusion.

so gnd on IC is connected to gnd on PCB but then I dont understand how I should connect ground to "DC gnd" because that and -34v is not the same.

Im confused of the separation of -DC and gnd isnt that the same thing?

Hi,

You should be using six 12V batteries ---- 3 to generate +36V and other 3 to generate -36V (not 34V). Centre point of 6 batteries which are connected in series is the ground point, with respect to which you measure +36V and -36V. Connect this ground with PCB ground.

If you are using lead-acid battery, voltage can go as high as 13.8V under fully charged condition. That means maximum terminal voltage can rise upto +/-41.4V. Make sure that the IC can withstand this supply.