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I am using a TDA2030L audio amplifier to make my own subwoofer at home. The amplifier works well with the sound input (from a PC) at around 14 percent. The power input is 19V and 2A which is about 38W and the gain for my amplifier is 50 since am using a 100k resistor as feedback between pin 2 and 4 and I have grounded pin 2 with 2k resistor grounded with 22uF capacitor (25V).

When I increase the volume beyond 24% in my PC the output of the amp at the speaker (4 ohm) is ok while playing in high frequency. BUT when I increase the bass the output gets distorted with the speaker playing in "PULSES", (some audio is not heard and it only booms at certain points with diaphgram of the speaker vibrating in a large displacement).

I have tried using a filter capacitor at the output to avoid DC output into the speakers but it doesn't help. When i use 20V, 1A source the problem still persists. Below is the circuit that I am using (I have not included the bass and volume control, but I am basically using potentiometers of 10k)The circuit digram below is the one i used the volltage i used was 19.5V, 2A not 12V and the resistor grounding the pin2 is 2k

The output from the pc at 100% Volume is about 0.5~0.7v with a current of about 0.02mA

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    \$\begingroup\$ Measure the voltage output from PC and report here. Maybe it is too high when turning the volume above 24%. If you assume the chip to be ideal, since you have about 20V of supply, the voltage at speaker will be 20Vpp max. You also have gain of 50 which means maximum input to TDA2030 can be 0.4Vpp maximum. Line outputs on devices can typically have much more voltage so your design just clips. Reduce the gain (24dB = 16x minimum) and/or put a volume control pot at the TDA input like in the schematics so you can use 100% at PC. \$\endgroup\$
    – Justme
    Oct 17, 2019 at 13:55
  • \$\begingroup\$ You need to LOOK at the input to the speaker to see if it's clipping. \$\endgroup\$
    – Scott Seidman
    Oct 17, 2019 at 13:55
  • \$\begingroup\$ What kind of heatsink do you have on the chip? It sounds like its thermal protection might be kicking in at low frequencies. \$\endgroup\$
    – Dave Tweed
    Oct 17, 2019 at 13:58
  • \$\begingroup\$ I am using a large aluminiuim heat sink...infact it is not heating very much \$\endgroup\$
    – Joe
    Oct 17, 2019 at 14:06
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    \$\begingroup\$ Gain of 50. Input of 0.7 V. Output of 35 V. Supply voltage of 19 V. I seem to detect a mismatch... \$\endgroup\$
    – JRE
    Oct 17, 2019 at 14:34

3 Answers 3

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"Pulses" and large cone displacement suggests the PSU may be shutting down due to too much current demand, then restarting to see if the demand has gone away, shutting down again ad infinitum. 2A isn't very much, with a low impedance speaker.

The large displacement comes from C4 discharging and then re-charging each time this happens.

If this is the case, a voltmeter on the 19V supply will show large fluctuations when the overload occurs.

Either uprate the PSU to about 4A, or try an 8 ohm speaker.

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  • \$\begingroup\$ Is 4A not too much for TDA2030 because its output current should be 3A? \$\endgroup\$
    – Joe
    Oct 18, 2019 at 7:48
  • \$\begingroup\$ i removed the C4 and surprisingly the clipping,pulses, now started at around 36%,i grounded pin 2 with 200k resistor and the distortion occured at around 50% with a gain of 40...whats the issue with grounding the pin 2 that solves half of the trouble \$\endgroup\$
    – Joe
    Oct 18, 2019 at 8:06
  • \$\begingroup\$ 3A then. Having excess current in reserve is not a bad idea however. Removing C4 is not a very good idea, you are now placing DC across the speaker , wasting power and potentially damaging it. I'd have to read the datasheet to comment on pin 2, and it isn't linked in the question, so... \$\endgroup\$
    – user16324
    Oct 18, 2019 at 8:56
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Based on your description and measurements, when the PC volume is set to over 24% the audio signal voltage is too high for the amplifier. Suitable solutions to allow higher signal voltages at amplifier input connector include attenuating the PC output voltage with a resistor divider or volume control potentiometer before the amplifier and reducing the amplifier gain so that the 100% PC volume does not clip.

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You say your supply is 19V but your schematic shows 12V which is the absolute minimum for a TDA2030. The schematic shows a diode which reduces the power supply voltage even lower. What is the power supply voltage reaching the IC after the diode? 18V?

If your power supply is really 19V then the output power when clipping distortion will be heard is a little less than only 7W into 4 ohms which is not much power. Maybe you are turning up the volume control to try to get impossible 70W? Maybe your heatsink is too small and the amplifier gets hot and shuts down for each bass pulse?

You should use a "bridged" amplifier sometimes called BTL (bridge tied load) such as a TDA7396. With a 16V supply its output is 25W into 4 ohms but then its heating is also 25W so it will need a huge heatsink.

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