TAS2505: questions about output of TA2505 when input 1KHz sine

Hello, 

1. The DC voltage almost looks like clipping on the output signal. Is your input an analog input or through the I2S communication? Could you also capture the input on a scope so we can compare it to the output?

2. This offset signal is very short and should not be an issue but I will double check with my team and get back to you. 

Best Regards, 
Justin Beigel

Hi Justin,

thank you. in customer applicaiton, they use I2S input, you can see their schmatic, attached before.

below file is the I2S 1kHz sine input source. you can test it on EVM.

does this DC voltage will impact the speaker? or any risk? does it need DC block capacitor? thank you.02 02 1kHz Sine Wave 0dB L&R.zip

Hello, 

I am double checking a few things still but wanted to comment. The DC voltage does not cause damage to the speaker but is not ideal. I am checking with a colleague on if DC blocking caps would be best or if we should pursue another solution and will get back to you soon. 

Best Regards, 

Justin Beigel

thanks Justin.

why there have DC voltage? and why the DC voltage will not damge speaker? My understanding is that the if the DC voltage flow to speaker, it will be demage speaker?

in other customer, sometimes they will add DC blocking caps, please help comment why need add DC blocking caps, so I can talk to customer.

 Hello Betty, 

I believe the DC voltage is simply due to the amplitude of the signal. I have attached a couple screen captures of different amplitudes below as an example. 

I am not sure that there needs to be any change here but here is some general information on DC voltage for speakers. The DC voltage can cause the speaker to heat up, but it will already be heating up with AC signals and since this DC voltage is only there for a short time, it is not a problem. Additionally, DC can sometimes add noise to the speaker so it is usually avoided. 

Max Volume: 

Lower Volume:

As you can see, the lower voltage looks more like a sine wave. 

Best Regards, 

Justin Beigel

Hi Justin,

sorry, I can't understand.

for question 1, you meand the DC voltage is because of max volume? below waveform is different with your attached. in the below capture, there have a consistant DC voltage I marked. we have concern that this DC will demage speaker.

thanks.

Hi Justin,

more information. customer test it with differenct volume. if the volume higher than 12db, such as 18dB, it will have DC voltage. if the volum is 12dB, the output is normal sine wave. 

can you help explain why will have this problem when it in High volume? does this have some limit in applicaiton?

thank you.

Hello, 

It seems like the DC is similar to clipping. When you play the sound at 18dB, does the speaker have any poor sound quality? I tested with a couple different speakers and only had issues with this on lower power ratings. If I remember correctly from a previous conversation, this is a 5W speaker correct? If so, I wouldn't expect any issues in sound quality due to this. 

Best Regards, 

Justin Beigel

Hi Justin,

how to understand the "clipping". it nor affact the sound quality, we want to know the root caue of  this DC voltage

thank you

Hi Betty, 

To better understand the DC, can you pass the output signal through an LC filter before reading it on the oscilloscope? Based on an 8 Ohm load, a good set of values for this would be 20uH and 0.68uF. 

Thank you, 

Justin Beigel

Hi  Justin,

one question, customer would like add a DC block capactior on the output of TA2505-Q1, how to select the DC block capacitor value?

thank you

Hello Betty, 

We don't have a general recommendation for DC blocking capacitors. Keep in mind that the DC blocking cap acts as a high pass filter and with the resistive load of a speaker, the corner frequency needs to be considered. 

Best Regards, 

Justin Beigel