TPA6120A2: Further assistance with my AC Frequency Signal, please?

Christopher James

Part Number: TPA6120A2

Dear Ivan,

I measured the AC voltage from my soundcard just before the connection to my coil setup at 7.19volts.

My setup at the moment comprises a frequency generating circuit which opens and closes a switch for my speaker connection at 500Hz +. Thus my sub 100Hz frequency from my sound-card oscillates at this higher frequency.

My frequency generating circuit originally controlled a 15v DC supply and to enable me to visually see if the connections to my coils were good, it has a 3.3volt LED in series with a 1k resistor.

Thus my 7.2v AC signal is passing through the 3.3v LED in series with the 1k resistor prior to my coil circuit.

As the indicator light is useful in determining that I have a good connection and that power is reaching the rig from my sound-card; are you able to advise, please, whether the LED and the resistor will be having a significant reduction on my AC frequency signal?

I await your further kind advice, please?

Thank you so much.

Christopher

over 5 years ago

0 Luis Fernando Rodriguez S. over 5 years ago

TI__Guru* 84915 points

Hi, Christopher,

Our team will take a look at this thread and will answer as soon as possible.

Best regards,
Luis Fernando Rodríguez S.

0 Ivan Salazar over 5 years ago

TI__Guru** 109395 points

Hi Christopher,

The reduction of the output signal due to the LED+resistor is basically based on the current through the resistor, the bigger the resistor the lower current, but this will reduce LED light intensity.

Do you have a diagram to better understand what is your connection now?

Best regards,
-Ivan Salazar
Applications Engineer - Low Power Audio & Actuator

0 Christopher James over 5 years ago in reply to Ivan Salazar

Intellectual 880 points

Dear Ivan,

Please forgive my crude layout below?

This is the spec for the LED, which was originally set up for a 15v DC signal hence the 1k R : VAOL-5LWY4 - LED, White, Through Hole, T-1 3/4 (5mm), 20 mA, 3.5 V, 5 cd

The Mosfet is cycling at circa 500 + Hz, switching the secondary frequency of circa 40Hz.

I have attached a stereo signal captured from the online tone generator dot com. at 40.6153846 Hz

I realise that I am asking a lot but would it be possible please to ask you to invert it and combine into one mono signal please?

When I export the file after inverting the RH track they effectively cancel each other out and create a silent track?

When I attempted to loop the signal it created a quirk in the signal at the beginning and end of each section, and whilst I cut and edit the file, surely it should not do that?

Obviously I am doing something wrong. I have not been able to find a pseudoDiff app to use?

Just to jump back, what I am trying to achieve is the equivalent of a stereo track combined into one mono track and at the same time to double the output voltage I am sending to my prototype rig.