need help to remove noise in intercom with tea1062

[medicaprotech]

need help to remove noise in intercom with tea1062
i use tea1062a in my intercom circuit and it work.When picking up the phone, a buzzing sound is heard . I can't reduce this noise unless I reduce the microphone gain and this is not good for me. I am looking for a way to reduce the noise without reducing the microphone gain. I would be grateful if you could help me.
circuit and parameter values
R6=100K
R7=68K
RVA=39K
ZBAL=680

 

[betwixt]

Please show the schematic of your design. The ones shown are for a single ended mic but the TEA1062 uses a balanced input and the QR signal is (I think) for the ringer when used in a telephone circuit. You mix a telephone application with an intercom one and they work in different ways, without knowing how you have connected them it isn't possible to advise.

Brian.

 

[KlausST]

Hi,

I agree with Brian.
I even want to go a step further. Show us photos of your circuit and the wiring. Tell us what cables you use and their length.

Also I´m a friend of "not suppressing the symptom" but avoid the existance of the noise at all. Thus I recommend to find out what´s the source of the noise. It may be the power supply, some internal circuit problems, some internal oscillations, externally introduced noise... and so on.

Thus the noise frequencies (and their overtones) give a lot of informations. Show us the spectrum of the noise, using an scope, an FFT, maybe use your PC´s audio card to record and process the signal.

Klaus

 

[medicaprotech]

Thank you for your attention
I connected the above microphone circuit to the mic-&mic+ pins
and I connected the above speaker circuit to QR &GAR pins
I dont have any shematics but uplode my pcb the bold line is phone line
I connect between two central lines

 

[KlausST]

Hi,

You don´t use a GND plane? So it´s rather linkely to pickup noise. Nowadays we have a lot of HF noise sources around and all your lengthy traces act as antennas. In my eyes using a true (uncut) GND plane is essential, especially when one wants low noise and want to comply with EMI/EMC regulations.

Klaus

 

[medicaprotech]

Do you mean that I connect the Tea1062 ground to the main ground of the circuit?
the bold line is tea ground

 

[KlausST]

Hi,

No.
A GND plane means there is one layer of the PCB to be used as GND. No single GND traces, no other signals, just a solid layer of GND.

Klaus

 

[medicaprotech]

Is there any other solution possible? I have printed the PCB

 

[medicaprotech]

that is

 

[KlausST]

Is there any other solution possible? I have printed the PCB

First of all: give the resquested informations.
The PCB is just one of many possible problems.

PCB:
the wider traces around the whole PCB in a closed loop: is the worst you can do. It is a perfect antenna. Not what one wants.

There are many documents and videos around that show you how to design PCB layouts. Usually every PCB layout software house gives good tutorials. I recommend to go through some of them.

Klaus