telephone recording, help me!

[hoanganhnh]

I'm working in the project "Telephone recording 4 channels".
I'm using the LM386, but I have some troubles.
When I test the board, I hear very much the noise.
Can you help me. I want to replace LM386 with other ICs.
Thank you very much

 

[Iouri]

LM386 it is not reason for the noise. post schematic here for review

 

[gerilla]

I'm working in the project "Telephone recording 4 channels".
I'm using the LM386, but I have some troubles.
When I test the board, I hear very much the noise.
Can you help me. I want to replace LM386 with other ICs.
Thank you very much

Hi. I wont tell much since my english is not enogh well.
I didn't see your circuit but You can separate your phone line and circuit's ground using transformer. Using phone line's ground could case noise but I am not sure if this will work.

 

[sabeti_1990]

hi body
for each phone line use a blue chock (with 16*19 EI & 300ohm in primery & 2*80 ohm in secondary) use secondary with a 100nf cap in seri to reccive sound if line & in primery give your sond
note: don't use 10uf cap between pin 1 & 8 of lm386

 

[the_risk_master]

Well, you did'nt bring up your circuit for detailed discussion here...

I'll just have a suggestion to replace LM386 with OPA2134UA, this is 0.0008% distortion, and ulta-low noise at 8nV/√Hz, what can you say huh

 

[sabeti_1990]

hi the_risk_master
it's good but in phone solution it's not necessary & lm386 is work good but your idea is too good
(in next week I let a sch for this application ok ?)