Here is a schematic of jbl charge 3 i just want to ask why 1k resistor divider is used in audio output from main chip and it goes to amplifier input , and what if i use 1k alone in series instead of divider ? I m making a Bluetooth speaker and I just want to reduce disortion at full volume..please help..
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You have two threads for this. You should not, against the rules.
The R together with C to ground filter HF switching hash from the outputs.
Jan
The R together with C to ground filter HF switching hash from the outputs.
Jan
Actually i m new to this , can u please explain more , i tried adding the same circuit it reduces the disortion but it reduces the volume too , what if use lower value resistor at r501,r502 ? And what if i use just 1k resistor in series and remove r550,r549 ?
Do you understand that it filters out higher frequencies?
Are you familiar with the -3dB frequency of filters?
The frequency where the signal has dropped 3dB (down to about 0.7 x original level)?
For a passive RC like you have here, that frequency is 1/(2*pi*R*C) which according to my Windows calculator is about 159kHz.
Now, this is without R549, R550. As you mentioned, those resistors form a divider with R501 and R502 (about factor 1/2).
Therefore, the -3dB frequency is doubled to about 320kHz (for the filter, it looks like the source has an impedance of 1/2 k instead of 1k).
I don't see any reason why you can't delete R549, R550, you get double the level and the filter is still far above audio.
I also would not trust distortion numbers in LTspice, it all depends on what's inside the model and usually distortion is badly modelled or not at all.
Jan
Are you familiar with the -3dB frequency of filters?
The frequency where the signal has dropped 3dB (down to about 0.7 x original level)?
For a passive RC like you have here, that frequency is 1/(2*pi*R*C) which according to my Windows calculator is about 159kHz.
Now, this is without R549, R550. As you mentioned, those resistors form a divider with R501 and R502 (about factor 1/2).
Therefore, the -3dB frequency is doubled to about 320kHz (for the filter, it looks like the source has an impedance of 1/2 k instead of 1k).
I don't see any reason why you can't delete R549, R550, you get double the level and the filter is still far above audio.
I also would not trust distortion numbers in LTspice, it all depends on what's inside the model and usually distortion is badly modelled or not at all.
Jan
Thanks for you reply sir, actually when i remove r549,r550 the volume gets increased but disortion comes at high bass audio at full volume , else its normal i just want to reduce that disortion..and when i keep the r549,r550 the disortion goes away , but volume gets reduced.. what should i do so that volume doesn't get reduced too much and i get clear bass at full volume..
leave those resistors out because they waste half the signal. The signal will double and you just turn down the volume and you get the best of two worlds.
Jan
Jan
Haha that's the best option , if i had to use it personally, but i m making it for consumers , that's why i m looking for a solution , let's remove all the resistors , is there anything i can add in input line to reduce disortion ?
How do you experience that distortion, what is it? It isn't the resistors, it's the fact that you overdrive the system.
I don't see why a logical solution all of a sudden is not good for a customer.
Jan
I don't see why a logical solution all of a sudden is not good for a customer.
Jan
I m not over driving i m using 2 - 10w 4ohm speakers with tpa3110d2 evaluation board at 12v supply.. and the audio is not clear at full volume its clear at around 80 percent after that the audio is not clear..that's the case when i don't use any resistor..in input line..
Of course it is not clear at full volume, you're overdriving that poor speaker at full volume!
Try it: remove those divider resistors and turn the volume down.
Dividing down the level instead of lowering the volume is not very smart.
It's like pressing the break in your car while leaving your foot on the gas because you go too fast. Get your foot off the gas!
jan
Try it: remove those divider resistors and turn the volume down.
Dividing down the level instead of lowering the volume is not very smart.
It's like pressing the break in your car while leaving your foot on the gas because you go too fast. Get your foot off the gas!
jan
What if i had to reduce volume by 20 percent by adding a L type attenuator at input line what resistor value i should use for r1 and r2..my input signal voltage is 2.1 to 2.3v
You would have 80% of the signal across R1 and 20% across R2. That gives you the ratio.
Keep it low impedance, otherwise the variation of 30k to 7.2k will influence the attenuation.
Use 1k for R1.
20% is insignificant. Chances are that you don't even hear it. It's just 2dB and audibility often sits at 3dB (70%).
Jan
Keep it low impedance, otherwise the variation of 30k to 7.2k will influence the attenuation.
Use 1k for R1.
20% is insignificant. Chances are that you don't even hear it. It's just 2dB and audibility often sits at 3dB (70%).
Jan
Can you please calculate the r1 and r2 value so that i get 80 percent signal according to the impedance and a good quality audio , i dont know that much about db and impedance..thanks
The gain has nothing to do with it. You want to attenuate the signal by 80%, it comes out the preamp or whatever, and you bring it down to the 80% level.
80% attenuation is about 2dB BTW. Two resistors, in ratio 8 to 2.
And maybe this is a good time to Google 'resistive attenuator'?
I won't be here for ever ;-)
Jan
80% attenuation is about 2dB BTW. Two resistors, in ratio 8 to 2.
And maybe this is a good time to Google 'resistive attenuator'?
I won't be here for ever ;-)
Jan
I just want to hear , what i hear at 80percent volume , in short i want that level to be 100 percent..I don't want anything else..