Hey all,
Working on a little wireless setup with some fm modules.
Wanting to be able to amplify the audio, going to use an lm386.
Wondering, as a general rule, Am i best to amplify the source, or to put the amplifier on the wireless rx modules?
Any idea would be great. Thanks!
Working on a little wireless setup with some fm modules.
Wanting to be able to amplify the audio, going to use an lm386.
Wondering, as a general rule, Am i best to amplify the source, or to put the amplifier on the wireless rx modules?
Any idea would be great. Thanks!
oh god.
you sent wirelessly a signal, that needs to be amplified.
you can not just take a singal, amplify the hell out of it, air it off as a verry strong rf signal, hook up a reciver with no further amplification and expect the same results.
(well.. actually it depends, but let us not go into that.)
so the chain is:
signal -> RF stuff to air it -> reciver that can "covert it back to signal level" -> amplifier -> speakers.
you sent wirelessly a signal, that needs to be amplified.
you can not just take a singal, amplify the hell out of it, air it off as a verry strong rf signal, hook up a reciver with no further amplification and expect the same results.
(well.. actually it depends, but let us not go into that.)
so the chain is:
signal -> RF stuff to air it -> reciver that can "covert it back to signal level" -> amplifier -> speakers.
Can you describe what your proposed system is? Arty has a first cut, I'm curious what your modulator/RF amp is, as well as what receiver/amp you are thinking of. My answer was a simplistic RF one, amplifying a signal on the receive end amplifies all noise, so it's better to have a strong RF signal. Note that a strong RF signal is not the same as a powerful audio signal. If you already know this, sorry to tell you it all over again.
Hey,
Thanks for getting back to me, i've been away so sorry for the delay.
The setup im chasing is by as simply as possibly, Using an fm transmitter to send some audio to an fm receiver, then amplify it to suit some headphones.
The transmitter side seems fairly easy as there are very simple commercial products available. The one i picked is -
Wireless Fm Transmitter radio For iPhone 6 6S 5 5S 4 iPod Samsung s3 s4 s5 note | eBay
Pulled it apart and will wire up the power and audio to suit my needs.
As for a FM receiver, I was looking for something as simple as the TX, but there doesnt seem to be anything so ready of the shelf to suit what im doing.
So i have played with a TEA5767 chip - http://www.voti.nl/docs/TEA5767.pdf
Hooked up to an arduino and the audio is very quick, so needs some amplification on the rx end. but is very noisy when i do so.
So im happy to take any suggestions here. The TX works well and im happy with it.
Just need to work on the RX side of things.
Thanks for getting back to me, i've been away so sorry for the delay.
The setup im chasing is by as simply as possibly, Using an fm transmitter to send some audio to an fm receiver, then amplify it to suit some headphones.
The transmitter side seems fairly easy as there are very simple commercial products available. The one i picked is -
Wireless Fm Transmitter radio For iPhone 6 6S 5 5S 4 iPod Samsung s3 s4 s5 note | eBay
Pulled it apart and will wire up the power and audio to suit my needs.
As for a FM receiver, I was looking for something as simple as the TX, but there doesnt seem to be anything so ready of the shelf to suit what im doing.
So i have played with a TEA5767 chip - http://www.voti.nl/docs/TEA5767.pdf
Hooked up to an arduino and the audio is very quick, so needs some amplification on the rx end. but is very noisy when i do so.
So im happy to take any suggestions here. The TX works well and im happy with it.
Just need to work on the RX side of things.
"Hooked up to an arduino and the audio is very quick, so needs some amplification on the rx end."
this fails to make sense to me..
this fails to make sense to me..
Oops, hooked up to the arduino, which programs the channel.
And the audio is very quiet*, so needs amplification.
And the audio is very quiet*, so needs amplification.
You adjust the audio level into the transmitter so that audio peaks reach almost 150KHz of carrier deviation, the standard for broadcast FM.
I doubt you have an FM Deviation Meter. The alternative is to adjust the audio to be almost as loud as the same receiver picking-up WKIT-FM (for me); or 2ABC, 1CBR, or 1ART (whatever your local FM broadcast station is).
"Almost as loud" because broadcast stations generally use very sophisticated processing to raise the average level over all tunes and announcements without exceeding peak deviation; and you won't. A very-good FM receiver has some margin for large deviation, but at some point they all distort inside the receiver before you can turn-down at receiver output.
I doubt you have an FM Deviation Meter. The alternative is to adjust the audio to be almost as loud as the same receiver picking-up WKIT-FM (for me); or 2ABC, 1CBR, or 1ART (whatever your local FM broadcast station is).
"Almost as loud" because broadcast stations generally use very sophisticated processing to raise the average level over all tunes and announcements without exceeding peak deviation; and you won't. A very-good FM receiver has some margin for large deviation, but at some point they all distort inside the receiver before you can turn-down at receiver output.
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> a TEA5767 chip ... audio is very quick(quiet)
Output of that chip is 75mV (0.075V) (bottom of page 2).
"Line inputs" are more often 0.1V to over 0.7V. So yes, quiet, you need some gain after this chip to interface with most audio inputs. (I'm sure the intent is to tuck it inside some larger toy with the controller and an an audio system scaled for this use.)
Output of that chip is 75mV (0.075V) (bottom of page 2).
"Line inputs" are more often 0.1V to over 0.7V. So yes, quiet, you need some gain after this chip to interface with most audio inputs. (I'm sure the intent is to tuck it inside some larger toy with the controller and an an audio system scaled for this use.)
It's a mixed signal system. Problems could be lurking everywhere. Still, something with an LM386 at minimum gain of IIRC 26 dB (it is a pure noise and distortion generator otherwise) should give really decent output with 75 mVrms tops. Make sure there isn't any muting active.
From the description I'd say deviation is very low, IOW input levels to the transmitter are low.
From the description I'd say deviation is very low, IOW input levels to the transmitter are low.
That is 75mV out with 22.5kHz deviation. Peak deviation for normal broadcast FM is 75kHz, or a bit less for stereo. I believe some analogue TV systems use 50kHz peak deviation.
The answer to the original question is "amplify what needs amplifying". Only measurement (or, possibly, calculation) will tell you which this is.
The answer to the original question is "amplify what needs amplifying". Only measurement (or, possibly, calculation) will tell you which this is.
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