Can I believe on this stereo encoder and its channel separation quality? Please

[Willen]

Check the schematic please

 

[audioguru]

I recognised this circuit designed by Harry Lythall. He said it is very crude without any audio filters but it works.
**broken link removed**

 

[Willen]

I recognised this circuit designed by Harry Lythall. He said it is very crude without any audio filters but it works.
**broken link removed**

I read whole article but confused on crystal's value. On PCB layout, he wrote ''4.860KHz'' and On article he worte ''4860KHz'' (4.860MHz). Can you say which he mean?

 

[audioguru]

The CD4060 IC divides a frequency by 128. Then the crystal should be 38kHz x 128= 4864kHz which is 4.864MHz.
4.860MHz is a little too low.

Newark in America lists 700 quartz crystals. It has none at those frequencies so it must be custom made.

 

[Willen]

-Won't the encoder work if I use 4.00Mhz or 4.096MHz Xtal instead of 4.860Mhz? What will happen?

- And may I use your pre-emphasis for this encoder?

 

[audioguru]

-Won't the encoder work if I use 4.00Mhz or 4.096MHz Xtal instead of 4.860Mhz? What will happen?

The 19kHz pilot tone and the 38kHz multiplexing must have accurate frequencies. Lookup the required accuracy in Google.
With a 4MHz Xtal the 19kHz will be 4M/256= 15,625Hz and the 38kHz will be 31,250Hz so a stereo decoder will not work.

may I use your pre-emphasis for this encoder?

Use a dual opamp instead then you can reduce the gain easily.

 

[kubeek]

You could use 38khz crystal and a PLL to multiply the frequency, if you can get one. But maybe using a different circuit will be easier in the end.

 

[Willen]

Use a dual opamp instead then you can reduce the gain easily.

I hope that it is simple but I cannot figure out.
(Also, there is already an opamp in encoder.)
Will a dual opamp (eg. LM358) work as pre-emphasis?
How to add a dual opamp as a pre-emphasis? May i see a schematic?

I've found two opposite sentence on his article
1st- ''A and B channels are each passed through a buffer amplifier, where any filtering and pre-emphasis is added.''

2nd- ''I have used Dual Opamp for two input buffer stages but even there could be eliminated and resistative filtering used.''

I am confusing reading his two sentence, 1st is saying that pre-emphasis has added and 2nd says that Dual opamp is only for buffer. Actually does it has pre-emphasis or not?

 

[audioguru]

I hope that it is simple but I cannot figure out.
(Also, there is already an opamp in encoder.)

It is simple. Harry almost did pre-emphasis but his values were wrong. I have attached a pre-emphasis circuit.

Will a dual opamp (eg. LM358) work as pre-emphasis?

No. It is lousy and old.
It has crossover distortion and noise (hiss). It performs poorly above 2kHz. I guess Harry didn't know.
Use a TL072 dual audio opamp instead.

 

[Willen]

Removed: same post

 

[Willen]

4.860MHz is a little too low.Newark in America lists 700 quartz crystals. It has none at those frequencies so it must be custom made.

-Yes there are no 4.864MHz crystals. But 4.860 MHz may work, isn't it?

It is simple. Harry almost did pre-emphasis but his values were wrong. I have attached a pre-emphasis circuit.

-Thank you but where is the attachements? Should I replace LM358 from his schematic with TL072?
- I found few opamps- TL592 and LM386, won't it work as a TL072?

I want to make harry's encoder, show me the schematic improving all his faults please. I have sent email to Harry ''harryvpo(at)hotmail.com'' asking about suitable transmitter for this encoder and then I will show you again.

 

[audioguru]

-Yes there are no 4.864MHz crystals. But 4.860 MHz may work, isn't it?

The wrong frequency crystal might work with some analog FM stereo radios but might not work with newer digital FM stereo radios.

where is the attachement?

I forgot to attach my schematic last night. I added it this morning.

Should I replace LM358 from his schematic with TL072?

Yes if you power and bias it correctly.

I found few opamps- TL592 and LM386, won't it work as a TL072?

No.
They are not opamps. You should read their datasheets.

I want to make harry's encoder, show me the schematic improving all his faults please. I have sent email to Harry ''harryvpo(at)hotmail.com'' asking about suitable transmitter for this encoder and then I will show you again.[/i]

On the attachment to my last post I fixed the stereo pre-emphasis. I don't like the high impedance adder at the output of harry's encoder circuit. An opamp added to it will fix it.

 

[audioguru]

I looked in Google for FM Stereo Encoder Circuit and found many old circuits that are better than Harry's old circuit.
One has the proper filters but uses an awful old 555 as the main oscillator instead of a crystal oscillator.

 

[Willen]

I think you forgot to attach your schematic again! Please edit his schematic on his 'Component placement PCB' (attached on my 1st thread), so that I can make it on his same PCB layout easily please! I am going to make this 'not perfect encoder' because I can found its components and crystals. I never found 38KHz crystal to make other encoders. I never found little unusual components, so.


Waiting for your best schematic....

 

[audioguru]

i added my stereo pre-emphasis schematic to my post #9.

 

[Willen]

Oh yes! I think TL072 opamp has also 8 pins and according to your schematic, I can simply replace with previous LM358.
-Feedback resistor to control gain means....just like an attenuator? Should i have to decrease the value of it to connect high audio source? (to set low gain)
-I think the 3rd resistor from left is a feedback resistor. And I think, according to your bias, now I can connect normal LINE OUT stereo audio from mp3 players or PC, isn't it?
-I found a oscillator which is connected to stereo encoder. I think I can use this oscillator with Harry's coder too. Check this schematic but there is also a capacitor connected base to ground.
what about it?

 

[audioguru]

I think TL072 opamp has also 8 pins and according to your schematic, I can simply replace with previous LM358?
Yes of course. A TL072 is a much better dual opamp. It has the same pins, it has low noise and extremely low distortion and works well up to 100kHz.

Feedback resistor to control gain means....just like an attenuator? Should i have to decrease the value of it to....

Everybody except you know that the feedack resistor value in an opamp circuit controls the amount of voltage gain. It can attenuate instead of have gain if you calculate the resistor value.
Please do not post more unless you learn about the basics of electronics and the basics of opamps.
Didn't you go to school like everyone else??

I think the 3rd resistor from lelt is a feedback resistor. And I think, according to your bias, now I can connect normal LINE OUT stereo audio from mp3 players or PC, isn't it?

Goodbye. You know nothing about electronics.

I found a oscillator which is connected to stereo encoder. I think I can use this oscillator with Harry's coder too. Check this schematic but there is also a capacitor connected base to ground.
what about it?

Goodbye.

 

[Willen]

Yes of course. A TL072 is a much better dual opamp. It has the same pins, it has low noise and extremely low distortion and works well up to 100kHz.

Thank you.

Everybody except you know that the feedack resistor value in an opamp circuit controls the amount of voltage gain. It can attenuate instead of have gain if you calculate the resistor value.

No, my 2 friends also don't know about feedback resistor.

Please do not post more unless you learn about the basics of electronics and the basics of opamps. Didn't you go to school like everyone else??

Here, only few people go to university to learn electronics. Here, nobody learns basic electronic at school. I want to post to learn not to teach. I have learnt few basic (only basic) but not theoretically, it was practically specially! May be my questions was redundant.
Hehehe

 

[Willen]

I looked in Google for FM Stereo Encoder Circuit and found many old circuits that are better than Harry's old circuit.
One has the proper filters but uses an awful old 555 as the main oscillator instead of a crystal oscillator.

Hi, after a long time on this thread,

did you mean this one?
**broken link removed**

Does it has better audio filtering? Didn't find any cryatals so starting to love this old 555 hee hee hee

 

[audioguru]

I never saw this project before.

It is missing filters that cut audio frequencies and their harmonics above 15kHz so they do not beat with the 38kHz sidebands.

It is missing very important pre-emphasis so it will sound like your stereo with its treble tone control turned all the way down.

The transmitter uses two GERMANIUM transistors!