Distortion in audio line while switiching

[rajaram04]

Hello sir

here i am posting a hand made circuit digram schematic



Here A & B are output from a music player or a cellphone or any small amplifier

T is any NPN transistor say BC 548 or 2N3055 etc

D is photo diode to sense IR rays just placed in front of it

L is the IR LED powered from an external battery & placed in front of photodiode

& right part is OUT which is fed direct to speakers or any amplifier as per input configurations



Now problem i have here is the distortion in the output of the circuitry

how to overcome the problem ? please rectify it

 

[FvM]

By their electrical characteristic, photo transistors aren't suited as analog switch. You can use:

- mechanical relays
- LDR optocouplers
- PhotoMos optocouplers

If you don't actually need complete isolation, you can refer to regular analog switches or FETs with respective level converters.

 

[rajaram04]

By their electrical characteristic, photo transistors aren't suited as analog switch. You can use:

- mechanical relays
- LDR optocouplers
- PhotoMos optocouplers

If you don't actually need complete isolation, you can refer to regular analog switches or FETs with respective level converters.

okk so what is PhotoMos optocouplers &

what are LDR optocouplers ? are they all hand made or commonly available 6 pin optocouplers ?

 

[FvM]

Google will show you the answer.

LDR couplers are commercially available, if "commonly" may depend on your region.
Photomos optocouplers (or "relays") are mostly made for high voltage medium current. They are suited for analog switching, but output capacitance may be too high, check the datasheets. Special "RF" types would best fit the audio switching problem. Panasonic/Matsushita has several of it

 

[rajaram04]

Google will show you the answer.

LDR couplers are commercially available, if "commonly" may depend on your region.
Photomos optocouplers (or "relays") are mostly made for high voltage medium current. They are suited for analog switching, but output capacitance may be too high, check the datasheets. Special "RF" types would best fit the audio switching problem. Panasonic/Matsushita has several of it

okk done thanks

so what if i use a bilateral switch i.c. ? CD 4066

 

[FvM]

CD4066 or possibly better analog switches with dual supply are a common way to switch audio signals.

 

[rajaram04]

CD4066 or possibly better analog switches with dual supply are a common way to switch audio signals.

so what you say ? should i proceed with this CD 4066 ?

 

[audiomik]

rajaram04
as you ask in your first post to be able to feed your switched signal directly into a 'Speaker, then the current capability to do this of a 4066 will be far too low.

Suggest that you look at using a Relay for what you are looking to do.
Mik

 

[rajaram04]

rajaram04
as you ask in your first post to be able to feed your switched signal directly into a 'Speaker, then the current capability to do this of a 4066 will be far too low.

Suggest that you look at using a Relay for what you are looking to do.
Mik

hmmm so as per you there is no option other than mechanical switching ?

 

[Audioguru]

Switching signals to a speaker are usually done at the input of the speaker's amplifier where the signal voltages and currents are very low.

 

[rajaram04]

Switching signals to a speaker are usually done at the input of the speaker's amplifier where the signal voltages and currents are very low.

okkkk so how this explanation matters our discussion here ? i mean what steps i ve to take further ?

 

[Audioguru]

okkkk so how this explanation matters our discussion here ? i mean what steps i ve to take further ?

You must decide to switch the speaker with relays or switch the amplifier inputs with CD4066 analog switches.

 

[rajaram04]

You must decide to switch the speaker with relays or switch the amplifier inputs with CD4066 analog switches.

ohh kk got it
actually i want to connect any of the musical player or a musical instrument with a P.A. SYSTEM material like amplifier (directly) or the mixers . . example i am showing



- - - Updated - - -

You must decide to switch the speaker with relays or switch the amplifier inputs with CD4066 analog switches.

 

[Audioguru]

The music player and musical instrument already have volume controls.
The PA amplifier and mixer also already have volume controls.
Then why add another volume control??

You are not switching anything. Simply plug the music player or musical instrument into the input of the PA amplifier or plug it into the input of the mixer.

 

[rajaram04]

The music player and musical instrument already have volume controls.
The PA amplifier and mixer also already have volume controls.
Then why add another volume control??

You are not switching anything. Simply plug the music player or musical instrument into the input of the PA amplifier or plug it into the input of the mixer.

Sir i am doing stage shows since 14 years near about so i too know well & i am also showing such mixers & ampli.in the diagram , but i need a digital volume control unit due to the reason that i don't want to move the knobs of such musical instrument , i just want to set the volume to a reasonable level & want to control the audio out level by means of external volume control

The main reson i am telling you that company stop designing some musical instruments model so as to sale its upgeaded products so in that case no parts are available for previous one & in these instrument two major problem we face in our region is

1) volume control disturbance (discontinuty)
2) LCD screen damage

i have this intrument which i bought in 2007



but now this one is not available as a too much upgraded version is available here



thats why company is not providing too much maintanance for such short things but which are major problem for us

& too all the time it is not possible to open the instrument for such repairing work as this are sampling modules with memory cards & contaning a lot of risk for internal setting damage

so i am going with external volume unit control externally

We use volume pedals but this require foot works & too having mechanical arrangments getting bulky . . .

 

[FvM]

None of the shown effects is directly switching power amplifier output (speaker level) signals. In so far I don't understand the relation to the previous discussion.

 

[Audioguru]

I also do not know what RAJ wants to do.

 

[rajaram04]

hmm kk
sir hv u heard about volume foot pedl connected in between PA SYSTEM & musical intruments ?
its a mechanical system which rotates 100k dual type potentiometer , the diagram is above i hv already shown
all funtions are driven out by pressing the pedal & releasing it , in such cases your hands are free totally to drive musical instruments
just i want to implant this operation by means digital circuits & control out with buttons thats it . .
i really want it due to the reason i explained in my last post , carefully read that sir please

i dont want to rotate or use the volume control bulit in the instrument itself

 

[FvM]

The confusion has been brought up by the term "speakers" in your initial post

right part is OUT which is fed direct to speakers or any amplifier

which raised the doubt that you want to control voltage at the amplifier output side by means of electronical switches.

As far as I understand, you clarified now that you are talking about line level (power amplifier input signal) only, means the voltage is restricted to e.g. 2 V AC and impedance is >= 600 ohm. Then analog switches like CD4066 are suitable.

You initially asked about signal switching, now it's continuous (or stepwise) level control, involving at least a number of switches and a resistor ladder. Multiplying DACs or digital potentiometers can be an alternative in this case.

 

[audiomik]

Perhaps the TI PGA4311 quad serial controlled Volume control IC, or an equivalent, is a candidate for this.
This would provide for 4 inputs from different sources.
Each of it's 4 outputs can be passively summed to then feed the Input(s) of the PA System.
An Evaluation kit is available for these from TI and with it's serial control then easy to implement an Infra-Red remote for it.
https://www.ti.com/product/pga4311

Mik