Circuit diagram analysis for speaker volume control structure

[rajaram04]

Hello sir

A very very very common idea of a circuit i am shoeing here which i gonna design as a base for a digital volume control unit



please tell would it work ?

if yes then is there any harm to amplifier unit due to external source as trigger to transistor ??????

What are the changes i ll ve to make then ?

The circuit i am showing is not the one i am designing but it is only an idea , may be i gonna use pnp transistor etc etc . . so please help

 

[BradtheRad]

It is only natural to think this would work. It appears to comply with the concepts of transistor gain.

However your schematic will only work during the signal's positive waveform.

Screenshot:



As soon as the signal goes negative, the transistor gain drops.

-----------------------

What about adding a transistor in parallel, to conduct in the opposite direction?

I tried simulating a few combinations of NPN, PNP, orientation, bias direction, etc.
Couldn't find one that works. None seem to provide current flow both ways, as well as smooth gain adjust.

-----------------------

Consider using an FET-based volume control:

https://freecircuitdiagram.com/2012/01/11/voltage-controlled-attenuator-volume-control-using-fet/

Or a photo-resistor:

https://www.instructables.com/id/Make-a-Voltage-Controlled-Resistor-and-Use-It/

 

[rajaram04]

It is only natural to think this would work. It appears to comply with the concepts of transistor gain.

However your schematic will only work during the signal's positive waveform.

Screenshot:



As soon as the signal goes negative, the transistor gain drops.

-----------------------

What about adding a transistor in parallel, to conduct in the opposite direction?

I tried simulating a few combinations of NPN, PNP, orientation, bias direction, etc.
Couldn't find one that works. None seem to provide current flow both ways, as well as smooth gain adjust.

-----------------------

Consider using an FET-based volume control:

https://freecircuitdiagram.com/2012/01/11/voltage-controlled-attenuator-volume-control-using-fet/

Or a photo-resistor:

https://www.instructables.com/id/Make-a-Voltage-Controlled-Resistor-and-Use-It/

kk sir thanks but tell me about first circuit diagram that if i can use a 2k resistor in place of 10 k ??

also tell me about the first link you gave that , is it possible to make it with a bjt ?

Too you told about the "signal goes negative" matter , so how to overcome that ??

Is it possible to design with a photo diode & infra red LED ???????????

please reply