[heatmizer]

Hi I'm trying to design headphone amp to automatically switch between ipod and cell phone looks like a vox circuit will do the trick but is there anyway i could do this without a relay say with transistors or maybe using a vox type circuit to power different opamps for ipod and cellphone

 

[colonelkernel8]

Do you want it to recognize what you are saying? If so, thats a whole different ballgame.

 

[heatmizer]

not my voice no

I want the circuit to switch the headphone out on say an ipod to the headphone out on a cell phone automatically when it detects signal from the cellphone and keep it switched for amount of time.
using this circuit eliminating input part and just using the.

i do not want to use a relay for the actual input switching if possible would like to use transistors of maybe use the circuit to power 2 opamps

 

[colonelkernel8]

Ah, I see. Here, I'll whip up something for you, maybe...

I made a circuit last year that was a switch activated by light, sooooo, if there is a component or circuit out there that will reduce resistance with sound, then I may be able to adapt it.

 

[heatmizer]

Thank You !!!!!

 

[colonelkernel8]

Don't rely on me though, I am a noob at this stuff. But it is a really good idea.

 

[heatmizer]

It looks like all the things I've seen use relays for switching

 

[splaz]

Why don't you want a relay ?

 

[heatmizer]

trying to keep small

 

[colonelkernel8]

You can get pretty small relays now-a-days that have pretty small current allowances, but plenty for the job at hand.

 

[splaz]

Yep you can get DIP and SMD relays, even small through hole ones.

I'm sure someone in America or Asia could find even smaller ones if need be.

 

[colonelkernel8]

Here is the light activated switch that I made.

It uses a transistor to switch the relay on when the current is sufficient through the base and emitter. So it is essentially a transistor switch that switches on a relay; the relay could be replaced. But as for the photodiode, there must be some replacement there for some circuit that switches with sound or something.

 

[heatmizer]

I also found these:

looks like the second one shorts the outputs dunno if thats a good thing though

 

[heatmizer]

protoboarded the 1st circuit:

it definitely has potential i need to get a multi turn pot though
the difference between the opamp going high and low is very touchy
looked at other u741 comparator circuit they have much lower value resistors on either side of the pot am going to try that

 

[heatmizer]

Have the basic switching circuit working with the output from my cell phone but
but need bit of help. the comparator opamp will be running single supply 12v and ground. The input of the comparator will also be hooked to iput of a basic cmoy amp
Will the comparator opamp (12v and grd) coexist with cmoy amp (+6v and -6)?
Am I going to have problems with the cmoy virtual ground or do i ned to look at at a single supply amp or rework the switching circuit to operate at +6v and -6 v?