Transistors for an Audio Switch

[5Beans6]

I want to make a custom audio switch box to be able to change between my headphones whenever i want just by the flick of a switch. I was wondering if i could just use regular npn transistors to direct the current from my computer or if i have to use a relay as audio is AC?

[fable]

Why not use 4052 or 4053 analog switch ic ?you can find them everywhere

[5Beans6]

Because those are multiplexers, doesn't that mean the signal will be turning on and off rapidly as that is what multiplexing does? This is very undesirable for an audio situation

[fable]

No.You control which switches are on by driving select pins high or low...read datasheet.
Sorry for my bad english.

[5Beans6]

Oh ok, cool! I was not aware of their existance. Thanks!

[Zero999]

An analogue switch is no good for switching power, i.e. the current flowing through headphones or a speaker. They are only suitable for small signals.

To switch headphones or a speaker, use a relay.

[f5r5e5d]

don't you have to take the headphones on/off your head? then switching a plug is too hard?

quality switching dynamic headphone directly could require handling up to few 100 mA (Orthodynamic headphones) and blocking few 10s of V

relays are the obvious candiates for mOhm metal-to-metal distortion free switching

for solid state there are opto isolated SS Relays with bidirectional MOSFET switches

bjt transitor bidirectional switching isn't pretty

[5Beans6]

don't you have to take the headphones on/off your head? then switching a plug is too hard?

quality switching dynamic headphone directly could require handling up to few 100 mA (Orthodynamic headphones) and blocking few 10s of V

relays are the obvious candiates for mOhm metal-to-metal distortion free switching

for solid state there are opto isolated SS Relays with bidirectional MOSFET switches

bjt transitor bidirectional switching isn't pretty

An analogue switch is no good for switching power, i.e. the current flowing through headphones or a speaker. They are only suitable for small signals.

To switch headphones or a speaker, use a relay.

So relays it is then?

[edavid]

I want to make a custom audio switch box to be able to change between my headphones whenever i want just by the flick of a switch. I was wondering if i could just use regular npn transistors to direct the current from my computer or if i have to use a relay as audio is AC?

"Change between my headphones" and what?

If you want to be able to switch between speakers and headphones without unplugging the headphones, an easy way is to take an audio plug and 2 audio jacks, and wire them to a manual DPDT switch.  No relay is required.

You could also buy this: http://www.ebay.com/itm/2-PORT-3-5mm-STEREO-Manual-Sharing-Switch-BOX-Audio-Speaker-selector-way-2-1-/222343690109

As you guessed, bipolar transistors are hard to use as audio switches.

[5Beans6]

Sorry, yes i do mean speakers and headphones. That looks like a viable device, however the quality kinda worry's me.  I was also thinking about including some extra features too that I can only achieve by doing this DIY style due to the way my amplifier is and such.

[Zero999]

don't you have to take the headphones on/off your head? then switching a plug is too hard?

quality switching dynamic headphone directly could require handling up to few 100 mA (Orthodynamic headphones) and blocking few 10s of V

relays are the obvious candiates for mOhm metal-to-metal distortion free switching

for solid state there are opto isolated SS Relays with bidirectional MOSFET switches

bjt transitor bidirectional switching isn't pretty

An analogue switch is no good for switching power, i.e. the current flowing through headphones or a speaker. They are only suitable for small signals.

To switch headphones or a speaker, use a relay.

So relays it is then?

Yes, a relay is your best bet. A small SPDT (Single Pole Double Through) unit will do.

[BrianHG]

Yes, a relay is your best bet. A small SPDT (Single Pole Double Through) unit will do.

Stereo?
Why not DPDT?

[Zero999]

Yes, a relay is your best bet. A small SPDT (Single Pole Double Through) unit will do.

Stereo?
Why not DPDT?

Yes, that would make much more sense.

[TheUnnamedNewbie]

I would argue that a more important question here is whether or not it's a good idea to drive headphones and speakers from the same source. Something built to drive external speakers might be expecting 4-8 ohms, but depending on the headphones, you could be looking at anywhere from 32 or lower to 350 ohm load.

[edavid]

I would argue that a more important question here is whether or not it's a good idea to drive headphones and speakers from the same source. Something built to drive external speakers might be expecting 4-8 ohms, but depending on the headphones, you could be looking at anywhere from 32 or lower to 350 ohm load.

I think we are talking about powered speakers.

[Zero999]

I would argue that a more important question here is whether or not it's a good idea to drive headphones and speakers from the same source. Something built to drive external speakers might be expecting 4-8 ohms, but depending on the headphones, you could be looking at anywhere from 32 or lower to 350 ohm load.

Headphones will work fine off the same amplifier designed to drive low power speakers, i.e. under a couple of Watts into 8 Ohm. If it's a much larger amplifier >10W or so, then use an attenuator, consisting of a potential divider (a couple of resistors) to drive the headphones. A common solution is to use bridge outputs to drive the speakers and single ended to the headphone socket.

[mikerj]

There are analogue switches that are suitable for switching headphone level signals e.g. MAX4762.

[Zero999]

There are analogue switches that are suitable for switching headphone level signals e.g. MAX4762.

They look good and reasonably priced too.

I wonder how they handle negative signals? Perhaps there's a built-in charge pump to generate negative voltages?