Common negative on LM3875?

[troystg]

Hi All-

I was wondering if I could use a common ground headphone jack with the output of BrianGT's LM3875 gainclone?

I am constructing my office desk unit now and would like a headphone jack on the front for private listening.

I searched and found lots of stuff saying it was overkill , but nothing saying I couldn't combine the two negative leads from the separate chips to the headphone jack.


Thanks in advance,

Troy

 

[troystg]

Tickle, or bump...

TTT

 

[officeboy]

I don't see how it would be a problem, it's just a ground for AC. So be sure your grounding stars are all grounding to each other, for both channels.

Just don't be hooking negative leads up together, There is an OUT pin. the other side of the connection is the ground.

 

[HDTVman]

I'm a little confused here. The question was

"
I was wondering if I could use a common ground headphone jack with the output of BrianGT's LM3875 gainclone?

I am constructing my office desk unit now and would like a headphone jack on the front for private listening.

I searched and found lots of stuff saying it was overkill , but nothing saying I couldn't combine the two negative leads from the separate chips to the headphone jack.

"
It's this part about the "two negitive leads from the separate chips" part that has me confused. If you mean the Negitive Power Supply rail then the answer is NO. If your talking about the signal/power supply common / Ground other wise known as the speaker negitive, then the answer is YES. You can connect the two channels together. I would suggest resistors in series with the headphone jack to reduce the signal level to the phones. 220 to 330 ohms should be fine. With out these you will be buying lots of new headphones and hearing aids before long.

Have fun BZ

 

[troystg]

Sorry for the ambiguity.

I was hoping to use a 3 connection headphone jack(TRS) and use the tip as right spkr +, ring as left spkr + and sleeve as COMMON spkr -.

Would that pose any problem for the separate chips?

Thanks again to those who replied!!

Troy

 

[officeboy]

Should be no problems, Just be sure that the "sleeve as COMMON spkr -" is ground, and NOT a negative connection.

And yeah, major overkill for headphones.

 

[troystg]

Well, its MAIN purpose is as a desk amplifier for a small line array.

But for those quiet days I would like to jack in my phones.

Thanks again!!

Troy


Edit: spelling

 

[Alcaid]

I would suggest to lower the gain. The chips are stable down to a gain of 10 I think, and for headphones, that would be a good place to start.

 

[officeboy]

You could also just add a switch to shunt some signal to ground.
Kind of a headphones level thing, use it to drop your signal 20-30dB.
It would at least help to give your volume control a more usable range when your using the headphones.

 

[troystg]

Thanks all for the help, now this thread can be achived for future searches..

Death to the thread!!

Troy

P.S.- I'm really a positive person.