speaker isolation

now I ask what is with that headphone use in a car?

On Wed, 1 Feb 2006 02:53:11 +0000 (UTC) in sci.electronics.misc, "ryan weihl" wrote,

So as not to distract the driver.

Hello,

As I said, it is built in a portable enclosure for use at home (using a 13.2 VDC power supply). The reason I am doing this is because it is a HD capable radio. Never to be used in a car. Once again, thank you for any help,

Ivan

Do you mean positive ground?

Forget that. The problem is the single rail operation. The "ground" outputs will probably be at mid rail (6V) so when the socket is connected to the chassis the capacitors have around 6V across them.

Can you use a plastic socket like this so the outer/common contact remains isolated from the chassis?

or mount a metal one on a piece of plain fiberglass board and mount that on the chassis?

Hello,

Sure can, but I was wondering if it was a problem that could be handled by a resistor bleeding off cap charge.

Oddly, the circuit performs well even when jack is attached to chassis ground, but with the only available 1/8" stereo closed switching jacks being cheap Radio Shack Japanese, I get the inevitable intermittent contact to the plug which results in the loud crackle and pop.

I will then turn down a delrin insulating shoulder bushing to isolate jack to chassis.

Thank you for your attention and suggestion.

Ivan

I had another think about this today. I'm not convinced the caps are doing anything when the socket is mounted on the chassis. When it's like that the caps are between the virtual earth (say 6v) and 0V/chassis. Then the headphone speakers are between the +ve outputs (also 6v) and 0V. I'm concerned this means you have DC across the headphone speaker and that it's this NOT the voltage on the caps that's causing the pops.

the

it's

You could try something like this

-ve -- No connection

-ve -- No connection

..but you will probably get a "switch on thump".

I still think an isolated socket is the best solution.

Thank you for taking the time to analyze my problem. I will be safest by isolating the jack from the chassis case, as you suggested.

Ivan

Has anyone determined that the outputs aren't H-bridges?

Hmm... just a thought, but what about connecting each speaker to a small transformer, and the relevant headphone to the other side?

Essentially the left and right channels would be separate, except you could tie the commons together and it'd be fine. Use maybe a pair of straight 32ohm : 32ohm audio transformers. If they exist. Just an idea, I don't do this sort of thing for a living.

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