[arm-allstar] AC coupled audio

[David McGough]

Hi,

I expect you're correct: DO NOT ground the speaker connection! ...I know 
that is for certain with most transformer-less radios.

Typically, the preferred way to get audio from the speaker terminals is to
use an isolation transformer, with an appropriate terminating resistor
across the primary.  I've got this exact setup on several GE-Rangr radios 
and it works well.

As for the terminating resistor, I used a 8-ohm, 5W resistor obtained from
a hamfest.  For the transformer, I bought several miniature 1:1 (600 ohm,
I think)  transformers off ebay (try searching: "audio isolation
transformer").

BTW, I have seen some coupling methods that simply used capacitors. I 
haven't tries that....As I think was already mentioned, the hot end of a 
volume pot is also an excellent spot to get audio--then you don't have to 
worry about the level getting accidentally changed.


73, David KB4FXC



On Thu, 9 Apr 2015, Robert Newberry wrote:

> What I am confused about is I have been reading not to ground the other
> lead. If using the speaker leads. I've read things such as using an audio
> transformer or a capacitor.
> 
> I'm am wondering if anyone has done this and can offer any input. I am
> guessing that tapping the high side of the audio pot would also be the same
> as using the speaker leads other than it being controlled by the volume
> control.
> 
> I'm just trying to avoid damaging my audio amplifier.
>