Thomas,
You pretty much nailed it. And there is an isolating capacitor on the
output, a 470uf one. It's a point I hadn't considered. The problem is
that when you connect that capacitor from the positive output of the
2822 to ground what happens to the 2822? It's going to look like a dead
short for audio. Is the 2822 designed to feed a dead short for AC? At
the very least you will get no audio output at the jack. At worst you
will get a large current load on the 2822 trying to feed the
short.
tim ab0wr
On Sat, 3 Mar 2018 03:59:14 +0000 (UTC)
"Thomas Sharka via Groups.Io" <sharkatw@...> wrote:
I'm with you. The standard for audio outputs on a communications rig
doesn't include stereo headphones. That said, the inclusion of an
isolating capacitor on the output just makes good sense.?
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On Friday, March 2, 2018 10:06 PM, Tim Gorman <tgorman2@...>
wrote:
Respectfully -
If you wire the positive output of the 2822 to both the tip and ring
terminal on the TRS jack and the ground lead to the sleeve terminal
and then plug in a mono plug you *will* short the positive lead from
the 2822 to ground.
Wiring the ground to the ring lead is *NOT* what the wiring
instructions for the ubitx show. It shows wiring the positive lead
from the 2822 to both the tip and the ring lead. That will be a
potential disaster for anyone plugging in a mono plug.
If you wire the ground lead to the ring terminal then how is a stereo
plug going to work? There will be no ground connected to the sleeve
lead of the headset.
I am going to use one of my mono jacks. Then I don't have to worry
about how the jack is wired. If I need a mono-stereo adapter I have
several. In fact, the headphones I use most often have a mono-stereo
switch built in.
tim ab0wr
On Fri, 2 Mar 2018 16:14:50 -0500
"Vince Vielhaber" <vev@...> wrote:
No, you missed the point.? It's not in bridge mode, so one side is
already ground.? If you hook the ground up to the ring and not the
sleeve, the sleeve will get ground in a mono plug but both speakers
in a stereo headset will get sound.? No need to butcher headphone
cables or buy an adapter, gold or otherwise.? Just wire it right.
Shit, you got a ham ticket and you managed to wire up your bitx, you
should be able to wire up a headphone jack - "you" not necessarily
referring to you, Tim, rather whoever is setting it up.
Vince.
On 03/02/2018 11:07 AM, Tim Gorman wrote:
Vince,
You missed the point. If you wire the tda2822 to both the tip and
the ring and then plug in a mono headphone you *will*, in almost
every case, short the output of the tda2822 to ground via the ring
lead.
You will melt the tda2822 sooner or later by doing so - plus get
nothing in the headphone.
tim ab0wr
On Thu, 1 Mar 2018 23:22:48 -0500
"Vince Vielhaber" <vev@...> wrote:
?
Ever cut the connector off of a pair of them and try to wire on a
new one?? The point, that you obviously missed, wasn't that
headphones are cheap, it's that there's no reason to do what Tim
was suggesting and that you can wire up to the tip and ring and
have it work with both stereo and mono headphones.
Vince.
On 03/01/2018 11:17 PM, Thomas Sharka via Groups.Io wrote:?
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On Thursday, March 1, 2018 11:12 PM, Vince Vielhaber
<vev@...> wrote:
So you're saying that if I want to use a pair of stereo
headphones I have around here I should cut the connector off of
it and wire it up to a mono plug?? Yeah...? I'll get right on
that.
Vince.
On 03/01/2018 10:49 PM, Tim Gorman wrote:?
If you insert a mono plug into a TRS jack the ring terminal of
the jack is almost always shorted to ground (i.e. the sleeve).
If you wire the output of the 2822 to both the tip and ring
terminals and then insert a mono plug there simply isn't any
doubt that you are probably going to short the output of the
2822 to ground. Bad things will happen.
There is no reason to wire the output of the 2822 to both the
tip and the ring terminals. If you have a stereo headset then
wire both headset leads to tip of the plug and only wire up
the tip lead on the socket. Then if someone inadvertently
plugs in a mono plug you won't short the output of the 2822 to
ground.
I agree that the large charging current going into the 470uf
cap could stress the 2822, perhaps only causing a failure
after a number of on/off cycles. That's something that would
be hard to diagnose!
I have modified my schematic to show using a 47uf cap being fed
with a 1 amp fuse from the 2822. If I ever get a chance to
actually finish up my ubitx it will be interesting to see if
the 1 amp fuse is sufficient.
tim ab0wr
On Thu, 01 Mar 2018 15:39:50 -0800
"Jerry Gaffke via Groups.Io" <jgaffke@...?
<mailto:[email protected]>> wrote:?
?
And subsequent replies have suggested this may not be
sufficient.
Some seem to fry when plugging something into the headphone
jack even if there is no short to ground involved. Or when
powering up the rig. Our best guess now is that there are
significant currents involved when that 470uF cap suddenly
has to charge up to Vcc/2 And that some clone TDA2822's may
be weaker than mainline manufacturers.
On Thu, Mar 1, 2018 at 03:31 pm, Christopher Miller wrote:
?
One of the first replies suggested not wiring the ring, and
using a mono to stereo adapter cable if stereo headphones are
required.
?
?
--
? Michigan VHF Corp.?
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