Re: B40 LM386 and µB TDA2822 and that 470µF Cap

Thomas Sharka
 

On Thursday, March 1, 2018 11:22 PM, 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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>
> Headphones are cheap. You can find them at the Dollar Store.
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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=yahoo.com@groups.io
> <mailto:yahoo.com@groups.io>> 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.
>>>>
>>>>
>>
>>
>>
>>
>
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