Topics

B40 LM386 and µB TDA2822 and that 470µF Cap

Arvo W0VRA
 

Someone said if you find a fence ask why it's there before you tear it down.

On the B40 there is a 470µF cap on the output, between the LM386 output and the speaker.  On the LM386's TI datasheet Figure 10 there is a 250µF cap in that spot.  It's not an unreasonable leap to surmise that someone thought, "Hmmm, a 470 would probably work there and I've got a bunch of them."  I can't find anything in the datasheet explaining the need for the capacitor.  It may be that there is some DC offset in the output that needs to be removed.

On the µB there is also a 470µF cap between the output of the TDA2822 and the speaker.  On the TDA2822's STMicroelectronics datasheet application circuits there are examples with both 100µF and 470µF capacitors.  Again, I can't find why those caps are there.

The presence of these caps in the manufacturer's guidelines makes the "too much capacitor in the µB" hypothesis much less probable.  Maximum input voltage rating of 15V in the TDA2822 datasheet imply that 12-14V supplies should not be a problem, either.

A dead short on the output should not be a catastrophic problem for the amps because the caps are blocking DC current, so any power to be dissipated is associated with how loud you've got the volume knob cranked.  So if you turn it up and don't hear anything, turn it back down!

All bets are off if we have parts of unknown provenance, ie, counterfeits.  Does HF Signals have a process in place to assure the supply of components that conform to the expected specifications?  Bad batches of parts shouldn't happen from reputable suppliers.

All that said, there should probably be a pretty plain heads up somewhere in the tribal knowledge that if you wire up the µB speaker jack per the website and plug a TS (tip-sleeve) as opposed to a TRS (tip-ring-sleeve) male connector into it, you will have a dead short across the jack and it won't work properly.

One way to avoid that trouble is to simply wire the output of the amp to the tip connector of the jack and leave the ring connector of the jack floating (unconnected).  If you plug in a mono speaker, or an old fashioned earphone, it will work.  If you plug in stereo headphones you'll only hear audio from one earpiece.

I'm leaving mine wired for stereo.

Gordon Gibby <ggibby@...>
 

The capacitor is there because this are you amplifier is designed to be operated with one supply voltage, +V, and ground.

The opamp output transistor circuit can only move between zero and a positive voltage.  

To avoid keeping a physical offset displacenent on the speaker cone, at the cost of significant current through its very low DC resistance! One adds a large capacitor in series to allow the speaker cone to rest at neutral position.

In the datasheet I looked at, they were using a 1000 µF capacitor.   That’s probably give you a better low frequency response, and basically the value isn’t that critical.



On Mar 1, 2018, at 17:20, Arvo KD9HLC via Groups.Io <arvopl@...> wrote:

Someone said if you find a fence ask why it's there before you tear it down.

On the B40 there is a 470µF cap on the output, between the LM386 output and the speaker.  On the LM386's TI datasheet Figure 10 there is a 250µF cap in that spot.  It's not an unreasonable leap to surmise that someone thought, "Hmmm, a 470 would probably work there and I've got a bunch of them."  I can't find anything in the datasheet explaining the need for the capacitor.  It may be that there is some DC offset in the output that needs to be removed.

On the µB there is also a 470µF cap between the output of the TDA2822 and the speaker.  On the TDA2822's STMicroelectronics datasheet application circuits there are examples with both 100µF and 470µF capacitors.  Again, I can't find why those caps are there.

The presence of these caps in the manufacturer's guidelines makes the "too much capacitor in the µB" hypothesis much less probable.  Maximum input voltage rating of 15V in the TDA2822 datasheet imply that 12-14V supplies should not be a problem, either.

A dead short on the output should not be a catastrophic problem for the amps because the caps are blocking DC current, so any power to be dissipated is associated with how loud you've got the volume knob cranked.  So if you turn it up and don't hear anything, turn it back down!

All bets are off if we have parts of unknown provenance, ie, counterfeits.  Does HF Signals have a process in place to assure the supply of components that conform to the expected specifications?  Bad batches of parts shouldn't happen from reputable suppliers.

All that said, there should probably be a pretty plain heads up somewhere in the tribal knowledge that if you wire up the µB speaker jack per the website and plug a TS (tip-sleeve) as opposed to a TRS (tip-ring-sleeve) male connector into it, you will have a dead short across the jack and it won't work properly.

One way to avoid that trouble is to simply wire the output of the amp to the tip connector of the jack and leave the ring connector of the jack floating (unconnected).  If you plug in a mono speaker, or an old fashioned earphone, it will work.  If you plug in stereo headphones you'll only hear audio from one earpiece.

I'm leaving mine wired for stereo.

Arvo W0VRA
 

On Thu, Mar 1, 2018 at 02:38 pm, Gordon Gibby wrote:
The opamp output transistor circuit can only move between zero and a positive voltage.  
Yes, but I'd think if someone was building an IC audio amp they'd go ahead and stick a cap inside it!

I suppose different applications would have different optimum caps.

Jerry Gaffke
 

It would be really really tough to fabricate a 100uF cap as part of a silicon wafer.
Datasheet specs the quiescent output voltage to be around half of the supply voltage,
right where you would expect it given the totem pole output driver.
As per post 43200.

And as alluded to in previous posts, the size of the cap is dictated by the impedance
of the load (typically 8 ohms) and the lowest frequencies you need to be hearing.

If you don't like the cap you can use the bridge topology in the datasheet,
using the two halves of the amp at 180 degrees out of phase.. 
But then neither side of your speaker is a ground potential. 
It's either that or a big cap, your choice. 


On Thu, Mar 1, 2018 at 02:56 pm, Arvo KD9HLC wrote:
Yes, but I'd think if someone was building an IC audio amp they'd go ahead and stick a cap inside it!

Christopher Miller
 

One of the first replies suggested not wiring the ring, and using a mono to stereo adapter cable if stereo headphones are required. 

Chris
KF4FTR

Jerry Gaffke
 

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. 
 

Jerry Gaffke
 

One observation that may or may not be relevant:
The datasheet from UTC spec's a supply voltage of 1.8 to 12v:  https://www.taydaelectronics.com/datasheets/A-1509.pdf
whereas the ST datasheet specs 1.8 to 15v:  https://www.taydaelectronics.com/datasheets/A-1003.pdf
Both spec an "Absolute Max" of 15v,
 


On Thu, Mar 1, 2018 at 03:39 pm, Jerry Gaffke wrote:
And that some clone TDA2822's may be weaker than mainline manufacturers.

Clark Martin
 

ICs are only capable of implementing rather small capacitors, well below what is needed for a DC isolation cap in an audio power amplifier.

Clark Martin
KK6ISP

On Mar 1, 2018, at 2:56 PM, Arvo KD9HLC via Groups.Io <arvopl@...> wrote:

On Thu, Mar 1, 2018 at 02:38 pm, Gordon Gibby wrote:
The opamp output transistor circuit can only move between zero and a positive voltage.  
Yes, but I'd think if someone was building an IC audio amp they'd go ahead and stick a cap inside it!

I suppose different applications would have different optimum caps.
_._

Tim Gorman
 

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> 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. 
 

Vince Vielhaber
 

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> 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.


Thomas Sharka
 

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> 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.  http://www.nobucks.net/   http://www.CDupe.com/
                          http://www.metalworkingfun.com





Vince Vielhaber
 

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:
Trendy Headphones Stereo 3.5mm Plug In-Ear Earbuds Earphones Headset For
Phones | eBay
<https://www.ebay.com/itm/Trendy-Headphones-Stereo-3-5mm-Plug-In-Ear-Earbuds-Earphones-Headset-For-Phones-/271924189930?_trksid=p2385738.m4383.l4275.c10>

Headphones are cheap. You can find them at the Dollar Store.
$ 0.99




Trendy Headphones Stereo 3.5mm Plug In-Ear Earbuds Earphones Headset
For Ph...

Headset Type: In-Ear. Connection: 3.5 mm Stereo Plug. Cable Length:
110cm/43.30"(Approx.). High quality in ...


<https://www.ebay.com/itm/Trendy-Headphones-Stereo-3-5mm-Plug-In-Ear-Earbuds-Earphones-Headset-For-Phones-/271924189930?_trksid=p2385738.m4383.l4275.c10>




Sent from Yahoo Mail. Get the app <https://yho.com/148vdq>


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.



--
Michigan VHF Corp. http://www.nobucks.net/ <http://www.nobucks.net/>
http://www.CDupe.com/ <http://www.cdupe.com/>
http://www.metalworkingfun.com
<http://www.metalworkingfun.com/>





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:
> Trendy Headphones Stereo 3.5mm Plug In-Ear Earbuds Earphones Headset For
> Phones | eBay
> <https://www.ebay.com/itm/Trendy-Headphones-Stereo-3-5mm-Plug-In-Ear-Earbuds-Earphones-Headset-For-Phones-/271924189930?_trksid=p2385738.m4383.l4275.c10>
>
> Headphones are cheap. You can find them at the Dollar Store.
> $ 0.99    
>
>    
>
>
>    Trendy Headphones Stereo 3.5mm Plug In-Ear Earbuds Earphones Headset
>    For Ph...
>
> Headset Type: In-Ear. Connection: 3.5 mm Stereo Plug. Cable Length:
> 110cm/43.30"(Approx.). High quality in ...
>    
>
> <https://www.ebay.com/itm/Trendy-Headphones-Stereo-3-5mm-Plug-In-Ear-Earbuds-Earphones-Headset-For-Phones-/271924189930?_trksid=p2385738.m4383.l4275.c10>
>
>
>
>
> Sent from Yahoo Mail. Get the app <https://yho.com/148vdq>
>
>
> 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.
>>>>
>>>>
>>
>>
>>
>>
>
> --
>  Michigan VHF Corp.  http://www.nobucks.net/ <http://www.nobucks.net/>
> http://www.CDupe.com/ <http://www.cdupe.com/>
>                          http://www.metalworkingfun.com
> <http://www.metalworkingfun.com/>
>
>
>
>
>
>

--
  Michigan VHF Corp.  http://www.nobucks.net/   http://www.CDupe.com/
                          http://www.metalworkingfun.com





Vince Vielhaber
 

Well that sure explains why you missed the point. Thanks for clarifying.

Vince.

On 03/01/2018 11:28 PM, Thomas Sharka via Groups.Io wrote:
Often.

http://3.bp.blogspot.com/-9FHusouOVIE/T_RT2O6Ul-I/AAAAAAAAAfE/U-l2_0i7N78/s1600/IMAG0090.jpg



Sent from Yahoo Mail. Get the app <https://yho.com/148vdq>


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:
Trendy Headphones Stereo 3.5mm Plug In-Ear Earbuds Earphones Headset For
Phones | eBay
<https://www.ebay.com/itm/Trendy-Headphones-Stereo-3-5mm-Plug-In-Ear-Earbuds-Earphones-Headset-For-Phones-/271924189930?_trksid=p2385738.m4383.l4275.c10>

Headphones are cheap. You can find them at the Dollar Store.
$ 0.99




Trendy Headphones Stereo 3.5mm Plug In-Ear Earbuds Earphones Headset
For Ph...

Headset Type: In-Ear. Connection: 3.5 mm Stereo Plug. Cable Length:
110cm/43.30"(Approx.). High quality in ...


<https://www.ebay.com/itm/Trendy-Headphones-Stereo-3-5mm-Plug-In-Ear-Earbuds-Earphones-Headset-For-Phones-/271924189930?_trksid=p2385738.m4383.l4275.c10>




Sent from Yahoo Mail. Get the app <https://yho.com/148vdq>


On Thursday, March 1, 2018 11:12 PM, Vince Vielhaber <vev@...
<mailto: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>
<mailto: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.



--
Michigan VHF Corp. http://www.nobucks.net/
<http://www.nobucks.net/><http://www.nobucks.net/>
http://www.CDupe.com/ <http://www.cdupe.com/><http://www.cdupe.com/>
http://www.metalworkingfun.com
<http://www.metalworkingfun.com/>
<http://www.metalworkingfun.com/>





--
Michigan VHF Corp. http://www.nobucks.net/ <http://www.nobucks.net/>
http://www.CDupe.com/ <http://www.cdupe.com/>
http://www.metalworkingfun.com
<http://www.metalworkingfun.com/>





Thomas Sharka
 

Yes, all those tiny, fiddly wires! How could anyone ever manage? Good thing that soldering SMD parts the size of a grain of pepper is so easy.
 


Sent from Yahoo Mail. Get the app


On Thursday, March 1, 2018 11:34 PM, Vince Vielhaber <vev@...> wrote:


Well that sure explains why you missed the point.  Thanks for clarifying.

Vince.



On 03/01/2018 11:28 PM, Thomas Sharka via Groups.Io wrote:
> Often.
>
> http://3.bp.blogspot.com/-9FHusouOVIE/T_RT2O6Ul-I/AAAAAAAAAfE/U-l2_0i7N78/s1600/IMAG0090.jpg
>
>
>
> Sent from Yahoo Mail. Get the app <https://yho.com/148vdq>
>
>
> 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:
>> Trendy Headphones Stereo 3.5mm Plug In-Ear Earbuds Earphones Headset For
>> Phones | eBay
>>
> <https://www.ebay.com/itm/Trendy-Headphones-Stereo-3-5mm-Plug-In-Ear-Earbuds-Earphones-Headset-For-Phones-/271924189930?_trksid=p2385738.m4383.l4275.c10>
>>
>> Headphones are cheap. You can find them at the Dollar Store.
>> $ 0.99
>>
>>
>>
>>
>>    Trendy Headphones Stereo 3.5mm Plug In-Ear Earbuds Earphones Headset
>>    For Ph...
>>
>> Headset Type: In-Ear. Connection: 3.5 mm Stereo Plug. Cable Length:
>> 110cm/43.30"(Approx.). High quality in ...
>>
>>
>>
> <https://www.ebay.com/itm/Trendy-Headphones-Stereo-3-5mm-Plug-In-Ear-Earbuds-Earphones-Headset-For-Phones-/271924189930?_trksid=p2385738.m4383.l4275.c10>
>>
>>
>>
>>
>> Sent from Yahoo Mail. Get the app <https://yho.com/148vdq>
>>
>>
>> On Thursday, March 1, 2018 11:12 PM, Vince Vielhaber <vev@...
> <mailto: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>
>> <mailto: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.
>>>>>
>>>>>
>>>
>>>
>>>
>>>
>>
>> --
>>  Michigan VHF Corp.  http://www.nobucks.net/
> <http://www.nobucks.net/><http://www.nobucks.net/>
>> http://www.CDupe.com/ <http://www.cdupe.com/><http://www.cdupe.com/>
>>                          http://www.metalworkingfun.com
> <http://www.metalworkingfun.com/>
>> <http://www.metalworkingfun.com/>
>>
>>
>>
>>
>>
>>
>
> --
>  Michigan VHF Corp.  http://www.nobucks.net/ <http://www.nobucks.net/>
> http://www.CDupe.com/ <http://www.cdupe.com/>
>                          http://www.metalworkingfun.com
> <http://www.metalworkingfun.com/>
>
>
>
>
>
>

--
  Michigan VHF Corp.  http://www.nobucks.net/   http://www.CDupe.com/
                          http://www.metalworkingfun.com





Randy
 

Jerry Gaffke
 

They're worth a try, maybe you managed to get some good ones.
But in my experience, anything under about $10 in headphones is not worth the bother.
Extremely low fidelity, to the point of not being good enough to listen to the news.

I agree with Vince, not trivial to put a new connector on most headphones these days.
Try it.
Better than hacking your $1 headphones is a mono to stereo adapter plug:
    https://www.monoprice.com/product?p_id=7128
As suggested in a post a couple days ago.

Not yet clear if avoiding shorts is sufficient to keep this chip from failing.
Some reports of plugging in stereo headphones causing it to fail.

Jerry


On Thu, Mar 1, 2018 at 08:17 pm, Thomas Sharka wrote:
Headphones are cheap. You can find them at the Dollar Store.

David Wilcox
 

Or get them free if you fly Delta with the video sets. They are cheap (not very hardy) but they do work.

Also, a side note.  Left my car with chrome wheels parked in Myrtle Beach, SC, while on vacation.  Did NOT go to the beach.  The car just sat a mile or so from the ocean.  To my surprise my chrome wheels showed significant corrosion upon my return. Protect your gear any way you can AND don't buy any radio that has been kept on a boat in a salt water marina.  Eventually the corrosion on the circuit board will get you.  I know from a close friend's experience.  His used IC 7000  failed after a few months.  The board showed unrepairable corrosion.

Dave K8WPE

On Mar 2, 2018, at 12:11 AM, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:

They're worth a try, maybe you managed to get some good ones.
But in my experience, anything under about $10 in headphones is not worth the bother.
Extremely low fidelity, to the point of not being good enough to listen to the news.

I agree with Vince, not trivial to put a new connector on most headphones these days.
Try it.
Better than hacking your $1 headphones is a mono to stereo adapter plug:
    https://www.monoprice.com/product?p_id=7128
As suggested in a post a couple days ago.

Not yet clear if avoiding shorts is sufficient to keep this chip from failing.
Some reports of plugging in stereo headphones causing it to fail.

Jerry


On Thu, Mar 1, 2018 at 08:17 pm, Thomas Sharka wrote:
Headphones are cheap. You can find them at the Dollar Store.

David Wilcox
 

Forgot to say I was parked in Myrtle Beach for two weeks.  Never saw that kind of corrosion in northern Michigan even with the salt used on the road in the winter.

Dave K8WPE

On Mar 2, 2018, at 3:01 AM, David Wilcox via Groups.Io <Djwilcox01@...> wrote:

Or get them free if you fly Delta with the video sets. They are cheap (not very hardy) but they do work.

Also, a side note.  Left my car with chrome wheels parked in Myrtle Beach, SC, while on vacation.  Did NOT go to the beach.  The car just sat a mile or so from the ocean.  To my surprise my chrome wheels showed significant corrosion upon my return. Protect your gear any way you can AND don't buy any radio that has been kept on a boat in a salt water marina.  Eventually the corrosion on the circuit board will get you.  I know from a close friend's experience.  His used IC 7000  failed after a few months.  The board showed unrepairable corrosion.

Dave K8WPE

On Mar 2, 2018, at 12:11 AM, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:

They're worth a try, maybe you managed to get some good ones.
But in my experience, anything under about $10 in headphones is not worth the bother.
Extremely low fidelity, to the point of not being good enough to listen to the news.

I agree with Vince, not trivial to put a new connector on most headphones these days.
Try it.
Better than hacking your $1 headphones is a mono to stereo adapter plug:
    https://www.monoprice.com/product?p_id=7128
As suggested in a post a couple days ago.

Not yet clear if avoiding shorts is sufficient to keep this chip from failing.
Some reports of plugging in stereo headphones causing it to fail.

Jerry


On Thu, Mar 1, 2018 at 08:17 pm, Thomas Sharka wrote:
Headphones are cheap. You can find them at the Dollar Store.

David Wilcox
 

I know that we get away with plugging and unplugging things hot on most of our radios but as for me I will turn off the radio before making any changes. Any thoughts on that?

Dave K8WPE

On Mar 1, 2018, at 10:49 PM, Tim Gorman <tgorman2@...> 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> 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.