Topics

LM386 CONNECTION

rajesh huddar
 

Hi,

Has anyone tried to connect LM386 instead of the stock audio chip. If I may request for the schematic.

Thanks

Rajesh
VU3RHU

On Tue, 30 Jun 2020, 20:01 BruceN, <k4tql@...> wrote:
Where is here?

BruceN/K4TQL
--
"To invent, you need a good imagination and a pile of junk"  -- Thomas Alva Edison (1847-1931)

MVS Sarma
 

In v5 and v6  only lm386 has been used. 
Even in ver 3  the component failed only because of plugging  mono external speaker pin into stereo socket. 
Secondly it failed due to higher voltages lije 13.8 or more  appled to rig. 

 Sarma vu3zmv

On Tue, 30 Jun 2020, 8:23 pm rajesh huddar, <pumerah@...> wrote:
Hi,

Has anyone tried to connect LM386 instead of the stock audio chip. If I may request for the schematic.

Thanks

Rajesh
VU3RHU

On Tue, 30 Jun 2020, 20:01 BruceN, <k4tql@...> wrote:
Where is here?

BruceN/K4TQL
--
"To invent, you need a good imagination and a pile of junk"  -- Thomas Alva Edison (1847-1931)

rajesh huddar
 

Hi 

Thanks for the revert. I wish to use LM386 as my audio is distorted and garbled.

Someone told.me that I need to calibrate while another input is to use LM386.

Inputs will be much appreciated.

Thanks

Rajesh
VU3RHU

On Tue, 30 Jun 2020, 20:30 MVS Sarma, <mvssarma@...> wrote:
In v5 and v6  only lm386 has been used. 
Even in ver 3  the component failed only because of plugging  mono external speaker pin into stereo socket. 
Secondly it failed due to higher voltages lije 13.8 or more  appled to rig. 

 Sarma vu3zmv

On Tue, 30 Jun 2020, 8:23 pm rajesh huddar, <pumerah@...> wrote:
Hi,

Has anyone tried to connect LM386 instead of the stock audio chip. If I may request for the schematic.

Thanks

Rajesh
VU3RHU

On Tue, 30 Jun 2020, 20:01 BruceN, <k4tql@...> wrote:
Where is here?

BruceN/K4TQL
--
"To invent, you need a good imagination and a pile of junk"  -- Thomas Alva Edison (1847-1931)

MVS Sarma
 

I fell that calibration is not related to lm386 or tda2822 ir discrete audio. 

Some one said that. I say this
 Msny say many things. It is for you too to try to analyse.  Namaste. 

On Tue, 30 Jun 2020, 8:38 pm rajesh huddar, <pumerah@...> wrote:
Hi 

Thanks for the revert. I wish to use LM386 as my audio is distorted and garbled.

Someone told.me that I need to calibrate while another input is to use LM386.

Inputs will be much appreciated.

Thanks

Rajesh
VU3RHU

On Tue, 30 Jun 2020, 20:30 MVS Sarma, <mvssarma@...> wrote:
In v5 and v6  only lm386 has been used. 
Even in ver 3  the component failed only because of plugging  mono external speaker pin into stereo socket. 
Secondly it failed due to higher voltages lije 13.8 or more  appled to rig. 

 Sarma vu3zmv

On Tue, 30 Jun 2020, 8:23 pm rajesh huddar, <pumerah@...> wrote:
Hi,

Has anyone tried to connect LM386 instead of the stock audio chip. If I may request for the schematic.

Thanks

Rajesh
VU3RHU

On Tue, 30 Jun 2020, 20:01 BruceN, <k4tql@...> wrote:
Where is here?

BruceN/K4TQL
--
"To invent, you need a good imagination and a pile of junk"  -- Thomas Alva Edison (1847-1931)

Evan Hand
 

Rajesh Huddar,
The short answer is yes, someone has.  The bigger question is how to connect the version that you have.  The connection will depend on the uBITX mainboard version.  Version 5 and later already have the LM386 as the audio amp.

If you have a version 3, then use the version 5 schematic to see how it was done there.  Here is part of the schematic with the audio amp:


There are also LM386 modules that could be added off-board.  You will need to run power, audio in, and speaker connection after removing the TDA2822 chip and jumpering the empty socket pin 3 to 5.  Connect the LM386 module to the SPK and the speaker to the output of the module.  Or just insert the module between pin 3 and 5 of the empty TDA2822 socket.  You still need to connect power and ground, then adjust the gain control on the module to not overdrive the speaker.
https://www.amazon.com/Youliang-Amplifier-Module-Adjustable-Resistance/dp/B07TRLSHMS/ref=sr_1_8?crid=28ZMCYOWP8HEG&dchild=1&keywords=lm386+audio+amplifier&qid=1593531727&sprefix=lm386%2Caps%2C162&sr=8-8

The alternative is to just replace the TDA2822 with a unit supplied by a reputable supplier.

For version 4 with low audio, I just connected an audio amp on the speaker connection of the mainboard with power and ground.

73
Evan
AC9TU

Vince Vielhaber
 

Every uBitx I've looked at the schematic for, IF WIRED CORRECTLY, the wiper of the volume pot will go to the amp. Remove the existing wire from the wiper of the volume pot and run a new wire from the wiper of the volume pot to your new amp. Then disable the current amplifier - that will depend on which version of the uBitx you have.

Vince - K8ZW.

On 06/30/2020 11:48 AM, Evan Hand wrote:
Rajesh Huddar,
The short answer is yes, someone has. The bigger question is how to
connect the version that you have. The connection will depend on the
uBITX mainboard version. Version 5 and later already have the LM386 as
the audio amp.

If you have a version 3, then use the version 5 schematic to see how it
was done there. Here is part of the schematic with the audio amp:


There are also LM386 modules that could be added off-board. You will
need to run power, audio in, and speaker connection after removing the
TDA2822 chip and jumpering the empty socket pin 3 to 5. Connect the
LM386 module to the SPK and the speaker to the output of the module. Or
just insert the module between pin 3 and 5 of the empty TDA2822 socket.
You still need to connect power and ground, then adjust the gain control
on the module to not overdrive the speaker.
https://www.amazon.com/Youliang-Amplifier-Module-Adjustable-Resistance/dp/B07TRLSHMS/ref=sr_1_8?crid=28ZMCYOWP8HEG&dchild=1&keywords=lm386+audio+amplifier&qid=1593531727&sprefix=lm386%2Caps%2C162&sr=8-8

The alternative is to just replace the TDA2822 with a unit supplied by a
reputable supplier.

For version 4 with low audio, I just connected an audio amp on the
speaker connection of the mainboard with power and ground.

73
Evan
AC9TU

Evan Hand
 

Rajesh Huddar,

I have been monitoring this board since 2018, and have not read of distorted audio solved by replacing the TDA2822.  I have read of failures like MVS Sarma has stated where they caused a failure of the TDA2822 and then decided to go to a different audio amp (LM386) or other amplifier modules off of the mainboard. 

Most of the distorted audio issues have been resolved by adjusting the BFO.  That would be where I would start before I tore into the board.

The above is just a suggestion, you will need to figure out if you can do the BFO adjustment as if it is done wrong it will make the situation worse.  A starting point (though the video is for the version 6) is the video on calibration from Ashhar Farhan:
https://www.youtube.com/watch?v=t6LGXhS4_O8
NOTE: ONLY do the BFO correction, then see if it fixes the issue.  The zero beating process should not be required UNLESS you have verified that the frequency displayed does not match the actual frequency received AFTER you have set and tested the BFO setting.  On the versions prior to 6, this can be done through the settings menu.

NOT 2: The stock version 5 will go into transmit mode if you go into the Calibration step.  For version 5 be sure you have a dummy load connected if you are going to calibrate the frequency display.  It is also a good idea to always connect a dummy load or tuned antenna when calibrating.

MVSSarma gave good advice on being sure you understand what is to be done and that you agree with the diagnosis.  YOU are responsible for the operation of the uBITX you have.

Side Note: I own version 4 and version 5 uBITX.  I have not worked with version 3, so there may be details that I do not know about that could cause issues.  I have reviewed the schematics for the above advice.

Good luck, and enjoy the learning experience.
73
Evan
AC9TU

Bill Cromwell
 

Hi,

My V3 has the original chip (not the one identified as sissy) and I run it from 13.8 volts regularly. I *never* plug/unplug earphones/speakers, key/paddles, mic, nor antenna with power turned on. If my audio chip does fail a 386 will take it's place.

73,

Bill KU8H

bark less - wag more

On 6/30/20 11:00 AM, MVS Sarma wrote:
In v5 and v6  only lm386 has been used.
Even in ver 3  the component failed only because of plugging  mono external speaker pin into stereo socket.
Secondly it failed due to higher voltages lije 13.8 or more  appled to rig.
 Sarma vu3zmv
On Tue, 30 Jun 2020, 8:23 pm rajesh huddar, <pumerah@... <mailto:pumerah@...>> wrote:
Hi,
Has anyone tried to connect LM386 instead of the stock audio chip.
If I may request for the schematic.
Thanks
Rajesh
VU3RHU
On Tue, 30 Jun 2020, 20:01 BruceN, <@bnebb
<mailto:@bnebb>> wrote:
Where is here?
BruceN/K4TQL
--
"To invent, you need a good imagination and a pile of junk"  --
Thomas Alva Edison (1847-1931)

jim
 

er ...not quite ...my version 3 was wired directly to speaker (no trs jack for phone) and ran ONLY on 12 volts

amp failed after about 3 months ..simply overspecified chip ...pure and simple

Jim



On Tuesday, June 30, 2020, 8:00:52 AM PDT, MVS Sarma <mvssarma@...> wrote:


In v5 and v6  only lm386 has been used. 
Even in ver 3  the component failed only because of plugging  mono external speaker pin into stereo socket. 
Secondly it failed due to higher voltages lije 13.8 or more  appled to rig. 

 Sarma vu3zmv

On Tue, 30 Jun 2020, 8:23 pm rajesh huddar, <pumerah@...> wrote:
Hi,

Has anyone tried to connect LM386 instead of the stock audio chip. If I may request for the schematic.

Thanks

Rajesh
VU3RHU

On Tue, 30 Jun 2020, 20:01 BruceN, <k4tql@...> wrote:
Where is here?

BruceN/K4TQL
--
"To invent, you need a good imagination and a pile of junk"  -- Thomas Alva Edison (1847-1931)

Bill Cromwell
 

Hi,

Apparently mine is far past due for failure. But it is okay because I have several 386s in the drawer. On the other had I may have one of the chips that was *not* an imposter. Those were mentioned by HF Signals. I have eluded the bogey man numerous times over the years. Been to war. Went to sea. Served the local fire dept for a long time. An audio amp that can't take the standard voltage and needs replacement seems kind of trivial.

73,

Bill KU8H

bark less - wag more

On 6/30/20 12:40 PM, jim via groups.io wrote:
er ...not quite ...my version 3 was wired directly to speaker (no trs jack for phone) and ran ONLY on 12 volts
amp failed after about 3 months ..simply overspecified chip ...pure and simple
Jim
On Tuesday, June 30, 2020, 8:00:52 AM PDT, MVS Sarma <mvssarma@...> wrote:
In v5 and v6  only lm386 has been used.
Even in ver 3  the component failed only because of plugging  mono external speaker pin into stereo socket.
Secondly it failed due to higher voltages lije 13.8 or more  appled to rig.
 Sarma vu3zmv
On Tue, 30 Jun 2020, 8:23 pm rajesh huddar, <pumerah@... <mailto:pumerah@...>> wrote:
Hi,
Has anyone tried to connect LM386 instead of the stock audio chip.
If I may request for the schematic.
Thanks
Rajesh
VU3RHU
On Tue, 30 Jun 2020, 20:01 BruceN, <@bnebb
<mailto:@bnebb>> wrote:
Where is here?
BruceN/K4TQL
--
"To invent, you need a good imagination and a pile of junk"  --
Thomas Alva Edison (1847-1931)

Curt
 

Rajesh

Do listen with headphones to see if audio is still very distorted.

These boards usually arrive with the BFO not properly adjusted. If the signal is coming too close or beyond the edge of the crystal filter passband this can cause significant distortion. Its the setting of the BFO that determines where the audio signal sits when it passes through the xtal filter.

A smaller thing, some of us modify the lm386 circuit for a better sound. This info is on the web. See la3za website,  but this is a minor aspect.

Check simple things before presuming its a circuit issue, it may not be.

Curt wb8yyy

 

Rajesh,

Always mention which version of Bitx/uBitx you are asking about!

Raj, vu2zap

At 30/06/2020, you wrote:
Hi,

Has anyone tried to connect LM386 instead of the stock audio chip. If I may request for the schematic.

Thanks

Rajesh
VU3RHU

rajesh huddar
 

Hi Curt,

Thanks for the revert.
I have tried to set the BFO to the best signal on 20m  but even then it is distorted.

There is also a 2Khan- ve shift.

I read on the forum a out a separate audio amp improving the audio quality. Hence thought about tinkering.

Some of the fellow hams in Mumbai which is my QTH also told me that the calibration also needs to be redone.

Am trying to locate a frequency counter to perform the 10mhz calibration my self.

Regard 

Rajesh
VU3RHU




On Wed, 1 Jul 2020, 07:41 Curt via groups.io, <wb8yyy=yahoo.com@groups.io> wrote:
Rajesh

Do listen with headphones to see if audio is still very distorted.

These boards usually arrive with the BFO not properly adjusted. If the signal is coming too close or beyond the edge of the crystal filter passband this can cause significant distortion. Its the setting of the BFO that determines where the audio signal sits when it passes through the xtal filter.

A smaller thing, some of us modify the lm386 circuit for a better sound. This info is on the web. See la3za website,  but this is a minor aspect.

Check simple things before presuming its a circuit issue, it may not be.

Curt wb8yyy