Topics

Low audio v6 candidate solution #bitx20


Kelly Mabry
 

I'm currently working on the low audio problem for my v6.  I see that an audio amp is used to drive the speaker. The existing LM386 amp is delivering terribly low audio. I am straining  to hear the radio.. i am thinking of using another between the speaker terminals and the speaker. This solution could very well be superceded by powered speakers, but would be more expensive.  And for using this portable as I plan to, it is better to be self contained, I think. Suggestions? Comments? Thanks in advance!

Kelly KD5AJ 


Curt
 

Kelly

The lm386 is not known to drive speakers well, and the ubitx intentionally implements less total gain to give better performance.  

When operating portable wouldn't the birds and critters, and other people enjoying outdoors prefer you use headphones?

Solutions to a self contained speaker involve adding a more powerful audio amplifier. There are boards out there, or if you find a cheap amplified speaker well use the stuff inside. Note more audio into speaker will drain the battery faster. 

As I do CW I did add a adjustable nescaf audio filter to mine. If you add something like it's you will need another audio stage anyway.

Curt


Evan Hand
 

Kelly,

I have been working on a v6 for a friend.  the audio was not very loud, but more than enough for use in my basement shack.  I have another v5 that has the same LM386 audio amp.  I bought a case with a bunch of aux kits that were included.  One of those was an audio amp.  I did install that andwas able to drive the speaker to a higher volume.  The reason for bringing this up is that I had audio instability that would go into oscillation with the LM386 gain as set by the bypass cap on the gain pins.  I had to lift pin 8 of the LM386, this drops the gain from 200 to 20, and then fed that into the audio amp module.  I also added the "bass boost" modification that is in the LM386 tech notes of the datasheet.


https://www.ti.com/lit/ds/symlink/lm386.pdf?ts=1614168879753&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FLM386

Have fun with the mods!  It is one of the key features of this rig!
73
Evan
AC9TU


Kelly Mabry
 

Curt,
Astute as always sir. I like the nescaf idea. Thank you!

Kelly KD5AJ 


_Dave_ AD0B
 

I have seen uBitx with weak audio and found that it didn't have the the bfo tuned correctly 
--
73
Dave
ADOB
Raduino bracket and Ham_Made_Keys


Kelly Mabry
 

Evan thank you for the info!  This is going to be fun, I know. I feel confident that the mods will do well.  

73, 
Kelly KD5AJ 


Richard Spohn
 

Except that you can't get a new NESCAF...and if you do get a lead on a NESCAF, can you PLEASE let me know!!!--Rich WB2GXM

Sent from my MetroPCS 4G LTE Android device

------ Original message------
From: Kelly Mabry
Date: Wed, Feb 24, 2021 11:32 AM
Cc:
Subject:Re: [BITX20] Low audio v6 candidate solution #bitx20

Curt,
Astute as always sir. I like the nescaf idea. Thank you!

Kelly KD5AJ 


Kelly Mabry
 

Hi Dave, I checked the bfo with the bfo tuning aid, and it falls dead on between 300 and 3000 as farhan shows in his video.  So I'm thinking lm 386 is not driving the speaker well. I borrowed a set of powered speakers and heard k4c @ 7174.00 plain and clear. This radio feels fine now, all I need is my new antenna system, I should be fine.

Note: successful upgrade to  Reeds R1.5.1 software.  Note, I had to use the "old bootloader" option in the Arduino IDE, before it would communicate with the raduino. 


Kelly KD5AJ 


_Dave_ AD0B
 

Hi Kelly
Glad you got working to  your satisfaction. A 386 might only put out a half of a watt. I have the bfo set for the sound that I hear the best. It isn't the most even type of sound level but it is what I can hear the best. Makes many station sound like they are DX,

Efficiency of a speaker can vary a lot too. A speaker attached to inside of a cabinet can sometimes make for a poor "resonator" as it were. On a couple of my ubitx radios I put in a small printed cabinet. If i have a quiet issue I get out all the salvaged speakers that might fit the box and try them out
73
Dave
ADOB
Raduino bracket and Ham_Made_Keys