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Forum Index : Microcontroller and PC projects : PicoMite: driving a small speaker

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matherp
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Posted: 05:23pm 25 Mar 2023
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  Quote   I still think for direct drive of a speaker we are better off simply buffering it for more current drive a


My argument about this is only the inability to have a common ground for the speakers which means we can't use a 3.5mm jack socket. Otherwise there are lots of good solutions specifically LM4871
 
thwill

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Posted: 05:23pm 25 Mar 2023
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  mozzie said  I'll have to sort out some music to try to see how it does.


Try: https://github.com/thwill1000/mmbasic-lazer-cycle/blob/main/src/spmusic.bas

Best wishes,

Tom
Game*Mite, CMM2 Welcome Tape, Creaky old text adventures
 
Mixtel90

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Posted: 05:25pm 25 Mar 2023
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This is why I ordered some. I think it will be possible to drive phones, simply by ignoring the output from the second op-amp and capacitively copuling from the output of the first. The fact that you only get half power into headphones doesn't matter - you don't need it. :)
Mick

Zilog Inside! nascom.info for Nascom & Gemini
Preliminary MMBasic docs & my PCB designs
 
matherp
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Posted: 05:37pm 25 Mar 2023
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  Quote  Try: https://github.com/thwill1000/mmbasic-lazer-cycle/blob/main/src/spmusic.bas


Need it using PLAY. In your code the PWM frequency varies which means you can't have a filter that matches. I hit the issue trying the "entertainer"
 
thwill

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Posted: 05:45pm 25 Mar 2023
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  matherp said  
  Quote  Try: https://github.com/thwill1000/mmbasic-lazer-cycle/blob/main/src/spmusic.bas


Need it using PLAY. In your code the PWM frequency varies which means you can't have a filter that matches. I hit the issue trying the "entertainer"


Qué?

It is using PLAY SOUND providing you don't change the PLAY_MODE constant from the default 0 isn't it?

Best wishes,

Tom
Game*Mite, CMM2 Welcome Tape, Creaky old text adventures
 
Turbo46

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Posted: 05:46pm 25 Mar 2023
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  mozzie said  I'll have to sort out some music to try to see how it does

Try it without the filter too please.

It might be prudent to add a 220R before the bases of the transistors on the left hand side just to protect the Pico's output.

Bill
Keep safe. Live long and prosper.
 
Turbo46

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Posted: 05:55pm 25 Mar 2023
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  Tom said  I am not intending to provide an audio jack plug on the build, it's the speaker or nothing.


Bill
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matherp
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Posted: 06:05pm 25 Mar 2023
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  Quote  It is using PLAY SOUND providing you don't change the PLAY_MODE constant from the default 0 isn't it?

Sorry, opened the link, first thing I saw was "setpin gpx, pwm" and gave up
 
Turbo46

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Posted: 06:06pm 25 Mar 2023
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  Volhout said  If you want 20Hz...20kHz

Tom doesn't need 20Hz...20kHz.

Bill
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matherp
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Posted: 06:17pm 25 Mar 2023
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  Quote  Tom doesn't need 20Hz...20kHz.

  Quote  I am not intending to provide an audio jack plug on the build, it's the speaker or nothing.

  Quote  etc.


This is all understood but it would be great to find a generic solution that can be used by everyone rather than multiple application specific variants.
 
thwill

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Posted: 06:18pm 25 Mar 2023
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  Turbo46 said  Tom doesn't need 20Hz...20kHz.


It's OK Bill, this conversation has a life of it's own now. If I've learnt anything, it is don't talk about audio with old hi-fi enthusiasts .

Best wishes,

Tom
Edited 2023-03-26 04:21 by thwill
Game*Mite, CMM2 Welcome Tape, Creaky old text adventures
 
Turbo46

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Posted: 06:23pm 25 Mar 2023
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Sorry Tom, I though this post was supposed to be about your Tomboy project.

Bill
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Mixtel90

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Posted: 06:30pm 25 Mar 2023
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I've put a couple of 6L6s, some octal bases for them and an odd output transformer in the post for Tom. The 6L6s might be a bit heavy on batteries though.
Mick

Zilog Inside! nascom.info for Nascom & Gemini
Preliminary MMBasic docs & my PCB designs
 
lizby
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Posted: 06:30pm 25 Mar 2023
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  thwill said  this conversation has a life of it's own now


I had hoped to learn something from this thread and the previous one, but I'm afraid it's back to the PAM8403 for me:



Adequate and convenient is all I'm looking for. Kudos to those seeking something better.
PicoMite, Armmite F4, SensorKits, MMBasic Hardware, Games, etc. on fruitoftheshed
 
Mixtel90

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Posted: 06:35pm 25 Mar 2023
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Just use a potential divider before the input of the PAM module. You probably need to drop the signal to less than a volt. The volume control will take it up or down from there. If you do that you can run the PicoMite with PLAY VOLUME 100,100 to get best quality without overloading the PAM. The resistors will give you better control over the volume.
Mick

Zilog Inside! nascom.info for Nascom & Gemini
Preliminary MMBasic docs & my PCB designs
 
mozzie
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Posted: 06:51pm 25 Mar 2023
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G'day All, if there is a better way of opening a can of worms than starting a discussion on audio / hifi then I'm yet to find it  

Agreed Mick, the inductor really should be air cored and with low series resistance, its going to be bigger and more expensive than other complete solutions  

Peter's generic solution would be great but it's going to be hard to find because we all have different expectations / output requirements / power supplies available / space available and battery life concerns. Connecting earphones to my circuit would certainly do ear damage due to the residual 40khz carrier  

Thanks Tom, I downloaded the file and it plays on the Pico with the last circuit I published, I'll make a recording and try to upload. I see what you mean by the "ticks" between notes.

Bill, the input side of the emitter followers are virtually open circuit, they have a current gain of 100+ and the output of the Pico swings 0-3.3v with very little loading so I'm not sure what the 220R resistors would be for, T5 in the bridge circuit requires a base resistor.

Regards,
Lyle.
 
Turbo46

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Posted: 06:57pm 25 Mar 2023
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  Quote  I'm not sure what the 220R resistors would be for

Just to protect the Pico if the transistor circuit fails. Belt and braces.

Bill
Keep safe. Live long and prosper.
 
thwill

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Posted: 07:33pm 25 Mar 2023
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  Mixtel90 said  I've put a couple of 6L6s, some octal bases for them and an odd output transformer in the post for Tom. The 6L6s might be a bit heavy on batteries though.


Unless you are jesting Google says you are sending me some valves ???

If that's the case then thanks, but .

Best wishes,

Tom
Edited 2023-03-26 05:34 by thwill
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stanleyella

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Posted: 07:37pm 25 Mar 2023
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while waiting for the 4.7mH chokes, I looked for caps for the filter in the manual.
2.7nF will be 2.2nF in parallel with two 1nF in series,
68nF will be 47nF and 22nF in parallel,
33nF will be 22nF and 10nF in parallel.
These are the nearest values I have. I can't find 2.7nF on ebay.
Looking forward to trying sound first time.
 
hitsware2

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Posted: 07:49pm 25 Mar 2023
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  lizby said  
  thwill said  this conversation has a life of it's own now


I had hoped to learn something from this thread and the previous one, but I'm afraid it's back to the PAM8403 for me:



Adequate and convenient is all I'm looking for. Kudos to those seeking something better.

99 % of the quality of the sound comes from the speakers , not the electronics .
my site
 
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