Wav from SD Card - reproduction very very poor

hi there - hoping can i've been struggling while.  couldn't joy out of sdcard module, i'm running ethernet shield micro sd card.

i have wav file formatted 8-bit unsigned, 8000khz, mono. (using http://audio.online-convert.com/ tool).

connected speaker between pin 10 , gnd (code below)

when load sound play speaker, best @ volume "4".  if volume sounds clips horribly.  if lower volume can hear flickering rumble (rumble replicating flashing led on ethernet card, prob around 6hz).  also, if connect powered pc speaker rather blank speaker, sound goes entirely robotic sounding mess causes sound fail entirely.

i can't believe else getting, must doing fundamental wrong - got ideas?  frustrating me...

the 2 main issues are;
quality of unpowered output - rumbling interference @ low vol, bad clipping above 5
not working powered pc speakers - sounds random digital signal

btw  - have tested pc speakers , work fine playing same sound file straight pc.

#include <tmrpcm.h>

#include <spi.h>
#include <sd.h>

char mychar;
const int cs_pin = 8;
tmrpcm tmrpcm;


void setup() {
  tmrpcm.speakerpin = 10;
  tmrpcm.setvolume(5);
  // put setup code here, run once:
  serial.begin(9600);
  serial.println("initializing card");
  pinmode(cs_pin, output);
  if(!sd.begin(cs_pin)) {
    serial.println("card failure");
    return;
  }
  serial.println("card ready");
  tmrpcm.play("1.wav");
  serial.println("done");

}

void loop() {
}


regards,
mark

have fitted reconstruction filer on output, 1k series resistor followed 10nf ground.

quote

i have wav file formatted 8-bit unsigned, 8000khz, mono.

when recorder sample did filter sound no greater frequency 4khz got through? need prevent aliasing, sounds horrible.

this sort of quality got same technique not same libiary. https://youtu.be/wshvfcrfpwu
it takes sample code out of program memory.

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