做USB声卡，能识别  采样率 改为48000 hz  

TIM_TimeBaseStructure.TIM_Period = 1500;
  TIM_TimeBaseStructure.TIM_Prescaler = 0x00;    /* TIM2CLK = 72 MHz */
  TIM_TimeBaseStructure.TIM_ClockDivision = 0x0;
  TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
  TIM_TimeBaseInit(TIM2, &TIM_TimeBaseStructure);


void TIM2_IRQHandler(void)
{
  if (TIM_GetITStatus(TIM2, TIM_IT_Update) != RESET)
  {
    /* Clear TIM2 update interrupt */
    TIM_ClearITPendingBit(TIM2, TIM_IT_Update);

    if ((Out_Data_Offset < In_Data_Offset) && ((uint8_t)(MUTE_DATA) == 0))
    {
     DAC_SetChannel1Data(DAC_Align_8b_R,Stream_Buff[Out_Data_Offset]*10);  
        //TIM_SetCompare3(TIM1, Stream_Buff[Out_Data_Offset]);
      Out_Data_Offset++;               
    }
       
  }
}

能出声，但是噪音很大听不清声音，没有加滤波  直接管脚输出 耳机  。一定要加滤波才能听清声音吗？