Wrong ASIO input signal frequency

[AlexK]

I have a signal generator, it delivers a saw signal ~4731 Hz. It is measured with oscilloscope. Signal goes to ASIO audio interface (48000 samplaes rate). Signal is recorded with Riper, Riper shows ~4742 Hz, that's OK.

I do the same with small test program:

  private static readonly int CONFIG_SAMPLE_RATE = 48000;

  public static void DemoAsioSingleChannel5(AsioOut asioOut, int sampleRate)
  {
      float[] samplesArray = new float[sampleRate * 2];
      WaveFormat waveFormat = new WaveFormat(sampleRate, 24, 2);
      using WaveFileWriter writer = new WaveFileWriter(@"c:\temp\output.wav", waveFormat);

      asioOut.InitRecordAndPlayback(null, 1, sampleRate);
      asioOut.AudioAvailable += OnAsioOutAudioAvailable;
      asioOut.Play(); // start recording

      Console.WriteLine("(press any key to exit)");
      Console.ReadKey();
      asioOut.Stop();
      asioOut.Dispose();

      writer.Close();

      void OnAsioOutAudioAvailable(object? sender, AsioAudioAvailableEventArgs e)
      {
          e.GetAsInterleavedSamples(samplesArray);
          writer.WriteSamples(samplesArray, 0, e.SamplesPerBuffer);
      }
  }

Then I open this file in Riper and measure frequency: 9607 Hz!

+/-% doesn't matter, but difference in this case is too big :-)

Can anyone tell me what I'm doing wrong here? Thank you!