- Support for 4x20 LCD Display and large number display
- Brightness and contrast adjustment with remote
- (OPUS/Wolfson WM8741) DAC volume control: remote and rotary encoder
- (OPUS/Wolfson WM8741) DAC random filter selection 1 to 5 with remote
- (OPUS/Wolfson WM8741) DAC upsampling selection (L, M, H -this is the OSR setting)
- I2C level shifting (5V to 3.3V)
- Optimized power-up sequence

Wednesday, June 24, 2009

More on Volume

In the latest code, I've fixed the volume values I used to program the WM8741. Previously I mistakenly used 0.25 dB as the smallest interval whereas it is .125 dB the smallest interval, so my volume readings were twice the actual value.

Also I did not see the need to use an interval of less than 1 dB because it is already not very discernible a difference of 1 dB.

Now, the typical listening level is above -50 dB, and mostly in the -30 dB to -15 dB. Therefore above the -48 dB at which point you will start experiencing (theoretically) some loss in information due to the nature of digital volume control.

I also got a response from Wolfson about how the volume control is implemented: Basically input less than 24 bit is padded to 24 bit, input that is 25 to 32 bit is reduced to to 24 bit with dither and the volume control is applied at the next stage.

1 comment:

Anonymous said...

Thanks for the info, i'm building an integrated wm8741 + ucd amp and I was hoping that the DAC's built'in volume was truly 24 bit. Sounds great !