My sansa clip + plays back with a frequency offset

 Hello everyone, I  got a sansa clip + as a christmas present, and being an electronics engineer and an avid hacker, I decided to subject it to a few tests I use to determine the audio quality of the device in an objective way. Most people would merely listen to the device through the headphones, and this gives only limited subjective information about how well the dacs and headphone amplifier are reproducing sound. I  created a binaural sine wave recording on my computer (using the freeware program SBAGEN ) with one channel having a 200hz  and the other channel a 207.8hz  tone (schumann resonance frequency).

   When I  played back and measured the left and right channel frequencies  coming out of my computer’s sound card using a radio shack 22-811 multimeter, they were correct. When I played the tone on a Muvo V100 player which I use as a reference, the frequencies were also correct. However, when I played the tone on the clip +, the frequencies measured 208.3 and 200.5 hz, a 0.5 hz frequency offset ! On the oscilloscope, my computer and the muvo were putting out very clean sine waveforms, but there seemed to be just the slightest amount of extraneous noise on the output of the clip. This 0.5 hz offset is comparable to a cassette player that has a motor that runs just a smidgen too fast, in other words the playback of the clip is slightly sped up.

    I know that this may seem like a small nitpick, and compared to all the other portable media players that I have tried, the sansa clip + has the best subjective sound quality.Also I did the same test with two chinese rk2608a rockchip players and they were incapable of even reproducing an undistorted sine wave, so no measurement was possible…

  Is this a hardware bug in the design of the codec, or could this be patched in the firmware? This might seem like a nitpick, but there are fanatical audiophiles out there who might consider this an issue!

This has been talked about for a long time. The pitch on the Clip+ is around 1/4% too fast. Very few people can actually hear this difference in blind ABX tests. The pitch error on the original Clip started out at 0.7% with the original firmware, which many people did hear. The 1/4% pitch error on the Clip+ is for practical purposes insignificant for most people.

@mroberts200 wrote:

  Is this a hardware bug in the design of the codec, or could this be patched in the firmware? This might seem like a nitpick, but there are fanatical audiophiles out there who might consider this an issue!

Its a software bug.  Its fixed in rockbox, so I guess if it really bothers you you’ll need to use that.  Personally I couldn’t notice a difference with actual music though. 

   I  think the reason Sandisk has not fixed this problem is because it is due to a bug in  sansa’s  vlsi custom chip design. The bug can be worked around by patching the firmware, but this would typically introduce other  problems, which unfortunately may end up being far more noticeable than a mere 0.25% pitch error. The cost of correcting the bug in the hardware design itself is probably too large for  it to make sense at this stage of the product’s life cycle.

  I  bought this player to experiment with brainwave synchronization, and particularly to listen to hemi sync files from the monroe institute and other sources. For binaural audio tones to have any effect, they must be listened to only on high quality audio playback equipment.Their effect depends on the brain perceiving a diffrence in pitch between two sinewave tones presented to the left and right ear.The monroe institute also uses proprietary and extremely sophisticated  digital audio processing techniques to supplement the binaural effect ;  these recordings have no effect if played on a cheap mp3 player, because all the extremely low level components of the recording are distorted or eliminated.

  The Sansa clip seems to be the lowest priced player with the capability to play this type of material. The pitch error sems to be irrelevant  because only the absolute difference in phase and frequency between left and right channels matter, the pitch error does not effect this in any way. The sansa clip + will now allow me to listen to these recordings without having to use the computer; none of the players I used before, including the muvo v100 gave very good results.

 Thanks, I have heard about the rockbox project.  I will check the latest versions of their software for the Sansa,  and I may do some further experimenting later this week.