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Pascal Hibon
2011-07-17, 10:04
My SB3 is connected to my TC Electronic Konnekt live http://www.tcelectronic.com/KonnektLive.asp by means of the coaxial SPDIF. I had my volume control set to fixed (100%). Iíve notice on several occasions that with certain songs there is a kind of distortion audible. Today I decided to have a closer look at what the possible cause could be. The TC Konnekt has a control panel and there Iím able to monitor incoming signals. The interesting thing is that with the volume control of the SB3 at 100% the SPDIF signal is hitting the 0 dB quite often as in the below example.

http://img37.imageshack.us/img37/2218/spdif.png (http://imageshack.us/photo/my-images/37/spdif.png/)

Especially new CDís today are recorded with high sound levels (reducing the dynamic range) but that could be a potential cause of the distortion Iím having with certain songs. As far as digital is concerned, 0 dB is the absolute maximum and this could be an explanation of what Iím seeing (or better yet, hearing). At least lowering the SB3 volume to between 84 and 90 seems to solve the distortion.
Does anyone have similar experiences with their SB connected to a DAC?

Phil Leigh
2011-07-18, 09:27
Are you using the TC as a DAC? - The problem is certainly within the TC or more likely whatever the TC is connected to. S/PDIF cannot "distort" or "overload" in the conventional sense, because there is nothing higher than 0dB so if the distortion goes away when you lower the volume it must be distorting in the analogue chain.

Pascal Hibon
2011-07-18, 09:39
Yes Iím using the TC as a DAC for my SB3.
The TC is a professional device that has very high headroom. Distortion is maybe not the correct wording. It is difficult to describe; maybe saturation is a better word. Vocals are usually the material where this Ďsaturationí is easiest to hear when it happens.

Iím struck by the fact that the signal output of the SPDIF is so high (with some songs). Iíll try to compare them with the original CD connected to the TC to investigate if there is a signal strength difference.

Phil Leigh
2011-07-18, 10:11
Yes Iím using the TC as a DAC for my SB3.
The TC is a professional device that has very high headroom. Distortion is maybe not the correct wording. It is difficult to describe; maybe saturation is a better word. Vocals are usually the material where this Ďsaturationí is easiest to hear when it happens.

Iím struck by the fact that the signal output of the SPDIF is so high (with some songs). Iíll try to compare them with the original CD connected to the TC to investigate if there is a signal strength difference.

Yes but what is the TC feeding its analogue output into? (I'm familiar with TC gear). Do you have all of the DSP functions of the TC (like the limiter etc) turned off?

Pascal Hibon
2011-07-18, 10:30
Yes, all DSP functions in the TC are off. There is nothing in the TC that is further amplifying the SPDIF signal. The TCís output is fed into a Cambridge Audio 840E preamp which should be able to handle it.

Phil Leigh
2011-07-18, 11:34
Yes, all DSP functions in the TC are off. There is nothing in the TC that is further amplifying the SPDIF signal. The TC’s output is fed into a Cambridge Audio 840E preamp which should be able to handle it.
My bet is that the TC output is slightly too hot for the Cambridge - all the evidence points to that. According to the manual the max output of the TC is +12dB...

Pascal Hibon
2011-07-18, 12:14
Iíll do some measuring to find out. Iíll report back with the results.

Pascal Hibon
2011-07-18, 14:03
Well, well, donít I feel stupid now... Canít believe I missed that one!
I did my measurements by running a WAV file with a 0 dB / 1 kHz sine wave signal through the SB3. The output of the TC is indeed way too high at 0 dB digital in. I lowered the TCís output stage so that it outputs 2 volts RMS at 0 dB which is about what most CD players do. That seems to work well now but Iíll do some more listening tests during the next couple of days.