Saturday, June 14, 2014

Sonos Line-In levels

I use the line-in feature of my Sonos system more than anything else.  It's incredibly convenient and sounds good.  The main things I listen through Sonos line-in are my two FM tuners (Kenwood KT-6040 and Pioneer F-26) which are set to Jazz/Indie KRTU and Classical KPAC.

But I often wonder about setting the input level.  Unfortunately Sonos provides no visible feedback of clipping through the line input.

Well here is what Sonos Support says about the line input levels.  Interpolating for levels 3-5 and 7, here are the max input levels as best I figure them now:

2.2V  Level 1 (low)
2.0V  Level 2
1.8V  Level 3
1.6V  Level 4
1.4V  Level 5
1.2V  Level 6
1.1V  Level 7
1.0V  Level 8
0.8V  Level 9
0.6V  Level 10

My Kenwood KT-6040 specs say output is 0.8V at 100% FM modulation.  Since modulation can go a bit higher than 100% in practice, this corresponds to a max output of about 1.0V, which was a standard line level before CD players were introduced (CD players have output of 2.1V).  Allowing a further bit of headroom, I've just set the Sonos to Level 5 which is 1.4V.  Previously I had been using Level 1 or 2, which is a waste of dynamic range.

It often takes a few minutes to get used to higher resolution, and that was true when I changed from Level 2 to Level 5.  But there is no audible clipping or harshness, just more information.

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