Help: ideas about speaker cut out

[Jhannah]

I have a whole home system
Source is non amplified sonos
Feeds to a Niles si-1260 12 channel amp x 60w
20-40 foot runs of 14awg structured speaker cable
Crs3 six in ceiling speakers-- 8 ohm
Each channel powering a single speaker

With this setup, I find I need a minimum volume to be high for the system to work. If I put on music at a low background level that I find pleasant, some channels will seemingly arbitrarily cut in and out. So suddenly the speakers in the kitchen are still playing but not the dining table. Then the dining table comes back in when the source material gets louder.
If I turn up the volume setting, they will stay live, but the minimum necessary is a bit too loud for pleasant background.

I have played with the gain setting on the various channels, to no improvement.

I'm at a loss! Any ideas?

I tried changing the amp switch on from music sensed to continuous with no effect.
I looked up minimum awg for speaker runs on this site but it seems like I should be fine.
I tried switching out sonos box to no improvement.

Any other suggestions? Thank you very much.

 

[Ponzio]

check ur speaker connections at both ends to make sure they're secure. i would re-wire them to be sure. banana plugs will sometimes fail; rarely but it can happen. then verify that the amp is not the source of the problem.

 

[Jhannah]

Thanks will do that now. Maybe will try ditching the bananas and wiring direct.

 

[lovinthehd]

The volume is controlled by the Sonos for all speakers simultaneously?

 

[Jhannah]

Yes. Volume is controlled via the sonos unit digitally. The amp has no volume.

The kitchen / dining / living is one zone. It has one sonos pre amp box. That feeds into a master input into the Niles amp. On each channel of the Niles amp you can either select this master input or hook one up directly. In the kitchen/ dining/ living zone I am using the one sonos box to the master input and selecting it to all of the channels, with the volume adjusted by the sonos pre amp box.

 

[Jhannah]

If anyone cares, I think I figured it out.

Basically I think the use of a pre-amp sonos unit connected via RCA to an amplifier is a bad architecture.

I think the cause: by controlling the volume in the pre-amp unit -- dropping the pre-amp signal level to lower the volume -- it just drops too low at low volumes and the amp gets no signal. I think the design of this amp was to have inputs with a constant signal level (i.e. a CD player, etc.), and control volume through a wall mounted rheostat on the amplified signal. If it had an optical signal input, maybe it would work, but this setup does not with this particular amplifier.

I think the easy fix for me is to replace the sonos pre-amp boxes with amplified sonos boxes, one per speaker pair. Since they presumably do all this in digital, it will work -- and I came to this by experimenting with a sonos connect:amp I had laying around which works fine at low volumes. I think I did the Niles amp originally under the idea of a higher quality audio, but in practice, ceiling speakers are pretty background anyway, and not being able to operate at low volumes is a much bigger problem than slightly worse audio, in this context.

Thanks for the suggestions, the idea of isolating out the amp led to this insight. Cheers.