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Kef Kube 2 Goes into standy

[email protected]

Established Member
I have just purchased the Kef 2003.5 package and the Sub keeps going into standby. The sub itself does not have a selectable auto standby mode and just has an on/off switch. The amp its connected to is the sony str 2400 and i have looked through its menus but cannot see anything that would cause the sub to go into stand by.

Anyone any ideas?

Thanks

wolfy!!!
 

dalehead

Established Member
Hi

I can't help specifically with the Kube, but I have the 3005SE speaker package, and hope the following might help:

  • Does this happen with all your sources?
  • Does this happen with true 5.1 signals or with processed signals?
  • Does it happen at all volume levels?

I notice that if I'm listening to regular tv through a stereo signal (i.e. not receiving a discreet .1 channel), and I'm listening at moderate volumes, my Sub will regularly turn itself off (light goes red instead of blue). However when watching Blueray/DVD/Xbox360 etc with a 5.1 signal, it remains on all the time.

I suspect it goes into power saving after a period of not receiving anything to do (which makes sense), and on low volumes, my amp just isn't sending anything to the Sub.

If its doing it in other situations of course, then its a different story.

My sub quickly turns back on when the volume is increased, or there is some base to handle.

Not sure that helps, but good luck !! :)
 

Crustyloafer

Distinguished Member
1) Make sure all your speaker are set to small. This will ensure there is plenty of audio being redirected to the subwoofer and will protect your satellite speakers from damage.

2) Turn the volume control on the sub down a bit and increase it on the amp's settings to compensate. This will ensure that a slightly higher voltage signal is sent to to subwoofer and will reduce the chance of it going into standby.
 

[email protected]

Established Member
Thanks to both of you for the replies, i must admit i was a bit confused as to why the Kef instructions said set the Sub to full volume when calibrating with the amp yet the sony manual said set to half volume.

With your help i will reduce the sub volume down to half and then re calibrate.

Regarding movies ETC you may be right as i have only noticed it switching off when watching sky channels that do not output in 5.1. I will test some more after calibrating.

Thanks again

Wolfy!!!!
 

Lightning01

Novice Member
Hi,

as I haven't found anything else useful on the web how to get rid of the annoying standby on a KEF KUBE2 I reversed the Preamp PCB to the point to understand how the standby function is implemented. Luckyly it is built with discrete parts, mainly one dual channel OPV (4560 - i.e . http://www.futurlec.com/Datasheet/ROHM/BA4560.pdf). Channel two is receiving the input signal, which is amplified, rectified through d101 and finally charges a large capacitor (C159) on the oposite site of the PCB. This CAP in turn is then fed into the positive input of channel one on the OPV which is used as comparator. The voltage divider +15V/R161(47k)/R125(1k5)/GND creates a midpoint Voltage of around 0,63V and is used as the negative input. Once C159 discharges (through R148) below this Voltage the output of the CH1 on the OPV goes negative (to -15V as there is no feedback) and activates the standby. To prevent this from happening one only needs to make sure C159 stays charged at all times. I have achived this by connecting a 33k resistor and two 1N4148, all three connected serially to +15V and the positive side of the CAP (the solderpoint above Label U111). Additionally I have added a little switch so I can enable and disable the auto standby function.

Attached are a few pictures of my modifications.
Circuit:
upload_2015-2-8_21-1-16.png


upload_2015-2-8_21-2-0.png


IMG_20150207_161217.JPG


upload_2015-2-8_21-3-54.png
Schematic-Overlay.jpg
 

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