Question BK sub and class D amp - please help

eastsoutheast

Well-known Member
Hi Fellow Members


I have just purchased a BKXXLS400 which I want to connect using the high level leads to my power amps. My problem is I just changed to class d digital power amps and the BK manual advises many class d amps do not like having the black/ground lead connected hence my problem.

I found instructions on Rel’s website that suggested floating (wrap in insulation tape) the black cable which should work without hum or issue for 70% of cases. I tried this and it didn’t work, lots of hum so turned off. There was further reference suggesting using a phone lead connected between the processor and sub which would provide the ground. Tried this but whilst the hum went the sub received no signal.

Has anyone successfully connected a BK sub via high level to class d amps and if so could you pleas,W advise how?

Thanks
Brian
 

Ultrasonic

Well-known Member
I would advise that you contact BK for advice. I have a feeling all Class D amps may not behave the same here and so you want to careful about what advice you follow. Get this wrong and you may damage something.
 

MaryWhitehouse

Well-known Member
I would advise that you contact BK for advice. I have a feeling all Class D amps may not behave the same here and so you want to careful about what advice you follow. Get this wrong and you may damage something.

Which is what they say in manuals :)
 

eastsoutheast

Well-known Member
Thanks, was hoping someone had been in the same position albeit appreciate I didn’t reference the amps!

XTZ P2-300’s with one connected to each speaker just in case anyone has tried these with a BK or Rel sub.

Thanks
Brian
 

AndreNewman

Active Member
If these amps are being driven from an AVR or preamp and volume control is done from there. Save yourself the hassle and risk of making the amp unstable or blowing it up by plugging the line level input that drives the XTZ in to the sub as well, simple T cable splitter should be fine.

Edit: for clarity, I mean use the phono connection.

I'm an Electronics Engineer and that's what I would do.
 

eastsoutheast

Well-known Member
Hi Andrew, just so I understand correctly. I have an xlr output from my processor feeding one XTZ amp in mono configuration for each of my front three speakers. My reason for using high level was music only and I thought the reason the high level lead connected to each channel (front left and right) was so the sub received all stereo info. My sub has a pair of phono inputs (red and white), should I split both xlr outputs from my processor and connect to the two phono inputs on the sub??

Many Thanks
brian
 

AndreNewman

Active Member
Hi Brian,

The XTZ is phono not xlr input, right? So you must have an xlr to phono lead or adaptor for the amp already. The two sub inputs are exactly for this purpose, they will mix the two inputs together for mono. So split the phono at the processor or at the amp or the sub whatever is most convenient and feed left and right separately to the sub.

Class D amps are really dependent on a well behaved load so at the slightest sign of problems with the high level I would run away and use the much simpler low level inputs if you can.

I just saw you said front three speakers, there won't be any center channel fed to the sub if you connect at high level or low level as there are only two inputs, low or high. Were you trying to connect three channels to the high level? That would explain the problems.

Doesn't your processor have bass management? Would be far easier and more capable if you fed a bass managed signal to the sub.
 

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