Using Two Nad C268 power amps with sub-woofer

Hughmoz

Novice Member
This was a conversation already happened recently, but I have another question. I am using a Denafripps Venus 1 DAC with a Naim 5i onto Kef LS50 speakers with an MJ Acoustics Pro 50 Mk 3 sub-woofer.

A friend has interested me in getting a fuller sound stage using two Nad 268 power amps using a Rotel RC03 pre-amp.

The issue seems to me that using the power amps in bridge mode ramps up the voltage and causes a floating earth, which is bad for the MJ Acoustic sub-woofer as, there is a risk of damaging the Sub-woofer electronics unless you use an interface, which is another £176 from MJAcoustics as, they do an integrated one to use for this situation.

Has anyone any experience of this please? Part of me thinks, shall I just keep my Naim 5i with my existing sub-woofer set up and forgot all the shenanigans of setting up new amps etc., in my snug, :)
 

wine man

Active Member
Why not use the spare pre out from the Rotel amp to connect the sub? This removes any complications with the new power amps.
 

Jules Tohpipi

Well-known Member
This was a conversation already happened recently, but I have another question. I am using a Denafripps Venus 1 DAC with a Naim 5i onto Kef LS50 speakers with an MJ Acoustics Pro 50 Mk 3 sub-woofer.

A friend has interested me in getting a fuller sound stage using two Nad 268 power amps using a Rotel RC03 pre-amp.

The issue seems to me that using the power amps in bridge mode ramps up the voltage and causes a floating earth, which is bad for the MJ Acoustic sub-woofer as, there is a risk of damaging the Sub-woofer electronics unless you use an interface, which is another £176 from MJAcoustics as, they do an integrated one to use for this situation.

Has anyone any experience of this please? Part of me thinks, shall I just keep my Naim 5i with my existing sub-woofer set up and forgot all the shenanigans of setting up new amps etc., in my snug, :)

Absolutely about the warnings. Wiring a pair of bridged amps into the high-level input of the sub will cause a loud bang and burning smells from the power amps. Don’t try it.
 

Hughmoz

Novice Member
Why not use the spare pre out from the Rotel amp to connect the sub? This removes any complications with the new power amps.
Thanks for your suggestion, however, that would only provide one channel. I think now that I have spoken to MJ Acoustics again I will get an MJ Acoustics high density interface. They make up cables from the outlets, which in my case will be the speakers as, there are no sub-woofer outlets on the Nad C268's and that gives one a positive and negative from both speakers into the interface and then onto the sub-woofer with a dedicated plug into the sub-woofer.
 

wine man

Active Member
Sorry if I'm missing something.. I used to run a decent Monitor Audio sub from spare pre outs on my Audiolab preamp. It was simply a long 2 channel phono to phono lead, the sub had stereo inputs. It worked perfectly, it had to as the MA didn't have any other inputs.
 

Hughmoz

Novice Member
Sorry if I'm missing something.. I used to run a decent Monitor Audio sub from spare pre outs on my Audiolab preamp. It was simply a long 2 channel phono to phono lead, the sub had stereo inputs. It worked perfectly, it had to as the MA didn't have any other inputs.
I am using one pre-out already so, there is only one em,aininh, which will only do one channel..
 

wine man

Active Member
Ah, I see your problem - both of my subs, the MA and now a BK have double phono inputs. If it were me I would abandon the idea of two power amps and stick with a high quality single stereo power amp.
 

Mark.Yudkin

Distinguished Member
If the only thing preventing your running a stereo phono lead from the amplifier's stereo pre-outs to the subwoofer is the lack of stereo inputs on the subwoofer, you could just use a Monacor SMC-1.
 

nielsoc

Standard Member
Instead of getting two C268's, might I suggest one C298. I believe this will gain a more precise result while still having a lot of power at your disposal. I'm still not sure about attaching a common ground device like your sub because I have read that these Class D amplifiers do not like that.
 

Hughmoz

Novice Member
Instead of getting two C268's, might I suggest one C298. I believe this will gain a more precise result while still having a lot of power at your disposal. I'm still not sure about attaching a common ground device like your sub because I have read that these Class D amplifiers do not like that.
I have abandoned this project and sold Nad's now. I am going run everything through my Naim Nait 5i, but use the Rotel RC-03 as the phono pre-amp as it is very clear, and far far better than the Rega Fono Mini A2D Mk2 pre-amplifier.
 

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