Using NAD c298 in bridge mode

[My adventures in stereo]

I am running a bookshelf speaker sub system
My stereo amp is currently a single NAD c 298, with minidsp SHD for dsp & preamp duty
Three SVS PB 2000 Pro's, eq'ed through the minidsp, provide the bass
Ever since picking up the NAD c 298, I have been wanting to try it in in bridged mono mode
Kal Rubinson, had mentioned here that he was happy with the NAD C 298 in bridged mode
I have felt the need for more headroom, especially with Vinyl playback

I have a bunch of bookshelf speakers
The latest are a pair of Mofi Source point 8's
Also have Revel M126 BE & Focal 906 speakers

My previous trial at bridged mode was with a pair of Parasound A 23 & was not too impressed with that
Everything sounded louder but also noisier

Anyone tried the NAD C298 in bridged mode, would love to hear from you
Also general discussion on bridging welcome

 

[audio_tony]

For stereo, you'll need two amps for bridged mode. I presume you realise that?

 

[My adventures in stereo]

Yes, just ordered a second

 

[staticV3]

To use bridged mode on the C298, you'd have to purchase a second C298.
Quite the investment considering that improvements are not guaranteed.

Also, NAD recommends load impedances of ≥8Ω when in bridged mode.

That disqualifies the M126Be and Aria 906.

 

[My adventures in stereo]

Stereophile had measured in bridged mode at 4 ohms " measured a clipping power of 880W into 4 ohms"

 

[pjug]

I have felt the need for more headroom, especially with Vinyl playback

Are you sure you are not just arbitrarily funneling some want for change into this direction? I would try to measure peaks for a case where you think you don't have enough power and see if they are anywhere near clipping (I think about 55 volts for the C298?). If you don't have an oscilloscope maybe that is where you should funnel a desire for doing something and purchase one. At least that's what I would do.

 

[Verig]

How much does your riaa output? Perhaps just too low preamp gain in that minidsp input?

 

[DVDdoug]

I have felt the need for more headroom, especially with Vinyl playback

You've already got enough power to burn-out the speakers! (I couldn't find the specs for the Focals but I'm pretty sure they aren't rated for your full amplifier power.)

Speaker power ratings are complicated and "statistical". (Although manufacturers don't always follow the standards.) A 100W speaker is supposed to handle regular program material from a 100W amplifier that's not clipping. When you drive an amplifier into clipping the peaks are limited but the average power goes-up, and harmonics are created which can damage the tweeter. You can also fry a 100W speaker with continuous 100W test-tones, and the tweeter can't handle as much power as the woofer.

There's a popular myth that clipping is worse than an over-powered amplifier. But you can fry a speaker either way and the higher power amplifier is actually more dangerous. Plus, you're more likely to turn-down the clipping amplifier if you hear distortion.

My previous trial at bridged mode was with a pair of Parasound A 23 & was not too impressed with that
Everything sounded louder but also noisier

Bridging makes 6dB more gain which increases the signal and noise by 6dB. That doesn't hurt the signal-to-noise ratio but the noise is more noticeable during silence. Turning-down the amplifier gain will reduce incoming noise (from a vinyl record and preamp, etc.) but any noise generated by the amplifier itself will still be 6dB worse.

 

[levimax]

While bridging amps can seem like a good idea at first glance when you factor in added distortion, noise, and especially reduced ability to handle complex or low impeadance loads it is almost always a better idea to get a more powerful amp.

 

[My adventures in stereo]

Got the 2nd NAD C298 today
I am really enjoying the additional headroom between 3-6 db depending on the recording
There is not a lot of info online on using these amps in bridged mode, other than the measurements provided on stereophile
Again have to thank Kal Rubinson, for his feedback after using them in bridged mode.

A few tips on setting up in Bridged mode for the NAD c298
You have to use the left channel only, for usage in bridged mode
The wiring for the speakers is unusual, you have to connect to the + on the left and negative blue terminal on the right
Also switch to bridged mode, physically flip the switch
There is a helpful blue light which comes on to indicate the bridged mode is engaged
using maximum output vs the fixed mode, yielded best results for me

The bass was tighter and quite enjoyable even without the subs
It is dead silent, no additional noise or hiss noticed

The minimal impedance for my speakers
Focal 906 4.8 Ohms
Revel M126 Be 4.8 Ohms
Mofi source Point 8 6.4 Ohms

I am planning to try them all, will update on how they sound

 

[My adventures in stereo]

Tried the Revel M 126 Be today
Very happy with the result
Plays effortlessly, 3 db of extra headroom, dead silent
Listening to on every street, Knopfler's guitars sound so dynamic !!

did a recording

 

[pogo]

The NAD bridge mode is really something special: Link