NAD bridging help

Discussion in 'High-End Separates from Years Past' started by fr3d, Mar 14, 2019.

  1. fr3d

    fr3d New Member

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    Hello,I have a NAD 7150 amp and a NAD 2150 amp and a NAD 1240 Pre-amp and want to bridge the amps.with the pre amp.And add a Velodyne Sub.Many years ago I bridged two 3155's with a sub but cannot remember how to properly do this.Thanx for any help.
     

     

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  2. Bob

    Bob AK Subscriber Subscriber

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    if you bridge, then there are only two channels for the stereo, and the subwoofer (SW) needs
    to have its own amp and the ability to pass high freq or treble signals back out.

    so, the preamp outputs go to the SW and the treble gets fed back to the to remaining channels
    but you'll have a problem if the two power amps are not identical - the volume setting may be
    tricky if one amp is more powerful and/or different sensitivity than the other.

    your better bet is to get a crossover, use it to feed treble signals to one of the power amps,
    then feed the bass signals to the other amp which then has the SW hooked up.

    or simply with one pair of speakers use only one power amp and decide how the SW is
    hooked up (this depends on whether the SW has an amp and how it filters the signal)
     
  3. fr3d

    fr3d New Member

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  4. fr3d

    fr3d New Member

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    Thank you for your suggestions.The amps are the same(one has a tuner and one is a power amp.) It seems I used a y connector as I still have it.But still can't remember what to do with it. fr3d
     
  5. the skipper

    the skipper Amateur Curmudgeon Subscriber

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    What Bob is talking about is bi-amping, not bridging, but it will work, You won't gain power but it does have it's benefits. But, he is right that it does help if both amps are the same

    I don't have those particular units but, from my NAD 214 manual it says:

    0) Turn the power off.

    1) Flipping a switch on the back to put it into the bridge mode.

    2) You feed the mono signal into the left input.

    3) You connect the speaker to the right and left "+" terminals.

    Repeat the process for the other amp.

    It helps if the amps are the same,

    Be aware that a bridged amp will see the speakers impedance as one half it's rated impedance. That's to say it'll see an 8 ohm speaker as four ohms and a four ohm speaker as two ohms. Keep that in mind. I was advised by the people that sold me the 214 to not use my four four ohm Maggies with these amps in bridge mode.

    Assuming your Velodyne sub is a powered sub, you would connect it to the pre-amp's output. You do NOT want to use that "Y" connector to combine the right and left channels. Feed the two pre-amp outputs to the two line level inputs on the sub.
     
    Last edited: Mar 17, 2019
    Ds2000 likes this.
  6. Bob

    Bob AK Subscriber Subscriber

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    @the skipper : spot on.

    unless both amps are identical, bridging each means different
    sensitivity and volume levels for each channel. and if they are
    different then bi-amping solves more problems.

    I am still not sure how all this is hooked up - the preamp out
    if there's only one set (for both channels) to the SW then MUST
    pass back the signal to feed both amps bridged or not.

    so the SW must have high-pass filter OR the NAD preamp has two
    sets of preamp out. in the second case the SW is duplicating the
    low end signals going to the bridged amp's left and right channels.

    maybe OK if the search is for more bass. but there are issues of
    two sets of bass signals going through std speakers and a SW;
    standing waves, null/peak points. and ability to control bass
    volume on both set of speakers to balance the bass.
     

     

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  7. the skipper

    the skipper Amateur Curmudgeon Subscriber

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    Yeah, I don't know exactly what he's got in mind so I just stuck to the basics.

    Matching both amps is critical to successful bridging of two amps but, he said they are the same. So be it,

    As for the sub, be could easily use a "Y" splitter on the preamp out for each channel, sending one leg to the amp(s) and the other to the subwoofer's line level inputs. Having had a Velodyne sub, I can say that they do have variable crossover frequencies and level controls, as well as others one can kerfutz with

    The key thing to remember about subs is that and are intended to simply extend the main speakers lower range, not impede on their natural range, When properly adjusted, there is no great need for a high pass filter. That's how I did it with my Maggies, and other speakers as well..
     
  8. fr3d

    fr3d New Member

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  9. fr3d

    fr3d New Member

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    Thank everyone for their replies. Look I am trying to turn each amplifier(and they are perfectly matched)into a mono amp so that one amp drives one speaker and the other amp drives the other speaker(ohm walsh two's) and have my Velodyne Sub in the mix in the best way for sound quality. I am not looking for ungodly bass,just tight and natural. I am also a bit burnt(64) so I literally need a picture drawn for me as far as getting the two amps and the pre-amp and the subwoofer all hooked up properly.I tried to talk to some younger audio techs. about this but all they know is surround. fr3d
     
  10. the skipper

    the skipper Amateur Curmudgeon Subscriber

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    Remember, we can't see what you have so drawing a picture is out of the question. That, plus my skills in that area suck,.

    I tried to simplify the steps involved as simply as possible in post five. If that doesn't help you, well, then I have nothing more I can offer. ...sorry.
     
  11. fr3d

    fr3d New Member

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    Thanks Skipper.Since my pre-amp does not have a dedicated SW hook-up what about that ?
     

     

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  12. the skipper

    the skipper Amateur Curmudgeon Subscriber

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    I've already covered this twice. Once in each of my two posts,

    Reread post five, paragraph 10 and for a bit more detail, reread post seven, paragraph three

    You've really got to put a little effort into reading and trying to understand the answers you've been given,
     
    Last edited: Mar 19, 2019 at 6:43 PM
  13. fr3d

    fr3d New Member

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    You're of course correct.Thank you for your help.
     

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