Hooking up 2 amps on a MX110Z?

Discussion in 'McIntosh Audio' started by bobivxx, Oct 20, 2015.

  1. bldozier

    bldozier AK Subscriber Subscriber

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    what if using a pair of mb amps, left and right, would the input rules still be relevant, I've read folks using mc 30/60/75 paired,
    but there issn't any mention of that here.

    i've also read the mx110 does not adhere well in multi-amp configurations, could anyone who has used it in this way expound.

    Id like to use two mb for a front stage + L+R for a sub, just due diligence 1st as i'm seeing conflicting statements.
     

     

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  2. 62caddy

    62caddy Trust but verify Subscriber

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    The input impedance of the amplifier(s) needs to be determined.
     
  3. bldozier

    bldozier AK Subscriber Subscriber

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    ok i will be sure to verify the imp is over that of the mx-110.
    if using a 4 way active network, do the same laws apply.
    how would the preamp see the amps through the active network?
    series or parallel, if its a series would the laws of impedance still apply to the preamp
     
  4. bldozier

    bldozier AK Subscriber Subscriber

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    any help please?
     
  5. 62caddy

    62caddy Trust but verify Subscriber

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    Need info on the active network device.
     
  6. KentTeffeteller

    KentTeffeteller Gimpus Stereophilus!

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    Better yet, feed the main out of the MX 110 to the C20 tuner input, then you have the MX 110 tuner and the entire preamp section at your disposal too.
     

     

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  7. 62caddy

    62caddy Trust but verify Subscriber

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    Well you may need to change your pants Tony :D - turns out the early MX110 has exactly that. Only recently learned this myself.

    http://mcc.berners.ch/tuner-pre-amps/MX110EARLY.pdf
     
  8. whoaru99

    whoaru99 Epic Member

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    The preamp does not "see through" something like that. It works with the input impedance of the connected device(s).

    I suggest you perform the measurement suggested a few posts back (post #16) to ascertain the approximate output impedance of the MX110. It might spare you a bunch of angst looking for something that "matches" because a lot of gear these days does not have 100k or higher input impedance. I've done that sort of test, but used a high value potentiometer instead of a resistance decade box. Start with the pot at max then dial down until the voltage is 1/2 of starting. Disconnect the pot (do not change adjustment) then measure the resistance of the pot. That is your approximate output impedance.

    Generally speaking, as long as the connect load impedance is 10x or more the output impedance of the preamp there is no problem with the "match".

    In other words, if you do the test and find the pre out impedance is, for example, 500 ohms (or whatever) as long as the input impedance of the connected device is 10x (5000 ohms) or more this example, it should work fine.
     
    Last edited: Jan 6, 2018
  9. rollcentre

    rollcentre Boom-tizzz

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    I find it interesting that they decided to get rid of the 2nd pair of main outs for the Z series. While on the C20 they added them on the later models.
     
  10. 62caddy

    62caddy Trust but verify Subscriber

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    Given the 10:1 impedance requirement, would it be correct to assume MX110's actual output impedance is ~ 10,000 ohm since Mc says it should be used with input of 100,000 ohm or greater? :idea:

    In any case, my own experience with the MX110 there is noticeable gain loss when paired with an MC2155 (which is 50,000 ohm input). I will add however there doesn't seem to be much loss to SQ but the volume needs to be set higher. Of course the 0.75 V input sensitivity setting helps quite a bit, although you get an increase in noise floor.

    Bottom line is that I tend to agree with Mc's recommendations regarding amplifiers the MX110 will be happiest with. Of course, YMMV.
     
  11. whoaru99

    whoaru99 Epic Member

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    I’d be extremely surprised, to the point of doubt, the output impedance is anywhere near 10k.

    Why is the magic number 100k? Perhaps that happens to nicely align with other Mc offerings.
     

     

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  12. bldozier

    bldozier AK Subscriber Subscriber

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    from my gathering so far the external actives, work well with all gear.
    input impedance of 50k & output of 4K MAX.
    an output RL of 50K
    Quoting from hifiengine. pionner d23.

    output for the mx110 is 100k, thats specified on page 1 of the thread.

    if the input impedance is 50k for the active crossover,
    would that figured be added to each amplifier connected w/ it.
    would each one of the 4 stages been seen independent by the preamp.

    my thought was the distribution amp already existed within the active crossover...

    EDIT:
    the preamp impedance could possibly be lower then stated, i do not have 1 ATM to test it.
     
    Last edited: Jan 7, 2018
  13. 62caddy

    62caddy Trust but verify Subscriber

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    I don't know...tube models in production when MX110 was being produced were 250K; first gen SS, 200K ohm which ran roughly through the late 70s. (MX110 production overlapped SS models for the first 2 years of being introduced)

    Maybe someone can definitively answer the question because I'd like to know myself.
     
  14. monkboughtlunch

    monkboughtlunch Super Member

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    So - is there any definitive answer about impedance compatibility? Can one use a vintage MX110 with a brand new 2018 MC275 VI with no ill sonic effects?
     
  15. whoaru99

    whoaru99 Epic Member

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    That is the recommended maximum load impedance, not the output impedance.

    It was common at the time to have high input impedance in amps but how well the MX110 would work with lower input impedance depends on output impedance of the MX110. Without someone measuring one then it's just a guess. My guess is it would be fine well below 100k loading, but that's just me...
     
  16. gmfgmfgmf1

    gmfgmfgmf1 Active Member

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    I have a C-20 with two mains - one runs my main amps to main speakers full range - the other runs a subwoofer amp low passed
     

     

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  17. bldozier

    bldozier AK Subscriber Subscriber

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    thanks all for your help.
    so in theory
    275 & 240 will be fine on the mx110,
    the 240 being 250k & the 275 being, i think i read 250k also.
    are the main pre channels independent on a mx110.

    could a third amp be introduced into this scenario. thanks for taking time to answer my questions
     
  18. twiiii

    twiiii Addicted Member

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    Tape out puts are not buffered so they are directly. off the source except for the phono which uses 12 Ax7's as I remember. You could make wye cables with each connector feeding the amps having a 100K ohms resistors in series with the hot lead feeding the amp. Keeping the load up. The problem is how much signal would you loose to the amp. 6 db worst case. Whats the sensitivity of the power amps. With 240 and 275 no problem, Use the twin inputs and set the volume controls as described in the owners manuals If its 2 volts you should be OK. Back when I was using a tuner or tape machine to feed two or more old pre-amps I had to put series resistors when I wired the sources because early Mac pre-amps and integrated MA 230's would short the inputs when not selected to prevent cross talk between inputs.

    What you are supposed to do is set the volume control of the MX 110 to 12:00 and then advance the level of the power amp to just a hair louder than you would normally listen. Do one amp at a time. It gives the lowest distortion and the best signal to noise..
     
  19. bldozier

    bldozier AK Subscriber Subscriber

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    right!

    i figured i could use each of the main outs for both amps.
    i was asking if they are independent from each other just as a factoid.. :)

    i wanted to introduce a y chain 3rd mc 2505,250, 2105
     
  20. 62caddy

    62caddy Trust but verify Subscriber

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    Combined input impedance of MC275 & MC240 is 125,000 ohm which is fine for the MX110. The addition of one of the models you mention and the total drops to ~ 77,000 ohm which is less than McIntosh's 100,000 ohm minimum recommendation. I can't say whether this will have any negative audible effects.
     

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