Hooking up 2 amps on a MX110Z?

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

  1. bobivxx

    bobivxx Tube Noob

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    Can't you just split/piggyback?

    I've been trying to sell mine and I just talked to a guy that said that only 1 pair of outs was a deal breaker. I'm not gonna try and talk a guy into nothin; But now I kinda want to know myself.

    Thanks!!!
     
  2. bobivxx

    bobivxx Tube Noob

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    or use the second amp in the tape out?
     
  3. dshoaf

    dshoaf That high voltage buzz Subscriber

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    The Tape Outputs are fixed level - they will not track the volume control. Driving 2 separate amps with a Y cable _might_ work ok but it will depend on the input impedance of both amps. Since they're connected in parallel, Ohm's Law of parallel resistance will apply.

    The output impedance of the MX-110 is not specified but I'd doubt that 2 amps, wired in parallel, at 10K ohms each (this is very low for most power amps) will work. That would make it appear that a single amp with a 5K ohm input impedance is being presented as a load to the MX-110. This is a worse-case scenario.

    Take 2 higher-impedance tube amps in parallel and you'll likely get more drive from the MX-110. That lower impedance scenario I painted would be a couple of older solid state amps more than likely.

    Cheers,

    David
     
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  4. bobivxx

    bobivxx Tube Noob

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    That's very clear. Thanks David! I'm tracking now.
     
    Last edited: Oct 20, 2015
  5. bobivxx

    bobivxx Tube Noob

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    Here's a maybe even dumber question. I don't suppose there is a way to hook up the MX110 as a separate tuner with a C-20?
     
  6. damacman

    damacman Blown and Injected

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    Sure. Feed the Tape OUT of the MX110 into the Tuner IN of the C20. Set the input selector on the MX110 to FM or MPX. Done.

    Dual MAIN outputs on a vintage tube tuner / preamp? I would have laughed so hard I'd of peed my pants . . . sure, you want RCA, XLR, or both? LOL!
     
  7. Guest113

    Guest113 Well-Known Member

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    751
    A distribution amp will allow this and match impedance.
     
  8. 62caddy

    62caddy Trust but verify Subscriber

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    Absolutely! * (Depending on the amplifiers)*

    Output impedance of MX110 is 100k ohm. If the combined impedance input of both amplifiers is => than that, you will be fine as David has said.

    I have Y RCA IC cables for the exact purpose as you describe to run a MC 2505 and MC 240 which have input impedance of 250k ohm and 200k ohm respectively which works out to over 100k ohm so no problem there.

    What are the amplifiers he wants to use?

    Tony - I wish the MX 110 had THREE sets of outs then I could try it in my main system! lol
     
    Last edited: Oct 21, 2015
  9. bobivxx

    bobivxx Tube Noob

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    Thanks Damacman and 62caddy!!! I almost want to thank the goofy bastard now too. It sure sounds great hooked up like you said; Thanks again damacman!

    What's better than one Mac? Two Macs! I don't see any reason to sell at all now!!!
     
  10. 62caddy

    62caddy Trust but verify Subscriber

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    May as well use it that way since you have the C20.

    Another advantage of using the TAPE OUTs is that the MX110 uses the 12AX7s for this feed, not the 6U8 tubes which are used in main output.
     
  11. bobivxx

    bobivxx Tube Noob

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    Thanks Caddy! Can I infer v13-v17 are where my best tubes should be?

    And is it 2-12ax7's for phono (13-14), 1-12ax7 for tape (15), and 2-6u8's for the aux(16-17)?
     
  12. damacman

    damacman Blown and Injected

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    You mean that thing ain't got a SPDIF input? I'm out ...

    Glad it all worked out! You can still connect other sources to the MX110 as well with your current arrangement.
     
  13. 62caddy

    62caddy Trust but verify Subscriber

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    I don't recall all the specifics but the tape outs are supposed to be off the 12AX7s. There are a couple of rather lengthy discussions of the MX110 on the Steve Hoffman forums and that was one of the more important points he made. In fact Steve himself used his 110 in a borrowed system costing near $200K where he found it more than held its own. He also likes its phono section so much that he has used it as a phono preamp taking output from - you guessed it - the REC OUT jacks.

    When you have the time, you may find these threads interesting reading:

    http://www.forums.stevehoffman.tv/t...-surprised-me-today-follow-up-post-61.268103/

    This one on tube rolling in the MX 110.

    http://forums.stevehoffman.tv/threa...-discussion-perfect-6u8-12ax7-etc-tube.51333/

    I've had my MX110 for 2 years now and once I got the bugs ironed out, I could not be more pleased with it.

    I think it is the best value in a vintage McIntosh tube preamplifier just as it is. The "free" MR 67 makes it the bargain in all McIntosh tube - IMHO.

    Cheers!
     
    Last edited: Oct 21, 2015
  14. bobivxx

    bobivxx Tube Noob

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    Thanks again damacman an 62caddy! Great links!

    So, It looks like I should try my turntable both ways as well? That could be fun!
     
  15. mech986

    mech986 Text ↓ optional Posts:>18,000 Subscriber

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    Yep, its a vintage unit so one set of outputs for one amplifier was the norm then. If the prospective buyer wants to run two separate stereo power amps, he should invest in a preamp or buffer stage that can drive said amps, using the MX110 as a source or as a preamp.
     
  16. twiiii

    twiiii Super Member

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    There's a way to determine the output impedance of an MX-110. It takes 3 pieces of equipment. An oscillator, a resistor substitution box, and a VTVM with a very high input impedance. Pick a frequency adjust the oscillator to 1 volt out using the meter and feed the MX-110. Measure the out put of the MX-110 and set to 2 volts. Connect the resistor substitution box to the output of the mx-110 thats connected to the VTVM. Select resistors with a high value one at a time until the voltage reads on the VTVM drops to 1 volt, that resistor value is the output impedance of the MX-110 at that frequency. I would check at 20, 1000, and 20 khz.
     
  17. 62caddy

    62caddy Trust but verify Subscriber

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    From p. 12 of the OM:

    The MAIN jacks are fed from cathode
    followers. Longer cables than are normally
    supplied can be connected between the
    MX110 and the amplifiers. The length of the
    cable is limited by the capacity of the cable.
    The total capacity must not exceed 1000
    mmf. For instance: cables with a capacity
    of 25 mmf per foot may be 40 feet long; 13.5
    mmf per foot cable may be 75 feet long. The
    input impedance of the amplifiers should be
    100,000 ohms or greater..

    http://akdatabase.org/AKview/albums/userpics/10004/MX110 Owners.pdf

    Note: "amplifiers" (plural) used.

    Input imp of a MC2505 - 250k; 240 - 200k. The result is 111,111 which is > 100,000.

    I have no idea what all the other amps are but it would seem to me MX110 is designed to drive 2 McIntosh amplifiers easily.

    62caddy.
     
    Last edited: Oct 21, 2015
  18. 62caddy

    62caddy Trust but verify Subscriber

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    Update:

    I did some checking last night and to make a long story short, input impedance falls with successive generations of McIntosh amplifiers.

    However, in a nutshell - MX110 can run up to any 2 McIntosh amplifiers made before the Power Guard generation including MC 2300 all of which have input impedance of 200K ohm or greater.

    Input impedance decreases to 100K on the earliest PG amplifiers such as MC 2205/2200, 2125/2120 etc which means the MX110 would only be able to operate correctly into a single amplifier at a time in this series.

    However with the slightly later MC 2155/2150 & MC 2255/2250, input impedance drops further to only 50K ohm which means amplifiers of this generation would not be compatible with the MX110 at all.

    Bottom line is to determine compatibility first when mating electronics - especially in cases when time of manufacture is most disparate.

    One other correction: Input impedance of MC 240 is 250K ohm; MC 2505 is 200K ohm. The figures were flip flopped in my earlier posts.

    Thanks.
     
    Last edited: Oct 22, 2015
  19. twiiii

    twiiii Super Member

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    It was fun reading the MX-110 manual of old. I wish Mac's newer endeavors were as flexible and easy to operate and comprehend. At least you didn't have to rely on a remote to operate the tone controls and there is no such thing as a mode selector now days unless you by the new C-22. Its no wonder folks back in the 60"s loved the MX-110 and 240 or 225 combination. I chose to go with separates as my second generation of Mac, with a C-22, 240 and MR-71. I had always thought of getting a MX-110, but the job at the radio station came along and I had money in my pocket.
     
  20. twiiii

    twiiii Super Member

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    4,770
    Location:
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    And wonders of wonders the MX-110 had separate tone controls for each channel, something I truly miss. When Davie asked me one time what I would like to see in a pre-amp. I said I wanted a midrange control, and please keep the separate tone controls. What happened. The C-30!
     

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