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Thread: McIntosh & Marantz bi-amp JBL 1400 Arrays...

  1. #16
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    Since I now have some time to play around with this concept I have an additional question. The Marantz pre has two RCA pre-outs. Currently, I am using one for the Amps and one for the 1500 Array. Would it be possible to use a Y-splitter on one to both the Marantz and McIntosh amps and keep the one for the Sub? Don't they have to have the same impedance or am I way off base?

    Please excuse my ignorance on this matter.
    I will take my leave of you now.

  2. #17
    Obviously... not a golfer grumpy's Avatar
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    My minor concern is that you may be effectively doing this "Y" connection already.
    Just because a unit has two pre-outs does not guarantee that they are isolated
    (i.e., have separate line-level amplifiers for each connector, vs. just making the "Y"
    connection inside the box).

    You'd want to look at the input impedance vs. frequency for each unit you want to supply
    a pre-out signal to. If the Marantz/McIntosh/1500 all have inputs rated at something like
    20Kohms, you might now be loading it with ~7Kohms ... probably not a huge
    problem electrically, but that 'rating' is a nominal and typically doesn't cover frequency
    extremes. If they all dropped to 12Kohms on the high end, you would now be driving
    about 4Kohms and the impedance variation from one end to the other of the audio frequency
    range -might- cause a rolloff or exaggeration that would not be present with a single amp
    connected.

    Again, I don't think you'd hurt anything, but if you don't have facilities to measure,
    you'll have to trust your ears.
    It's uh... uh... it's down there somewhere, let me take another look...

  3. #18
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    Perhaps my post was not correct. As it currently stands, I am using one pre-out to the 1500 sub and one for the Marantz mono-blocks. I said 'amps' in my first post-perhaps, if I understand your response, I may have implied that I am using the Marantz/McIntosh already-which I am not.

    I am sorry if I misunderstood. I do think the Marantz SC7S2 has two dedicated unbalanced RCA pre-outs and one balanced. You cannot use both at the same time, hence the reason I am using the unbalanced for the Amps(Marantz) and the sub. I am unclear whether I can, using a Y-splitter from one unbalanced pre-out, hook up two totally different power amps at the same time without some kind of issue. Conversely, Perhaps I could use one amp with a y-splitter with the sub & one or the other amp? Perhaps a active crossover would solve this issue?

    Grumpy, I am sorry if you answered my question and I not smart enough to understand the answer. However, I thank you.
    I will take my leave of you now.

  4. #19
    Obviously... not a golfer grumpy's Avatar
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    No problem, I've now looked up your particular preamp user manual.
    That is one unusual preamp ... but the gist of what I was attempting
    to convey remains. The SC7S2 has a 70ohm output impedance ... it's good
    that it's low. It will probably drive 3 normal amp-input loads without issue
    (unless you use really high capacitance cables). Generally going past -two- line
    level splits is a poor idea for a blind recommendation... hence my initial caution.

    If you look at the block diagram in the User Manual (pg20) you can see
    that it is showing 1/2 of the preamp signal chain (ch A). Also, the RCA
    output jacks are internally wired as a Y-connection. Adding an external Y
    adapter will mean you are then driving three loads in parallel
    from one pre-out line amp (regardless of the number of pre-out connectors).

    When using the RCA pre-outs you are leaving the top section of a
    balanced design out (the negative half, connected to pin 2 of the XLR)...
    which explains why they want you to use XLR -or- RCA, not both...
    you would be unbalancing the circuit (loading one leg more than the other)
    and losing much of the benefit of using a balanced connection.

    The bi-amp function of this pre requires a full passive filter (the same signal drives both
    the LF and MF/HF amps... it is the speakers filter that provides the crossover)
    so signal-wise, the multi-way split to amps and subs (with it's own crossover)
    is fine. If you want the full-range speakers to not run full range, and the crossover
    in the sub to define the low end of those speakers, you'd send the pre-out
    to the sub, then the high-passed output to the amp for the full-range speaker
    (using the sub's electronics as an active filter).

    As you can see, there are many connection options and the user manual is just a
    start. Hope this helps some
    It's uh... uh... it's down there somewhere, let me take another look...

  5. #20
    Senior Member timc's Avatar
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    Quote Originally Posted by tom1040 View Post
    You cannot use both at the same time, hence the reason I am using the unbalanced for the Amps(Marantz) and the sub.
    Are you sure about this? A friend of mine has the SC7 and he uses the balanced set for the MA-9's and a unbalanced set for another amplifier. He then dials the MA'9s to -6db on the input.

    -Tim
    2213 + 2435HPL w/aquaplas + H9800 (Matsj edition)

  6. #21
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    Quote Originally Posted by timc View Post
    Are you sure about this? A friend of mine has the SC7 and he uses the balanced set for the MA-9's and a unbalanced set for another amplifier. He then dials the MA'9s to -6db on the input.

    -Tim
    Interesting. I will review the manual again. First, a question: Does he use them @ the same time? You can hook them up, I think, but use the switch on the front of the Marantz Ma9S2 amps to switch from unbalanced to balanced. Perhaps he uses them that way. Nonetheless I will check. Thanks guys.

    So, an active crossover is of no use to correct this?
    I will take my leave of you now.

  7. #22
    Obviously... not a golfer grumpy's Avatar
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    All I got from the manual is that it wasn't recommended, not that it wouldn't 'work'.
    An external crossover could work fine, ... Getting it done properly would be the challenge.
    Passive bi-amp seems like a good start if you can level match your amps.
    RCA attenuators exist (don't have to build anything).
    It's uh... uh... it's down there somewhere, let me take another look...

  8. #23
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    Quote Originally Posted by grumpy View Post
    Passive bi-amp seems like a good start if you can level match your amps.
    RCA attenuators exist (don't have to build anything).
    By RCA attenuators, do you mean line level passive volume controls? If so, those can be very impedance sensitive. (For those confused by this, the impedance of the amp/preamp, not the speakers.)


    Widget

  9. #24
    Obviously... not a golfer grumpy's Avatar
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    Sure. I figured there would be some empirical level adjusting going on, vs trying to hit an exact value. If we had all the numbers (gains and impedances), and some construction was OK, we could get pretty close.
    It's uh... uh... it's down there somewhere, let me take another look...

  10. #25
    Senior Member timc's Avatar
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    Quote Originally Posted by tom1040 View Post
    Interesting. I will review the manual again. First, a question: Does he use them @ the same time? You can hook them up, I think, but use the switch on the front of the Marantz Ma9S2 amps to switch from unbalanced to balanced. Perhaps he uses them that way. Nonetheless I will check. Thanks guys.

    So, an active crossover is of no use to correct this?

    He uses them at the same time, with passive biamping. BUT this is the S1 model. Maybe they changed it for the S2?
    2213 + 2435HPL w/aquaplas + H9800 (Matsj edition)

  11. #26
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    Quote Originally Posted by timc View Post
    He uses them at the same time, with passive biamping. BUT this is the S1 model. Maybe they changed it for the S2?

    It appears the 'instructions' of both the S1 and S2 seem to indicate that it should not be done. I am a bit curious why your friend does it that way-in other words, not just to use the unbalanced RCA connectors-unless one is for a sub, such as the case with my situation-or perhaps the benefits provided by the balanced connections. I may be reading the instructions wrong.


    I suspect that I just need lug the McIntosh (no easy task!) out of storage and try some configuations or just forget about it and leave well enough alone.
    I will take my leave of you now.

  12. #27
    Obviously... not a golfer grumpy's Avatar
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    The gain difference between the MC402 (using the 8 ohm autoformer tap) and the Marantz MA-9S1/2 is
    about 0.6dB (unbalanced inputs) if the specs are listed correctly.

    If the attenuator on the back of the Marantz is continuous (not stepped), this would be the
    simplest place to adjust levels.

    Another "simple" option would be to insert a 1.4Kohm resistor in series with the Marantz
    (essentially a very custom, but easy to make cable). With the 20K input impedance of
    the Marantz, that would drop the sensitivity ~0.6dB.

    So much for morning bench racing... this would be much better done by someone who can verify
    measurements in-situ.
    It's uh... uh... it's down there somewhere, let me take another look...

  13. #28
    Senior Member timc's Avatar
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    Quote Originally Posted by tom1040 View Post
    It appears the 'instructions' of both the S1 and S2 seem to indicate that it should not be done. I am a bit curious why your friend does it that way-in other words, not just to use the unbalanced RCA connectors-unless one is for a sub, such as the case with my situation-or perhaps the benefits provided by the balanced connections. I may be reading the instructions wrong.


    I suspect that I just need lug the McIntosh (no easy task!) out of storage and try some configuations or just forget about it and leave well enough alone.
    He (me too) feels that it sounds best when the mid/treble is run balanced. Might got to do with the lower noise.
    2213 + 2435HPL w/aquaplas + H9800 (Matsj edition)

  14. #29
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    Well, perhaps this was not meant to happen. I have a strong feeling that I have the McIntosh sold. I guess I will know by next week. At least I will not need to ship it!
    I will take my leave of you now.

  15. #30
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    Quote Originally Posted by grumpy View Post
    The gain difference between the MC402 (using the 8 ohm autoformer tap) and the Marantz MA-9S1/2 is
    about 0.6dB (unbalanced inputs) if the specs are listed correctly.

    If the attenuator on the back of the Marantz is continuous (not stepped), this would be the
    simplest place to adjust levels.

    Another "simple" option would be to insert a 1.4Kohm resistor in series with the Marantz
    (essentially a very custom, but easy to make cable). With the 20K input impedance of
    the Marantz, that would drop the sensitivity ~0.6dB.

    So much for morning bench racing... this would be much better done by someone who can verify
    measurements in-situ.

    Pardon my ignorance but are you speaking of something like this?




    http://www.ebay.com/itm/10-NEW-RCA-M...ash=item53dfa0
    I will take my leave of you now.

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