RB-1070 or RMB-1075 for fronts.

Discussion in 'AV Receivers & Amplifiers' started by chips, Jul 18, 2003.

  1. chips

    chips
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    I've just picked up my new Rotel amps. I was intending to use the 1075 for LCR + surrounds and the 1070 for the rears. Looking at the units though, the transformer in the 1075 doesn't look 2.5 times the size of the one in the 1075. Would I therefore be better off using the 1070 for front L+R and the 1075 for the rest? Or doesn't it matter?
     
  2. nathan_silly

    nathan_silly
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    I would use the 1070 (2 channel) for the left & rights, and the 1075 for the centre & rears.

    The 1070 has a higher damping factor (higher=better I think) with a higher Signal to Noise.

    Using the best poweramp for left/right centre is probably the best method, and using lesser poweramps for sides/rears.

    No doubt a 2 channel poweramp has less current draw on the PSU; compared to a 5 channel sharing the same poweramp.
     
  3. nathan_silly

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    Oh you could always later on consider another 1070 to bi-amp the left/rights, or another and replace the centre (1075) to bi-amp the centre.

    Basically lots of methods, depending on your goal (bi-amp or normal) and which speaker you wish to biamp (maybe just the left/rights, centre only, or all front three)

    I have four identical 2 channel poweramps (centre only is biamped), take up alot of space but IMO worth it (I can always find a cheap 2 channel for rears, then move that amp to the l/r's to biamp them)
     
  4. chips

    chips
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    Thanks Nathan, 1070 for the fronts it is then. I've also just noticed that the 1070 is rated at 130WPC into 8R and the 1075 120WPC into 8R. Also power consumption for the 1070 is 400W for two channels and the 1075 800W for five channels. So it looks like the 1070 should have a little more grunt for the transients.
     
  5. Steve.EX

    Steve.EX
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    Just to throw a spanner in the works you will find that quite a few of "those transients" live on the center channel, if your goal was purely home theatre then there is certainly an argument for sticking lots of power to the center.

    Steven
     
  6. nathan_silly

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    That's why I mentioned the possibilty of getting another 1070 to biamp the centre (if he's using a hefty centre)

    I guess once the amps bed in- try comparing the 1070 on the fronts & centre, and 1075 the left/right/centre/rears.

    If you feel that the centre needs more oomph, move the amps around or get a another higher- powered amp or get another 1070.
     
  7. mick23

    mick23
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    chips i had 985 mk1 5 channel forrunner to 1075 100watts, and 981 forunner to 1070 130 watts, i assume you have 7 speaker set up???

    i found i got a bigger improvement as regards sterio biamping fronts with 5 channel power ,rather than using the 981 for fronts on its own, do not know what you are using with rotels but if an av with inbuilt amps you could use 2 for rears.
     
  8. chips

    chips
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    I bought the Rotels to use with the Lexicon MC-1 I bought a few days ago on these forums. My speakers are M&K S85 LCR & SS150 sides and rears.

    Since I don't usually listen at very high levels (normally -15DB) I don't think that I'll have any shortage of power, so its probably academic but thanks for your suggestions guys :).

    At least I have the flexibility to change things around.
     
  9. chips

    chips
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    Just noticed this in the M&K manual regarding the centre channel. "Very often this channel produces more output than the left and right channels combined..........it is important to have as much power as possible for the centre channel. As a minimum, we recommend that the three front channels be identical in power output. Preferably, the centre channel will have the greatest amount of power".

    If I'm short of power, It would indeed seem sensible to get another 1070 for the centre channel. I'm still waiting for my metalworker to make the shelf I need to fit the new stuff so I've not yet been able to listen to it :(.

    Is bi-amping the same as using a 1070 in bridged mono mode, or does it involve powering the tweeter and main driver with seperate amps?
     
  10. Chrissywis

    Chrissywis
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    The second part of your question is the correct answer.:)
     
  11. chips

    chips
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    That was what I thought, but I don't think the S85s have that option without opening the cabinet and re-wiring.
     
  12. nathan_silly

    nathan_silly
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    See pic. To biamp a centre with a 2 channel poweramp, you need to split the single phono to 2 phono's, either by using a Y splitter, Y adaptor, Audiolab load/input function or like Arcam Alpha range (Mono-link)

    I'm currently using a PX (100Wx2) with a Kef Reference 200 -4 Ohm- seems fine; using load-input mode to copy the signal to the other channel.
     

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  13. chips

    chips
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    Thanks Nathan, but reading the M&K book again, it states; "Your M&K satellites are not designed for bi-wiring. Do not use the four input terminals to bi-wire your satellites, as this may damage your amplifier and speakers."

    Looks like my only option would be to use a 1070 in bridged mono mode. Of course, I may well not need more power anyway.
     
  14. nathan_silly

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    Bridging a amp usually triples the wattage output, but lowers the amp's ability to drive low impedance loads. Being that M&K are 4Ohm normal, I would be warey bridging a amp into already- low impedance speakers.

    You should have gone for the RB-1090 in the first place :)
     
  15. chips

    chips
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    Yup, you're right, Rotel say that the load must have an impedance of 8 ohms or more for operation in bridged mode.

    Plan "C", use one channel of the 1070 to drive the centre and the other on one of the rears ;).
     
  16. nathan_silly

    nathan_silly
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    Plan "D" Don't bother with AV gear, get rid of all your possesions and become a monk. :p
     
  17. chips

    chips
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    I've got enough dirty habits thanks :laugh:.
     
  18. nathan_silly

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    The M&K manual states NOT to bi-wire.. but does it say anything about bi-amping?

    Oh one bonus about coming a monk- no nagging wife & kids!! :)
     
  19. chips

    chips
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    Yes, it says you can bi-amp them using a high-pass filter between the pre and power amps, but I think they are talking about systems driving the sub from the front two channels. It doesn't make much sense to me.
     
  20. chips

    chips
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    Thanks again to everyone for your advice, just to report back, I adopted plan “C” (as above) and am happy to report that it sounds superb. Plenty of power available to drive my M&Ks.
     
  21. nathan_silly

    nathan_silly
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    ??

    Thanking yourself?

    :p
     

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