Rotel RB-1080 - Unable to drive low impedance spkrs?

Discussion in 'AV Receivers' started by JohMabe, Nov 3, 2003.

  1. JohMabe

    JohMabe Stunt Coordinator

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    I finished my amp research, and concluded between the Rotel RB-1080 and the Adcom 5800 (5802 off my price). Anyway, I was looking at the specs of the Rotel, and it is only listed as 200w output at 8ohms. I'd use it to drive 6ohms Dynaudio LR120+, so does anyone know what is the Rotel rated at 4ohms? And if it can deliver at this impedance?

    Between the Rotel and the Adcom, which would you choose? People complain alot about the Adcom ruggedness and noisy fan, that's why I'm putting it off. Anyone agrees?

    Another option is the Acurus A250, but that seems like a bad choice.

    All imput is welcome
     
  2. Andrew Pratt

    Andrew Pratt Producer

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    All Rotel amps can drive 4 ohm loads so it wouldn't have any issues there and the 1090 is their flagship power amp and what I lust after[​IMG]
     
  3. RichardHOS

    RichardHOS Second Unit

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    I've seen the 1080 listed as I think either 350 or 380 Watts into 4 ohms somewhere on the Rotel site, but I had to search forever to find that and I'm not sure where it was. Could have been specs for the older RB-991, which is electrically identical (in the power amp section) to the 1080. In any case, I'm sure it would be between 350 and 380 watts per channel @ 4 ohms, so probably around 275 watts or so @ 6 ohms.

    And the 1080 should be perfectly happy with a 6 ohm load. I've personally tested my two 991's into a 2 ohm load with no problems other than excessive heat. I don't run them that way daily, but I wanted to know how rugged they were for extended use into 4 ohms.
     
  4. RichardHOS

    RichardHOS Second Unit

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    Ah, yes, here it is in the owner's manual for the 991: http://www.rotel.com/support/pdfs/manuals/RB991.pdf

    There it states 300 wpc into 4 ohms. I believe it was in an email from a Rotel engineer where I obtained the above figures, as in his opinion that 300 wpc rating was a bit conservative (as is probably the 8 ohm rating as well). In any case, figure on a minimum of 250 watts per channel into 6 ohms, and the 1080 should be cooly coasting along into that impedance.

    As far as sonics, I think the Adcom, Rotel, and Acurus would all sound identical, so make your choice based on looks, warranty, price, fan noise, etc.
     
  5. Mark All

    Mark All Second Unit

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    I think Rotel's power output ratings for their amps are ballpark figures. My RMB-1075 certainly seems to be putting out more than 120 wpc. The RB-1080 manual states that it is rated to 4 ohms minimum but doesn't provide an output rating into that load. Rotel's Web site does identify the RMB-1095 at 330 watts into 4 ohms, so I'd guess the RB-1080 is somewhere near that figure. I'd guess anywhere between 330 and 350 wpc for the RB-1080 into 4 ohm rated speakers. I'd agree with Rich above that the output into 6 ohm speakers woud be around 250 wpc minimum.

    I'd avoid any amp that has a fan myself. You may also want to consider the RMB-1075 if your speakers can be biamped. Same price as the RB-1080 but lacks balanced inputs.
     
  6. JohMabe

    JohMabe Stunt Coordinator

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    Oh, I see... Thank you very much, Richard. Do you think the Acurus is a safe bet too? In AudioReview they say it's crap! Anyway, what's different in the Rotel RB-1080 compared to the RB-991? I can get the latter much cheaper, if it's any good.
     
  7. Jason.Soko

    Jason.Soko Stunt Coordinator

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    Mark , an how would one know that an amp is putting out more than 120wpc? Without actually measuring it.
     
  8. Kevin C Brown

    Kevin C Brown Producer

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    There is a review of the RB-1080 at Stereophile. They basically say that it is good down to 2 ohms, but don't go below that. I'd personally choose Rotel over Adcom.

    BTW, Acurus ain't "crap". [​IMG] I know, because I have two of 'em. 1 two channel and 1 five channel. And when I got the Acurus, I looked at Rotel, ATI, B&K, Sherbourn, and some others. I personally came to the conclusion that there wasn't going to be much difference between Acurus, Rotel, and B&K: the final 3 I looked at.
     
  9. JohMabe

    JohMabe Stunt Coordinator

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    Oh, sorry, no pun intended. It's just the Acurus A250 is about half the price of a used Rotel here... I might try it, who knows
     
  10. Kevin C Brown

    Kevin C Brown Producer

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    I actually have a copy of a review that Stereo Review did on the A250 a long time ago. Here's some info:

    Manufacturer's rating: 250W/ch into 8 ohms, 350W/ch into 4 ohms from 20 to 20 kHz (not at just 1 kHz as some amps are rated) with no more than 0.06% THD. A-weighted s/n is 110 dB.

    Measured results: freq response 20 - 20 kHz +/- 0.02 dB; -0.5 dB at 110 kHz (those are SACD/DVD-A capable numbers). Actual power tested was 300W/ch into 8 ohms, and 480 W/ch into 4 ohms, *both* channels driven. A single channel yields 350 W and 600W respectively. (Did anyone ever mention how conservatively rated Acurus amps were? [​IMG] ) Dynamic power was measured at 400W/700W into 8/4 ohms, for dynamic headroom of 2 and 3 dB. Measured distortion at 250 W into 8 ohms gave 0.012%. At 350 W into 4 ohms, 0.023%. They say "the Acurus A250 is an enormously powerful amplifier." "Considering the A250's power capabilities and current reserves, we would expect very few loudspeaker loads to present any serious challenge to its performance." They talk about a test they did, where they shut the amp off, and to illustrate its power reserves, the amp continued playing for 30s. They finish up with "It is an outstanding product in terms of both performance and value."

    And like I said, you can look up that RB-1080 review on Stereophile, and it did not test as well as the A250.

    Now, with all that in mind, why can you get them so cheap today? [​IMG] The A250 came out about 10 years ago and listed for $900, and lasted until about 5 years ago, until when the A200 came out. Acurus was built by Mondial Designs who also builds Aragon. Klipsch bought Mondial Designs maybe 2 years ago, and decided to put the Acurus name on the backburner and focus their efforts on Aragon.

    So if you're not afraid of buying used, it would be a great deal. If you PM me, I can get you a copy of that review, and some others too. And yes, Klipsch (and Mondial Designs) still supports service on Acurus equipment.

    One more thing if you're curious, and I just found this out reading about Rotel recently. All Acurus amps were made in the U.S. to mil spec standards. (I have a copy of an interview with a Mondial Designs guy.) But also in that Stereophile review of the Rotel, is the fact that the RB-1080 is made in China.
     
  11. Mark All

    Mark All Second Unit

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  12. Jason.Soko

    Jason.Soko Stunt Coordinator

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  13. JohMabe

    JohMabe Stunt Coordinator

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    Yea, I'd like a copy of that review... The Acurus is not so cheap by american standards, it's $750,00, but considering Brazilian prices, it's less than half of a Rotel RB-1080 ($1680,00). I might buy it, and still get a fair discount.
     
  14. Andrew Pratt

    Andrew Pratt Producer

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    Remember also that although some Rotel gear is made in China they're all made in Rotel factories under their direct control which means their QC is much higher then other chinese plants
     
  15. RichardHOS

    RichardHOS Second Unit

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    JohMabe,

    The RB-991 and RB-1080 are, as far as I can discern, practically identical. Their electrical power-amp sections are identical, unless there was some minor component swapping that I didn't catch (PCB layout seems to be a perfect match). Cosmetically they are also essentially identical, except that the 1080 can be found in silver/black whereas the 991 was only available in black.

    The only difference that is of any note, I believe, is that the 1080 contains a 12V trigger and the 991 does not. They should be the same power and sonic wise, and this was confirmed to me by a Rotel engineer. Picking up a used 991 seems to me to be a good value compared to a new or used 1080 (which is why I bought two used 991's a couple of months ago).


    About the Acurus... if the specs given above for the A250 are accurate, then it seems to be a very competent amplifier. Distortion is low enough to make it indistinguishable from the Rotel sonically, yet it appears to have a bit more power on tap than the 991. Not a huge difference, but it is certainly there.

    If it were my money, and the A250 were available to me at half the price of the Rotel, I'd surely buy the Acurus.
     
  16. Mark All

    Mark All Second Unit

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    There's an Acurus A250 on Audiogon for $475. The owner lists its condition as 7/10, but he's willing to ship worldwide.
     
  17. JohMabe

    JohMabe Stunt Coordinator

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    I'll get the Acurus, most likely. I want a "competent" amp, not the best amp... I spent more than 4k in audio components this year already, and budget cuts are welcome... Thank you all for the imput, this helped me alot. Now, if a find a Rotel for the same price, things might change. We'll see.
     
  18. JohMabe

    JohMabe Stunt Coordinator

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    Hmm, well after all this discussion, my amp selection still goes on. I now have to choose between a new Rotel RB-1070 and an used Acurus A250.

    I'd pair it with a Rotel pre-amp MC-1070 or an Acurus RL11 preamp or maybe even an Acurus Act3 Processor, depending upon my choice. The source would be a Rotel RCD-02 CD Player.

    I know there's a huge power difference between these two, but isn't +3db a little of a difference? Or not quite, considering It'll be driving Dynaudios?

    My priority is quality sound, so would I be better off with the Rotel? Or you guys still prefer the Acurus choice?
     

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