A View into the Rotel 15 Series Class D Amps

Collapse
This topic is closed.
X
X
 
  • Time
  • Show
Clear All
new posts
  • =AirCeej=
    Junior Member
    • Apr 2009
    • 6

    A View into the Rotel 15 Series Class D Amps

    During the process of putting another HT together, I began auditioning amps to replace a Sunfire Series 1 Load Invariant and an Anthem MCA20 – noteworthy at the respective price points in their day and for the Sunfire: novel. Appreciating the ideas and most of the execution designed into the Sunfire, I continued on a path of operational efficiency, while needing the replacements to: edit the signal as little as possible, remain stable under varying load and signal conditions, offer logically laid-out/easily accessible connections, pleasing aesthetics, utilitarian machine functions – under 2.5 grand for 7 channels.

    Through researching a good cross-section of designs core to my interest for the past year, I became intrigued by the favorable reviews and comments in the direction of designs employing either Hypex or B&O (ICE) modules. This quickly turned into a solidified interest and diligence as it does many times paid off in the form of a press release: touting the introduction of Rotel’s 15 Series.

    Admittedly my last brush with Rotel was many years ago having given a high school graduation present to a nephew consisting of a PS Audio 4.5, Rotel RB-981 and Eminent Technology LFT VIII’s. Back then it was a fun setup, but since then Rotel (for a few specific reasons) has been off the radar as a serious consideration for anything I’d put into a “cost-effective” system. Mild reservations aside, along with knowing the 15’s were just introduced at the ’08 CEDIA with updated Class D amps, in my price range and they just started shipping... I quickly made way to my local friendly neighborhood Rotel 15 Series merchant in Ann Arbor to see if they’re worth it!

    Day 1

    Before hitting the mid-fi area, I looked through their high-end room knowing that I most likely would want to audition the amp(s) there. This practice helps me discern what a component may be adding to/deleting from the signal and better understand if I want to pass on the component, audition further at home or just buy it. It also helps an open-minded high-end dealer become better aware of their mid-fi equipment and eschew possibly pre-conceived notions concerning limitations; therefore I, the dealer and prospective customers to a given product - benefit.

    After a tour of wares from Wilson Audio, B&W, JL Audio, Krell, Wadia and Runco, I made my way to the ‘mid-fi room’ containing the Rotels, met a very cool member of the staff and began an all too brief encounter with the RMB-1565 (5 channels 100w/8Ω 200w/4Ω). With ~ 50 hours under it’s belt, it helped convey a strong campaign for putting the 2-channel version through its paces in one of their better rigs on the following day. The salesperson agreed and told me he would have it set up and running before I got there. Excellent; we said our goodbyes and the stage was set!

    Program Material
    • Patricia Barber – Café Blue

    Room:
    Roughly 14' x 16' x 10'

    Rig:
    • Denon DVD1800 Blu-ray player
    • Transparent HPHDMI (when video)
    • Rotel RSP-1570 Processor
    • Transparent MusicLink interconnects
    • Rotel RB-1572 250w 2-channel amp
    • Rotel RMB-1565 100w 5-channel amp
    • Tranparent The Wall Plus speaker cable
    • B&W 703 series 7.1 system
    • ~ $15.5k in equip. and cabling

    • Evaluation component: RMB-1565 (5 channels 100w/8Ω 200w/4Ω) with roughly 50 hours on it.


    Day 2 (High-end Room)
    Program Material
    • Patricia Barber – Café Blue
    • Stephen King's The Stand – Original Television Soundtrack
    • Cantate Domino by Oscar's Motet Choir
    • Loreena McKennitt – The Mask and Mirror

    Room:
    Roughly 15' x 18' x 10' treated with Real Traps

    Rig:
    • Wadía 781i Mult-format player
    • Krell EVO707 Preamp
    • Transparent (single-ended) Super interconnects
    • Krell Evolution 600 Monoblocks
    • Transparent Reference MM2 Speaker Cable
    • Wilson WATT/Puppy System 8
    • ~ $100K in equip. and cabling

    • Evaluation component: RB-1572 (2 channels 250/8Ω 500w/4Ω) with roughly 50 hours on it.

    Given the company it was in, I entertained the possibility that the 1572 would give a valiant effort and possibly fail to one degree or another with its variation of common characteristics found in relatively inexpensive Class A/B amps (leaner side of neutral, tight somewhat dry bass, good dynamics, slight loss of instrument body in the midrange, appreciable but somewhat bright upper-octave performance, etc.), which can be very easy to hear. However, seeing that Rotel is spinning their latest take with ICE Topology in this series, I was certainly open as to why...

    Before the first track of Café Blue hit the Wadia, I remembered my nephew and the first Rotel I purchased as I was about to compare its diminutive “statement” Class D successor against Krell’s sizeable statement Class A Monoblocks in a very revealing system. Amused at the David and Goliath visage sitting on the floor, I was sure that David was just about to get his ass kicked… As I’ve been a musician since age 3 and got into audio ‘bout the time I was 8, I’m no stranger to live music and certainly know what to listen for when it’s reproduced. Even still, it’s always fun in this hobby when something pleasantly catches you completely off guard, because roughly 30 seconds into the disc - I was not fully prepared for the levels of nuance, neutrality, micro dynamics soundstaging and imaging being reproduced; I sat surprised at what this rogue started to do. From there it was a series of 7 or so bouts between the Krells and Rotel with the sales person moving interconnects and cables when I needed.

    Roughly two hours later, it came down to this: Between the frequency extremes, the Rotel is just as neutral as the Krell except the latter squeezes out a tiny bit more information at the upper and lower octaves; and the soundstage was slightly more defined as was the imaging. Comparatively its presentation is neither forward nor laid back; dynamic swells in choral music are accomplished without congealing individual voices and the soundstage into a globular mass as everything remains stable with the sonic signature and position of each voice unaltered. By way of contrast, reproduction of acoustic instruments such as drums and stand-up bass keep the attack and sustain along with the character of the instrument body – unaltered except for an incredibly small degree in the lower end. In other words its roughly 98% there, the Krell just does it that much better. It never clipped, lost composure or turn noticeably warm to the touch and it was being done at realistic volume levels for that room. In fact, seeing that the Krells raised the room temp. to roughly 80 degrees, the Rotels were noticeably cooler than the warmer air just above them.

    Pros:
    • Incredible sonic performance across the board!
    • Ree-DICULOUS bang-for-the-buck!
    • Efficient (Tech. Support wasn't sure how much).
    • Output doubles as ohms are halved.
    • Temporarily handles 2Ω dips.
    • RB-1572 provides an extra set of outputs for bi-amping, or driving another pair of speakers.
    • 12v trigger input and output.
    • Very light weight.
    • Local support (providing there’s a dealer in your area): hopefully they’ll be knowledgeable and down-to-Earth enough to take time to work with you as they did with me in Ann Arbor. Conversely I had to be respectable of their foot traffic and worked with my salesperson to find time slots to get the things done that I needed.
    • Don’t have to wait for shipping before you can audition (providing your dealer is stocked).
    • 5 year warranty garnering a free replacement in the first year should the amp fail for any reason.
    • finished in silver or black.
    • Contemporary inoffensive utilitarian look.

    Cons:
    • Blue light around the power button doesn’t dim; there should be a user-selectable switch for this function (i.e.: Theater Dimming – disengaged, Level 1, level 2, Off).
    • Connections on the rear aren’t logically laid-out on the 5-channel.
    • No balanced inputs (ICE Modules are balanced in and out).
    • Output connections are too close together.

    In summary: The 15 Series amplifier execution works in such a big way that hearing it serves an explanation as to why Rotel stayed with ICE. They are high-end amps without apology and hang directly with better statements of the world at a fraction of the purchase and maintenance (electric bill) costs. Given that, I didn’t need to audition further and duly purchased an RB-1572 and an RMB-1565 in black.

    In closing: Unless something drastically changes in the state-of-the-art-for-the-money-sweepstakes, these are the last amps I will need for my current system; the Sunfire and Anthem are up for sale.


    Rotel 15 Series

    RMB-1565 - Five-Channel Home Theater Power Amp (5x100W Class D, 2U height) $1299.00
    RMB-1575 - Five -Channel Home Theater Power Amp (5x250W Class D, 3U height) $2799.00
    RB-1562 - Two-Channel Home Theater Power Amp (2x100W Class D, 2U height) $799.00
    RB-1572 - Two-Channel Home Theater Power Amp (2x250W Class D, 2U height) $1299.00
    RB-1510 - Two-Channel Installation Amplifier (2x65W Class D, 1U height) $499.00
    RMB-1512 - Twelve-Channel Installation Amplifier (12x100W Class D, 3U height) $2999.00
    Last edited by =AirCeej=; 29 April 2009, 00:49 Wednesday.
  • btf1980
    Senior Member
    • Aug 2007
    • 704

    #2
    Great review. Thanks for taking the time out to write it.
    A camera, passport, good music, good food and good company is all I need.

    Comment

    • keytrnr
      Junior Member
      • Jan 2008
      • 27

      #3
      Anyone able to compare the new Rotel class D's to the old Rotel 1075,1095?

      Comment

      • =AirCeej=
        Junior Member
        • Apr 2009
        • 6

        #4
        Originally posted by btf1980
        Great review. Thanks for taking the time out to write it.
        Thank you, and you're very welcome! The 15 Series Class D's are world-class amps that also happen to be light weight (broadening placement possibilities), efficient (providing a much gentler hit on one's utility bill) and because of their efficiency they wont heat a room let alone a cabinet.

        However, (from a Product Finishing Consultant/End User POV) they need help to be functionally on top of the bell curve...

        Comment

        • ray5
          Senior Member
          • Dec 2008
          • 444

          #5
          Thanks a lot for the review. I also invested in the 15 series and am waiting for the system to be hooked up. But it is comforting to see people are liking it.
          Ray

          Comment

          • lvhung
            Senior Member
            • Jun 2005
            • 301

            #6
            This is certainly a set-up of "cost-no-subject"

            Comment

            • =AirCeej=
              Junior Member
              • Apr 2009
              • 6

              #7
              Originally posted by ray5
              Thanks a lot for the review. I also invested in the 15 series and am waiting for the system to be hooked up. But it is comforting to see people are liking it.
              Ray
              Hi ray5,

              You're welcome; looking forward to your impressions along with knowing the ancillary equipment and room setup. As fair warning, I went through the following before getting a correctly functioning '72 in my rig:

              1. As soon as the 12V TRIG Switch was turned on (with the preamp off) - an annoying high pitched squeal emanated from inside the amp.

              2. To see what would happen with program material, I turned the preamp on (triggering the amp on), listened briefly to FM, turned the preamp off (the amp triggered off) and the noise came back as well as a 60Hz hum from the speakers (I'm using Nordost Blue Heaven Interconnects which can be microphonic), which means the circuitry in the amp isn’t shutting-off the outputs.

              3. I removed the interconnects, speaker cables and 12V trigger line from the amp, kept the 12V TRIG Switch on – and the squeal persisted.

              4. Turned off the 12V TRIG Switch and it went away.

              5. I returned the unit to the dealer, they tested it as well as another one for the noise, and both exhibited the problem.

              Given the above, it would be wise to test a 15 series amp for the two problems at the dealer's shop before taking it home. Much to the credit of the Ann Arbor Rotel Dealer and the North American Rotel Service Manager, I received and installed a new '1572 a week later and report that all is well!

              Regards,
              =AirCeej=
              Last edited by =AirCeej=; 28 April 2009, 07:15 Tuesday.

              Comment

              • WelshOne
                Senior Member
                • Jan 2009
                • 117

                #8
                I would also like to thank you for the review and the time you had taken to do it. :T

                It was certainly an influence in my decision making process for my newly acquired 1570 and 1575.

                Very well written too may I add.

                Comment

                • =AirCeej=
                  Junior Member
                  • Apr 2009
                  • 6

                  #9
                  Originally posted by WelshOne
                  I would also like to thank you for the review and the time you had taken to do it. :T

                  It was certainly an influence in my decision making process for my newly acquired 1570 and 1575.

                  Very well written too may I add.

                  Ah then it's "Cheers!" all around and "well done"! Certainly looking forward to your impressions, equipment and application notes!

                  Comment

                  • ray5
                    Senior Member
                    • Dec 2008
                    • 444

                    #10
                    I am in the process of setting up my system. I ran into an issue due to the limited space in the entertainment center and so I have to stack the 1091 and 1092 on each other. When I do that there is about1.25"-1.5" of space between them. Is that enough for ventilation or should I try to raise the top one some more? I have few inches more to spare in the cabinet and can go some more but how do I raise the top one? Between the two any reason to put one on top versus the other? The 1570 will be in aseparate enclosure right above the amps.
                    BTW, the black is awesome! Initially I liked the silver finish but the black is way better.
                    Ray
                    Last edited by ray5; 28 April 2009, 12:06 Tuesday.

                    Comment

                    • =AirCeej=
                      Junior Member
                      • Apr 2009
                      • 6

                      #11
                      My bad ray', I thought you had 15 Series Amps; nonetheless, to address your issues without straying too far OT - it comes down to a few variables that need to be accounted for as they react with each other:

                      1. Ambient room temperature.
                      2. Rack (entertainment center) ambient temperature.
                      3. Rack's (E.C.) design/ability to exchange air.
                      4. Placement within the rack (E.C.).
                      5. Amps ability to generate heat at idle and just above normal usage (as a healthy buffer/piece of mind).
                      6. Quality electrical connections (AC, 12V triggers, interconnects, speaker cables, etc.).
                      7. Speaker load.
                      8. User's playback level preferences.

                      All of which are weighed against Rotel's recommendations.

                      For instance: Class-A stereo amps driving 1Ω loads, installed in a tight wooden rack in an attic with little ventilation, along with program material played at "spirited levels" is a recipe for a Darwin Award and loss of residence. The other "extreme" would be an efficient amp (Class D) in a temperature controlled metal rack installed in a cool environment (i.e. basement), driving a straight 8Ω resistive load at polite conversational levels...

                      Between those bookends presumably stands the majority of A/V Equipment installations - yours being one of them. Ergo, one of the easiest/basic ways to determine stress on Class A/B and more efficient designs is to: play program material louder than you're normally comfortable with for 1-10 minutes and feel how the amps are doing. The chassis of ICE-based amps (depending on specs and vintage) should feel cooler than the ambient room temp. If they are getting too warm, then improve their immediate environment and/or load.

                      In my case, the '1565 has about 3" of clearance and the '1572 has about 1.5". They are installed in a basement rack, driving modified Mirage OMD 5's that will never see reference levels in a ~4000CF room. The only thing that gets close to body temp is the '72's power supply...

                      Comment

                      • ray5
                        Senior Member
                        • Dec 2008
                        • 444

                        #12
                        Originally posted by =AirCeej=
                        My bad ray', I thought you had 15 Series Amps; nonetheless, to address your issues without straying too far OT - it comes down to a few variables that need to be accounted for as they react with each other:

                        1. Ambient room temperature.
                        2. Rack (entertainment center) ambient temperature.
                        3. Rack's (E.C.) design/ability to exchange air.
                        4. Placement within the rack (E.C.).
                        5. Amps ability to generate heat at idle and just above normal usage (as a healthy buffer/piece of mind).
                        6. Quality electrical connections (AC, 12V triggers, interconnects, speaker cables, etc.).
                        7. Speaker load.
                        8. User's playback level preferences.

                        All of which are weighed against Rotel's recommendations.

                        For instance: Class-A stereo amps driving 1Ω loads, installed in a tight wooden rack in an attic with little ventilation, along with program material played at "spirited levels" is a recipe for a Darwin Award and loss of residence. The other "extreme" would be an efficient amp (Class D) in a temperature controlled metal rack installed in a cool environment (i.e. basement), driving a straight 8Ω resistive load at polite conversational levels...

                        Between those bookends presumably stands the majority of A/V Equipment installations - yours being one of them. Ergo, one of the easiest/basic ways to determine stress on Class A/B and more efficient designs is to: play program material louder than you're normally comfortable with for 1-10 minutes and feel how the amps are doing. The chassis of ICE-based amps (depending on specs and vintage) should feel cooler than the ambient room temp. If they are getting too warm, then improve their immediate environment and/or load.

                        In my case, the '1565 has about 3" of clearance and the '1572 has about 1.5". They are installed in a basement rack, driving modified Mirage OMD 5's that will never see reference levels in a ~4000CF room. The only thing that gets close to body temp is the '72's power supply...
                        Thanks. You know, you have a flair for writing! I guess I'll just have to use and see what happens. I am not sure I misunderstood but the 1091 and 1092 are Class D ice power also. Somebody suggested hockey pucks to elevate the top one! Interesting!
                        Ray

                        Comment

                        • peepaj
                          Member
                          • Jan 2009
                          • 50

                          #13
                          I used 2 pieces of wood cut the same depth as the amps to stack on top of the other 1092 was on top. I did this until I got a new rack. Think they were 1" x 3".

                          Comment

                          • ray5
                            Senior Member
                            • Dec 2008
                            • 444

                            #14
                            Originally posted by peepaj
                            I used 2 pieces of wood cut the same depth as the amps to stack on top of the other 1092 was on top. I did this until I got a new rack. Think they were 1" x 3".
                            That is a good suggestion. Did you have a closed entertainment ctr or open? If closed did you have heating issues?
                            Ray

                            Comment

                            • peepaj
                              Member
                              • Jan 2009
                              • 50

                              #15
                              It was a open stand, I put the 1092 on top figuring it was 2 channel and would probably produce the most heat. I have found that my amps do not give off to much heat and that the bottoms felt warmer to the touch, with the wood blocks the 1092 had better ventilation. As far as heating issues I have not had any, I have ran the 1092 for up to 14 hours straight listening to music at a normal level on my rsp-1069 that is between 50 and 60 on the volume with no heat problems. Hope this helps.
                              peepaj

                              Comment

                              • ray5
                                Senior Member
                                • Dec 2008
                                • 444

                                #16
                                Originally posted by peepaj
                                It was a open stand, I put the 1092 on top figuring it was 2 channel and would probably produce the most heat. I have found that my amps do not give off to much heat and that the bottoms felt warmer to the touch, with the wood blocks the 1092 had better ventilation. As far as heating issues I have not had any, I have ran the 1092 for up to 14 hours straight listening to music at a normal level on my rsp-1069 that is between 50 and 60 on the volume with no heat problems. Hope this helps.
                                peepaj
                                Thanks, it does help. Will try them out and report back.
                                Ray

                                Comment

                                • watchnerd
                                  Member
                                  • Sep 2008
                                  • 42

                                  #17
                                  Originally posted by =AirCeej=

                                  For instance: Class-A stereo amps driving 1Ω loads, installed in a tight wooden rack in an attic with little ventilation, along with program material played at "spirited levels" is a recipe for a Darwin Award and loss of residence. The other "extreme" would be an efficient amp (Class D) in a temperature controlled metal rack installed in a cool environment (i.e. basement), driving a straight 8Ω resistive load at polite conversational levels...
                                  I'm somewhat close to this Darwin award:

                                  Driving vintage Martin Logan Sequels, which spend most of their life below 4 ohms, in a rack with the RSP-1570 processor right on top of the RB-1572 amp. There is maybe 1 cm clearance between the top of the RB-1572 and the bottom of the RSP-1570. And about 1 cm between the top of the RSP-1570 and the glass shelf above it.

                                  Despite all this, the RB-1572 runs cool as a cucumber. The 1570, on the other hand, gets quite warm.

                                  Comment

                                  • ray5
                                    Senior Member
                                    • Dec 2008
                                    • 444

                                    #18
                                    Reporting back. I now have them running a couple of weeks. The Rotel 1091 and 1092 are amazingly cool. Even after 4 hrs straight they are not even warm to touch. WHereas the 1570 gets certainly warm, not hot but warm. I have very little clearance due to space constraints. So the two are separated by hockey pucks with about 1.5 inches and an inch above and an inch below the two. I am very relieved as that was my worry . Hope this helps.
                                    Ray

                                    Comment

                                    Working...
                                    Searching...Please wait.
                                    An unexpected error was returned: 'Your submission could not be processed because you have logged in since the previous page was loaded.

                                    Please push the back button and reload the previous window.'
                                    An unexpected error was returned: 'Your submission could not be processed because the token has expired.

                                    Please push the back button and reload the previous window.'
                                    An internal error has occurred and the module cannot be displayed.
                                    There are no results that meet this criteria.
                                    Search Result for "|||"