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Thread: Preamp/Amp Suggestion for Sierra 2

  1. #31
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    Default Re: Preamp/Amp Suggestion for Sierra 2

    The Benchmark AHB2 amplifier is Stereophile Class A rated in their recent "recommended components" list. The reviews all seem to tout its incredibly low distortion and noise floor.

    The design appears to be some new variation on class AB / class H / class D ??

    The manufacturer claims the technology "virtually eliminates all forms of distortion".

    https://benchmarkmedia.com/products/...ower-amplifier

    I'd love to be able to someday replace my ~90 lb. beast with something this small and light...

  2. #32
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    Default Re: Preamp/Amp Suggestion for Sierra 2

    Quote Originally Posted by SteveM View Post
    I understand the concern about switching noise with Class D amps and RAAL tweeters, but am curious if this applies to Class G, such as the Outlaw 2200 mono blocks? I've heard Class G referred to as "hybrid" amps, but admit I don't really understand the concept at this point. Can anyone enlighten me?
    After doing some reading I think I can explain the gist of it.

    Class G and H are modifications to a class AB amplifier's output stages to improve its efficiency and reduce wasted heat/electricity.

    The modifications are to the output stage rail voltages, so technically not in the signal path(?)

    Class G: Several rail voltages are available, and the lowest one that will do the job at any given moment is selected. For example, during a quiet music passage the rail voltages are +/- 10 V, when the music gets louder the rails switch to +/- 20 V, and at the loudest levels +/- 40 V is selected.

    Class H: The rail voltage is a continuously variable analog voltage. Based on the input music signal, just enough voltage is supplied to the output devices for them to reproduce an amplified version of the input.

    Class H is more efficient than class G, but also more complex.

    https://en.wikipedia.org/wiki/Power_amplifier_classes

  3. #33
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    Default Re: Preamp/Amp Suggestion for Sierra 2

    Quote Originally Posted by dkuster View Post
    After doing some reading I think I can explain the gist of it.

    Class G and H are modifications to a class AB amplifier's output stages to improve its efficiency and reduce wasted heat/electricity.

    The modifications are to the output stage rail voltages, so technically not in the signal path(?)

    Class G: Several rail voltages are available, and the lowest one that will do the job at any given moment is selected. For example, during a quiet music passage the rail voltages are +/- 10 V, when the music gets louder the rails switch to +/- 20 V, and at the loudest levels +/- 40 V is selected.

    Class H: The rail voltage is a continuously variable analog voltage. Based on the input music signal, just enough voltage is supplied to the output devices for them to reproduce an amplified version of the input.

    Class H is more efficient than class G, but also more complex.

    https://en.wikipedia.org/wiki/Power_amplifier_classes
    Thanks very much, very interesting. So you think Class G may immune from the switching noise Dave warned of in Class D?

  4. #34
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    Default Re: Preamp/Amp Suggestion for Sierra 2

    Quote Originally Posted by SteveM View Post
    Thanks very much, very interesting. So you think Class G may immune from the switching noise Dave warned of in Class D?
    Yes, possibly. That Benchmark AHB2 amplifier I referenced appears to be a class H or class G variant, and the specs claim incredibly low distortion and noise floor.

    Again, the basis of class H/G is a class AB amplifier topology. So the input signal is not being modeled as a PWM pulse train as in class D.

    But I still wonder if switching between different output stage voltage rails (class G) or continuously varying it (class H) might introduce artifacts that can be audible?

  5. #35
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    Default Re: Preamp/Amp Suggestion for Sierra 2

    Quote Originally Posted by dkuster View Post
    Yes, possibly. That Benchmark AHB2 amplifier I referenced appears to be a class H or class G variant, and the specs claim incredibly low distortion and noise floor.

    Again, the basis of class H/G is a class AB amplifier topology. So the input signal is not being modeled as a PWM pulse train as in class D.

    But I still wonder if switching between different output stage voltage rails (class G) or continuously varying it (class H) might introduce artifacts that can be audible?
    This is an interesting technology and could be the best of both worlds... Due to the output transistors always receiving voltage (from either the high or low voltage rails) - I believe the switching noise in Class D variants would be eliminated.
    .
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    Good Sound To You!

    David Fabrikant
    www.ascendacoustics.com

  6. #36
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    Default Re: Preamp/Amp Suggestion for Sierra 2

    Very interesting! Thank you, Dave and dkuster, for the input. Anybody have experience with the Outlaw 2200 mono block amps? Wonder how they might match up with my Lunas, or the Sierra 2s?

  7. #37
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    Default Re: Preamp/Amp Suggestion for Sierra 2

    Quote Originally Posted by SteveM View Post
    Very interesting! Thank you, Dave and dkuster, for the input. Anybody have experience with the Outlaw 2200 mono block amps? Wonder how they might match up with my Lunas, or the Sierra 2s?
    I have 5 Outlaw 2200 monoblocks. I use them to drive the center, surrounds, and backs in my all Vandersteen 7.1 home theater/music room.

    I should say, "until recently all Vandersteen", as I've sold my heavy and expensive Vandersteen Model 5's after auditioning Sierra Towers w/ RAAL. I would have made the switch to the Towers if they were just able to hold their own against the Vandys.

    Turns out I liked them _much_ better. Smoother, more extended highs, tighter, more articulate bass - although not quite as much bass. Still I'm amazed at how much bass is possible from a couple of 5"-ish drivers.

    So I sold the Model 5's and used the money to pay for the RAAL Towers plus a pair of Rythmik F12 subs. Now when I sit down for a listen I can't wipe the silly grin off my face.

    Next I'm (patiently - NOT) waiting for the bamboo shortage to end so I can take delivery on a Horizon Center w/ RAAL to replace my Vandersteen VCC-5.

    Long term plan is to replace the Vandersteen VSM-1 wall mount speakers with 4 Lunas for surrounds and backs.

    Anyway, back on topic - I've driven the Towers with a ModWright KWA-150SE amplifier in the past, but I'm currently using a modified McCormack DNA-1 Deluxe (both 150W per channel, solid state.)

    I can swap some wiring and try the Towers with two of the Outlaw 2200's and report back with my impressions on how they compare. If the 2200s can do well with the Towers I think you'd have no problems at all with Sierra 2s or Lunas...

  8. #38
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    Default Re: Preamp/Amp Suggestion for Sierra 2

    Definitely would be interested in your impressions if you have time to do that, dkuster. Your trade is quite a compliment to Ascend and the Towers. I'm a beginner who is very grateful I happened on Ascend and the Lunas (which are my LCR). They are powered by my AVR right now, but I'd like to find a nice amp, or in this case amps, for them, and the Outlaws caught my eye.
    My Lunas give me a version of that same silly grin you mention. I imagine my face might actually freeze in that position if I were listening to the system you describe!

  9. #39
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    Default Re: Preamp/Amp Suggestion for Sierra 2

    Quote Originally Posted by SteveM View Post
    Definitely would be interested in your impressions if you have time to do that, dkuster. Your trade is quite a compliment to Ascend and the Towers. I'm a beginner who is very grateful I happened on Ascend and the Lunas (which are my LCR). They are powered by my AVR right now, but I'd like to find a nice amp, or in this case amps, for them, and the Outlaws caught my eye.
    My Lunas give me a version of that same silly grin you mention. I imagine my face might actually freeze in that position if I were listening to the system you describe!
    Ok, last night I hooked up two Outlaw M2200's to my Towers and had a listen.

    First off, I usually don't do reviews as I'm not good with the flowery language and audiophile buzzwords. I can't even give a good definition for some of the terms commonly bandied about.

    Second, it's been my experience that unless one is being driven to the point of clipping, or can't handle a certain speaker load, it is very difficult to reliably tell the difference between two well-designed solid state amplifiers.

    McCormack DNA-1 vs. ModWright KWA-150SE:
    I've had the DNA-1 since the 90's. It is an audiophile classic and has racked up a slew of great reviews. Several years ago I acquired the KWA-150SE. I give the KWA-150SE the slight win over the DNA-1 because to my ears the bass is a bit tighter and punchier. This is a subjective opinion. If you blindfolded me and ran a scientific test the results might be different.

    Outlaw M2200 vs. McCormack DNA-1:
    This is the only direct comparison I could make, as the KWA-150SE is out for service (needs a bias adjustment to prevent overheating.) And the result? I couldn't tell any difference. I listened to some jazz, female vocals, and rock. It all sounded great - with either amplifier. The Outlaw amps got only slightly warm to the touch.

    So maybe a bit anticlimactic and not very insightful, but I think it's high praise for the Outlaw and impressive that it compares well to the McCormack.

    I think two of the 2200's would work well for what you propose, and the price is very reasonable.

    DISCLAIMER: This is all just my opinion with my gear in my room, and my ears are not as golden as they used to be

  10. #40
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    Default Re: Preamp/Amp Suggestion for Sierra 2

    Very helpful. Thanks for taking the trouble to work on this. As soon as the Outlaws have another sale, I think I will probably take the plunge and get three 2200s. I think they probably fit my needs and price range better than anything else. Outlaw just announced a new 7-channel for about $1,000, if anyone is interested in that.

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