MOT discussions

Discussion in 'Random Thoughts' started by tomchr, Jan 30, 2017.

  1. tomchr

    tomchr MOT - Neurochrome

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    First thought: Definitely not enough heat sinking. The clones may be adequate for easy listening, but if you push them to 30-40 W into 4 Ω for any length of time they'll very likely overheat. I'd expect them to get rather toasty even with music at moderate listening levels.

    The basic LM3886 is a pretty decent amp if you take proper care of it (i.e. follow all the recommendations in the data sheet, including the application section). Sadly many don't. The end result range from amps that provide mediocre performance to amps that oscillate under certain load conditions. This has given chipamps and the LM3886 a bad reputation in some circles, which is unfortunate as it's actually a capable amp in the right hands. I aimed to right this by providing the LM3886 Done Right, which provides performance slightly better than the LM3886 data sheet indicates.

    The Modulus-86 and -286 take it up a notch by applying error correction to the LM3886. That combined with the layout techniques used is why the Modulus-86 and -286 provide world class performance. The only commercial product I've come across that meets the performance of the MOD86/286 is the Benchmark ABH-2, which last I checked would set you back a cool $4k. A stereo Modulus-86 can be built for $400, including the chassis.

    Tom
     
  2. zerodeefex

    zerodeefex SBAF's Imelda Marcos

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    Performance is a loaded term in this hobby. Consider your audience. You may want to be more specific.
     
  3. tomchr

    tomchr MOT - Neurochrome

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    The Oxford English Dictionary offers the following definition: "A task or operation seen in terms of how successfully it is performed"
    Performance in my book means measured performance. This should be fairly obvious if you visit my website or generally read my posts... ;)
    I'm curious which other definitions are in common use here. Would you kindly help me understand this?

    Which term would you rather that I use to describe measured, quantifiably performance if the word "performance" is somehow inadequate or loaded?

    Tom
     
  4. tomchr

    tomchr MOT - Neurochrome

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    I'll do my best to remember. I can't promise a 100 % success rate. I am human.

    One thing, though: There is a large body of research which points to good measurements leading to a good perceived listening experience. Thus, performance = performance = performance, which is why I use the term performance. Just saying...

    Tom
     
    Last edited: Jan 30, 2017
  5. ultrabike

    ultrabike Measurbator - Admin

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    I recommend to let folks arrive to their own conclusions Tom.

    EDIT: I really hope this post does not come the wrong way Tom. @Marvey explains it best below.
     
    Last edited: Jan 30, 2017
  6. zerodeefex

    zerodeefex SBAF's Imelda Marcos

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    Just a general word of advice: consider your audience. It never hurts to contextualize your message to the person(s) reading your post. Not all of us visit to your website or are aware of your work (this was the first I've heard of it). In fact, if I look at site analytics exploded against your posting, the vast majority of members never see anything you post and redirect/incoming traffic to/from your site is quite low from SBAF. I'd argue that for the the average person reading this thread, it's not obvious.

    Additionally, how "successfully it is performed" is ambiguous. How the heck was I supposed to know you meant measured performance? How do I know which measurements? How do you know what performance metrics the people reading this thread find relevant in order to be sure that your usage of a loaded term is genuinely understood by others? What if heat output is genuinely important to me given the nature of my environment? Or thermal efficiency under load? What if overall power output is the most relevant performance metric for me? What if power noise rejection is important? What if it's MTTF? What if it's material properties? What if it's interference rejection from powerful emitters? What if it's load capacity because I have to stack things on my amp?

    Using loaded terms like performance on a forum like this without being more specific tells everyone else that you don't care if they have a different perspective than you. Not everyone shares your context so your assumption that this should be common sense is slightly demeaning to our readers.
     
  7. purr1n

    purr1n Desire for betterer is endless.

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    What UB means is to be careful when making statements about your amps in comparison to other manufacturers amps. I know you were replying to a question from @yotacowboy, but he should not have asked you that question in the first place because you are an MOT.

    The last thing I want is another manufacturer reading your statements, creating an account, and starting a food fight of sorts.
     
  8. yotacowboy

    yotacowboy McRibs Kind of Guy

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    I didn't intend to start a food fight. Apologies if it seemed that way. Tom's post was helpful with regards to the dissipation requirements and heat sinking, without needing to get into "performance".
     
  9. tomchr

    tomchr MOT - Neurochrome

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    I'm getting used to the MOT status as well, so perhaps we can learn together. I have a hard time not responding to a direct question that I know the answer to. My degrees are in engineering, not English, and English is not my first language. So please excuse me if I don't communicate flawlessly.

    Tom
     
  10. purr1n

    purr1n Desire for betterer is endless.

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    Not any of your guys' fault. We haven't taken the time to formalize guidelines and rules for MOTs.
     
  11. ultrabike

    ultrabike Measurbator - Admin

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    Moved this discussion here to avoid loading the "Solid-State Power Amp Adventures" thread. Kept @tomchr's original response back there though as it has some fairly valuable information pertaining to the thread's discussion, and replicated it here for context.

    I'm also an EE. And my first language is Spanish. And can understand.

    The concern is more related to keeping things clean. Whatever our focus may be (DIY, perceived performance, measured performance, and so forth), allowing vendors to evaluate other vendor's equipment in this forum, may turn ugly.

    It's perhaps less of a problem if such things (measurements and evaluation) are dealt with by a third party with less of an direct vendor involvement (customers or a professional/non-professional reviewer). Like @Marvey said, we'll come up with some guidelines about this.
     
    Last edited: Jan 31, 2017
  12. atomicbob

    atomicbob dScope Yoda

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    Amen! Thank-you!
     

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