MCM Make good amps?

Discussion in 'Home Theater Projects' started by MichaelBAr, Jan 22, 2004.

  1. MichaelBAr

    MichaelBAr Stunt Coordinator

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    Wondering because I was planning on buying one of their amps for my budget diy sub. It will most likely be mcm then partsexpress if mcm isn't good.
     
  2. Aaron Gilbert

    Aaron Gilbert Second Unit

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    Which ones are you looking at? Amplifier design is not rocket science, so it's pretty easy these days to make a reliable amplifier. I would venture that the MCM units are no worse (or better) than the Parts Express units similarly priced. I think it's pretty safe to buy based on which ones have the features you need in your price range. More power is almost always a good thing though, so keep an eye on the power output. For instance, MCM has a 50w amp (8 ohms) for only $71, but their 150w amp is only $129.

    You could also check out http://www.apexjr.com for a few more options. It's amazing how inexpensive subwoofer amplifiers are these days.


    Aaron Gilbert
     
  3. Dave Poehlman

    Dave Poehlman Producer

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    I bought one of their 50w amps. The first one I got had a bad high-level output channel. MCM was quick to replace it no questions asked.

    Other than that, I've had no problems with it. I also have the ApexJr amp, that one works well also. It seems a little more beefy in its construction. The knobs feel more solid. Other than that, they're both reliable.
     
  4. MichaelBAr

    MichaelBAr Stunt Coordinator

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  5. Aaron Gilbert

    Aaron Gilbert Second Unit

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    Holy cow, that one is only $90?! That was the $129 I mentioned, the price it shows in my catalog. That is a steal for 250w at 4 ohms. I would snap that up right away, although it doesn't appear to be on sale. Odd. I don't know that I have seen an amp that powerful with a regular price below $100. I really like the detachable AC cord, power switch, phase adjustment, and crossover bypass. The only thing I don't see it having is a sealed back. That's not a mandatory feature (almost no commercial subs have it), but certainly nice.


    Aaron Gilbert
     
  6. Rory Buszka

    Rory Buszka Supporting Actor

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    I would have to disagree. I think that companies add sealed backs as an easier way to seal the amp to the outside air, but the often flimsy construction of the sealed-back piece could flex under high output. I recently purchased the Parts Express 500-watt subwoofer amplifier for a project (which is on hold indefinitely until I manage to get a hold of Stryke's proprietor John J. and have my driver shipped that I won as part of their name-change contest; it's been just over a month now with no word and I still need to order PR's) and I thumped the sealed back of the amplifier and found that a little puff of air came out around the volume controls and the RCA connector. On the other hand, I have always thought that the PE/MCM 250W amp (they are the same, I think) was sealed using glue or expando-foam or something around its inputs and controls, which would be better IMHO.
     
  7. Aaron Howell

    Aaron Howell Stunt Coordinator

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    I have many of the 6281a, and they are all open back.
     
  8. Dave Poehlman

    Dave Poehlman Producer

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    Wow, an amp with a built in passive radiator... some might pay extra for a feature like that. [​IMG]
     
  9. Aaron Gilbert

    Aaron Gilbert Second Unit

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    That's certainly a possibility. The question becomes which is more objectionable, the sealed back flexing, or air puffing out of unusused RCA jacks and binding posts? Now some companies cover the internal side of all the binding posts and RCA connectors with hot glue. That works.

    Aaron Gilbert
     
  10. perry web

    perry web Stunt Coordinator

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    Does MCM amps come w/ a warrenty? I can not find anything on the website (sucks)

    I got the money to build my amp and I wanted to save $40 bucks over the PE amp and put that towards a better woofer.
     
  11. Aaron Gilbert

    Aaron Gilbert Second Unit

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    The warranty isn't listed in their print catalog, either. I just called them, and the 50-6281 has a one year warranty.

    Aaron Gilbert
     
  12. perry web

    perry web Stunt Coordinator

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    wow thanks for enabling me to be lazy :)
    I guess there is not 40 bucks worth of difference between mcm and Pe so I guess i will hit "proceed w/ order"

    thanks
     
  13. Bob Kavanaugh

    Bob Kavanaugh Second Unit

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    What about a rumble filter? I didn't see where the MCM has one. I'm building a ported sub and I don't want it to unload below 20hz.
     
  14. Baldemar Garcia

    Baldemar Garcia Stunt Coordinator

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    Bob,

    The mcm has the same rumble filter as the PE, just the resistor numbers are different. Search this forum for "new mcm plate amp" (or for posts by me) and it should give details. good luck.
     
  15. Frank Carter

    Frank Carter Screenwriter

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    When talked to MCM tech support about this, they said it had no rumble filter.
     
  16. Bob Kavanaugh

    Bob Kavanaugh Second Unit

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    Will the correct answer please stand up? Seriously though, thanks for the help guys, i'm leaning toward the PE amp now.
     
  17. Baldemar Garcia

    Baldemar Garcia Stunt Coordinator

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    The question may be answered correctly my MCM if they are asked: "Does this amp have a bass boost?"

    If the schematic that they sent me is correct for what they are presently shipping, then the answer is yes.
     
  18. Frank Carter

    Frank Carter Screenwriter

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    When I takled to MCM they said the original version of this amp was a copy of the PE 300-796. They said the current MCM 50-6281a was "upgraded"(not sure what they meant by that) and it no longer has the boost or rumble filter.

    I measured the frequency response of a sub powered by the MCM amp I got about 2 months ago. There was nothing special happening around 30Hz to indicate a boost and the sub started to drop off ~15Hz indicating no rubmle filter in place. I can post the graph if you guys want.
     
  19. Baldemar Garcia

    Baldemar Garcia Stunt Coordinator

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    That's very interesting Frank, and it does sound like there's no longer a bass boost in place. You may have noticed I had problems with the unit I received about one year ago, relating to its turn-on circuitry (don't know if it was defective or a bad design). It's possible a new preamp design was implemented to fix that issue, and it also eliminated the bass boost. I may have to buy one to see the present resistor values used in the 'bass boost' circuit, or if anyone cares to check, they are R226 and R227.
     
  20. Frank Carter

    Frank Carter Screenwriter

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    I'll check for you later today since it's not mounted. I'm using the cardboard box it came in to house it for now.
     

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