PE Sub Amp Auto Bypass

Discussion in 'Home Theater Projects' started by Robert_CA, Sep 2, 2005.

  1. Robert_CA

    Robert_CA Stunt Coordinator

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    I was experiencing some auto turn-on sensitivity problems with a recently purchased a PartsExpress #300-806 500-watt sub amp. The PE is a pretty good plate amp with plenty of power to drive my AVA15 driver. In it's stock form, the PE amp's auto turn-on circuit worked pretty good with most HT movies but it did not work as well as I liked when I listened to music or watched cable at low listening levels. Since PE said that this circuit is gain dependent, I also tried every combination of available gain settings with my sub amp and my Outlaw 950 pre/pro and got mixed results. I also tried the suggested PE resistor fix on the auto turn on circuit but it still wasn't as responsive as I expected so I finally decided to try a suggested fix that I found in an earlier HTForum thread on the similar #300-808 1000-watt PE amp to bypass the circuit entirely. That fix involved the installation of a jumper across J2 on the left hand side of the amp board. I decided to go a step further by making it switchable. This is how I did it:

    I purchased a single pole, mini rocker switch (a $3.00 part) from a local electronics supply house. After removing the rear cover to expose the circuit boards, I soldered the two leads that would go to the switch contact onto each side of J2 on the amp board using solid copper hookup wire. I then cut out the opening out for the rocker switch in the aluminum panel on the left side of the power cord connector and mounted it. I then connected the leads from the amp board to the mounted switch using spade connectors.

    The amp now works equally well in both positions. I can the "bypass" the auto circuit when I'm listening at low levels (night viewing, watching movies with lower bass content or watching cable) or I can engage the auto circuit when I'm watching those high energy action movies. Maybe other PE amp owners out there that have been experiencing this condition with these PE amp models could possibly benifit from this. Anyone wanting to do this fix could probably obtain a rocker (or toggle) switch from the PartsExpress catalog or Radio Shack. Finally,I'd like to thank those who had discussed this issue in the previous HTForum thread. You gave me the idea to give this fix a try. :b:
     
  2. LanceEAR

    LanceEAR Agent

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    Thanks for the info. Looks like the best of both worlds. I'll have to try this out!
     
  3. Mark--M

    Mark--M Stunt Coordinator

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    Mine was terrible too. Didnt come on till over 80 dB output. I added the resistor and now it works perfect. Comes on at such a low level I cant even detect it sometimes.

    If you add the resistor and its still not sensitive enough, you could always add a smaller one. I believe I used 750 ohms which was the lower limit (most sensitive) of what they suggested.
     
  4. Robert_CA

    Robert_CA Stunt Coordinator

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    I went that route as well. My circuit was still a little sluggish - must be particular to my unit. I listen at some fairly low levels and with the bypass engaged I have the sub on all the time and I don't have it turning off when there are long "quiet" passages during my movies.
     

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