HK 525 modifications ! ? !

Discussion in 'AV Receivers' started by DerrickW, Apr 18, 2003.

  1. DerrickW

    DerrickW Stunt Coordinator

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    Just pulled the trigger at JandR and should have the HK525 next week.

    Anybody opened one of these up and have some pictures/descriptions? Not that I'd ever void my warranty [​IMG] but these are some mods I think could help the 525 for my setup:

    1. THE FAN. Either disconnecting or replacing with a quieter one. If nobody knows what type is in there, and what the power to it is, I'll have to research it myself. After you read #2, you may understand why this doesn't seem to risky to me to just disconnect completely! Remember the HK520 was very similar, but only had 5 channels from the same PS, and needed no fan.

    2. DISCONNECT AMPS. Yup, this will be a pre/pro for my separate amps, and if there is an easy way to disconnect the amp section from the power supply to turn it up, I'd like to try it. Of course, if this can be reconnected later it would be best. Improvements that I might expect: less interference to the pre/pro section, less heat generated, less power consumption, and more power available for the pre/pro.

    3. HEADPHONE JACK. I'm going to AB the HK against $500 and $2000 headphone amplifiers that a friend has using our Senn HD600's and see how the HK jack stacks up. Ways to improve the jack depend on what's inside of course. An easy way would be to use the 6&7 channel amps (ie using a/b speaker selection to turn on) through a resistor network to drive the 300ohm load of the HD600. Another method could be to replace the existing circuit with upgraded op-amps, caps, and resistors if the board is setup that way. Or even just stick my own design like a META42.

    Anyone else tried stuff like this? Any help you can offer? Anyone else interested in trying projects too? I'd like to put my engineering degree to some use, but without a roadmap to the internal guts I might be lost.
     
  2. altan

    altan Stunt Coordinator

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    Interesting stuff.. never tried it.

    Just wanted to point out I've had the 525 for 3 months now and have never noticed the fan. That means if it has ever turned on, I didn't notice it. I doubt it has --- I would have noticed.

    I watch dvds at about -10db from reference (which happens to be zero on the volume after calibrating)

    ... Altan
     
  3. JohnSer

    JohnSer Stunt Coordinator

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    Derrick, try it without any speakers hooked up. With no load, it shouldn't get hot enough to turn the fan on. No need to do that internal disconnecting. The 525 gained weight over the 520, so I suspect the transformer got a little larger.

    JohnS
     
  4. Andy_Steb

    Andy_Steb Stunt Coordinator

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    Before tearing apart your new 525, I would suggest hooking it up without all the mods.
    I don't know why everyone is so hung up on the fan one the 525. When I had speakers hooked up to 5 channels the fan only came on when I cranked up the volume and 5 Ch stereo. Who can hear a 4 inch computer fan running over 5 speakers pushing 100dB? I now have my mains running off a separate amp and the fan never comes on.
    Using your receiver as a pre/pro will automatically reduce heat and power consumption. I can't see how giving the pre/pro more available power will benefit anything. It consumes so little power to begin with.
    If the built in headphone jack isn't enough plugging into the surround back or multiroom should work, although it has a separate volume control and is a bit of a pain in the ass to adjust the volume. How about building a custom headphone amp incorporating some sort of Abus controller, I think that would be cool.
     
  5. DerrickW

    DerrickW Stunt Coordinator

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    All this common sense reasoning is killing my excitement for chopping up the 525 for 1% more performance! Where's the fun in that?

    Yeah, the headphone amp is probably the biggest deal here. If you guys do just speakers, then you'd be shocked at the prices of headphone amps. Most of the stuff under $300 is junky. Can you imagine paying $500 for under one watt of power? My friend's amp cost $2000... after speaker amps I would have expected these to cost a lot less. It seems crazy to me since even high end headphones like the Sennheiser HD600 are under $300.
     
  6. Mike Kao

    Mike Kao Second Unit

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    Here's an upgrade that won't involve tearing apart your receiver and voiding the warrantee... upgrade the power cord. It comes with the detachable cord, so swap it with a nice custom-made cord, and reap in the benefits!
     

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