Splitting a Receiver

Discussion in 'Archived Threads 2001-2004' started by DanStephens, Jan 27, 2003.

  1. DanStephens

    DanStephens Auditioning

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    Hello, I want to get in-between the preamp and power amp in my Sony STR-DE675 Receiver. Can anyone help? Let me know if I'm not making the question clear. Thanks.
     
  2. Kevin Deacon

    Kevin Deacon Second Unit

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    Not Clear!!
     
  3. DanStephens

    DanStephens Auditioning

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    I want to put a "Preamp out" output on the back (All Channels) and a "Power Amp In" Input on the back of the receiver.
     
  4. Yogi

    Yogi Screenwriter

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    I dont think anyone here has done anything like that. If they have I would like to hear about it. I think thats substantial amount of work and given the cost of a new receiver these days that has preouts, it wouldn't be a worthwhile task to do. For less than a few hundred $$$ you can get a receiver that will do what you are asking.

    My 2 cents.
     
  5. AaronBatiuk

    AaronBatiuk Second Unit

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    This should be possible, but I can't say that it will necessarily work well.

    You need to find the amp board and the main audio board. In general on Sony receivers, the amp board is in the middle and contains several power transistors attached to the big main heatsinks. It should be easy to spot. The analog board is usually along the right side (if you are facing the front panel. The back usually contains all the audio/video switching circuitry. There will be several cables running into the amp board to carry the sound into it. The cables usually have a red and/or white wire (usually right and left channels respectively) and at least another wire (probably black, grey, green, etc.) which is ground. These cables will run to either the main audio board or the volume control. It is these cables that you want to "intercept". You may be able to determine which cables are the audio and which are for which channel using the test tones. I don't recommend powering up the receiver with the cover off, though.

    Note that these cables do not necessarily caryy "pre-amp level" signals. Pre-amp level signals are usually about 2 V peak-to-peak at maximum, but I have no idea what level these signals are at. You would be wise to be careful when connecting this signal to another piece of equipment like an amp or equaliser or whatever it is you want to do.

    Everything you do is at your own risk.
     
  6. Jonathan M

    Jonathan M Second Unit

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    Dan,

    Although I hate to refer people to other forums, you may wish to ask in both the DIY forum here, or the diyaudio.com forum.

    It IS possible, but how easy it is will depend on what your amp looks like. If the power amp is on the same board as the preamp (Fairly likely in this unit) then it may be tricky. It will have a digital volume control, so you're out of luck there.

    As Aaron said, you want to find the connection from preamp out to power amp in. This may be either a cable, or a PCB track. I would work backwards from the main power transistors. Then, cut the link and check that the amp now produces no sound.

    You may need to add input and output buffers and/or coupling caps to make sure you are not loading the preamp or external equalizer too much.

    BTW: What is it you are trying to achieve - biamplification?? If so, I'd seriously consider starting from scratch!!
     
  7. JohnSer

    JohnSer Stunt Coordinator

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    I agree with the others here, that this is a pretty radical mod. Also has the potential of adding hum to the system if not done correctly. I would recommend trying to get the schematics for this receiver, before attempting. I considered adding preouts to Onkyo 575X, figuring if I got the schematics to it and the next higher unit which did have preouts. Never did find schematics for them, and while I'm OK with a soldering iron and such, if it turned out to be tacking wires to surface mount components, it can be very tricky. Hard to justify ruining a perfectly good receiver.

    JohnS
     
  8. Yogi

    Yogi Screenwriter

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  9. DanStephens

    DanStephens Auditioning

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    2 reasons, one being I can't leave stuff alone, the other being money.

    BTW I want to put my equalizer inbetween the amp and preamp & Thanks for all your help so far everyone.
     

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