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  1. #1

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    Default Adding Preamp Outputs to an Integrated Amp with No Outputs??

    I've been running a mid-1980's vintage Yamaha Integrated Amp, model A-700.
    My sources are a Meridian 508.20 CDP and a Music Hall MMF.7 Turntable (with Eroica Cartridge). Speakers are LSi9s.

    After a long upgrade waiting period, I just purchased a McCormack DNA-125 Amp and I want to put it into my system. Until I can afford a preamp upgrade, which may be a long wait (I've had my eye on an Audible Illusions M3A), I intended to use the preamp and phono-pre section of the Yamaha Integrated amp. That is to say I wanted to BYPASS the amplifier section of the A-700 and just use the Preamp and Phono Pre sections of the Yamaha.

    Unfortunately, I now see now that there is no way to connect the McCormack to the Yamaha. See this thread for details:

    http://www.polkaudio.com/forums/showthread.php?t=74536


    Is it feasible to hack the Yamaha and convert it to include a preamp outputs (including the phono stage as I use a TT)?
    Just how involved would it be to convert the electronics on the Yamaha to include an output jack? 3 years back I had asked a member of another forum for a schematic of the A-700 but he never forwarded it: I'm sure I could locate one if I searched harder. The Yamaha only cost me around $85 so it is essentially free audio. But still, it is the only functional amp/preamp I have now, so I do not want to totally butcher it. I have some basic electronics skills, a basic home electronics workshop, but I am no expert. In other words, I could do all the soldering/assembling/mechanical work, but I wouldn't be able to design the circuit. What would a modification like this involve?


    Here's what the back of the Yamaha A-700 has by way of single ended jacks:

    ----------------
    PHONO: L/R
    ----------------
    INPUTS:
    -TUNER, L/R
    -DAD, L/R
    -AUX, L/R
    ----------------
    TAPE 1
    -TAPE PB, L/R
    -REC OUT, L/R
    ----------------
    TAPE 2
    -TAPE PB, L/R
    -REC OUT, L/R
    ----------------



    Thanks a bunch for any ideas.

  2. #2

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    Default

    you could buy on of these
    http://www.partsexpress.com/pe/pshow...number=302-307

    or use that 65.00, towards a preamp that you need
    Dodd - Battery Preamp
    Monarchy Audio SE100 Delux - mono power amps
    Sony DVP-NS999ES - SACD player
    ADS 1230 - Polk SDA 2B
    DIY Stereo Subwoofer towers w/(4) 12 drivers each
    Crown K1 - Subwoofer amp
    Outlaw ICBM - crossover
    Beringher BFD - sub eq

    Where is the remote? Where is the $%#$% remote!

    "I've always been mad, I know I've been mad, like the most of us have...very hard to explain why you're mad, even if you're not mad..."

  3. #3
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    Default

    It seems like you could tap into the inputs and just run their signal out with a separate set of wires and jacks. Its seems pretty straight forward, but I'm sure someone will shoot a hole in my simple plan.

  4. #4

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    Default

    hoosier21,
    Thanks for the link. I wonder how well that would work, reviews seem mixed. I probably would rather put the $65 towards a preamp.

    zingo,
    I am thinking along these lines.

    Anyone care to elaborate how to do this with some opinions about how involved it would likely be?

  5. #5
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    If actually the idea works; open the top on the amp and find the incoming signal wires. Strip off a bit of the insulation on the wires and solder onto it with the new wires. Connect those pairs to your new outputs and you should have a signal. Note that these outputs will be always on, and a switch could be installed if you wanted the ability to toggle them off.

  6. #6

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    Quote Originally Posted by zingo View Post
    If actually the idea works; open the top on the amp and find the incoming signal wires. Strip off a bit of the insulation on the wires and solder onto it with the new wires. Connect those pairs to your new outputs and you should have a signal. Note that these outputs will be always on, and a switch could be installed if you wanted the ability to toggle them off.
    Not a good idea.
    You can easily build a passive volume control to use with the tape monitor outs. A linear taper 50k pot, and 4 RCA jacks, and you are good to go. The bad news is you have to turn the volume manually. No remote.
    Ben
    Please. Please contact me a ben62670 @ yahoo.com. Make sure to include who you are, and you are from Polk so I don't delete your email. Also I am now physically unable to work on any projects. If you need help let these guys know. There are many people who will help if you let them know where you are.
    Thanks
    Ben

  7. #7
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    Quote Originally Posted by zingo View Post
    but i'm sure someone will shoot a hole in my simple plan.
    ;) :p

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