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'70s Receiver Wars

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  • #16
    Critical listening impressions 20 hours after receiving my 1975 Sansui vintage AU-7700 back from QRX Restore the top Sansui restorer in the country.
    I placed the two tiny tube FX Audio 01j in between it's preamp outs and main ins, loaded with the best NOS tubes from Holland.
    It was recapped, upgraded and an interesting modification was done, it's known as the differential balance mod. It reduces the distortion from .1% to only .01%.
    By putting the tubes in the circuit, I added vacuum tube distortion after lowering, by a factor of 10 the Solid State distortion.
    It creates a very pleasing hybrid sound, which is going to get better and better because both the tubes and the unit, should be played in for between 150 to 200 hours, but I can already notice a tighter and crispier bottom end.

    Right now it's about a tie with my QRX-6500 unrestored QUAD unit because I discovered a new to me great pair of "middle speakers", which are about 2 feet in front of the listener as shown in the instruction manual under setup 2-2. They are Infinity Kappa 200's, made in Denmark with excellent craftsmanship.

    For one on one critical listening I already prefer the somewhat raw AU-7700, but, if we ever have parties again, I would favor the QRX-6500 because it produces a lot more music, even though they share the same front towers, the "middles" add a lot.

    All of the components should be considered best buys and they are all getting hard to find in good condition.

    I doubt that any of you have heard this type of setup before, you can have it all for the price of decent set of interconnects and speaker cables.