Super Pas Three output buffer

Discussion in 'Audio by Van Alstine' started by sberger, Jun 21, 2016.

  1. sberger

    sberger Hard Core Geezer Subscriber

    A couple of years ago I acquired a Super Pas Three from a friend. He had bought it from somebody else, so I haven't a clue as to exactly what went into the building process. It's definitely an older build. Anyway, it works fine and I like it, and have used it with several different amps all with good results. My understanding is that an output buffer helps provide needed flexibility for these preamps, particularly when using them with solid state amps. Is there a way to know by looking if a buffer was added to mine? And if not, would it be advisable to add one ? What improvements, sonically, might I hear?

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  2. avahifi

    avahifi AK Member

    Messages:
    39
    Location:
    Woodbury, Minnesota
    This unit appears to have been built from one of our do it yourself kits. It has one strangeness. Although it appears to have the Noble balance control we supplied with the kit, it does not have the matching Noble volume control, but something a lot cheaper looking. I have no idea why.

    It does not have the buffered line or phono output circuits. These were built on additional small circuit boards that are missing as this photo shows.

    These circuit were simple unity gain current amplifier buffers that provided a low output impedance and high drive current. They isolated the relatively high impedance tube line and phono circuits from low impedance loads, such as some solid state amplifiers. They provided a very high input impedance to the tubes, allowing them to run just driving "air" (1M ohm load) which improved the tube linearity about 10dB too. Unfortunately these circuits are now out of production and no longer availabie.

    This still should be a really nice sounding preamp, musical and forgiving.

    Regards,

    Frank Van Alstine
     
    sberger likes this.
  3. sberger

    sberger Hard Core Geezer Subscriber

    Thank you very much for your reply Mr. Van Alstine. It's very much appreciated.
     
  4. Bostown

    Bostown Low End Audio Enthusiast! Subscriber

    Messages:
    4,522
    Location:
    Boston MA.
    Oddly enough , One of these just landed at my place courtesy of a BarterTown sale here in AK I'm testing it now. So far , not too shabby. It's paired with a McIntosh MC7300 but will ultimately get paired with a rebuilt ST-70 and/or set of MKIIII Monos This one appears to have the correct pots and the Buffer stage mentioned. I'll have to try the Phono section tomorrow. I assume it's MM ?
     
  5. sberger

    sberger Hard Core Geezer Subscriber

    Yes the stage(and it's a good one) is MM.

    Go Sox!
     
  6. Bostown

    Bostown Low End Audio Enthusiast! Subscriber

    Messages:
    4,522
    Location:
    Boston MA.
    here's the unit mentioned earlier.

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  7. sberger

    sberger Hard Core Geezer Subscriber

    Nice! Bet the phono will sound great.
     

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