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Voltage Question on '70s Sound City Head

Discussion in 'Amps and Cabs [BG]' started by Tweaker27, Apr 6, 2015.

  1. Tweaker27


    Aug 28, 2014
    New Haven, CT
    So, I just got my hands on a Sound City 50 Plus
    I Love It! It's dirty and Lemmy-esque, it's awesome.
    My question is with the voltage switch... Should I be running it at 105V or 115V ?
    And if you could tell me why as well, that would be great!
    Also, would I need different fuses by running at different voltage?

    2015-04-06 14.57.00. 2015-04-06 16.22.35.
  2. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    Set it at the closest setting to you line voltage. In the US, the line voltage is typically 120 VAC but it could be higher or lower. So set it at 115VAC.

    Some other countries use 110VAC as their standard. Japan for example uses 100v. Standards have changed since when your amp was built. At one time 115VAc was the standard in the US and Canada. It has crept up. Higher voltages are more economical for the power company to distribute.
    Last edited: Apr 7, 2015
  3. Tweaker27


    Aug 28, 2014
    New Haven, CT
    Thanks... That's what I thought.
    beans-on-toast likes this.
  4. You should install a 5A fuse too. That's the fuse to use in the Americas.

    To explain further, If your amp is switched to 105V and plugged into a nominal 120V supply all the secondary voltages are going to be correspondingly higher. That increase could put voltages above that which the caps are rated for. That leads to early failure.
  5. Mr. Foxen

    Mr. Foxen Commercial User

    Jul 24, 2009
    Bristol, UK
    Amp tinkerer at Ampstack
    Due a recap and new ones are prob higher voltage to get them big enough for the clamps anyway. Be cooking off the valves and arcing that is where the higher voltage will cause trouble.
    BassmanPaul likes this.
  6. Bassmec


    May 9, 2008
    Ipswich UK
    Proprietor Springvale Studios
    What a great litte amp they are.:)
  7. Tweaker27


    Aug 28, 2014
    New Haven, CT
    The head appears to have been recently recapped (within the last 5 years).
  8. Jim C

    Jim C Is that what you meant to play or is this jazz? Supporting Member

    Nov 29, 2008
    Bethesda, MD
    Nice find
  9. JimmyM

    JimmyM Supporting Member

    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups

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