Amp/Preamp Asylum

• My B&K ST-140 works fine with 4 ohm speakers... - Mr Blue Sky 18:38:11 07/08/11 (0)
  In Reply to: RE: What's the deal w/ the B&K ST-140 and 4 ohm speakers? What is the danger of using this amp this way? posted by Mr Blue Sky on July 06, 2011 at 17:19:37

  I've run my B&K ST-140 extensively with my AR-3a 4 ohm loudspeakers over the course of 3 days at very loud volume and it has not overheated, clipped, or blown fuses. Source material has been rock 'n' roll and soul on vinyl. It's 100 degrees outside and my house has no air conditioning. This should clear up any confusion about whether or not the black w/gold handle 100 watt version of the ST-140 can be used in this configuration without problems. Apparently it can.
  

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• RE: What's the deal w/ the B&K ST-140 and 4 ohm speakers? What is the danger of using this amp this way? - Mr Blue Sky 23:52:15 07/06/11 (1)
  In Reply to: RE: What's the deal w/ the B&K ST-140 and 4 ohm speakers? What is the danger of using this amp this way? posted by Mr Blue Sky on July 06, 2011 at 17:19:37

  Can a standard B&K ST140 be bridged into mono to solve the issue with the difficulty in driving 4 ohm speakers?
  

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  • In short, no, because... - JimL 15:18:26 07/07/11 (0)
    In Reply to: RE: What's the deal w/ the B&K ST-140 and 4 ohm speakers? What is the danger of using this amp this way? posted by Mr Blue Sky on July 06, 2011 at 23:52:15

    bridging a solid state amp means that the effective impedance it sees is cut in half, so a 4 ohm load looks to the amp like a 2 ohm load, which is even worse.
    

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• RE: What's the deal w/ the B&K ST-140 and 4 ohm speakers? What is the danger of using this amp this way? - djk 18:36:07 07/06/11 (2)
  In Reply to: RE: What's the deal w/ the B&K ST-140 and 4 ohm speakers? What is the danger of using this amp this way? posted by Mr Blue Sky on July 06, 2011 at 17:19:37

  The peak current rating on the output device is 7A.
  
  The amp runs on ±63V.
  
  Your speakers are 4Ω.
  
  Do you know Ohm's Law?
  
  You will be running way more current than what the device is rated at if you turn the volume up. Don't even ask about heat.
  
  
  

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  • Then why would B&K publish in their own literature... - Mr Blue Sky 21:18:40 07/06/11 (1)
    In Reply to: RE: What's the deal w/ the B&K ST-140 and 4 ohm speakers? What is the danger of using this amp this way? posted by djk on July 06, 2011 at 18:36:07

    ...specifications for the ST140 and quote the power into 4 ohm speakers as well as 8 ohm? Never did they issue a warning to discourage use of this amp with 4 ohm speakers that I'm aware of.
    

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    • RE: Then why would B&K publish in their own literature... - djk 22:39:51 07/06/11 (0)
      In Reply to: RE: Then why would B&K publish in their own literature... posted by Mr Blue Sky on July 06, 2011 at 21:18:40

      
      It is well known that an MBA allows you to alter the laws of physics by a factor of 10 or 0.1 as needed.
      
      One pair of outputs will drive 5A RMS, 100W at 4Ω.
      
      A Hafler XL280 runs on the same rail voltage with three pair. It does 280W/4Ω.
      
      
      

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