On Saturday, November 3, 2012 10:00:02 PM UTC-4, Phil Allison wrote:   
   > ** Hi all,   
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   > a neatly built, home brew SET amp arrived on my bench this week, I   
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   > understand it is about 10 years old.   
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   > The tube line up is two 300Bs in parallel and one 6SN7 per channel, the HT   
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   > is 550 volts and each 300B has its own grid bias adjustment. There is no NFB   
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   > used and the PSU has diodes and a metal bridge for DC heaters on the 300Bs.   
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   > One of the output transformers ( UBT-1s by One Electron ) was open primary   
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   > and two of the Chinese 300Bs were stuffed.   
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   > I have one good channel and I so did few tests, grid bias set at  -105V  and   
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   > plate current is close to 55mA per tube.   
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   > Max power is 21 watts at 2.2% THD -  mostly 3H.   
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   > At 10 watts, the THD is 0.85%  -  mostly 3H.   
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   > At 1 watt, the THD is 0.14%,  mostly 2H.   
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   > The damping factor is 4.5   
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   > Signal to noise is  -80 dB rel full power.   
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   > Input sensitivity is 260mV.   
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   > All the above is with an 8 ohm load on the 4 ohm tapping of the OT.   
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   > These numbers are a rather better than I expected.   
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   > Any comments ?   
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   > ....   Phil   
      
   UBT-1 is rated at 160mA on the primary... Did those 300Bs develope a dead   
   short?   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)