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OTL Asylum OTL, Output Transformerless Amplifier User Group. |
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In Reply to: Re: parallel output tubes - no need to match? posted by rick57 on March 17, 2005 at 22:24:10:
The Futterman output circuit (used I think by Transcendent) is not balanced. Futterman invented or was the first to implement a "totem pole" output topology, where the plates of the tubes forming the "bottom" or ground side of the circuit are essentially connected to the cathodes of the tubes on the "top" or positive supply voltage side. It may be that any two tubes of the same type and matched within random standards will share the current adequately and well enough that selecting tubes is not necessary. Many years ago, Julius Futterman used to sell replacement 6LF6s that he had merely tested for function to customers for $5 each, no matching necessary according to Julius. (Interestingly, in later years after Julius passed away, I had to go to NYAL in the person of Harvey Rosenberg for a single replacement tube. He told me that he alone had Julius' "data" for my amplifiers and that if I gave him the serial numbers he would select a matched 6LF6 for me at the cost of $50. Go figure.)
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Follow Ups
- Just a guess... - Lew 06:59:28 03/18/05 (2)
- The reason no matching is needed... - C.B. 06:44:50 03/19/05 (1)
- Thanks for your answers! NT - RG 00:26:36 03/27/05 (0)
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