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OTL Asylum OTL, Output Transformerless Amplifier User Group. |
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In Reply to: Mark I tube complement posted by Al Sekela on November 21, 2003 at 08:31:01:
Based on your information and other scuttlebutt I've absorbed, it seems the first version of the Mark I used 12AT7s +12AU7 for input stage, plus a 12AU7 for driver (as I now realize for the first time). Somewhere along the line Ralph developed a preference for an all-12AT7 input stage, and there may be versions of the Mark I that use this configuration with a 12AU7 driver and later with a 6SN7 driver. My amps were evidently of the last type, with all (4) 12AT7s as input stage and a 6SN7 driver. (The MA240 was delivered with the MA2-type input stage that used paralleled sections to form the lower half of the dual-differential cascode, hence 4 tubes were required instead of 3.) I say "were" because now my amps are up to Mark II-ish status with the 6900s and EC99 subbing for all the input stage 6SN7s but still with the 6SN7/12SX7 as driver. This reminds me of my old hobby of restoring old Porsches, where the discussions re what was factory original and when a certain distinctive element came into and went out of production are endless. Even now I can't stand looking at an old 356 Porsche with incorrect bumper guards.
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Follow Ups
- Re: Mark I tube complement - Lew 12:04:08 11/21/03 (3)
- Re: Mark I tube complement - Ralph 17:47:17 11/21/03 (2)
- Re: Mark I tube complement - Lew 07:16:45 11/24/03 (1)
- Re: Mark I tube complement - Ralph 14:54:29 11/26/03 (0)
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