I too have made the AU-90 baseplate mod to my M-1's, but I have measured far lower impedances than others have (less than two Ohms at high frequencies). I'm still puzzled about why I should be getting lower impedance readings than everyone else, but let's assume my readings are correct.
My problem is this. I have Atma-Sphere MA-1MKII Silver Ed monos that I bought off Audiogon. All the tubes lit up and they seemed to play just fine. But they won't play high frequencies: roll-off starts around 2 KHz.
Ralph referred me to the support tab in his website, which has instructions for inspecting the output tubes. It turns out that each tube has two built-in filaments that act as fuses. To my dismay, I found that 5 of the output tubes on one amp were faulty.
As I remember OTL theory, each pair of tubes halves the output impedance. If I have 2 1/2 pairs of tubes not working, does this impair the amp's ability to handle high frequencies? Would the answer to my problem be as simple as getting some replacement tubes?
Thanks.
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Topic - Driving Sound Labs with Atma's - throwback 16:34:27 06/13/12 (43)
- form Dr. Roger West - Penguin 13:32:14 07/08/12 (0)
- RE: Driving Sound Labs with Atma's - throwback 16:24:07 06/15/12 (19)
- RE: Driving Sound Labs with Atma's - tyu 04:04:31 06/16/12 (18)
- RE: Driving Sound Labs with Atma's - throwback 04:43:09 06/16/12 (17)
- Sounds do disappear in thin air :) - Penguin 08:51:49 06/18/12 (15)
- I am impressed.... - Lew 14:12:34 06/18/12 (14)
- do not be... - Penguin 19:10:17 06/18/12 (13)
- RE: do not be... - Lew 22:11:45 06/18/12 (12)
- RE: do not be... - throwback 10:46:09 06/19/12 (11)
- Quite a coincidence... - Lew 11:56:21 06/19/12 (10)
- RE: Quite a coincidence... - throwback 12:17:25 06/19/12 (9)
- ESL high power output - tyu 13:26:30 06/29/12 (8)
- Colorado wildfires - Lew 17:41:08 06/29/12 (7)
- RE: I spoke to Chuck on Monday :) - Ralph 10:23:31 07/04/12 (4)
- Great news! - Lew 07:29:40 07/06/12 (2)
- RE: Great news! - tyu 09:11:37 07/07/12 (1)
- 103 degrees F today - Lew 12:55:30 07/07/12 (0)
- RE: I spoke to Chuck on Monday :) - tyu 12:02:40 07/04/12 (0)
- RE: Colorado wildfires - tyu 07:16:49 06/30/12 (1)
- i will try the bike - Penguin 10:03:44 06/30/12 (0)
- RE: Driving Sound Labs with Atma's - tyu 06:42:14 06/16/12 (0)
- RE: Driving Sound Labs with Atma's - Lew 08:16:42 06/14/12 (2)
- RE: Driving Sound Labs with Atma's - throwback 11:27:23 06/14/12 (1)
- RE: Driving Sound Labs with Atma's - Lew 11:52:26 06/15/12 (0)
- RE: Driving Sound Labs with Atma's - tyu 05:51:02 06/14/12 (10)
- RE: Driving Sound Labs with Atma's - throwback 07:51:54 06/14/12 (9)
- What are your readings? - Lew 08:24:10 06/14/12 (8)
- RE: What are your readings? - throwback 11:12:38 06/14/12 (7)
- RE: What are your readings? - Lew 11:42:53 06/15/12 (1)
- RE: What are your readings? - throwback 16:16:42 06/15/12 (0)
- RE: What are your readings? - Ralph 08:29:06 06/15/12 (4)
- RE: What are your readings? - Lew 11:47:26 06/15/12 (3)
- RE: What are your readings? - throwback 16:18:51 06/15/12 (0)
- yes, I don't doubt that it rolls off - Ralph 12:15:44 06/15/12 (1)
- RE: yes, I don't doubt that it rolls off - Lew 14:30:02 06/15/12 (0)
- that is very odd - Penguin 19:32:15 06/13/12 (7)
- RE: that is very odd - throwback 19:45:33 06/13/12 (6)
- RE: that is very odd - Lew 08:26:35 06/14/12 (1)
- RE: that is very odd - throwback 15:04:44 06/14/12 (0)
- do you have enough tubes to make sure one is complete? - Penguin 19:49:54 06/13/12 (3)
- RE: do you have enough tubes to make sure one is complete? - throwback 20:01:05 06/13/12 (2)
- RE: do you have enough tubes to make sure one is complete? - Lew 08:35:06 06/14/12 (1)
- RE: do you have enough tubes to make sure one is complete? - throwback 14:52:48 06/14/12 (0)