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Driving Sound Labs with Atma's

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)

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