I've gone down the OTL rabbit hole in a big way. Part of it is just chance; some amazing pieces from estates came available in my area at the same time. I have another thread on the original, first produced H3aa monoblocks. These are a different beast altogether. Advertised at 200 wpc into 8Ω!
If you don't know the history, it's fascinating. Julius Futterman was in the Army Signal Corps (like Saul Marantz). In 1958 he invented a tube amp that used horizontal sweep tubes instead of transformers as the output device(s). He built and licensed them in several configurations until his death in 1981. After that, Harvey Rosenberg bought the rights, revised the circuits, and marketed them under New York Audio Labs as the Julius Futterman OTL. There was OTL 1 through 4. Rosenberg died untimely, NYAL died, and the Futterman legacy struggled.
One person kept it alive somewhat: George Kaye, who had been the engineer at NYAL. He hung out his own shingle repairing and modifying NYAL (which included the Moscode line) and Futterman gear. George was also a bassist of some renown. He unfortunately passed last year, and I have these from his estate. They started life as OTL-3s from NYAL (stamped on the xformer). In 2004 Kaye launched a premium upgrade package for the OTLs, which these received. He did that for quite some time; don't actually know when, or if, he stopped before he died. So the pair that I have is from somewhere on or after 2004.
These are large and very heavy. Each channel has:
If you don't know the history, it's fascinating. Julius Futterman was in the Army Signal Corps (like Saul Marantz). In 1958 he invented a tube amp that used horizontal sweep tubes instead of transformers as the output device(s). He built and licensed them in several configurations until his death in 1981. After that, Harvey Rosenberg bought the rights, revised the circuits, and marketed them under New York Audio Labs as the Julius Futterman OTL. There was OTL 1 through 4. Rosenberg died untimely, NYAL died, and the Futterman legacy struggled.
One person kept it alive somewhat: George Kaye, who had been the engineer at NYAL. He hung out his own shingle repairing and modifying NYAL (which included the Moscode line) and Futterman gear. George was also a bassist of some renown. He unfortunately passed last year, and I have these from his estate. They started life as OTL-3s from NYAL (stamped on the xformer). In 2004 Kaye launched a premium upgrade package for the OTLs, which these received. He did that for quite some time; don't actually know when, or if, he stopped before he died. So the pair that I have is from somewhere on or after 2004.
These are large and very heavy. Each channel has:
- 10x 6KG6A output tubes
- 2x 5814A
- 6EJ7
- 6SN6
- 9x 1200µf 450V
- 4x 2000µf 450V
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