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Re: A "most refined" OTL

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Posted by Phil Sieg on January 13, 2000 at 13:55:38

In Reply to: A "most refined" OTL posted by DrM on January 13, 2000 at 12:52:40:

I have used modified M-60s with 4 6AS7Gs/chassis on the 97.5 dB-efficient T-1 Project hybrid horns from Classic Audio Reproductions. With NOS RCA 6AS7Gs and NOS Sylvania VT-231s, I found the sound to be more detailed, more relaxed with no sacrifice of bass or dynamics. I have yet to try 2 6AS7Gs/side.

However, compared to a pair of Parallel-Feed 45 monoblocks on the same speakers - 1.5W is more than enought on all but the most demanding orchestral crescendos - the M-60s sound a tad more mechanical, less palpable and less adept at microdynamics and inner detail. With the 45, Pres is here.

The output iron on the 45s are the Nature Sound NS-70SEs (47% permalloy), the plate loading choke is the Brooklyn BCP-15. A Cunningham CX-345 is the output, driven by a WE 417A direct-coupled to the 45's grid with a constant current source loading the plate of the 417.

Steve Bench has a flea-powered single-ended OTL on his website and it's an interesting design. Definitely not a novice's project.

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