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LOL...Get to know your 8B better...

Posted by Steve O (A) on November 6, 2017 at 06:39:03

In Reply to: I guess neither of us is 100% correct - posted by mgbpuff on November 6, 2017 at 03:40:46:

"The Marantz instruction manual (I of course have it) does not mention operation w/o load, but it does mention connecting a speaker load to the correct tap and if the correct matching tap does not exist, attach it to the lower tap and not the higher which may cause "distortion"."

Recall that the issue under discussion is potential damage w/o load, not sound or distortion. Although the nature of the distortion due to mismatched impedance isn't discussed, it's most likely premature onset of clipping at high level because max power won't be delivered with mis match. Surely you've experimented with the different output trappings. I have and there's NEVER been "distortion" with any reasonable impedance at any reasonable level .

Also, there is no such claim of absolute stability under any load condition.

These claims were in their advertising and promotion materials. While one may rightfully be sceptical of advert claims, in this case I've verified them to be true as did the magazine tests of the day.

"If when testing and adjusting AC ballance, a dummy load equivalent in resistance to the tap used is recommended. If a dummy load is not availabe, the instructions are to 'short' the output transformer.

So the warning to not run with the output open is not direct, but by omission.

This is essentially a full power adjustment and some form of a load is necessary to be properly done. It could be understood to be a warning "to not run with the output open" under full power but again, that's not really what we're discussing.

As far as the 8B being a Williamson dirivation, you are just wrong. Syd Smith, himself, said that he designed a "Willy" amp for Saul Marantz. Triod connected or Ultra Linear connected, it is still a Williamson type circuit.

I've never heard that one. Got a source? Regardless, the 8B circuit is not a Williamson almost by definition. Just compare schematics. A traditional "Willy" uses a triode input amp direct coupled to a split load PI that is in turn cap coupled to a PP triode driver stage that is cap coupled to the PP finals. The 8B uses a triode strapped pentode input direct coupled to an LTP PI that is cap coupled to the finals. This is essentially the mullard 20-20 design right up to the UL finals. 4 stages for the "willy" vs 3 for the 8B. Also, FWIW, Williamson the man considered the UL output stage an abomination.

HTH

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