Quote:
Originally Posted by Charles
PP low end, SE high end? Didn't know they ever made such an animal.
Always wanted to try the SE amps, but have grown accustomed to PP. If anything, I'd probably be more interested in a hybrid at this stage of the game.
Chas
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Magnavox had a few of these biamp models that they put out, mine are the 150 model made in 1957 for a mono console. I found two of them. It's all 6V6 power tubes.
The low freq. is actually paralell push pull (4 X 6V6 + 12AT7) and a single (6V6 + 6AV6) for the high freq. There's a volume control circuit on the high freq. that allows for easy control of the tweets, which makes it easily adjustable to a lot of different speakers.
The factory crossovers are set at about 1100hz. I just bypassed the speakers internal crossovers, actually the mids & tweets use the speakers internal Xover.
With the help of Gordon Waters over at AK I upgraded the power supply by replacing all of the electrolytics and bumped up the coupling caps (orange drops) and replaced all of the carbon comp resistors with carbon film resistors. Otherwise I left the Magnavox circuit alone and they are dead quiet.
I get a kick out of some of the younger cats touting their biamp set ups as the newest shizzle on the block. I just offhandedly tell 'em about this 1957 set up and their first objection is ,"Wait a minute, you do know Magnavox didn't have stereo consoles until years later!" I just tell 'em, "Well it's simple you've got to have two of them."
It's a gas to pop some guys bubble when they start with their condesending attitude about how their systems are the newest thing under the sun and that we old farts just don't get it. Heh, I've got about $200-$225 in parts in 'em including the original consoles + about 20 - 25 hours of my time into each of them. First pic is before I made the surrounds, I moved the on/off switches to the top[rather than keep them on the front once I made the wood bases. The base material is solid bamboo flooring I had left over from my place.
With the wood bases the labor was more like 70 hours total for the both of them. I left the three old can caps on there for looks. It was a hell of an intro into tube electronics for me. I had already rebuilt a couple of those Magnavox 175 push pull stereo amps but these were something else in comparison.