KT88 push-pull amplifier with integrated phono stage

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Mars

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Hi All

I have amplifier coming out of the shed, that is a KT88 push-pull amplifier with fixed bias and phono stage. Me and the client decided to use octal tubes throughout, including the phono stage.

I demonstrated the Mars Stereo 70, but the conclusion was: we need more power! So I suggested we go for a more complex build with fixed bias on this one, and there will be enough mojo to rock the town.

The power limiting criteria on this amp turned out to be the physical size of the transformers. The customer requested transformer covers, and to fit the whole kaboodle on my chassis design, the power transformer will have to be a EI114 (114mm) type.

Moving on to the output transformers: Ampdog pointed out that 5K at about 420V should give us the power we need. According to this graph:

kt88b.jpg


one can get more than 55 watts out of two KT88's in push-pull. We should be able to squeeze that kind of power out of my regular design output transformer and still have decent bandwidth.
 
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