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Jens Rasmussen Leach clone group buy

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T

tryonziess

Member
Joined 2007
Here is one shot of my amp from last year. Tad
 

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brutepuppy

brutepuppy

Member
Joined 2008
I haven't got very far on the new Leach but here is a pic of the first one I built about thirty years ago and it still keeps giving me pleasurable sound.
It's the four TO3 per Channel version built on an HP 5" Chassis, big Signal transformer (57 volt rails), and two 12000 mfd/75v caps.

Ray
 

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brutepuppy

brutepuppy

Member
Joined 2008
That would be 57-057 with the formula from the Leach Article;

"The power supply uses a transformer with a center tapped secondary and a bridge rectifier to produce bipolar supply voltages. The approximate dc voltage on each side of the power supply is given be the ac rms secondary transformer rating divided by 1.414 minus 0.5. The recommended transformers have a secondary rating of 80 V AC rms. Wth these transformers, the powerr supply is about 40 joules. This is enough energy to lifft a 20 pound dog almost 3 feet off the floor." (??????? by jumping? BP)

So by that formula: 80 divided by 1.414 equals 56.57 minus 0.5 equals 56.07 volts per rail. So I rounded up and should have rounded down. I should have said 56-0-56.

The output transistors are 2N5631NPN and 2N6031PNP Mot's. 140volt/16Amp rated
 
BobEllis

BobEllis

Member
Joined 2003
As it stands, 2 x 35VAC or 35-0-35 is the lowest standard voltage transformer that would work. The cascodes use 40V references, so you need your rails a bit above that to allow a bit of breathing room.

You could go a bit lower if needed by reducing the values of the zeners in the front end.
 
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