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Juma's LSK Preamp - SMD version

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Z

ZUM911

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Joined 2006
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Looks like the ground of C11 doesn't go anywhere. The lead from the diode should reach to complete the connection.

Buzz, can you confirm we need a 2 x 18v secondary transformer? I can't see where we get 33v dc from 18v ac secondaries unless they are in series and then both rectifier sets per channel are fed from the same 36v ac? Maybe better off with 2 x 32-36v ac secondaries?

Thanks
Rick
 
Z

ZUM911

Member
Joined 2006
Paid Member
Looks like Buzz may be away. Anyone else know about the power transformer needed?

Also, Buzz'z resistors 6.1, 6.2, 6.3, 6.4. I can't understand what they are for. The path through them goes to the pot but there is also a direct path to the pot from the same pin of the jfets without resistors as on Juma's schematic. Possibly if you are using unmatched jfets but that doesn't explain the 2 paths to the pot. Looks like they should be left unpopulated.
 
buzzforb

buzzforb

Member
Joined 2010
You need a transformer with dual 32-36v secondaries. The resistors 6.1-4 are the gate resistors for the Jfets. You only need to populate according to the number of Jfets you are using. I am sorry for the absence. Taking over a small business has my time consumed. Look a couple post back for the changes that need to be made. They are important. Also check to make sure that your pot is 50 ohm not 5k, as there may have been some misplacement.
 
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