query on the PSU of a preamp - diyAudio
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Old 25th December 2005, 03:14 AM   #1
ray_ben is offline ray_ben  Hong Kong
diyAudio Member
Join Date: Oct 2005
Default query on the PSU of a preamp

Hello all,

I DIY a tube preamp based on a circuit from a old magazine.
It based on a 6DJ8 and 12AU7. I have some query on the power supply circuit. The circuit is attached.

Are the 2 Zener diodes (27V and 12V) in the right positions or they should be swapped?

Do you know the purpose of these 2 diodes?

regards, Ray
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Old 25th December 2005, 05:20 AM   #2
hacknet is offline hacknet  Singapore
diyAudio Member
Join Date: Nov 2002
Location: sg
i think its alright..

the 12v zener is to prevent the mosfet from destruction when the Voltage across the gate and drain exceeds the maxium allowable.

the 27v zener is supposed to do the same for the regulator.
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Old 1st January 2006, 10:40 PM   #3
marconi is offline marconi  Europe
diyAudio Member
Join Date: Apr 2004
Location: at home
between gate and source you mean...
But you are correct for the rest.
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