DC Servo MOSFET Amplifier

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apexaudio

apexaudio

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Joined 2010
MOSFET drivers...
 

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stcboy

Member
Joined 2008
apexaudio said:
You must connect separate ground wire from PSU to input GND. Yellow LED lit when the amp is normally oprational.
Regards
Click to expand...


thanks Mr. Mile, the amp working after replacing Q1 & Q2 with 2n5401 the original bc556 are ok when tested with a VOM but for some reason it is the reason i have the +44v in the output now i have 0.018v and the yellow LED is lit and testing with the sound, I might have to replace the transformer though as it dip to less than 43 when I increase the volume. Can you recommend a preamp for this? Thanks again.;)

Regards,
STCBOY
 
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apexaudio

apexaudio

Member
Joined 2010
stcboy said:
thanks Mr. Mile, the amp working after replacing Q1 & Q2 with 2n5401 the original bc556 are ok when tested with a VOM but for some reason it is the reason i have the +44v in the output now i have 0.018v and the yellow LED is lit and testing with the sound, I might have to replace the transformer though as it dip to less than 43 when I increase the volume. Can you recommend a preamp for this? Thanks again.;)

Regards,
STCBOY
Click to expand...
What kind of preamp you need, for Hi-Fi or PA, with tone control...? Can you post pictures, and what speakers you use?
Regards
 
Last edited:
apexaudio

apexaudio

Member
Joined 2010
stcboy said:
thanks Mr. Mile, the amp working after replacing Q1 & Q2 with 2n5401 the original bc556 are ok when tested with a VOM but for some reason it is the reason i have the +44v in the output now i have 0.018v and the yellow LED is lit and testing with the sound, I might have to replace the transformer though as it dip to less than 43 when I increase the volume. Can you recommend a preamp for this? Thanks again.;)

Regards,
STCBOY
Click to expand...
Offset under +/-20mV DC is OK without matching and adjust, but I expect about +/-1mV with DC servo.
Regards
 
apexaudio

apexaudio

Member
Joined 2010
stcboy said:
what should be the input voltage ( or rather ouput of preamp or source) to realize the 120watts of this amp? And what size of transformer V & I for the two channels?

Regards
Click to expand...
For 120W/8R you need 32v rms output voltage, 775mV on amp input. With preamp with 1-1,5V output you can realize full power before end of volume pot. For two channels you need 600w 2x42v ac transformer.
Regards
 
H

HMKD

Member
Joined 2010
apexaudio said:
This amp is based on F100 amp, see post #60, and there is no mistake.
Regards
Click to expand...

C6, C8, C12 is superfluous and should be removed. If you think there is C8, C12 would be better, it is because of your Q4, Q5 current is too small, the level current to 10mA we go. Although you use for a long time, but this is unreasonable. I will not English, it is the Google translation, hoping to understand some.
Sincerely,
 
apexaudio

apexaudio

Member
Joined 2010
English is also my problem, but I understand you basicly. I use OP amp for auto adjust DC offset, and I keep C6 for safety (amp was use for PA at the first time, before 20years ago). I use 2SK135/2SJ50 in first version, and BF420/BF421 in VAS run with 3mA (0,2W disipation). You are right 10mA will be better, but BF420/BF421 must be replaced, and VAS transistor with 0,7W must have heatsink. I have MOSFET amp use 4xIRFP240/IRFP9240 with CFP VAS run at 30mA (VAS transistor on main heatsink), and run without EF drivers. As I use F100 for long time without problems I want to redesign basic circuit up to Hi-Fi level.
Regards
 
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