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100w Hi-End Hybrid Amplifier - last version
started on January 6 st , 2012 

INTRODUCTION

The original version of this amplifier have good measurement performances but the sound was not good.
Now after same changes on the driver stage I have got a very good sound.
The Amplifier End  is still superior in realism and speed but now some my friends consider this amplifier better than my pure vacuum tube design.
Using the 4.7uF Superior Z-Cap there is the best sonic result, you can try different caps on cathode, no bypass cap. or led bias.
If the Z-Cap is too expensive for your budget use a Solen MKP and forget normal Intertechnik Audyn Cap QS.
All the pcb can be produced at low cost by Quanghao or you can download the Eagle files.
The cathode bypass on driver stage change the sound and it eliminate the local feedback 5dB but increase the distortion.

POWER SUPPLY

To get the max sonic performances the my choice is a slow turn on power supply for the filaments using a common LM317 and a virtual battery operation power supply for the anodic with a power mosfet.

The power supply for all the stages use a a single custom toroidal  transformer  created on my specification by Italtras.
It have an electromagnetic flux 80% than normal and it born with these secondaries:

33-0-33   6A
9-0          2A
200-0     0.3A

You can create this with 2 secondaries for the power stages to get a better channels separation so the new transformer will have:

33-0-33  4A
33-0-33  4A
9-0          2A
200-0     0.3A

To reduce the distortion of the driver stage you can increase the anodic secondary to 220-240V 0.3A to get about 300-320V DC.

For the power stage I have used the FWB1 rectifier module with Schottky Full Wave Bridge Rectifier got by Avondale Audio.
You can also use the bridge pcb used in my
Amplifier End or a common diode bridge like the IRF 36MB60.  

The power stage use 4 x 22000uF 63v Jensen electrolytic mod. 022670 (dimension 50x65 mm), if you add a soft start is possible to use 4 x 33000 or 4 x 47000uF.

 

MEASUREMENTS

If you want to see the measurement of the output stage only see on the original version.

Follows the measurement at the max power about 100W on 8ohm and 180W on 4 ohm.