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tube amps

SOHA

preview comments
pic pic all panels (front, top, bottom, rear, side) by Frontpanelexpress.com
pic pic case tied directly to signal ground and via ground loop braker to mains earth
65VA 2x18V potted toroidal transformer + Dynalo PSU as buffer psu
30VA 2x15V toroidal transfomer for SOHA main board
Alps RK27 50k "blue velvet" volume potentiometer
Neutrik NC J6FI-S locking headphone jack
pic pic ε12 muting delay and offset protection from AMB labs
class-A hybrid buffers (jfet input stage, bjt push-pull output stage) set to 50mA, design by courtesy of AMB
Elna Silmic-II electrolytic capacitors, Toshiba 2sk30a JFETs for cascoded ccs
Mundorf MCapZN caps (tin foil + polypropylene film) as coupling caps

tube: JJ ECC82 at 0.85mA (alternatively I recommend GE 5963 at 0.7mA or Electroharmonix 12AU7/ECC82 at 1.0mA)
SOHA project page at hadwize.com

 

EHHA (prototype)

preview comments
pic pic adjustable gain of 6, 9 and 12 set via a rotary switch
dedicated AKG K1000 jack
pic pic heaters wired in series and powered by a separate transformer and a TREAD psu set at 12.6V
board powered by a 65VA potted and shielded toroidal Avel-Lindberg transformer and a β22 psu at ± 30V
ε12 muting delay and offset protection
pic 6GM8 tubes

 

Millett Hybrid MAX

preview comments
pic pic MH-max project page
acrylic frontpanel made by Frontpanelexpress.com
pic pic BJT version
Panasonic FM / FC electrolytic caps, Wima film caps
Alps RK27 "blue velvet" volume pot
black painted acrylic rear panel
Neutrick RCA input jacks
built Dec 2007

 

Millett Hybrid (head-fi revised), tubes pcb mounted

view preview size comments
front pic 800x600
125 kB
by Frontpanelexpress.com
front, above pic 800x600
108 kB
aluminum front and acrylic top by Frontpanelexpress.com
bias adjust pic 800x600
132 kB
holes straight above trimpots for direct adjustment with a screwdriver, air wired 2mm laboratory jacks for external bias measurement, easy tube rolling and adjusting
board pic 800x600
148 kB
Elna Silmic + Panasonic ECQ-P polypropylene film caps in the signal path, Panasonic FM + Wima MKP caps for power rail bypassing, discrete diamond buffers
rear pic 800x600
109 kB
 
dayglow pic 800x600
113 kB
3500mcd ultrabright LEDs
nightglow pic 800x600
93 kB
3500mcd ultrabright LEDs
DIYforums.org
Pete Millet hp (original designer)

 

Millett Hybrid (head-fi revised), maxed out

view preview comments
front pic aluminum front and acrylic top by Frontpanelexpress.com
rear pic
top pic holes straight above trimpots for direct adjustment with a screwdriver, air wired 2mm laboratory jacks for external bias measurement, easy tube rolling and adjusting, ventilation holes
top pic ultrabright blue LEDs
DIYforums.org
Pete Millet hp (original designer)