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Dynaco PAS-3 tube preamp mods and parts
original circuit replacements
Z-mod upgrades
PAS3-AIKIDO upgrade
Tone Control Line Amp upgrade
regulated power supply upgrade
PAS3 upgrade catalog
VTA-Z preamp
original circuit replacement PCBs
Dynaco PAS3 preamp rebuild
for those on a budget but wanting an updated/upgraded PAS3, we offer high-quality original circuit replacement PCBs with better than original parts.
PC6 phono amplifier and PC5 line amplifier . . . . . . . . . . . . . . new power supply board
click here to see our PAS3 upgrade catalog
VTA PAS3-Z modification
Vacuum Tube Audio Zmod upgrades for the PAS3
Finally, a set of hi-end modifications for the Dynaco PAS3 preamp. We haven't seen anything new in the past dozen years or so,and the only real alternatives are the Curcio kit for $662 and the VanAlstine kit for $449, now VacuumTubeAudio at www.tubes4hfi.com
offers an easy plug-in 3 piece circuit upgrade for the PAS3 that is identical to it's highly reviewed SP6 preamp kit.
This is for customers that want to KEEP their PAS3 chassis rather than building an all new preamp in a newer chassis.
Our Vacuum Tube Audio upgrade circuits for the PAS3 replace the 50 year old circuit designs with modern high performance high fidelity drop-in replacements.
Our Zmod-PC6 phono preamp uses a 12AX7 gain stage followed by a highly accurate passive EQ, followed by another 12AX7 gain stage, for a total gain of 45 db.
This has higher accuracy and uses no negative feedback, for much improved sound quality and frequency accuracy, with no flabby bass and a clear natural hi-end.
The Zmod-PC5 line stage uses a pair of 12AU7 in a cascode SRPP gain stage with excellent linearity and low output impedance.
This is a pure hi-end design with no tone controls and no negative feedback for perfect reproduction of the original source.
For those who want to maintain a tone-control design, see below for our Zmod-TCLA circuit as an alternative.
The Zmod-PS power supply makes use of the original 12X4 tube rectifier for soft-start, replacing the old "quad cap" with 266uF of B+ power supply capacitance
(compared to the original 80uF) with more reserve power for bass and complex music reproduction, and a lower power supply impedance.
The filament supply is also improved with 6600uF of capacitance for lower noise and more reserve power (compared to original 4000uF).
Printed Circuit Boards are mil-spec FR4 double-sided with plated-thru holes. Easy installation, with full documentation included.
An assembly manual, schematic, layout diagrams, parts list, and installation instructions are included, along with online tech support.
We also have available every part that is used in a PAS3 preamp, most are higher quality than the original types.
See our parts listing of volume, balance, selector switch, slides switches, LED power indicator, and our very high quality RCA jacks for input-output.
click here to see our PAS3 upgrade catalog
PAS3-AIKIDO modification/upgrade
Zmod TCLA (tone control line amplifier) modification/upgrade
Finally, a hi-end modification for the Dynaco PAS3 preamp that INCLUDES TONE CONTROLS !!
This modern circuit uses four 12AX7 tubes in an active Baxandall design for the extra required gain and tone control processing.New accurate linear tone controls are included that allow +/-12db of boost/cut for bass and treble frequencies.
Easy installation takes about 1 hour. Full documentation included with the kit includes assembly manual, schematic, layout diagrams,
parts list, and installation instructions.
. 
our new regulated power supply for the PAS preamp
This includes two new power transformers (one for B+ and one for filaments) and fits right where the old transformer and power supply were.
It will require drilling two small holes. Simple installation. Fantastic performance, our ultimate power supply for the PAS preamp.
click here to see our PAS3 upgrade catalog
NEW input-output RCA jack panel
Our 2nd most popular upgrade (after the power supply) is this high quality RCA jack panel.The old cheap quality RCA jacks that are crowded together too closely are replaced with a PCB with wider spacing and gold-plated RCA jacks.
This has 7 pairs of jacks rather than the original 9 pair (most of those were never used anyway!).
. . 
replace this mess with this . . .
Our new selector switch replaces the old fragile original with a modern 2P6T rotary switch, a nice match to the new RCA jack panel.
This will eliminate the "rats-nest" of wiring on the original.
click here to see our PAS3 upgrade catalog
VTA-Z preamp
This alternative is less expensive than building a new reproduction PAS3, and it sounds twice as good!!
The VTA-Z preamp kit is an alternative to the 50 year old Dynaco PAS3 preamp, offered in a new, modern chassis with a contemporary design, and more space inside.
New power transformers have 4X the current capability of the originals. The high voltage B+ power supply has 4X as much current capability.
The filament supply is regulated at the optimum voltage for the tubes, to maximize performance, and to cut noise and hum to an absolute minimum.
KITS include ALL parts to build a complete preamp, including the tubes - chassis, transformer, circuit boards, volume, balance, source selector,
power switch and LED indicator, front panel knobs, rear panel RCA jacks, AC cord, rubber feet, EVERYTHING for completion !
This preamp also includes higher quality blue ALPs volume and balance controls.
Delivery time is 2-3 weeks - priced starting at $599 !!
Our Zmod-PC6 phono preamp uses a 12AX7 gain stage followed by a highly accurate passive EQ, followed by another 12AX7 gain stage, for a total gain of 45 db.
This has higher accuracy and uses no negative feedback, for much improved sound quality and frequency accuracy, with no flabby bass and a clear natural hi-end.
The Zmod-PC5 line stage uses a pair of 12AU7 in a cascode SRPP gain stage with excellent linearity and low output impedance.
This is a pure hi-end design with no tone controls and no negative feedback for perfect reproduction of the original source.
For those who want to maintain a tone-control design, see below for our Zmod-TCLA circuit as an alternative.
The Zmod-PSR power supply makes use of a 12X4 tube rectifier for soft-start, with 266uF of B+ power supply capacitance
for more reserve power for bass and complex music reproduction, and a lower power supply impedance.
The filament supply has 6600uF of capacitance for low noise and more reserve power..
Printed Circuit Boards are mil-spec FR4 double-sided with plated-thru holes. Easy installation, with full documentation included.
An assembly manual, schematic, layout diagrams, parts list, and installation instructions are included, along with online tech support.
  complete VTA-Z preamp kit $599 plus $30 shipping in USA, includes all parts and tubes also available withOUT the phono section for $100 less !! |
 Also available with the TCLA option for those that prefer to have tone controls VTA-Z-TCLA preamp kit $679 plus $30 shipping in USA includes all parts and tubes also available withOUT the phono section for $100 less !! |
PAS3 upgrade catalog
return to VTA home page
send us email at: info@tubes4hifi.com
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