Assembling a Dynaco PAS4 klon

Questions suggestions: tubular.well <( -at- )> gmail.com

As i never got my hands on a Dynaco PAS4 i will attemt to recreate one. A circuitboard from Roy Mottram is the starting point.

Roy's manual
Dynaco/Panors manual

Pictures will follow Empty board Input selector mains transformer enclosure

Latest change: 200914

Board fixes

Double fault, removal of copper and addition of missing connection

E88CC internal screen connects to ground

I have no -3V bias, ground this ( Use a LED in cathode instead)


The use of odd component values forces me to build composit resistors

One of the ECC83 sockets

Higher powered resistors mounted higher for better cooling


As i have no -3V on board to use as bias to V2 and V5 i use a white LED. It is mounted in a free grounded hole and a wirewrap wire connects to pin 3 of the V2 and V5


LED soldered in place.


Wirewrap wire inserted before mounting tube socket


A long forgotten technology : wirewrapping. It's perfect for making remavable connections or strapping. It also exists connectors that fits on wirewrap pins to make connections outside the board.


Tubes in place verifying filament function.

Now i have applied B+ from an external powersupply. No fire not even smoke !
Starting with riaa stage. Some bugs sorted out :
- 240k instead of 240 ohm in R12 and R112
- one white led was only 2.44 Volt, tested several variants but 2 RED LED in series seemed best, then gave 4.04 Volt
- R12 and E112 changed to 300 ohm to reduce current in E88CC Dist now 0.06% at 1Volt out ( app 10mV in @1khz ). This THD includes HUM from the workbench.


Work in progress, as the object is flat on a wooden table hum is present everywhere.

Honor the board source at tubes4hifi.com

Feel trapped ?