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Frequency central 

Build documentation for: 

MU system X 

Dual amplifier 

 

Based on the Roland System 100M VCA

. MU System X Dual Amplifier 

features:

  

Main PCB

Sockets PCB x 12 

 

 

 
Key to PCB screen print: 
n:

 This signifies NPN BC547 transistors. Note the correct pinout as shown by the half circles. 

p:

 This signifies PNP BC557 transistors. Note the correct pinout as shown by the half circles. 

f:

 This signifies 2N5485 FETs. Note the correct pinout as shown by the half circles. 

 
The PCB shows the correct orientation for BC547/BC557. Other transistor types can be used 
(eg 2N3904/2N3906), but please observe the correct pinout. Please observe the correct 
polarity of the electrolytic capacitors. 

Summary of Contents for MU System X Dual Amplifier

Page 1: ...e the correct pinout as shown by the half circles p This signifies PNP BC557 transistors Note the correct pinout as shown by the half circles f This signifies 2N5485 FETs Note the correct pinout as shown by the half circles The PCB shows the correct orientation for BC547 BC557 Other transistor types can be used eg 2N3904 2N3906 but please observe the correct pinout Please observe the correct polar...

Page 2: ...180K x 4 1M x 2 All resistors watt metal film 47pF x 2 10nF x 2 22uF x 8 47uF x 4 LM13700 x 1 TL072 x 1 BC547 x 4 BC557 x 4 2N5485 x 2 16 pin IC socket 8 pin IC socket x 1 A100K x 2 B100K x 4 20K trimmer x 2 100K trimmer x 4 SPDT toggle x 2 6 3mm socket x 12 Male 40 pin header x 2 6 pin female header x 12 DOTCOM 6 pin header ...

Page 3: ...pots and the two switches Make sure they fit snug to the PCB Main assembly REAR 1 Solder all trimmers 2 Solder all of the 6 pin female headers These will later accept the Socket PCBs 3 Solder the DOTCOM power header Don t for get to make it keyed by removing the second pin in the PCB won t accept it otherwise it s keyed too 4 Solder the electrolytic capacitors ...

Page 4: ...pcb bolt into place making sure that the male headers line up with their places on the socket pcbs Solder the male headers to the sockets pcbs Calibration Bias Adjust Bias trimmer to sweet spot ie a nice clean undistorted VCA output with no thunk when a snappy ADSR is applied to a CV input I do this without any audio at the inputs The chances are that that the sweet spot is around the mid position...

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