Transformerless Vari Mu Compressor build thread

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Heikki

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Joined
Jul 31, 2008
Messages
235
Location
Finland
There was a lot more interest in this project than I expected, so here is a help thread.

Schematics, BOM and instructions can be found here. In case I don’t pay server hosting fees, backup is here.

Scott2000 has already built his and he has extra boards for 3 stereo compressors to sell. He might also have kit/partial kit to sell. He is located in the US so anyone in that part of the world still interested getting boards should contact him. He will probably chime in here how best to contact him.

I still have 1 set of boards left and I can be contacted at [email protected] (No boards left but more coming soon.)

Big thanks to Scott for helping with the instructions. Now the instructions should make at least some sense.

Here is a RightMark Audio Analyzer test report made with using Focusrite Scarlett 2i2. (Using the line input where 0dBFS = +22dBu)

Sound samples, same song with different amounts of compression.

Mouser cart which should have almost all of the components needed. Missing are tubes, tube sockets and the 36V wall wart. Double check everything before ordering!
 
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Heikki

Well-known member
Joined
Jul 31, 2008
Messages
235
Location
Finland
I have been asked a couple of times via email if there are any alternatives for the wall wart. Best to answer it here too. Almost any wall wart/AC adapter with 36V output and at least 800mA current capability should work. There are cheap 36V led power supplies and 36V printer AC adapters that will work perfectly. I think Scott used a Kodak 36V/3A power brick.
 

manulaudic

Well-known member
Joined
Nov 7, 2011
Messages
271
Location
Finland
Hi, I am currently building the main board and in the place for R31 R32 R33 and R34 on the schematic it is 4,99k but on the board there is 8 resistors slots. Is it to get the proper 4,99k with a combination of resistors in parallel or is it to be inserted with 8 4.99k which would bring the total resistance off from the schematic.

Thanks
Manu
 
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