Alctron Passive 2 channel DI 120 Jensen Transformer Mod

Written by  on December 29, 2021 

I wanted a good performing DI so decided to modify the Alctron DI120 passive two channel DI as it was a cheap starting point and built in a good solid case with enough room for the transformers. I bought the donor DI for $35 AU (Australian Dollars on Catch) which was cheaper than the usual price. The soldering was a bit dogey in spots but nothing to bad after a quick touch up. I bought the 2 x Jensen JT-DB-E Premium Direct Box Transformer 12:1 second hand off Ebay from the US for $45 US each an after import duty and shipping they cost where $156 US = about $216 AU so the total cost in Australian dollars was about $250 versus about $750 for the stereo Radial Jensen equipped DI in Australia. The job can easily be done in under two hours.

Alctron DI and two transformers
Unscrew just the ends with the XLR’s
Undo the input socket nuts on the opposite
end and slide the circuit board out
Unsolder the transformers. I used a solder sucker.
The original transformers were 20:1 Whereas The Jensen are 12:1
The circuit board from underneath clearly shows which trace goes where.
The est of the board is earth so well shielded
The original Jensen circuit. Note the color code of the wires and that there is a 6k8 resistor in series on the input
I bent the transformer brackets so they would sit slightly above he board to allow clearance for the wires
After finding the best position for the brackets drill a hole for each transformer, clip the wires but not to short and solder in place and bolt up.
Pock he excess wires underneath. The should be pretty well shielded
between the earth plane of the board and the transformer can
Cut the trace between the yellow input wire and the first resistor for each channel. Check the position wont interfere with the case.
solder in the 6k8 resistor, which in the 0 db switch position with not include any of the other resistors of the pad network. The pad should still work but the values might need to be changed to optimize the amount of attenuation to match the figures.
Ready to put back together
Fits perfectly!!!

Comments

One Response

  1. Hudson Achata says:

    Good job!

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