Hafler DH-110 Pre-amp Filter Boards

After answer­ing a ques­tion in the com­ment sec­tion of the Hafler DH-110 Preamplifier Refresh. I decid­ed to design a board to hold sur­face mount film capac­i­tors for capac­i­tors C19 and C119.

Hafler DH-110 LF fil­ter boards

I have been quite pleased with the per­for­mance of my DH-110 pre-amp with my cur­rent set­up, but want­ed to see what dif­fer­ence chang­ing the val­ue of the line amp input fil­ter capac­i­tors made.

Original C19  C119 LF fil­ter capac­i­tor assembly

The orig­i­nal fil­ter capac­i­tors were 0.82 uF with a 4.7K ohm series resis­tor fit­ted to a cir­cuit board with two leads. The 0.82 uF capac­i­tor is a sur­face mount type with a pair of wire leads attached which are then sol­dered to the traces on the back side of the sin­gle sided car­ri­er board.
The new board accom­mo­dates a 1812 size sur­face mount capac­i­tor, and a 1206 size resis­tor. I kept the resis­tor val­ue the same, and increased the capac­i­tor to 1.5 uF.

New LF fil­ter boards fit­ted into the pre-amp for testing

While I was work­ing on the pre-amp I also changed out the pow­er rail fil­ter capac­i­tors from the bi-polar ver­sions, to some low ESR Nichicon capac­i­tors of the same value.

After some test­ing and lis­ten­ing, I have decid­ed that the capac­i­tor change had lit­tle if any change on the audio range qual­i­ty.
It was a fun project, but noth­ing mag­i­cal hap­pened. My rec­om­men­da­tion would be to spend or save up your mon­ey for bet­ter speakers.

Another view of the LF fil­ter boards installed in the Hafler DH-110

The board is avail­able on OSH Park for down­load and order­ing:
Hafler DH-110 LF Filter Rev. 1.0

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