A footnote in audio history: Begun as Dynaco in the 1950s by David Hafler his new line of Hafler products began appearing in the late 1970s. Hugely popular in the budget audiophile market the company was later acquired by the Rockford Corporation in 1987. Rockford took an active role and over the next couple of years preamps changed from a brown color to a black-pebbled finish. Internal capacitors changed from polycarbonate to polypropylene and new designs like the Iris preamp appeared. In a final push in the early 1990s Rockford released a new line of Hafler preamps which were of superior quality. Then abruptly in 1995 Rockford ceased producing Hafler equipment for the consumer market. The brief Hafler period from 1979-1995 was an exciting time because it was heavily responsible for the hobby of modifying audio equipment. The availability of affordable, high quality Hafler products had made it very easy for audiophiles to experiment and share ideas.

I was lucky to work for an audio salon that sold Hafler during this era and bought this preamp new in late 1991. It was the very last DH110 preamp shipped into our warehouse and likely one of the last built before the model was discontinued by Rockford. Produced in a black-finish the factory had installed polypropylene capacitors in places and metal film resistors in critical locations. Also included were gold RCA connectors on the rear which I believe only occurred on the final models. As evidenced by the rear panel and sticker on the bottom this was essentially a Hafler preamp upgraded to Rockford levels.

In the late 1990s I upgraded the circuit using the Musical Concepts "Line-mod" to modify the Line (CD) section and later upgraded the phono section as well. The photos below are from about 2004.

Musical Concepts mods are not merely parts substitutions. The process heavily redesigns the circuit, the feedback loop and time constants are altered, and there are no capacitors in the Line signal path with the exception of a single specialized one. The brown electrolytics below are polarized Roderstein "EK" caps which were considered high performance in the 1990s. I have since replaced these power supply caps with modern versions.

ABOVE: No longer produced by Musical Concepts was an optional LIPS II (low impedance power supply). Fed by the transformer it used NE5534 op amps and quality parts to create an ultra low-noise, super-quick 22.3V power supply for the preamp.

A good tip is to remove the tone control board and clean the pins with a good contact enhancer. Spraying out the tone buttons to reduce the crackling these buttons is a good practice. Also I like to remove the two web cables and clean the pins on the board with Deoxit. If you're feeling ambitious, unscrew the RCA board from the rear panel and remove the web cables from behind it and clean those pins too. I found this last step to produce an audible increase in sound quality as those hidden pins get grungy after 30 years. Visible in the photo above are purple Panasonic "Z" electrolytics and Panasonic "HFQ"s which were popular in the 1990s. The large yellow 4mf input caps were proprietary from Musical Concepts.

BELOW TODAY: I changed the line section resistors to Dale CMF RN55s, the signal path electrolytics to Silmics, and low impendance Nichicon PMs for the power supply and rails. In early 2017 I replaced the stock IN4003 bridge diodes with 1A 60V MBR160G Schottky versions.

Now in 2024 this 30 year old preamp is a favored piece in my listening salon and I use it for all my analog remastering. Whether its from phono, CD or other sources I find it adds an ultra-low noise, dynamic clarity to any signal passed through it. The phono section rivals CD for it's pure and accurate dynamics. I expect it to last a lifetime, with new electrolytics added every decade or so(!)