MODIFICATIONS
ART USB Dual Pre
Behringer B2 Pro
CME UF8
Denon DP-61F
Dynaco ST-70
Hafler DH-500
Hafler XL-280









  Klipsch Promedia 2.1
Klipsch KG1
Nakamichi CM-300
Scarlett 2i2
Mogami/Canare RCAs
Tannoy 603
VOX Pathfinder 15










HAFLER DH-110 PREAMP
UPGRADES and MODIFICATIONS










  • A footnote in audio history: Begun as Dynaco in the 1950s by David Hafler, his Hafler products began appearing in the mid 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 by the early '90s amps and preamps changed from a chalky brown color to a black-pebbled finish and the amps received sculpted faceplates. Internal capacitors changed from mylar to polypropylene and new designs like the Iris preamp and XL-280/XL-600 power-amps were produced, even a line of Hafler CD players and speakers. The 9000 series amps and preamps made in the early 1990s were of even higher quality until Rockford ceased producing Hafler equipment for the consumer market in 1995. It was brief and exciting time because modifying audio equipment really took off during this period...bolstered by affordable, high quality Hafler units which made it easy to experiment.

    As I mention on my other pages, I was lucky to work for an audio salon that sold Hafler during this era... I loved the 110 and bought this one new in 1993. It was the very last 110 preamp shipped into our warehouse and likely one of the last made before the model was discontinued by Rockford. Produced in the late black-finish, the factory had installed tape-wound polypropylene capacitors in places and metal film resistors in critical locations. Also included were gold RCA connectors across the rear which I believe only occurred on the final models. As evidenced by the sticker on the bottom this was essentially a Rockford preamp at this point.





  • In the late '90s I upgraded the circuit using the Musical Concepts "Line-mod" which modified the Line (CD) section, and later upgraded the phono section to the Musical Concepts mod as well. The photos below are from about 2004.


  • Musical Concepts mods are not merely parts substitutions. The process removes quite a few parts from the board...the feedback loop and time constants are changed, in fact there are no capacitors in the Line signal path with the exception of a single mica. The brown electrolytics with white lettering sit across the power-supply rail and were polarized Roderstein "EK" caps which were considered high performance in the '90s. I have since replaced the power supply caps with more modern versions.


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


    ABOVE: the signal path passes through the small raised board visible on the left...from the pins coming off the board. A good tip is to remove this board and clean the pins with a good contact enhancer. Spray out the tone buttons while you're in there to reduce the crackling these buttons produce out of the speakers when dirty. Also... remove the two web cables and also clean the pins on the board. If you're feeling ambitious, unscrew the RCA jack board from the rear panel and remove the web cables from behind it...cleaning those pins too. I found this last step to produce an audible increase in sound quality...those hidden pins can get grungy after 20 years. Visible on the board are purple Panasonic "Z" electrolytics which were the capacitor of choice in the 1990s. Also visible are Panasonic "HFQ" and Wondercap film caps. The yellow 4mf input caps were proprietary from Musical Concepts.

    BELOW TODAY: I have changed the line section resistors to Dale RN55s and updated the signal path electrolytics to Silmics and Nichicon PMs for the power supply rails. I don't use the tone circuit so those caps were left stock. In early 2017 I accidentally shorted a lead and damaged the LIPS powers supply (still in photo) and could not resurrect it...oh well, it had a nice long life. So I converted the power supply back to the original Musical Concepts line-mod values. I went a step farther and replaced the stock IN4003 bridge diodes with 1A 60V MBR160G Schottky versions.

    Now in 2017...this 25 year old preamp is the center of my home salon and I use it as the first step in the chain of all my musical remastering. Whether its from phono, CD or other analog sources I find it adds an ultra-low noise, realistic, 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(!)

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