Hafler DH-106
A twenty-dollar bag of parts that quietly turned an early DH-101 into a better preamp — and the only Hafler "component" that isn't really a component at all.
Overview
The DH-106 is not an amplifier, a preamp, or even a box. It is a modification kit, a set of parts sold by Hafler to upgrade the DH-101 preamplifier. Dealers like Oxford Audio Consultants sold it for $19.95 and advertised it repeatedly in Audio through 1980. For the cost of a decent LP, an owner could take a preamp they already owned and, according to the dealer listings, bring it up to a later specification. Upgrading usually meant trading in and starting over. Hafler sold it as a bag of components.
The dealer ads state the kit's purpose plainly: it was meant for DH-101s produced before May 1979. Later production apparently had the change built in at the factory, so earlier owners had to retrofit it themselves. Audio (April 1980, p.105) carried the same Oxford Audio listing that ran across the magazine's classified section that spring. It quoted the DH-101K kit at $199.95 and the factory-wired DH-101A at $299.95. The DH-106 was the cheapest line item in the whole Hafler preamp lineup, cheaper than the rack-mount panel, the cabinet and the head amp.
The documentation gets thin on what the kit actually changes. The dealer listings call it only a "mod kit" for early DH-101s and don't itemize the circuit changes. A separate dealer, Oxford Audio, offered a related service called the OACH-1, described as "a 106 type mod using precision components," for $50. That suggests the trade understood the DH-106 as a recognizable upgrade package, one a shop could also install with tighter-tolerance parts for a premium. That is about as close as the period record comes to describing what's inside the bag.
The DH-106 is a period-correct accessory for anyone restoring an early DH-101. Its low original price means surviving examples are more likely to be incomplete than valuable, since a kit half-installed in 1980 is a kit half-lost today. It is not a standalone component, it has no specifications of its own, and it should not be confused with the DH-101 itself.
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