When Fostex first marketed the PD4 as a second-generation descendant of the landmark PD2, the company was faced with a price point of half its current selling price from its main competitor, HHB. This is tough for any manufacturer; the apparent guiding principle was to streamline the new machine to be competitive.
Fostex did a fine job of it except for several glaring particulars. One of these lapses was in the area of resident monitoring options in the machine. Sound Techniques, from New Zealand, has built an after-market installable solution to this problem, the HPB-01.
The HPB-01 ($220, plus installation) is a headphone amplifier and switch on a very compact, surface-mount circuit board, designed for installation into any PD4 of V2.3 or newer vintage. It is well manufactured and built with high-quality components. Everything needed, from cables to zip ties, are included with the installation kit.
The HPB-01 provides comprehensive headphone switching, giving stereo, mono, left-only, right-only and MS decoding/difference monitoring options. It also includes a high-grade stereo headphone amplifier, replacing the on-board amp of the PD4.
I had my installation done by Neil Stone, Jr. in North Hollywood. His company, Save Our Sound, did a very clean job. Stone informed me that the installation required a complete disassembly of the top, front and input panel, as well as a small amount of drilling and cutting to make the rotary pot fit into the unused Aaton porthole.
Some soldering was required in some places that are rather difficult to get at. While the instructions are quite self-explanatory, it would be easy for a nontechnical person to do some serious damage to the unit if installation was done incorrectly – get a pro to do the job for you. Someone who has done it before should take about 90 minutes, a first timer closer to two hours.
If you had the gain turned way up at first listen, you might think the amp was substantially noisier than Fostex’s original. This increase in noise, however, is inherent to the PD4. The board can only increase the amplification available and it definitely improves the audio quality. The system noise is not noticeable at normal listening levels.
One possible negative is that the side-mounted rotary switch is of a higher physical profile than I would like and is made with a plastic shank. This creates the potential for snapping the switch off if you are in a fast, running gun mode and get jammed up against a wall or doorway.
That such a specialized improvement is available is a miracle. If you use the PD4, I suggest that you jump all over this upgrade to take full advantage of its potential. Reasonably priced, well made and no outboard kluge. What more could you ask for?
Contact: Sound Techniques at 64-9-846-3349; e-mail: firstname.lastname@example.org;