HAMPTONe9. OPERATIONAL NOTES / THERMAL CONSIDERATIONS / LONG TERM RELIABILITY
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The pad switch serves a dual function. When using a mic, it provides a –14dB pad. When using the ¼" jack, it switches it from an instrument to a line input. For high output condenser and dynamic mics, the pad may be needed to prevent overloading the input (unless that is your desire). For ribbon mics, you will typically leave it out. With the pad switch out, or "Inst" mode (pad out of circuit), the ¼" jack is a 2.2M high Z input for low level sources (basses, guitars, piezio/transducer pickups without preamps, unbalanced microphones…). Do not use the pad for these sources. When switched to "Line" (pad switch in), the ¼" input has an input Z of 160K, with a –14dB pad in front of the first gain stage. This is for line level signals, keyboards, tape machines, computer interfaces…. If you want to change the pad value, it is simply a matter of changing the ratio of R3 and R4, while keeping the sum of the two the same. A table is provided on our website that gives R3 and R4 values for pad values ranging from –14dB to –24dB. Click here to change the pad and for other mods and upgrades.
When powering up the unit, it is best to wait a few seconds to allow the power supply to reach full/stable voltage, before turning on phantom power to microphones. Each channel card has a two stage LP filter to prevent power on "pop" and to provide added filtering. These filters provide the proper turn on profile for microphones.
THERMAL CONSIDERATIONS / LONG TERM RELIABILITY
If you plan on putting the HJFP2 in a rack shelf, I recommend using a 3U. Though the unit will fit in a 2U shelf with the handle off, it doesn’t leave much room for ventilation on the top. Generally, gear in racks should have space above them, to decrease internal temperature. Heat is the enemy of electronics, and generally speaking the hotter something is forced to operate at, the shorter its life span will be.
Also, don’t keep the unit where it will be subjected to vibration, like on top of a speaker, amp, or monitor of any kind. This is generally bad for all electronics. Also keep the unit away from large transformers and other power sources which can induce AC noise in the audio. The chassis is made of 16 gauge steel so it provides an excellent shield to electric/magnetic fields, its just good practice to separate low level audio (i.e. microphone inputs to micpres) from AC.