Last
update 10/8/07
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HJFP2: two channel JFET micpre/ microphone preamplifier Order with Check or Money Order (Save 3%) Order with PAYPAL
2 Channel Transformer Balanced Class A JFET Microphone Preamplifier (micpre) FEATURES / SPECIFICATIONS: GAIN = 66dB 3 dB BANDWIDTH = 10Hz to 50KHz or better THD = <1% at 0vu out, +4dBm. INPUT Z, DI = 2.2Mohms (pad out), 200Kohms (pad in, i.e. hi Z line), Mic input 2.5Kohms (pad in or out) CONTROLS = Gain (opt precision step attns), Pad, +48, Phase DESCRIPTION: The HJFP2 kits come complete with everything you need to build the micpre down to the last screw. Controls include: microphone, line, and DI inputs, gain, +48VDC, Pad, and phase per channel. High grade capacitors, 1% metal film resistors, custom audio transformers with large iron/nickel cores on both input and output of each channel (4 in total). Both audio transformers are pc mount, the input is Mu-metal shielded. PC mount audio connectors minimize point-point wiring, and audio proximity to the power supply. The chassis is designed so two will sit side by side in a standard rack shelf (i.e. 4 channels), 2U high with the handle off, and 12.5" deep. The picture below far right shows the HVTP2 and HJFP2 prototypes in a 3U rack shelf. Approximate weight 12lbs.
Heavy duty toroidal power transformer (running at 18% of its rated value) that can be wired for 120vac or 220/240vac. Fully regulated "slow ramping" power supplies (+24 & +48 vdc). Compact, low noise, linear regulation with passive filtering. Safely over designed.
Completely machined chassis made of 16 gauge cold rolled electro plated steel with a separate power supply compartment. Two color powder coated, with two color screen printing with same color scheme as our power supplies. Insanely robust (see picture below with 190lb engineer +70lb husky standing on prototype). Integrated standoffs for easy pcb mounting.
4 extra holes on the back for Neutrik/Switchcraft 1/4" jacks allowing optional rear panel wiring. True EMI filtered power entry module, fuse holder, and power switch. Professionally made, drilled, and solder masked printed circuit boards for solid and easy assembly (solder mask covers everything except what you are supposed to solder, makes it hard to mess up) Prototyping section on each channel card for experimentation. Allows you to utilize the HJFP2s power supply, chassis, and I/O section with your own gain stages, or mod the ones provided for infinite possibilities.
Though we have tried to simplify the assemble by providing all the parts and detailed documentation, it still requires some elementary understand of electronics, how to use a volt meter, how to solder .... If you are new to DIYing, this may be a bit advanced. The kind of people who should take this on, are people who have built things before, know how to do simple AC/DC measurements, can solder, and can do clean point-point wiring, or have friend that does. At the same time, the last thing I want to do is discourage anyone from trying to learn new skills, and there is no better way to learn than by throwing yourself in the fire. I am just trying to avoid people getting in over their heads, and not being able to complete it. On the flipside, a number of people with no experience have built it successfully, and were ecstatic about the end result, and their new found ability. SH. |
