 Drip Four Seven
Drip is pleased to announce the release of the FOUR SEVEN version 2 printed circuit board. The FOUR SEVEN is Drip’s design of the famed REDD 47 British preamplifier.
 The Drip FOUR SEVEN design is verbatim to the EMI Redd schematic, including the use of two 0A2 voltage regulator tubes. Drip even included the option to use a GZ34 tube rectifier. The use of vacuum tube regulators and rectifier gives the unit it's beautiful 'sag' when pushed hard, ideal for cutting edge vocals and shredding guitar. However, the FOUR SEVEN can also be soft with hyper clarity for critical applications such as recording acoustic instruments or sultry vocals.
The new FOURSEVEN design is an amazing feat of symmetrical layout balanced with super direct signal routing. No zigzag traces - pure and direct .
One of the hot features Drip has added is the use of a discreet ground system.
Meaning: every resistor in the amplifier circuit has a 2mm thick trace separately returning it to a main star ground point. This feat alone gives Drip the edge when it comes to the noise ratio of the FOUR SEVEN. This is a feature that very few manufacturers take care to execute.
As for components:
THE SKY IS THE LIMIT:
The pcb has been designed to use both audiophile grade mundorf capacitors or for the budget- minded, smaller radial caps can be implemented just the same. Drip gives you the option to use parts that no other manufacturer would dare to use. Mundorf silver and oil capacitors / Mundorf polypropylene tube caps. All the resistor foot prints can also accommodate up to 5 watt metal film or 2 watt carbon composition resistors. Nothing has been spared in the design of this pcb.
 The PCB is massive, measuring 16.75 " x 8.25". The use of 3oz copper insures the highest performance and safety. Most traces are over 2mm thick ( on 3oz copper that makes almost 6mm per trace!). A thick .093" FR4 pcb core ensures stability and less susceptibility to vibration and mechanical failure. The Pcb is shielded top side by a solid copper plane (plane is used for shielding only).
TRANSFORMERS :
Sowter has faithfully recreated the Redd47 input and output transformers. They are encased in beautifully milled MU metal cases. Their tone is beyond amazing. The pcb is designed for the input and output transformers to be mounted onto the board, insuring a very short signal path from input to output. The Sowter transformers are available for a modest price of 243$(USD)
SPACE IS THE KEY:
Many designers use the bare minimum track spacing when designing pcbs. Drip uses up to 10 times the IPC / creepage rules when designing . This keeps high voltage traces away from critical areas sensitive to electromagnetic pollution, (i.e. you don't put a 500v trace next to a 6v trace).
DESIGN SYMMETRY:
Every trace on the pcb is curved , a technique used by Drip to capture the same electrical response as point to point wiring. (For audiophiles, curved traces tend to take the 'ringing' out of the tone), a design ethic inspired by early neve designs, back when pcbs were designed with hand and tape.
COST OF BUILD :
It was Drip’s goal to provide you with a world class microphone preamplifier for under 500$ (total approximate cost of build including pcb , parts and case)
If you choose the audiophile path, your imagination is the limit.
LEVEL OF DIFFICULTY:
As with most of our products, Drip has done all the hard work for you. This is one of the easiest builds to tackle. There is moderate soldering and only a few switches and pots to hook up. The transformer sections are simple and color coded so you can avoid any mistakes.
DIFFERENCES BETWEEN THE VERSION 1 AND VERSION 2 FOUR SEVEN:
The power supply of the Ver 1 Fourseven has a NASA grade fully regulated high voltageand low voltage power supply (solid state). The Ver 2 has a pure vacuum tube supply.
Version 1 uses a ground plane for its ground structure.
Version 2 uses a discreet ground structure.
(The Version 1 (solid state) pcb will be available again in the spring of 2010). Check our website regularly for information.
Special Pre-order Price: $125.00 (until 2/5/2010)
 Pre-Order the Four Seven at the Drip Store
Four Seven Photo Gallery
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Specifications