PR5 Tube Phono Preamp
Do you want to play Vinyl? If so, you need an RIAA Phono Preamplifier kit.
The Red Roo PR5 phono preamplifier kit is a perfect partner for our SE5 power amplifier or any other power amplifier. If you want to upgrade your system to play vinyl records, this is a great choice.
The tubes used are four 12AX7/ECC83/7025 configured as two constant current draw (CCDA) amplifiers. Cathode followers in the output of each CCDA provide a low-impedance drive for the RIAA equalisation network (to maintain RIAA accuracy as tubes age), and a low output impedance (for driving low input-impedance power amplifiers or long/high-capacitance cables).
The phono preamplifier kit has, as standard, two switchable moving-magnet (MM) phono inputs. Great if you have two turntables and want to queue music.
For those lucky enough to have a moving-coil (MC) cartridge, one of the inputs can be converted to moving-coil by inserting two Lundahl cobalt-based amorphous core LL9226 step-up transformers onto the PC Board, or by using external step-up transformers (both options are an additional cost). You would then be able to switch between an MC input for really serious listening and a MM input for everyday music.
Step-up transformers are a low-noise way to amplify the tiny microvolt level signals of a moving coil phono cartridge, without having to resort to solid-state circuitry in the audio path.
The PR5 phono preamplifier kit is very compact, measuring only 154mm wide by 240mm deep, and 115mm high; a perfect partner to our SE5 stereo amplifier. It doesn't take up nearly as much shelf space as other tube preamplifiers that are often large, heavy, and cumbersome.
The front panel holds a large solid-metal Balance knob, and attractive toggle switches for power on-off and phono input selection.
The rear panel holds the input and output connectors and a turntable earth wire connection (if your turntable has one). Blue LEDs shine up under the tubes when the power is on (can be changed to any other LED colour).
The solderless kit makes it as simple as possible to build, without any soldering or tricky point-to-point wiring. Only the best quality components are used and audio-grade polycarbonate coupling capacitors preserve the delicate detail of the music.
For added safety, mains power does not enter the chassis. The unique power supply design, DC heaters, and earth-loop protection mean that there is no power supply-induced hum or buzz.
The Red Roo PR5 phono preamplifier kit is the result of many years of engineering and experimentation. You will be impressed by the energy and dynamics of such a compact and affordable preamplifier.
It's also a superbly quiet low-noise preamplifier.
The 'solderless' option will save you a lot of time and will guarantee success: all PC Boards supplied have the components loaded and are 100% tested. If you can use a screwdriver you can build the solderless option.
For those who want the ultimate experience, a weekend 'amp camp' is available in the Blue Mountains west of Sydney. Why not come with a friend and build one each?
There is nothing like saying "I built it myself".
Care is required as the circuit contains hazardous voltages up to 280V DC.
