PR5 Phono Preamplifier

PR5 Phono Preamplifier

Do you want to play Vinyl? If so, you need an RIAA Phono Preamplifier.

The RedRoo PR5 phono preamplifier kitset 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.

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 preamp output impedance (required for driving low input-impedance amplifiers, or long/high-capacitance audio cables). 

The preamplifier has, as standard, two switchable moving-magnet (MM) phono inputs. Great if you have two turntables and want to que 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 cobalt based amorphous core LL9226 step-up transformers onto the PC Board, or by using external step-up transformers (both options are additional cost). You would then be able to switch between a MC input for really serious listening and a MM input for everyday music.

Step-up transformers amplify the tiny microvolt level signals of a moving coil phono cartridge, without having to resort to solid-state circuitry in the audio path to minimise noise.

The PR5 phono preamplifier is designed to be simple to build, yet very compact, measuring only 154mm wide by 240mm deep, and 115mm high. 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 toggle switches for power on-off and two-way phono input selection. The rear panel holds the input and output connectors and a turntable earth wire connection (if your turntable has one). Blue LED's shine up under the tubes when the power is on (can be changed for any LED colour).

We've made it as simple as possible to build while still keeping the highest quality of components and performance. Just like the SE5 power amplifier, this phono preamplifier kitset has been designed to eliminate any tricky assembly and any point-to-point wiring. Only the best quality components are used. Audio grade polycarbonate coupling capacitors preserve the delicate detail of the music.

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.

 For added safety, mains power does not enter the chassis. The unique power supply design, DC heaters, and earth-loop protection, means that there is no power supply induced hum or buzz. It's a surprisingly quiet low-noise preamplifier.

We rate this preamp difficulty level 3  - it contains hazardous voltages of 280V DC.

The RedRoo SE5 will impress with the energy and dynamics from such a compact and affordable tube amplifier, and there is nothing like saying "I built it myself".

*PC Boards are also available together with the power supply module and full technical details for experienced constructors who prefer to source their own components and make their own bespoke chassis.

PC Board without MC transformers
PC Board without MC transformers


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