Pännäri Revenge JFET RIAA -kit

Pännäri Revenge JFET RIAA - Kit

The popular tube-based RIAA preamp designed by Mauri Pännäri now continues as a discrete JFET implementation. The original circuit guide was published as an article on audiovideo.fi (in Finnish) and has been further developed by UralTone into a DIY kit. The structure is based on the familiar Hammond 1455 enclosure used in the tube version, now in a smaller size.

The DIY kit is available in two versions, adapted for either an MM cartridge or an MC cartridge. The kit includes a carefully selected and matched NOS JFET set, a through-hole plated PCB, and the best possible components in terms of quality.

The purpose of this article is to familiarize you with the construction of the device before starting and to serve as a guide during the assembly process. Review the images and instructions carefully before beginning to build. This will give you a good understanding of the work involved.

Always follow the component list and circuit diagram provided with the kit. We occasionally update the circuit designs, and over time, improvements or changes may be made, for example, due to component availability. Some differences from the illustrated build steps may occur. The component list included in the kit is always correct and specific to the version.

The layout diagram and component list also serve as an assembly log. Always mark installed components or connected wires on the component list or layout diagram. This way, you can ensure that all parts and solder joints are completed.

Pännäri Revenge JFET RIAA Component List - BOM - Bill of Materials

Identifying Components

Soldering Instructions

Always check first that all components are included in the shipment. If you find any missing parts, contact us via email (orders@uraltone.com) or the "Contact Us" form on the website. Note that components may look slightly different from the pictures. Also, component voltage ratings may be higher than what is listed. We strive to keep the component models the same, but due to availability issues, we may sometimes need to change the manufacturer or model. So, if a component is slightly different in color, don't worry—each component has the required values marked on its surface. Read the notes in the component list carefully.

The assembly follows the familiar low-profile-first order. When assembled this way, components remain neatly in place on the board when it is flipped over for soldering.

The circuit board layout. Each component has a printed part number on the board, and the corresponding component value can be found in the component list.

Solder the resistors, diodes D1 and D3, and jumper wires (R3 and R15) onto the board. Resistors do not have a specific installation direction. The board indicates the correct orientation for diodes—align the striped end (cathode) according to the board markings. Use trimmed resistor leads as jumper wires.

Solder the regulator U1 and JFET transistors Q1-Q6 onto the board. Note! Before soldering the transistors, check their installation direction (pinout). The correct pinout can be found at the bottom of the component list. Install the transistor leads (drain, gate, source) according to the D/G/S markings on the PCB. The image shows 2N5485 transistors installed.

Note: The pin configuration of 2N3819 transistors varies depending on the manufacturer. The Fairchild 2N3819 FET has a different pinout. Compare with the pin diagrams in the component list. The Fairchild FET can be identified by the F logo printed on the casing.

Note: From 2024 onwards, the MM version of the kit is supplied with a 2SK208 FET pre-soldered onto an auxiliary PCB, replacing the BF245.

Solder the cut-off leads from resistors or other components onto the auxiliary PCB. When soldering the component onto the board, align the D, G, S pins according to the markings on both PCBs. (This applies only to the MM version!)

Solder the ceramic capacitors (C16, C17) and the 22nF and 100nF film capacitors (C2, C3, C4, C8, C9, C10) onto the board.

Solder the DC jack and power switch onto the board. Ensure that the components are firmly seated against the board surface.

Solder the electrolytic capacitors and the 470nF film capacitors (C5, C11) onto the board. Electrolytic capacitors have a designated polarity—the negative lead is marked on the board with a white semicircle. The capacitor itself also has a printed stripe indicating the negative terminal, and the negative lead is shorter. If you are assembling the MM version, also install the Silver Mica capacitors (C1 and C7).

Same step, MM version.

Solder capacitors C6 and C12 onto the board.

Attach the RCA connectors and grounding banana jack to the back panel. The kit includes a pre-drilled back panel where the connectors are isolated from the chassis ground. This back panel does not require insulating washers.

If you are using the undrilled aluminum panel supplied with the enclosure, use insulating washers for the RCA connectors.

Bend the soldering tab of the RCA connectors backward.

Attach the front panel to the enclosure. Bend the LED leads at a 90° angle and insert the LED into its pads. Pay attention to polarity—the square pad is the negative terminal. The LED's negative lead is shorter and can also be identified by the beveled side of the casing. Do not solder the LED yet.

Slide the circuit board into the enclosure, positioning it in the second highest slot as shown in the image.

Guide the LED through the front panel hole and solder it to the board. Finally, trim the LED leads.

Next, proceed with the wiring. Strip about 15mm of the outer insulation from the shielded cable. Twist the braided wire together but do not twist it all the way to the base. A good technique is to first twist the entire wire and then turn the base counterclockwise so that the inner signal conductor and its insulation are not compressed.

Slide a piece of thin heat shrink tubing over the braid and apply a small amount of solder to the wire ends. The heat shrink will shrink from the soldering heat.

Finish the cable by heating a wider piece of heat shrink tubing over the joint.

Remove the board from the enclosure, measure the correct wire lengths, and prepare four cables following the instructions above.

Wire the connections between the back panel and the circuit board:

• Chassis GND to the back panel banana jack
• Input (CH1 IN / CH2 IN) and output (CH1 OUT / CH2 OUT) wiring to RCA connectors, including signal ground (GND)

Slide the top cover into place, insert the circuit board into the enclosure, and secure the screws on the back panel. The device is now ready for use!

The RIAA preamp operates with a 24V power supply featuring a 2.1/5.5mm center-positive connector. The online store product page lists compatible and tested power supplies.