The RIAA designed by amplifier-guru Mauri Pännäri is a popular and highly appreciated project. The circuit is based on two amplifier tubes and one FET transistor per channel. By changing the type of FET, the circuit is suitable for both MM and MC cartridges. The kit is delivered with transistors selected for MM cartridges.

As always with UralTone kits, no compromises have been made on durability, sound, and high-quality components!

This article goes through the building steps in quite some detail. Not every detail of construction is discussed separately, and the idea of the article is mainly to familiarize oneself with the construction before starting work and to assist during the work. Carefully review the pictures and instructions before starting the build. This will give you a good understanding of what the work involves.

Always follow the layout image and part list provided with the kit. We occasionally update the circuits of the kits, and over time there will always be improvements or changes based on part availability. Deviations from the picture series are possible. Check that the versions of the paper instructions and parts list that came with the kit match those delivered. In exceptional cases, make sure which version is correct by asking us first.

The layout image and parts list also serve as book keeping for assembly work. Always mark the installed part or connected wire in the parts list or layout image. This way you can ensure that all parts and solder joints are made.

  1. UralTone / Mauri Pännäri RIAA v2.0 kit

    As low as €285.00 €229.84

    Rating:
    97 % of 100

    Very good quality TUBE RIAA DIY kit. Learn More

UralTone RIAA 2.0 - Parts List - BOM - Bill of Materials

Tone RIAA 2.0 - Layout

Preparations

Always first check that all parts are included in the delivery. If you find something missing, contact us by email or through the 'contact us' form on the pages. Note that components may look slightly different than in the photos. Also note that the voltage ratings of the parts may be higher than what is listed. Read the notes on the parts list carefully.

Follow the assembly sequence in the images below. We strive to keep component models the same, so sometimes we have to change the manufacturer or model due to poor availability. If a part is slightly different in color, don't be alarmed; each component has the necessary values marked on the side of the part.

If you are an inexperienced builder, first learn the secrets of a good solder joint and the basics of safe working. Safety first! We do not cover these issues here. Follow this guideline throughout the project:

If you don't know what you are doing, or are unsure, do not do it!

First read the instructions, google for more information, or ask us for advice.

The PCB of the RIAA circuit has part numbers printed on it. Resistors are marked with a prefix R, capacitors with C, etc. Start with the lowest components - this keeps the components neatly on the surface of the board when the board is flipped over for soldering.

Lay the resistors on the board. The resistors do not have a specified direction of installation.

Note that the leads to the tube sockets share a common pad with some of the resistors. These pads are located on the lower side of the board. Do not solder these pads yet, but only cut the connecting leg of the resistor to the appropriate length. Save a few connecting wires as they will be needed in the next work step.

The latest version of the RIAA 2.0 circuit uses a surface-mount FET, which is soldered onto a small PCB. Solder jumper wires to the FET board. Bend a small 90° angle at the end of the wire and push this bent end through the pad.

Solder the FETs to the board at the places indicated in the picture. The board has four pads that allow compatibility with all different pin out types.

Note: If the kit includes a FET in a TO92 package, install it according to the instructions on the flip side of the board. Install BF245 according to the white marking and 2N3819 according to the black marking. The shape of the marking/pattern matches the orientation of the part during installation.

Solder the film resistors to the board. These do not have a specified direction of installation.

Note: C4 partially covers the installation holes on the board. It is advisable to install the spacers before installing the capacitors on the board.

Install the electrolytic capacitors on the board. These have a specified direction of installation: A white semicircle is printed on the board (symbol at the top of the picture). Align the negative terminal of the capacitor accordingly. The negative terminal is marked on the side of the capacitor with a stripe, and the negative terminal's connecting lead is also shorter.

The PCB now looks like this.

Set aside the board and continue building with the power supply PCB. Start by soldering the resistors to the board.

Note: 2W metal oxide resistors may be replaced with metal film resistors.

Solder the diodes and diode bridge to the board. Diodes have a specified direction of installation: align the stripe printed on the casing with the print on the PCB. The diode bridge has a marked plus pin, which is aligned with the print on the board.

Note: It is advisable to install the zener diode D1 on the board slightly raised from the surface. This diode will break if the power supply short-circuits. This makes it easy to replace as you can grab it with a tool.

Solder the trimmers, fuse holders, and capacitors to the board. Remember to consider the polarity of the electrolytic capacitors.

Note: Trimmer P1 is marked 504 (50 and 4 zeroes, i.e., 500,000 or 5k) and trimmer P2 502. Do not mix and misplace these.

Do not install the MOSFET and regulator yet and set aside the board.

Attach the RCA connectors, the grounding banana plug, and the tube sockets to the front panel. Use insulation plates with the RCA connectors.

Note: If you are building an older version of the kit, the tubes have a specific installation bracket where the tube sockets are installed.

The same installation from the reverse side. Contrary to the picture, the tube sockets supplied with the kit do not have a flange for mounting the cap. (Removal of the tube is more easy with non flanged sockets)

Attach the RIAA circuit board to the bottom of the case and solder the wires between the front panel and the PCB. Start with the tube filament wiring (the yellow-white wire pair in the picture). Then solder the wires between the tube socket and the PCB. The board is marked with numbers indicating to which pin of the socket the wire is soldered. Keep the wires relatively short and separate from each other. Finally, solder the shielded cables for the input and output.

Be particularly careful when soldering a shielded wire: the insulation of the inner conductor melts easily. It is advisable to use heat shrink tubing with a shielded wire; twist the shielded ground braid into a conductor, slip it into heat shrink tubing, and tin the end with a drop of solder. The tubing shrinks to insulate and evens out the thermal load on the conductor's insulation.

Attach the power supply PCB to the bottom. Bend the legs of the MOSFET and regulator upwards and insert them into the pads. When the aforementioned parts and the PCB are attached to the case, solder the connection legs.

Note: An insulating plate (mica) is installed between the regulator and the case, and a plastic insulating sleeve is placed between the nut and the component's case.

Solder the wires between the power supply and RIAA boards, as well as the tube filament wires. Note the jumper wire F and the AC pins.

Attach the IEC connector/fuse holder/power switch assembly to the mounting hole on the rear panel. Solder the protective ground wire as well as the wires between the IEC connector and the switch. It is advisable to protect these connections with heat shrink tubing so that the live pins are protected during testing.

Install the toroidal transformer on the board and solder its wires. Attach the ring terminal connected to the protective ground from the rear panel to the case. Leave this wire long so that it detaches last if the rear panel is torn off.

Note: Also check the transformer connections from the sides of the transformers/packages. Make sure that the color codes on the layout match the correct voltages (specified in the layout image). Sometimes manufacturers change color codes without notification.

The toroidal transformer's protective ground is attached with a ring terminal and another wire, which is soldered to the grounding terminal on the front panel.

Finally, bundle the wires so that the result looks neat.

The RIAA is ready for testing. Install the fuses in place. Note that the rear panel fuse is installed in the furthest slot back. Before turning on the power, check your work thoroughly. Be meticulous. In building electronic kits, the most important thing is to patiently check your own work for human errors. Everyone makes mistakes, but a professional notices them before anything fatal happens. Correcting a mistake is easier before turning on the power than afterwards, when parts may have been damaged. Ensure from under the board that no wire rises more than a few millimeters from the surface of the board and that parts with specified polarity are installed correctly. Check that the wires are soldered to the correct places.

When everything has been checked and found to be correct, turn on the power without the tubes. If you notice any suspicious noise, smell, or sparking, etc., immediately pull the plug from the wall. If there are no problems, you can perform the voltage measurements / adjustments.

Connect the black probe of the multimeter to the grounding point on the front panel, and with the other probe, first measure the voltage at the H+ pad of the power supply. Adjust the voltage to 6.3V with trimmer P2. Then measure the B+ pad of the power supply and adjust the power supply voltage to 195V.

Once the voltages are adjusted, turn off the power and install the tubes in place. Ensure that the point B+ is de-energized with a multimeter from pad B+.

Connect the voltages and measure the voltage at test point A. The easiest place to measure is from the at resistor R4 on the end towards closer the center of the pcb. (R4 is the only small 0.6W resistor in the circuit). Adjust trimmer P1 so that the voltage at the measuring point is about 70V. Since there is variation in components, measure both channels in turn and adjust the voltage so that there is the same amount of deviation in both channels (e.g., ChL: 68V and ChR: 72V). If the aforementioned voltages are not correct, instructions for troubleshooting can be found at the end of the article.

Once the adjustments are made, put your favorite record on and slowly raise the volume until you hear music from the speakers.

If something doesn't work, sounds odd, or suspicious, turn off the power and continue to investigate and search for possible issues related to the problem.

Possible hums may be due to the grounding of the equipment. If your turntable has a separate grounding wire, connect this to the ground point on the RIAA's front panel. If necessary, pull a grounding wire to the amplifier's ground. You can also try grounding the turntable directly to the amplifier. Equipment grounding is experimental, and there is no one right way or style.

If everything works well, secure the device in the case, enjoy the great music, and congratulate yourself. Not everyone builds a top-class tube amplifier!

We gladly provide technical support! For the best possible support, approach us by email and mention the following in your first message:

  1. Which kit is in question
  2. Your name, phone number, and order number (if available)
  3. Describe the problem as precisely as possible. We receive many messages and calls, so we do not always remember even if the issue has been discussed, e.g., on the phone. So always explain all the details again.
  4. You can send a picture or a few pictures (under 1M but detailed) of the inside of the device, so we can see roughly if the device is built correctly.
  5. Never remove old messages from the chain
  6. We aim to respond within 12-24 hours on weekdays, but sometimes support is busy. If you do not receive a response within two days, please contact us again.

Typical problems:

  • B+ voltage does not adjust:
    1: Too high voltage, does not adjust: Trimmers P1 and P2 are installed crosswise.
    2: Too low voltage, does not adjust: Zener D1 is short-circuited. Replace it with a new one. Ensure that the power supply is not short-circuited.
  • Voltage at point B about 0V, voltage at point A low: FET short-circuited. Replace with a new one. Ensure that the tube is not broken.

If the RIAA is for an MC cartridge, the FETs can be replaced with type 2SK170. These are available from the UralTone online store:
https://uraltone.com/2sk170gr-audio-fet-nos-idss-matched-pair.html
Select an IDSS current of 4.0 - 4.4mA.