UralTone SR 2.0 Amplifier Kit – Illustrated Assembly Guide

UralTone SR 2.0 Amplifier Kit – Illustrated Assembly Guide

UralTone SR 2.0 is a compact enclosure version of the UralTone SR series. The circuit is the same as the basic version of the SR series, with tremolo and reverb omitted. All other features and the sound remain the same.

UralTone SR 2.0 Layout

UralTone SR 2.0 BOM – Bill of Materials

Soldering Guide

Component Identification for Amplifier Building

Building the Amplifier

Always check that all parts are included in the package. If anything is missing, contact us via email or through the "Contact Us" form on our website. Note that some components may look different from the photos. Also, some component voltage ratings may be higher than listed in the BOM. Carefully read the notes in the parts list and layout images.

The layout and BOM linked above are always the latest versions, whereas the images on this page are meant to assist in assembly by helping to understand the structure of the device. Always use the layout image and BOM as your primary guide. The images on this page serve as supplementary assembly references.

There are three main stages in assembling the amplifier: mounting chassis components, installing the circuit board, and mounting and wiring the board to the chassis. The first two steps can be completed in any order. This guide follows the sequence mentioned above.

The images in this article were taken during the assembly of the SR 2.0 prototype. The image set is not exhaustive but provides general guidance for the build.

Attach all front and rear panel components, such as switches, potentiometers, and connectors. Install the front and rear panels at this stage.

Once the panels are installed, mount the transformer pass-throughs and tube sockets onto the chassis top. Install the circuit board standoffs—two of these go under the power transformer, so they must be installed before the transformers. Use countersunk screws for these. Finally, install the transformers.

As the final step, install the transformers. In some kits, the power transformer is designed to be mounted through the chassis. The kit includes upright mounting end bells. Remove the screws from the transformer assembly and attach the corner-mounted end bells. Install the grommets on one end.

Complete all wiring that can be done using the transformer leads, including the AC power input, power switch, high-voltage fuse, output transformer secondary (impedance selector and speaker outputs), and anode wires from the output transformer to the tube sockets.

NOTE: The image above was taken during a prototype build between circuit board swaps. It shows the tube socket wiring and heater wiring. Do not complete these steps yet. Heater wiring is easier to install later when the wires are not in the way during assembly. Also, do not shorten the unconnected transformer wires yet.

Rear panel wiring.

Front panel wiring.

The chassis assembly is now complete, and it can be set aside for circuit board construction.

Solder all components onto the circuit board. Each component number corresponds to a value found in the parts list. Some important notes: The power tube cathode resistor is mounted on turret terminals, similar to the screen grid resistors. These can be pressed into place using a dedicated tool or soldered directly. Do not solder resistors R4, R5, and R17 onto the board; these are mounted directly onto the preamp tube socket and input jack. It is best to solder components by type (resistors, diodes, etc.) and by height, ensuring they stay flush with the board. Organizing components in this manner also helps with workflow management. Once the board matches the image, install it in the chassis.

Once the board is installed, mount the power supply MOSFET. A detailed guide for this step is provided in the layout diagram. Solder short wires from the tube sockets to the circuit board, ensuring each numbered socket pin matches the corresponding PCB pad. Keep the wires as short as possible and route them individually rather than bundling them together. Also, solder short wires to the front panel potentiometers. Longer wires for the rear panel potentiometers should be twisted together. Solder the resistors between the power tube sockets and the board.

As the final step, complete the heater wiring. Split the green single-core wire included in the kit into two sections. Start at the preamp tube, solder the leads, and begin twisting them. Maintain a neat, tight twist to minimize noise. Continue to the next tube socket, cut and solder the leads, then attach two new wires and repeat for the next socket, continuing in the same manner.

Some of the rotary switch wiring can be done using clipped component leads. For longer runs or crossings over unshielded wires, use shielded wire or cover the lead with heat shrink tubing.

The screen grid resistor is installed at one end on a turret terminal. Note the adjacent grid-stopper resistor.

The preamp grid wires should be made from shielded cable, with the shielding trimmed short at the resistor end. Ground the shield only on one side. Solder the resistor to the signal wire and protect the joint with heat shrink tubing.

The shielded wire is soldered at both the shield ground and the signal wire at the output side.

The middle terminals of the distortion channel’s tone and gain potentiometers are bridged, and a shielded cable is used to connect the middle terminals to the preamp tube.

The amplifier is now fully assembled! Before powering it up, double-check the wiring. Once everything looks good, install the mains fuse and the high-voltage fuses in the rear panel. Do not connect power yet, and leave the tubes uninstalled. Using a multimeter, measure the resistance between the metal chassis and the PCB GND REF point. It should read zero. Next, measure the resistance between test point TP A, the cathode of diode D8, and the chassis. The reading should initially be low but should rise quickly to tens or hundreds of kilo-ohms. If the meter shows a small resistance or zero, there is a short circuit. Once the acceptable measurements are confirmed, you can power up the amplifier. Without the tubes installed, TP A will have some voltage, depending on the headroom control position. Turn the control to maximum voltage.

Install the tubes and connect the amplifier to a dummy load or speaker. Slowly increase the volume and gain controls. If everything appears to be working correctly, check the test point voltages against the layout diagram. The test point values are given with the headroom control set to maximum.

If the amplifier produces abnormal sounds, crackles, pops, or smoke, turn off the power immediately and carefully check the wiring. Deviations in test point voltages often indicate potential faults.

Support

We are happy to provide technical support! To receive the best possible assistance, please contact us via email and include the following details in your first message:

1. The specific kit you are working on
2. Your name, phone number, and order number (if available)
3. A detailed description of the issue. We receive many messages and may not remember previous discussions, so please provide all relevant details again.
4. Do not delete previous messages from the email thread.
5. We aim to respond within 12-24 hours on weekdays, but during busy periods, support may take longer. If you do not receive a response within two days, please follow up.

We prefer email communication. While email may seem slower than a phone call, it often leads to quicker problem resolution as we can research and prepare a response in advance. Phone support is generally more limited in scope.