UralTone High Gain Amplifier Build Guide

UralTone High Gain Amplifier Build Guide

The UralTone High Gain differs in style from the more traditional side of our series. The High Gain offers two channels (clean and distortion) and enough power for more demanding uses. Despite the more modern approach, the series is designed according to the same principles as our other series. Structural durability and very easy maintenance are important features both on a deserted island and on tours. All parts of the amplifier are of high quality and very durable.

As a construction project, UralTone High Gain is easy and moderately labor-intensive. Construction takes a few days for an experienced builder. The large case offers enough working space and the spacious circuit boards are easy to solder. There is relatively little wiring in the amplifier.

This article outlines the main stages of the build process. The purpose of the article is both to familiarize you with the construction before starting the work and to serve as a guide during the build. Study the pictures and instructions carefully before beginning the construction so that you get a good understanding of the work involved. The assembly is done by using the layout picture and BOM. The pictorial guide works as additional help to understand the assembly process and as well the correct order of it.

UralTone High Gain osalista - BOM

UralTone HighGain Layout

UralTone HighGain Schematics - kytkentäkaavio

Instructions for measuring and startup

Follow the construction order of the images below. We try to keep the models of the components the same, but the world of components changes rapidly, so we sometimes have to change part manufacturers or sets due to poor availability. So, if a part is a slightly different color, don't panic, each component has the necessary values ​​marked on the side of the part. Possible changes to the series will be published as additional images as updates to this article or, if necessary, as their own article.

First, always check that all parts are included in the delivery. If you find any deficiencies, please get in touch with us by e-mail or via the "contact us" form on the website. Also, note that the voltage rating of the parts may be higher than what is written in the list. Read the notes on the parts list carefully.

Step 1 - Preliminary preparations

If you are an inexperienced builder, first learn the secrets of good soldering and the basics of safe working. The most important thing is your own safety! We will not go through these points here. Follow this guideline throughout the project:

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

It is better to go through the instructions first, google for more information or ask us for advice.

Step 2 - Checking the parts of the build kit

Check that all the parts according to the parts list have been delivered and sort them by component type (resistors, capacitors, connectors, tube sockets, etc.).

If something is missing, please contact us and we will correct our mistakes.

Phase 3 - Construction area and peace

Reserve desk space for the project so that you will not need anything else during the entire project. Construction takes about 2 working days for a professional, 2-3 times more for beginners.

Have coffee or tea next to you, relax and focus your thoughts only on this project.

Step 4 - Starting to assemble

Sidenote: If you have a combo or head case for the amplifier ready or are in the process of making one, drill the mounting holes for it already at this stage. After attaching the transformers, setting the position of the mounting holes is more difficult because the finished amplifier weighs more than 11 kg and it is tedious to clean the inside from wood shavings etc.

The first step in assembling is attaching the mechanical parts (hardware) and transformers to the chassis. Attach the tube sockets, transformers, potentiometers, connectors, switches, etc. according to the layout image and the attached example images. The front and back panels are also installed in this work phase.

Typical errors:

- The sockets of the output tubes are mounted to the wrong side of the housing (check the pictures for correct mounting)
- The sockets of the output tubes are mounted in the wrong direction. Check that the guide rail/notch of the octal sockets (large sockets) points in the same direction as in the pictures. Check the noval sockets (preamp tube sockets) that the pin gap points in the same direction as in the pictures.

Note:
- Remove the potentiometer locking peg with cutters or pliers. The control must not protrude beyond the outer surface of the case, this prevents the installation of the front panel.
- Ensure the installation direction of the rocker switches. Removing these from the case is laborious.
- Please note that the washers are mounted on the correct side of the case, see the models in the pictures. The star washers come inside the housing to prevent the component from rotating, the smooth washers come between the housing and the nut.
- Preliminaries for potentiometer grounding: Sand the grease, coating and oxidation from the soldering point of the potentiometer housing with sandpaper and finally clean with IPA (isopropanol). Be careful that sanding dust does not get inside the potentiometer on the resistance track.

Step 5 - The first punches

Solder the wires that do not connect to the PCB at any point, as well as the components that are soldered to the sockets of the output tubes. These are easier to solder before installing the PCB. The wires that go to the PCB will only be soldered later. These include the cabling between the mains transformer and the switch, protective ground, wiring of the output tubes and the output transformer, and the cabling of the speaker jacks.

The heater wiring of the output tubes is twisted around each other. Cut the heater wire that comes with the kit into two parts and solder the ends of these to the base of the output tube on the side of the effect loop. Twist the wire moving forward to the next tube socket. The cables should run along the corner of the chassis. Once all four are in place, leave the remaining piece waiting to be soldered to the PSU board. Follow the layout picture for all cable runs.

The protective ground wire must be left longer according to the layout picture, so that if the mains connector fails, it is the last to come off. This is the most important connection of the amplifier. Put it on absolutely tightly so that there is a lock washer between each side.

Notes:
- Check the mains transformer connections also on the mains transformer package and/or on the manufacturer's website. Make sure that the correct voltages correspond to the color codes of the layout (indicated layout in the picture). Sometimes manufacturers change color codes without notice.
- Keep cables length to an appropriate level. Too tight connections do not last in use, and too long ones cause interference.

Step 6 - Mounting Components to the PCB

Place the components on the PCB of the amplifier. First, solder the tube sockets in place. After that, you should proceed by type (all resistors as a group, all diodes as a group, etc.) and proceed with the lowest-in-height parts first. This way the parts stay on the surface of the board when it is turned over for soldering. Note the following points:

- The electrolytic capacitors must be mounted in the right direction. The positive pole is marked with a groove and the negative with a line. Make sure that each electrolytic capacitor is mounted in the right direction! A capacitor connected the wrong way around can explode (!).
- Stack all the components so that the values ​​on their sides remain visible. Always connect different parts, e.g. resistors, in the same direction. This way, reading the values ​​is easier and the end result looks professional. The PCB can be soldered on both sides of the board, but we recommend soldering from the reverse side. This way you won't accidentally hit sensitive components. Soldering should be done from below the board also because the flux residue from the soldering iron remains invisible on the underside. The board is also easier to clean from the "solder side".

The circuit board of the power supply is made according to the same principles as the circuit board of the amplifier. Start with the short parts and work your way up to the tall ones. Increasing in series makes sense. Note: The regulator is not soldered on at this stage, this will be installed when the board is installed in the case.

Finally, assemble the effects loop PCB. On this board, the jacks and the two largest capacitors are mounted on the solder side of the board. These should be installed last. When installing the jacks, you should use the case as an aid, attach the Jacks to the case and push the plate onto the jacks. This way, the Jaks are installed directly parallel to the case.

After you have laid all the parts on the board, check all the parts one by one and compare with the pictures. Make sure all parts are in the right places and facing the right way!

Notes and possible points of failure:
- Make sure the components are facing the right way.
- Make sure the soldering iron has not hit the side of any component. Capacitors break because of this, because they have thin films inside, between which a short circuit occurs easily. Replace the parts with soldering iron marks.
- Check each solder joint with a good eye or a magnifying glass. Cold solder joints usually look bad from the outside as well (not always though) and good solder joints are often clean on the surface as well.

Step 7 - Installing the PCBs in the case and soldering the wires

Attach the PCBs to the case. Follow the instructions in the layout picture regarding the types of risers and screws/nuts to use. Under the jacks of the effect loop, there will be insulation pads. Leave the screws on the cover a little loose, so that the riser piece gives a little movement during installation and finds its place when the circuit board is screwed on. Finally, tighten all the screws.

Start soldering from the amplifier board. Start soldering the PCB from the input jack and work your way systematically to the other end. You can cut the wires of the potentiometers to the specified size at once and pre-tin the ends of the wires. If the copper strands of the cables stick out from the surface of the solder, cut them cleanly without damaging the solder. Leave the other wires unsoldered for now.

Continue with the power supply board. Screw the regulator to the housing. A mica insulating plate is placed under this and a plastic insulating washer is placed on the end of the regulator screw. Fold the legs of the regulator to point upwards and align the solder pads of the circuit board with the legs. Screw the plate on and solder the regulato. You can check the installation and insulation by measuring the resistance between the middle pin of the regulator and the body with a multimeter. This should be (almost) infinitely large.

Shorten the wires of the transformer to a suitable length and solder its wires to the power supply board. Solder the other wires of the board to the switches for the mains and standby switch.

Lastly, the circuit board of the effect loop is attached. This attaches to the housing from the jacks. Like the regulator above, the jacks should be isolated from the grounding of the case. You can verify the insulation by measuring the resistance / conductivity from the body of the jacks to the chassis of the amplifier. Solder the wires coming from the effect loop board.

Finally, wire the cables of the amplifier board to the channel switching jack and the output tubes. The grid wires of the output tubes are twisted together and soldered to the turrets of the output tubes (cf. pictures).

Be careful not to melt the protective sheath of the cable. If the cable melts, replace it with a new one! The cable is cheap. If the wire runs on the board through a grommet, thread the wire in place only after soldering. This way you avoid that the bent wire does not get burned when soldering. When soldering PVC wires, reasonable speed and determination is an advantage - but don't be sloppy.

Notes and possible points of failure:
- Observe the colors of the cables. This makes troubleshooting easier. If one of the cables runs out, you can replace it with another color - the sound is the same.
- Only the wire intended for the heaters are used for the heater plugs.
- The yellow-green protective ground wire is only used for the grounding of the mains connector.
- If the instructions mention the size of the wires, follow it.
- Make sure the soldering iron hasn't hit the side of any wire and exposed the threads inside.
- Check each solder joint with a good eye or a magnifying glass. Make sure that the end of the wire is not open and its strands are short-circuiting the adjacent pads.

8 - Review round

When all the parts have been soldered and screwed in place, everything has to be reviewed once more. Now is a good time to take a little break and take a little distance. You notice your mistakes more easily after a short break.

Check every joint, solder, component mounting direction and wiring point by point. The best thing is to go through each connection point and follow the components and wires coming from it, comparing them to the layout image. At the same time, mark in the picture which components, wires and eyelet pins have been checked. When everything has been gone through, it's time to connect power to the machine!

9. Power on

When you are 100% sure that everything is correct, it is time to turn on the power. We assume here that the only test device you have is a multimeter.

Make sure the device is on a table that is clean. Extra parts, wires, etc. must be cleaned off the table where the amplifier is used, so that they do not accidentally cause a short circuit. For example, pieces of tin wire and strands of wires that are hard to see with the eye can be destructive if they are left inside the amplifier. Lift the amplifier in the air with the component side down and make sure that there is no extra loose material left inside the case.

Use the multimeter's ohmmeter to measure the resistance of the ground points relative to the housing. That is, put the multimeter on the resistance measurement (smallest range), attach the black test lead to the housing and go through all the ground points on the layout picture (ground points / GND). The meter should read zero or close to zero (a few ohms at most). If this is not the case, check the connections of the problem point one more time. Also check the resistance from the ground point to the positive terminals of the filter capacitor (points B1, B2, BIAS, V+). After charging the filter capacitor, the resistance should rise to several tens of kilo-ohms.

Make sure the fuses are installed in the fuse holders.

Turn the power and stand-by switches to the "on" position. Make sure the tubes are not in the sockets. Plug the device into the wall. If you notice any suspicious sound, smell or sparking, etc., immediately pull the plug from the wall. If there are no problems, you can make the first voltage measurements.

Set the multimeter to the maximum direct voltage (DC) measuring range. (400VDC minimum). Attach the black test lead to the housing, e.g. with an alligator clip or use the holes in the housing as an aid. Measure using one hand, the other hand is in the back pocket during the measurements. This prevents an electric shock in panic situations, where the current passes from hand to hand through the heart. Measure the voltages on the power supply board and compare the results with the voltages in the layout picture. The voltages must be within 15% of those given. Verify the voltages from the filter capacitors on the amplifier board. With no load, this voltage is higher than expected. Unplug the power cord between all measurements.

When everything has been found to be correct, it is time to put the tubes in the sockets. Make sure the tubes go in the right direction. In many modern tubes, the base breaks easily if you try to install the tube in a crooked or wrong position in the base. The guide notch tells you which way the tube should be installed on its base. Connect the speaker to the speaker socket. You can also use an artificial load if you have one. Adjust all the pots to zero from the front panel and the bias pot halfway.

Turn the power back on. Wait a moment before turning the stand-by switch on. Again, if you notice anything suspicious, unplug the power cord immediately. Measure and check the measuring points. The tolerance is approx. 15%, i.e. the measurement results should not be identical. The voltages are affected by the mains voltage of the measurement location and the tolerances of the components (especially tubes). If the voltages are missing or incorrect, it is easier to understand the location and cause of a possible fault.

Note that voltage may be charged to the capacitors of the power supply. So you can get an electric shock even if the device is not connected to the national grid.

10. Regulation of resting current, i.e. BIASING

More detailed biasing instructions can be found here: Biasing a tube amplifier.

Biasing the UralTone High Gain amplifier is easy, as all tubes have their own measuring resistors. Biasing should be studied in more depth at some point so that the work can be done for any amplifier, but in this case it is easy to follow according to the layout instructions:

Set the multimeter to measure DC voltage (2V range). Measure the voltage of pin 8 (marked A in the blue circle in the layout) of any output tube with respect to ground (points B, C, D or E). Adjust the power supply trimmer until the multimeter reads 30mV or 0.030V.

Make sure by measuring all measurement points A-B, A-C, A-D and A-E. If there are large deviations in the results, check the connections and replace the deviating output tube with the one that gave the correct result. The set always comes with a matched quad, so the problem is more likely to be found in an error in the circuit.

The adjustment instructions given above apply to the EL34 tubes supplied with the kit, and in this case the tubes are biased to approx. 60% anode loss. Other tubes can also be used in the series. These provide more output power and headroom.
- EL34 / 0.03V (60%) - output power 100W
- 6L6GC / 0.043V (64%) - output power 102W
- 6550 / 0.062V (60%) - output power 110W
- KT120 / 0.082 (55%) - output power 120W

11. Guitar in hand and ears open

When everything is in order, you can connect the guitar to the input jack, open the volume and tone controls and enjoy the sound of the new amplifier.

If something doesn't work, sounds strange or suspicious, turn off the power and continue to examine the points that may be related to the fault and search for the fault.

12. Support

We are happy to provide technical support! To get the best possible support, contact us by email and mention the following in the first message:

1. Which build series is in question
2. Your name, phone number and order number (if available)
3. Describe the problem as accurately as possible. We receive a lot of messages, so we don't always remember even if the matter was discussed on the phone, for example. That is, always say everything again.
4. Never delete old messages from the thread
5. We try to answer within 12-24 hours on weekdays, but sometimes the support is backlogged. If you don't get an answer within two days, please contact us again.

13. Final thoughts

Fortunately, you now have in your hands a very high-quality tube amplifier that will last for decades of playing as long as you remember to change the tubes regularly. Every few years you should check the bias and replace the tubes if necessary. In general, output tubes last 2-5 years depending on use, and preamp tubes a little longer.