UralTone PP-EL34 v2.0 building instructions
UralTone PP-EL34 is our most popular HIFI amplifier kit. It has enough power to drive almost any speakers and the sound quality is top-notch. Construction is carefully designed so that it is relatively easy to build and at the same time super durable.
When you build it by yourself, you can also repair it. So this is the amp for life.
As a new feature with version 2.0, the PP-EL34 now has an option for integrated RIAA. The phono section is based on a design by famous HiFi designer Mauri Pännäri.
This guide is written to build a PP-EL34 amplifier without the RIAA option.
This article goes through the construction with photos. Always give priority to the layout image and BOM (bill of materials) provided with the kit. Some components may look different, but the most important thing is that the electrical values are in accordance with the BOM.
Step 1 - Prepare
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 safety! Follow this guideline throughout the project:
If you don't know what you're doing, or you're unsure, don't do! < / p>
Rather re-read instructions, google for more information, or ask us for advice.
These general articles should be read before starting work:
PLEASE NOTE: Pictures are from the earlier version, but there is only minor changes. We will update new picture asap!
Step 2 - Check the parts of the kit
Check that all parts according to the BOM 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 error.
Some components may look different from our images. The most important thing is that the values of the resistors and capacitors are correct. Note, however: the declared voltage rating of the parts is minimum. For example, the 400V on the list can actually be even 630V.
Step 3 - Peace of mind
Reserve table space for the project that you will not need for anything else during the entire project. It takes about 2 working days for a professional to build this kit and 2 times more for beginners.
Make some coffee or tea, relax and focus your thoughts on this project alone.
Step 4 - let's build a high-quality tube amp
The first step is to attach the mechanical parts (hardware) and transformers to the chassis. Attach the transformers and rear panel connectors and other components as shown in the layout diagram. If the RIAA kit is not installed in the amplifier, also install the cover plates in the outermost holes of the preamplifier tubes.
When installing output transformers, 10mm spacers are used for cables. Transformer mounting holes are wide, so transformers and platform pieces must be matched. Leave spacer and transformer side nut slightly loose. Then attach the transformer to its chassis. Finally, tighten the nuts.
If an EI-CORE transformer is used in the amplifier, make the necessary changes to the transformer according to the layout diagram. Turn the L-irons over and install extension pieces (M5 / M6, 20mm / 25mm depending on the version) on the transformer. Opening varnished screws can be facilitated with acetone. When removing the L-irons from the transformer, be careful not to tear the copper protection of the transformer.
A rubber plate is installed under the toroidal core transformer. The ends of unused conductors are insulated with a heat shrink tube.
-Make sure that the washers are on the right side of the case (check layout and pictures).
Step 5 - First solderings
Solder the wires that do not connect to the circuit board at all. The exception is the front panel power switch, which should only be installed once the circuit board is installed. Braid and pre-solder the feedback cables (comes from speaker terminals).
The safety ground cable must be left longer as shown so that it will be the last to be detached if the mains cable fails. This is the most important connection of the amplifier, put it absolutely tight so that there is a lock washer between every part.
Also, check the connection of the transformers on the side / packages of the transformers. Make sure that the color codes of the layout correspond to the correct voltages (indicated in the layout picture). Sometimes manufacturers change color codes without notice.
Step 6 - Populate and solder the circuit board
Place all the components on a component board. In our experience, it is good practice to start with low parts (resistors) and move on to higher ones (axial plastic caps and finally vertical caps). This keeps the parts on the surface of the circuit board when the board is turned upside down for soldering. You can see from the layout that there are pads where goes component lead and wire. Do not solder these yet.
The LED is not yet installed. LED will be soldered when the circuit board is mounted in the housing.
Cut off the long legs of the components before soldering. If the legs or copper strands of the cables comes out from the solders, cut them clean without damaging the solder.
Be very careful not to leave long component feets or wires under the plate. The feet and other conductors must be cut short.
When all components are soldered, route the circuit board heater wires. The heater wiring runs above the circuit board. In the power tubes, soldering is done directly to the sockets, in the preamplifier tubes, solder lugs can be found on the circuit board. Braid the glow cable into a tight double cable. The solid core wore is easy to fit in place before soldering.
Please note the following:
First, install the tube sockets on the board. Note installation direction and installation side. The sockets of the power tubes can also be installed in the wrong direction, ie the installation direction must be just right. The tubes are finally installed on the soldering side of the plate, i.e. these are soldered from the component side.
-Install the resistors with turret tags on the soldering side. The Turret tags is soldered to the circuit board.
-Electrolytic capacitors must be installed in the correct direction. The plus pole is marked with a groove and a minus with the line. Make sure that each electrolytic capacitor is facing the right way! An incorrectly connected capacitor can explode (!). This is super important.
-Load all components so that the values on their side remain visible.
-Make sure that the soldering tip does not hit the side of any of the components. It's easy to damaged capacitors with hot soldering tip because there inside capacitors are thin films that are easily shorted. Replace parts with melted marks.
Step 8 - Solder input selector and volume control boards
The easiest way to solder the input selector circuit board is to use the case as a jig. Install both the 3.5mm jack and rotary switch to the chassis and press the circuit board onto these. Note: The rotary switch is not pressed onto the plate, but the plate remains level with the jack.
When the input selector board is ready, solder the potentiometer to the volume circuit board.
Step 9 - Attach the component boards to the chassis
When the component boards are ready, it is time to attach them to the chassis. Make sure that the screws on the component boards do not hit the component leads and cause a short circuit.
Install the main circuit board first. It is advisable to visually check the board before installation. Check the correct installation directions for the terminals, electrolyte capacitors, and rectifier. Check all solderings.
Start soldering the wires from the transformers onto the circuit board as shown in the layout. The filaments from the mains transformer and the primary conductors of the output transformers are braided together, as is the feedback wires. Try to cut all the wires to correct length. A small margin is also an advantage if the device needs to be serviced at some point, but do not leave the cabling unintentionally long. Finally, install the LED.
Proceed from the rear panel connector one wire at a time. Follow the circuit board markings (channel / number). Install all six wires inside braid, solder the wires.
When the input wiring is complete, secure the braid of input wires to the chassis with cable ties and anchors. Solder the feedback wires to the circuit board.
Notes and possible faults:
-Follow the colors of the cables, that makes troubleshooting easier. But if one cable runs out in the middle you can replace it with another color - the sound is the same.
-Do not replace thick heater wires with a thin wire. Wire thicknesses and types are selected.
-Shielded cables easily go short-circuited when soldering, if the insulation layer melts.
-Secure each solder with an eye or magnifying glass. Cold solders usually look bad on the outside as well (but not always) and good solders are often clean on the surface as well.
10 - Double check
Once all the parts have been soldered in and screwed in place, you have to go through everything again. Check each connection, solder, component installation direction and wiring step by step. It is best to go through each solder pad and follow the components and wires coming out of it comparing them to the layout picture. At the same time, mark which components, wires and eyelet pins have been checked. When it's all over, it's time to turn on the machine!
11. It works!
Once 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. Excess parts, wires, etc. must be cleaned off the test table to prevent them from being accidentally short-circuited. For example, fragments of soldering wire that are difficult to see with the eye can be devastating if are trapped inside the amplifier. Swing the amplifier in the air with the component side down and make sure that no excess loose material is left inside the case.
Using a multimeter ohmmeter, measure the resistance of the ground points relative to the housing. Switch the multimeter for resistance measurement (smallest area), connect the black test lead in the chassis and go through all the ground points of the layout image one by one. The meter should show zero or near zero (maximum a few ohms). Measure the resistance over large filter capacitors. If the result is a few ohms, there is a short circuit in the device. (Note that the measurement result is small at first, but it becomes large.)
Make sure that the (correct) fuses are installed in the (correct) fuse holders.
Turn the Power Switches to the "on" position. Make sure the tubes are not in the sockets. Connect the appliance to the wall. If you notice any suspicious sound, odor, or sparking, unplug immediately. If there are no signs of problems, you can make the first voltage measurements.
Place the multimeter in the AC voltage measuring range. Select the highest voltage range (400VAC minimum). Attach the black test lead to the chassis. Measure using one hand, the other hand is in the back pocket during the measurements.
Measure measuring points starting with AC, eg AC 330V. At this point, the meter should display 330V with a tolerance of about 15% (i.e. 330V + -15% / 280 - 380V is ok at this point). Unplug the power cord between all measurements.
Once everything is found to be correct, it’s time to put the tubes in the stocks. Make sure the tubes go in the correct orientation. In many modern tubes, the base will break easily if the tube is attempted to be installed in an oblique or incorrect position on the base. The guide slot of the end tubes tells you in which direction the tube should be installed in its base.
Turn on the power again. Again, if you notice any suspicion, unplug the power cord immediately. Measure the voltage from point A to I. At this point, the measurement tolerance is 20%, as the measured values in the layout image have been measured with all tubes installed. The voltages are affected by the mains voltage at the measuring point and the tolerances of the components (especially the tubes).
Voltage (tolerance 10%)
|225V (voltages at points F and G should be approximately the same)|
If all is well you can connect the speakers to the speaker terminals and the input to the source. Make sure the volume is turned to zero.
Note that voltage is charged to the capacitors of the power supply at this stage. So you can get an electric shock even if the device is not connected to the mains.
PP-EL34 is a cathode-biased amplifier, meaning that the iddle current ("bias") does not need to be adjusted when changing tubes.
13. How does it sound?
Put your favorite album on the player and slowly increase the volume so you can hear the music through the speakers.
If something does not work, system sounds strange or suspicious turn off the power and continue to troubleshoot any issues that may be related to the problem.
If all goes well, install the cover and base plate. Enjoy great music and congratulate yourself:
Not everyone has built a state-of-the-art tube amplifier!
We are happy to provide technical support! To get the best support, please email us and mention the following in the first post:
- Name and version of the kit
- Your name and order number (if available)
- Describe the issue as accurately as possible. We get a lot of messages and calls, so we don’t always remember even if the matter was talked about, for example, on the phone. That is, always say it all over again.
- Never delete old messages from a thread
- We try to respond within 24 hours on weekdays, but sometimes support is congested. If you do not receive a response within two days, please contact us again.
15. Enjoy the sound of tubes
So, you have a very high-quality tube amplifier in your hands that will last for decades as long as you remember to change the tubes now and the. Every few years, it is a good idea to check the bias (i.e., measure the voltage across the cathode resistor and compare with the reference voltages) and replace the tubes if necessary. Usually the power tubes last 2-5 years depending on the use and the preamplifiers a little longer.