- Getting Started
- Tube Sockets
- Final Assembly
- Setting the Bias
There have been several requests for a drill template to mark the chassis. Here is a PDF of the PC board silkscreen layer. It can be printed and used as a drill template. Make sure that your printer output is 1 to 1 before drilling (lay the board on the paper and compare).
A Tubelab SE with 45’s in a clear Lexan case
Thank you for purchasing our board. Please read this page carefully and understand it before soldering any parts on the board. Please look over the complete assembly instructions,
The Tubelab SE board was designed originally for me to use in building the Tubelab SE amplifiers that I have been selling since 2004. The amplifier was designed as a no compromises amplifier. It uses DC filaments and fixed bias. This requires setting the bias current when the amplifier is built, and every time the tubes are changed. This involves making voltage measurements on a live board and adjusting a potentiometer to obtain the desired reading.
There is some risk involved whenever working on any live circuit. One of the many delays in getting this manual written was completely rewriting the Checkout and Setup pages in a manner that greatly reduces this risk. This requires the use of multiple low cost digital multimeters to perform final checkout and adjustments. I have added sections on Electrical Safety, Meter use, and proper Equipment Grounding. Please read the entire sections before beginning on your board. If you do not understand these sections, do not attempt to power up the board (or any electronic device with exposed components) without the aid of an experienced technician.
Please understand the need for safety. This project (and all vacuum tube equipment) operates at potentially LETHAL voltage levels. If this is your first vacuum tube project please enlist the assistance of an experienced person to check your work and be present from the moment you first apply power until the amplifier is completely in its cabinet such that no internal components may be accidentally touched. Make sure that you complete the ground continuity tests outlined in on the checkout and setup page before using the amplifier. If the amplifier does not pass these tests DO NOT USE IT, even if it otherwise functions. There MUST be a low resistance from ANY exposed metal to the ground terminal on the power cord. This includes the volume knob, the transformers, and all of the connectors. I know that many commercial and home built amplifiers do not have the negative speaker terminals grounded. This is potentially unsafe, especially if using vintage transformers. The life you save may be yours, or your kids, spouse, or pets.
Please read the checkout and setup page before starting assembly. In fact it would be a good idea to read all of this manual before starting assembly. Look at all of the parts, match them up with the parts list and make sure that you understand what each part is and where it goes before you start. If you are not sure GET HELP. Improper assembly can result in damaged parts or worse. Make sure that you understand the checkout procedure and follow it. Do not skip steps, even if you are an experienced technician. This procedure is designed to minimize the risk of damage or injury if anything is not properly assembled. All of the testing and setup is designed so that you are not in contact with the amplifier when it is powered up. It is important that you do not try to work on this (or any high voltage equipment) when it is powered up. This procedure may take some time but it is designed to be safe. The heat sinks on this board operate with about 200 volts on them. NEVER touch them to see if they are hot! Assume that ANY exposed metal on the board can KILL YOU if you touch it. That includes the exposed metal ends of the two tall capacitors. I know this from a personally SHOCKING experience. If you do not completely understand electrical safety, the checkout procedure in this manual and the reasons for following it, DO NOT PROCEED! Get help from an experienced person.
The board MUST be completely enclosed in some type of cabinet before using the amplifier. This can be a simple wooden box or it can be an elaborate work of art. It is up to you. There are only two requirements: isolation and ventilation. Most of the electronic components on the circuit board carry potentially lethal amounts of electricity. They must be isolated from accidental contact. Again, assume that ANY exposed metal on the board can KILL YOU if you touch it. Your personal situation will dictate the level of isolation. If you have children or pets (cats are particularly curious) consider a completely closed box with GROUNDED metal screen over any vent holes. Many audiophiles like to have the tubes sticking up out of the cabinet. The tubes get HOT and can cause burns. If you build your amplifier in this manner consider putting it in some type of outer enclosure like an equipment rack with a glass door.
The amplifier requires some ventilation. The resistors, the components mounted on heat sinks, and the tubes all produce heat. Like any electronic component their lifetime is inversely related to their operating temperature. This is also true of the tubes themselves, even though they produce the most heat. Any enclosure that traps the heat will reduce the lifetime of the components. The Lexan cabinet shown above really needs more ventilation. That is why I had to add a large heat sink on the filament regulator. Please see the Enclosure Options page for more ideas.
This board is very flexible in its applications. This requires some decisions to be made before construction can begin. This is especially important if you purchased a board only or a board and parts kit (not a complete kit) and are purchasing your own transformers or other parts. The choice of output tube and your intended application will influence the choice of transformers and possibly some of the parts on the board. See the section on Tubes and Applications before assembly.
One More Word About Safety
This manual (and board or kit) deals with audio amplifier design using vacuum tubes and high voltage solid state devices. The voltage and current levels associated with the designs presented here are potentially lethal. If you have no experience working with high voltages, please enlist the help of a qualified technician who has experience with vacuum tubes. We are presenting this information for use by qualified individuals for educational purposes. We are not responsible for injury, accidents, acts of random stupidity, burning your house down, exploding parts, and other undesired actions (all of which are possible) resulting from the use of ANY information contained herein. Should you decide to attempt to build any equipment based upon information provided here, you are doing so at your own risk. If this sounds serious, it is. All vacuum tube circuits operate at dangerous voltage levels. This manual, board, or kit is provided without warrantee. We will offer to refund the purchase price (less shipping) or replace the board if it is defective. It is your responsibility to determine if this board or kit is suitable for your purpose, and its construction is within your capabilities before attempting any work of this type.
It is wise to have all of your power supplies and other equipment controlled by a master switch. I have all of my equipment connected through a surge suppressor which is mounted on the corner of the workbench so that it is easily accessible. Make sure that everyone in your household knows where the switch is, and how to kill all power if there is an emergency. It is also a good idea to have someone else present (who knows CPR) whenever experimentation with high voltage electronics is underway. Never experiment on vacuum tube equipment if no one else is present. Always assume that voltage is present until proven otherwise. Electrolytic capacitors can hold a charge for several hours, oil and polypropylene capacitors can hold a charge for MONTHS. If you don't know if the bleeder resistors are good (or even present) check for voltage before proceeding.
If you don't understand and agree with everything explained above, RETURN YOUR PURCHASE NOW! If you don't agree to follow the procedures outlined in this manual, RETURN YOUR PURCHASE NOW! If you don't agree not to operate your amplifier until it is in a proper enclosure, RETURN YOUR PURCHASE NOW! We don't want to sound like a broken record, but it is our intention to create a SAFE enjoyable experience for all involved. That is why the procedures in this manual were written with SAFETY in mind.
When you are ready to begin assembly of your board go to the Getting Started page.