AMP BUILDING - TIPS & TRICKS

written by Kenny Prochazka

Building a working tube amplifier can be a daunting task, but if you are up for the challenge it can also be one of the most rewarding processes that you ever go through. In order to demystify this undertaking, we asked our Mojotone amp building team for their best tips

• For a more detailed breakdown of specific components and best-practices, please read our Mojotone Amp Kit Building Primer

1.) Before you start, do some research on the type of amp that you want to build, but don't overthink everything about it. The more builds that you get under your belt, the more you will realize that they all follow very similar patterns, and that almost everything you learn can be applied to your next build of a 'different' circuit.

• One of the most highly recommended books for tube amp builders is Gerald Weber's Tube Guitar Amplifier Essentials

2.) Make sure that you have the right tools and supplies, because it is beyond frustrating to come to a standstill due to poor planning. At a minimum, you should have:

• A quality soldering iron with temperature control - This can ensure that you are supplying enough heat to run the solder, without also melting or cooking the component that you are attaching. Trust us, a cheap soldering iron will be more trouble than it was worth.

• A clear and stable work surface and area - Scrambling to find a tool, a part or a diagram is no fun, and can lead to serious problems if clutter gets in the way of your work. Also, make sure that your chosen workspace is separate or private enough that you can leave your build there while you aren't working on it - the more you move it around, the less you will remember where you were in the process.

• Plenty of high-quality 60/40 or 63/37 rosin-core solder - The right type of leaded solder is important to a good amp build, because it has a lower melting point and makes for more reliable joints. The rosin core will act like a flux to help the solder adhere.

• A decent multimeter with settings for voltage and ohms - Use this to check the values of every component, and also to check voltages when you are preparing to start up the amp for the first time. You do not need a fancy, expensive meter, just one that will consistently do the job correctly.

• One or more good sources of light - You want to be able to see as well as possible to avoid shocking yourself or damaging your work. Some builders use lighted magnifying visors to reduce eye strain if they are putting in long days.

• A chopstick or other non-conductive probing tool - There are times when you will need to literally "poke" around inside of the amp to locate a loose/cold solder joint or test a component's functionality.

Some will go farther, with such amenities as:

• A Mojotone Amplifier Chassis Stand - This not only gets the chassis up off of your work surface, but also allows it to be locked into different positions, depending on which part/side you are currently working on. Our chassis stand can fit almost any size and type of amplifier chassis.

• A variac device for the final testing stages - This allows you to observe the behavior of your amp by slowly increasing the voltage, which can help you to find issues and save components before they go up in smoke or flames.

3.) You do not need to spend exorbitant amounts of money on the most expensive capacitors, resistors or potentiometers. While today's builders have access to components approaching 1% tolerance, the glory days of tube amp design were built entirely on components with tolerances in the 10-20% range. The early guitar legends on whom we base our quests for tone did not have these modern luxuries, and most of them didn't care. No matter the amp, Jimi sounded like Jimi, Stevie sounded like Stevie and so on.

4.) Before building your amplifier, use your multimeter to verify the values of all components. In general, you can expect to find some slightly above and some slightly below their posted tolerances, but anything that is way too far off should certainly be swapped to avoid damaging the circuit.

5.) Work in small sections, and don't rush. Don't be in such a hurry to finish your build that you populate and solder the main eyelet/turret board all in one pass - that will create a fairly good chance that you have missed or mis-soldered something. Take your time and go at your own pace.

6.) Make sure that your solder joints are 'shiny'. A dull bit of solder typically means that it has not made a good connection, due to over- or under-heating, a cold solder joint, or oxidation/contamination.

• If you use too much solder, it will run and drip, which can cause unwanted shorts or grounds in your circuit. Clean up any excess solder before moving on.

• If you drip solder into the body of a potentiometer, it will most likely render the part unusable and in need of replacement.

7.) Make sure that you have plenty of ventilation when soldering, and be sure to WASH YOUR HANDS every time you finish with a soldering session. The proper solder is over 50% lead, which you do NOT want to ingest or have contaminate other surfaces.

8.) When troubleshooting your build, it is important to have patience and not give up. Take a break, go for a walk, or do something else to get your mind out of the circuit. Often, it only takes some fresh, rested eyes to see what you couldn't the night before.

9.) Don't be disappointed if your build sounds different than another example of the same circuit. (Remember our discussion on tolerances from point #3) Every hand-wired amp will have its own personality and tone, even if made back-to-back by the same builder. In this way, these amps become instruments in their own right, with unique ways of interacting with the guitar and the player.

10.) Have fun! Don't get overly frustrated and run to your shed to find a tool to smash your chassis. If you followed the diagram and schematic, the chances are that you will find something small and/or simple out of place that you just haven't noticed yet. The build process should be enlightening and enjoyable, so remember to keep your focus and appreciate the journey.