Building A Tube Headphone Amp, A Learning Experience

I’m a music junkie – I’ll freely admit it. And I’ll also admit that I’m old school. I love listening on the couch, in a “sweet spot” perfectly situated between the two speakers. When I reached a point of owning my own house I was ready to invest in a decent way to play my music – and I quickly found out how much this could cost. However, I also discovered whole groups of folks online building their own equipment, experimenting and tweaking. I also discovered that this could cost a whole lot less! Being a tinkerer by nature, I was hooked, and by the time I was done I had built a tube preamplifier, solid state amplifier and speakers, tweaking parts and wringing the best sound out of components I had built myself.

Fast forward to this year when my wife and I sold our house and moved into an apartment. Suddenly I was not at liberty to play my music at the hours (or volume levels) I had been accustomed to. So, I started researching headphones, and learned about using a headphone amplifier to get the best sound. I was immediately excited – an opportunity for a new project!

I decided right off the bat that I wanted to build an all vacuum tube amplifier. I love the sound that tubes offer, and I found a design online, the Bijou, that a well-known audio designer ( had come up with and offered to the DIY community: buy the circuit boards, buy the parts and follow the instructions.

Gedore Bolt Cutters Cutting 8-32 Rod

I quickly realized that building the case would be the most challenging part of the project. I used pieces of curly maple for the sides, which not only looked good with the aluminum, but made it easy to screw the front and back panels straight into the wood. Glued on pieces of 1 x 1 made perfect braces to allow the top and bottom to be secured. I was also lucky here in town, as local fixture, Metal by the Foot, cut the pieces of aluminum to size. All would have been well, had I given the correct dimensions. Two pieces were too big, but a little work with my jigsaw and several files had them close enough to fit.

I also knew that the tubes had to stick out of the top, not only for the esthetic joy of glowing tubes, but also to dissipate the fair amount of heat they put off. I carefully marked off the mounting holes on the bottom, lined those up with the top where the tubes would extend, took a deep breath, and got out the hole saws. This arrangement required that the circuit boards be carefully fixed six inches up from the bottom of the case, parts soldered to the underside and tubes extending up. A pair of Gedore small bolt cutters made short work of 8-32 threaded rod, and some lengths of Pex tubing worked perfectly as spacers. The final step was using a power drill and a wire brush attachment to give the aluminum a matte, brushed finish.

After fitting the case together without the parts inside (and a fair amount of filing to get everything to fit just right), I was ready to actually solder. This part went fairly quickly, except for a couple of days lost to needing just one more resistor. Thankfully, Mouser, the electronics supply store, has no minimum order.

Once the parts were soldered on, it was time to do the wiring. Being red-green colorblind, my wife helps out by labelling each color wire on the transformer, which steps up the voltage from the power outlet to 520 volts. The tricky part of the placement of the circuit boards is that one wants the wiring of the signal to be as far away from the wiring for the power, which tends to give off noise which would be picked up and amplified. Not good. So I carefully twisted all the pairs of wires, trying to route them as far away from each other as possible.

The Finished Tube Amp, In All Its Retro Glory

Once the wiring was complete, I took a deep breath, plugged in the power cord, and flipped the switch. ZZZZTTT! A spark and smoke was instantaneous. I immediately shut everything off. I had wired the small LED in the power switch backwards by mistake. Luckily nothing critical was broken. I tried a second time and everything was good. The only remaining step was to adjust the main voltage on the power supply. This involved taking a reading of the 250 volts and adjusting by turning a very small screw, very near the bare wires. I brought out my trusty insulated Wera screwdriver and carefully adjusted until the voltage was spot on.

Now it was time for the real test. I plugged in a pair of cheap headphones, just in case, and carefully turned the volume. Everything was good! New electronics always take a few hours of use to “break in”, and the sound has improved with each hour. I’m floored by how you can close your eyes and feel like you can point to the instruments in space: the drums are in the back in the middle, the guitar is nearer to the right, etc. I always learn my strengths and limitations on these types of projects, but in the end building something from scratch that brings me such pleasure is immensely satisfying.

I got all my tools at KC Tool, of course.


Torx Screws, Torx Tools Available at KC Tool

A Brief Guide to Torx and Its (Many) Variations

­­We have discussed previously on this blog about the highly specific “Pentalobe” screw head and the tools used in conjunction. The Pentalobe shape is a relatively new invention compared to one its cousins, the Hexalobular screw, which many people call a star or Torx. Torx is actually a trademark of Camcar Textron, so the use of its name is another example of genericized trademark, like we use the term Allen Wrench for Hex Keys.

A Torx Screw Up Close and Personal, Made By Spax, KC Tool
A Torx Screw Up Close and Personal, Made By Spax

The original six pointed profile has similarities to a hex-end head but the sides are concave, providing six points opposed to sides. This creates essentially 12 points of contact opposed to the hex’s six, allowing for much more torque to be applied.  There is a theory out there that Phillips screws were INTENTIONALLY designed to cam out, so the screw would not be over-tightened in the end. Torx is just the opposite, as its design prevents the tool from camming out, providing a better grip in the fastener.

Torx screws are used in several applications, from automobiles to computers. They also come in a number of varieties. They come in external versions (for use in a socket wrench or ratchet), security (with a pin in the center of the screw head to prevent tampering), and what is known as Torx Plus. When the patent to the original Torx design was about to expire in the early nineties, Textron improved on the design by squaring off the lobes slightly to minimize wear and maximize torque. A standard Torx driver will fit into a Torx Plus screw, but a Torx Plus will not work in a standard so be sure to know which one you will be working with.

Finally, a note on sizing and nomenclature: One of the beauties of Torx sizes is that they are universal, meaning there is not an SAE vs Metric version. They are all the same. For the standard Torx, sizes are distinguished using a T before a number. The number is a point-to-point dimension that runs from T1 all the way up to T100. Some of the most common sizes are T10, T15, and T25, but there are many specialized sizes including T47 and even T5.5. If you need the security version, an S is added to the end of the number. External Torx use an E before their size, but do not correspond to the internal sizes. For example, an E8 external Torx is equivalent to a T40 internal Torx. And then rounding it all out is Torx Plus, which uses IP (internal plus) and EP (external plus) for designating size. Kinda complicated, huh? OH! Did I mention you can get them with a Ball-end as well?

Torx, Torx Plus, External Torx, Ball-End Torx, KC Tool
Left to Right: Torx, Torx Plus, External Torx, Ball-End Torx

There is one thing that is not complicated, though, and that is the best Torx tools can be found in one place, KC Tool.


Ball-End Hex Tools: A Guide

Hex Key, Allen Wrench, L-Key, no matter what name you call it, if you have ever assembled anything you have probably used one. You can get them in Metric or SAE and they come in all kinds of sizes, from the tiny .028 inch to massive one inch. They are commonly used for furniture assembly because they are cheap to manufacture and can be tossed in the box for the customer to use (evidently they are like paperclips at IKEA and they will give you one if you ask nicely).

We have grown so accustomed to getting free L-keys in our furniture boxes that we take for granted the inferior quality of them and are very likely just to throw the tool away with the plastic bag it came in when we’re done. As any reader of this blog should know though, we buy good quality tools and demand only the best, so why use that freebie in the first place? A good set of L-keys will last you decades without showing wear and tear. But there is one big advantage to buying a quality set of L-keys and that’s the ball end.Read More »

What is a DIN number?

There are various sets of standards in the tool world.  In America we have The American National Standards Institute or ANSI for short.  On a global level, there is the International Organization for Standardization, or ISO.  Since this is a blog about specifically German made tools we will look at the German version: DIN.

DIN stands for Deutsches Institut Für Normung or German Institute for Standardization in English.  They have been operating for literally 100 years and have always been highly regarded in the standards community.  Though the name implies an exclusively German operation, the DIN standards have been adopted across the world and influenced many other standards organizations including the ISO.  The best example of this is the DIN standard 476 from 1922 introducing the A sizes of paper which would later become ISO 216 in 1975.Read More »

Spotlight on Gedore’s TL Series

Gedore has released (to the States) a series pliers designated the TL series. Gedore’s TL (or dipped handle) series provides an inexpensive alternative to the flagship JC (or 2-component handle) series. The JC series still lead the way in Gedore’s pliers’ series, but there is great value in having options.

I love this decision from Gedore to release this series to the US. We are always pleading with all of our German manufacturers to release more product to the US (especially lower cost options). This is an awesome step from Gedore for us and our customers.

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Christmas Gift Tool Ideas

Seems like Christmas (or preparation for Christmas) gets earlier and earlier each year. My wife and I went to pick out Christmas trees at Lowe’s last night. I am very much a Scrooge, but she adores the Christmas season. She was asking me before Halloween if we could hang Christmas lights. At the time I resisted, saying; “We have to wait for after Thanksgiving”. My reasoning to her is that each season needs its proper time and respect. That was a lie, I was just trying to delay the inevitable. She wore me down over the last two weeks. Finally, after the Chiefs late win over the Panthers, I was feeling especially buoyant (and vulnerable). I gave in. We bought a tree. We did compromise on the size of tree though (moral victory). She was looking for a gigantic 12’ artificial tree. I was hoping for a small fern. Instead, we got a 3’ tall Norfolk Island Pine which is probably around 6 months old. I have read they can grow to over 200 ft tall…which could be a huge problem.  I will have to keep it pruned up to keep it inside.  The name implies it is a pine tree but it isn’t, it is a weird Araucariaceae from the sub-tropical island of Norfolk which is way the hell out near Australia.  I was disappointed to find that it is going to have to stay in the house in a large pot because it doesn’t like cold weather. Oh well…would have looked perfect in the backyard. Minor drawback.  Hopefully I’ll be able to keep it alive for several Christmas seasons.   It should be almost perfect: it isn’t going to be too big, isn’t going to shed needles, and I can care for it after the season. I have a green thumb in addition to being a German Hand Tool aficionado. Cross your fingers that I made a good move…


We at KC Tool decided to get in on the early Christmas action too. We have a new section on our website designated “Gift Ideas”. These are some of our favorites and some of our best sellers. Many of these are already on sale, limited supply offers (Wera Advent Calendar and the Kraftform Kompakt Christmas), or hard to get items. If there are other items, you think would make great gift ideas give us a heads up below in the comments section. Take a look and remember to wish list your items for your loved ones to purchase for you early to beat the Christmas rush.

The Fall Classic Sale

Whether you are an engineer working on a self-driving car prototype, a blue collar professional, or a DIY’er; we are here with the right German engineered hand tools for the job.

Save now with manufacturer’s discounts plus our 10% off coupon code* (NEWKCT) to celebrate our new website. Enjoy manufacturer discounts from great brands like Wiha, Wera, and Gedore through December 31, 2016.

Shop Wera:

Shop Gedore:

*Two uses per customer only. Valid only through October 31, 2016.

Gedore 2016/2017 Sale


Gedore has announced their Autumn Promo! Gedore on sale now! These products are a selection of Gedore’s projected top sellers for 2016-2017. Remember to combine the sale items with the new website discount code (NEWKCT) and save even more!

The headliner of this group is the “Red Dot Award Winner for 2015” the 6Pc Striking Screwdriver Set. Why have a screwdriver set when you can have a striking screwdriver set?  These rugged screwdrivers are built like a brick outdoor lavatory. Use them as a professional shipbuilder, plumber, carpenter, or hobbyist. You will be the envy of your friends or colleagues. Tell them over a cold one that your striking screwdriver set won the Nobel Prize of tools. Gedore Part# GR1878743

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