Building A Tube Headphone Amp, A Learning Experience

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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 (cavalliaudio.com) had come up with and offered to the DIY community: buy the circuit boards, buy the parts and follow the instructions.

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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.

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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.

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Why You Need Screw Extractors And How Rennsteig Stands Apart

collin37 Comments

It’s a horrible feeling. You have been working in the shop for hours, laboring over your work and all-of-a-sudden everything comes to a halt. Why? A fastener broke and you can’t get it out. You can try and dig it out somehow, but most of the time the best option is to use some form of extractor, or as many call it, an “easy out”.

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Spiral Fluted Screw Extractor in Tap Wrench

I’m going to be honest and tell you that when I set out to write this post, I was hoping to give a ton of historical perspective about who invented the idea and when. I searched patents and documents to the best of my meager ability and couldn’t find a thing! Even the Wikipedia page doesn’t clue us in too much. The earliest info I can find is a 1914 patent for an “EZY-out” screw extractor made by the Cleveland Twist Drill Company. This is the only place I have seen the name spelled with a Y (EZY) and most modern spellings either leave the letter Y out or spell out the full word (easy). So, I am suspect to the true origins of the original design. The Cleveland Twist Drill Company merged with Acme in the sixties and are now produced through Greenfield Industries. I went so far as to contact Greenfield to see if they had any information, but to no avail.

What I can inform you about is the use and design of such a tool and how one of our German favorites has a unique variation on the original. All extractors use basically the same principle. A hole is drilled down through the broken fastener, the extractor is hammered into the hole and twisted in the proper direction to bite the fastener and remove it. This is typically done with a tap wrench since the shank of the extractor is square shaped. The most common extractor is of the “Spiral Fluted” design and looks like a cross between a drill bit and a screw thread, and in many ways, that is exactly what it is. The threading is backwards to the screws thread so as to dig into the fastener and extract it back the way in which it came.

Rennsteig Tools was founded in 1959 and became a member of the Knipex group in 1991. Among their over 50 national and international patents is their creative design for screw extractors. Though they have their own version of a spiral extractor, it is their “Dual-Edged” version that sets them apart. Made of high-strength chrome vanadium steel, the tools are tapered like any other extractor, but are fluted and double-edged, meaning they can be used in both right and left-handed (clockwise and counter-clockwise) fasteners. The dual edge cutting heads give you eight points of contact (four each direction), ensuring a solid bite into the damaged fastener. Not only that, it has a hardened center punch for starting your drilling hole and a hexagonal shank so that it can be used with a typical wrench or socket, eliminating the need for a tap wrench.

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Rennsteig Dual Edged Screw Extractors with Hexagonal Shank

Check out this great demonstration of these by Tyler King of Rennsteig. Got a broken screw or bolt you need extracting? Get the Rennsteig Screw Extractors at your home for the best German Tools, KC Tool.

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Torx Screws, Torx Tools Available at KC Tool

A Brief Guide to Torx and Its (Many) Variations

collin83 Comments

­­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.

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Hold On To Your Bolts! (and screws and nuts and….)

collin1 Comment

Some tools are truly utilitarian like hammers, screwdrivers, and ratchets. Some tools are uber-specific. There are tools for protection, for grabbing, for seeing, for oiling, and for just looking cool. Then there are those certain tools that make your life just a bit easier and specifically in this case, tools that HOLD things. Now I don’t mean clamps, vices, and the like, I mean holding the small things that can get lost in the machine or the carpet. Some of our loved German tool brands make grippers, magnets, and adapters to secure fasteners to our tools as we are working. Let’s look at some.

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Wera Screw Gripper

The most basic one to look at is a simple magnetizer. Many companies make their own magnetizer, some as their own tool, others built in to a tool or set. So what is the advantage? By simply running the shaft of a screwdriver through (or on, depending) a magnetizer, the tool will then become (surprise!) a magnet. This means it will magnetically hold on to a screw or bolt or whatever fastener you are working with. If it’s light enough, this might mean that the head of the fastener will stay latched on the tool, making for an easy job. It should also not be missed that if you drop something metal in a place you can’t get to, a magnetic tool could aid in retrieving your lost soldier.

Maybe you need something a little more secure to hold your fastener. This is where screw Grippers come in. Wera makes a great example of this and were featured in the May 2015 edition of This Old House magazine in their “What is it?” feature. You can place these on the end of a screwdriver (they even come in bigger sizes to accommodate insulated shafts) and it will securely hold screws and bolts in place without the use of magnets. The holder will also slowly cam out when they reach the material you are fastening into. Both Wiha And Felo also make screwdrivers with this feature built in to the driver.

Finally, we come to those holders that are geared more towards hex, nuts, and socket tools. For hard to reach places to get a nut secured, Gedore makes a combination holding tool that will hold one securely in place where fat fingers may not be able to reach. If you would rather have a nut secured to the wrench itself, Gedore also makes a retaining clip that fits directly on the tool and magnetically holds the nut in place.

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Gedore Magnetic Extension

Gedore excels in this arena though, so we must discuss their socket extensions with built in magnet, which comes in both 1/2” and 3/8” drive versions. Who knew such a simple addition could make work so much easier. The magnet fits through the socket and secures it inside so that it goes nowhere. It is even spring loaded, so it will stay with you for most of the process. This was so clever that it won the prestigious Eisen Award For Innovation in 2014.

Check out this youtube video for a demonstration of a few of these and as always, shop all your little helper tools at KC Tool.

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Ball-End Hex Tools: A Guide

collin6 Comments

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?

collin1 Comment

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 »

Penta-What? Pentalobe!

collin2 Comments

What is a pentalobe screw and why would you need a pentalobe screwdriver?  Let’s examine a brief history of this little beast.

Firstly, like a Pentagon (shape with five sides) a Pentalobe is a screw or screwdriver with five points.  They come in six sizes from 1 to 6.  The nomenclature of this can be confusing though, as different companies have different ways of naming their pentalobe sizes.  You will see TS1, which can easily be mistaken for Torx size.  You will also see variations on the letter P (P1, P2, Etc..) and PL (PL1, PL2…).  There even some who make it as clear as possible and call it Five Lobe.

Pents up close 2.jpgThe confusion doesn’t stop there, though.    In 2009 Apple launched the pentalobe screw, and that’s about all they did.  There was no regulatory sizing so the brains at iFixit reverse engineered the screw and made a driver to work with it.  Since it was similar in size to a Torx T2, the called it a P2.  After they did this, Apple released sizing information and revealed that iFixit’s P2 was actually a size 1.  It was after all this commotion that WIha released their set of pentalobes (to Apple Standards), so their PL1 is actually the same size as iFixit’s P2.  Did you get all that?  To keep things simple (and since this is the GERMAN tool blog) we will use Wiha’s sizing standard, PL1-PL6.Read More »