Off-topic: Copyrights and Piracy

Piracy and copyright are topics close to my heart. In fact, my day job is in music publishing (digital, physical, and distribution). A recent post over at The Journeyman’s Toolbox provoked some thoughts on the topic of piracy. Reading through my blog, you’ll rightly come to the conclusion that I believe strongly in the importance of the creative process and sharing ideas and knowledge. I hope you find this slightly-off-topic discussion interesting. Back to circuits soon.

Rafael’s conclusion (see link above) that piracy often boils down to availability is a good one supported by research from NGOs and industry groups. Technology has spread across the planet faster than either secure distribution platforms or ethical/legal understanding of copyrights. In short the demand (for legal IP) is there, but the supply often is not. Today’s big challenge lies in the ‘flatness’ of the digital world and transitioning from piracy culture to one that supports creator rights. 

The forefathers of today’s copyright law (Statute of Anne in UK, US Constitution, Berne Convention) drew a direct line between authorship and ownership, progressively strengthening the rights of the creator. The idea was/is that creators need some financial incentive to create and protecting the right to (e.g.) reproduce or license a work gives original creators an exclusive commercial advantage. Technology, like copyright, has moved in the direction of empowering individuals through universally accessible distribution platforms (YouTube, WordPress, etc).

However, ethics and regulation have not kept pace with technology. As a result, we see continuous violations of copyrights without practical mechanisms for authors to combat it. Education is also lacking as users often have no idea they are violating someone else’s rights when they share, borrow, or download protected works. Finally, there is the question of consumer access to legal channels, the presence or absence of digital services or payment standards. These are practical drivers of pirated content that may eventually be solved with better services and updated laws (consider for a moment the pace of technology and the average age of legislative representatives).

In the USA, the SCOTUS asks four questions in weighing copyright/fair use cases: what is the purpose and character of the use, what is the nature of the underlying copyrighted work, how much is used in relation to the whole, and what effect does it have on the market for the work? It is this last point that is often most salient. Where pirated content is available and legal content is not, it is hard to blame the ‘pirate’ even if they are technically breaking the law. Pleading ignorance is an understandable excuse, though the platforms benefiting from the content and traffic (not the individuals themselves) should be held to a higher standard when it comes to copyright education and oversight.

Setting aside these practical factors, we are left with ethical issues. Specifically, many take the ethical stance that piracy preserves or democratizes culture. This is a common theme in copyright discussions that appeals to emotion, but it contains critical missteps in logic. The most fundamental flaw here is that copyright covers expression, not underlying ideas. Culture is not a library of distinct units (expressions); it is a collective understanding of society and the world (ideas). Copyright does not privatize ideas and therefore does not seek to regulate or control culture.

Dissolving copyrights as a legal/financial mechanism in order to declare artistic works public domain suggests that culture and monetization are mutually exclusive. While there might be some productive discussion with regards to copyright duration, the idea that author protection could be abandoned and result in a positive impact to the creative market ignores basic realities of survival and specialization. Today’s public domain cornerstones like Beethoven, Mozart, da Vinci, or Shakespeare would not have existed or endured to be appreciated without the contemporary financial support of patrons (i.e. monetization). Predictable and protected incentives, not spontaneous generosity or exposure, are required to liberate and motivate the creative spirit. 

Most worryingly, the piracy-for-culture argument assumes that no better solution to the practical problems (availability, education) can be had. In that way, piracy stands in the way of commercial/civil services that could serve the same public function without violating the rights of original creators (a win-win). Personally, I’m happy to see more subscription-streaming services (Spotify, etc) become available; even if they are not perfect, they are a step in the right direction. There is no denying though that these services compete with (intentional and unintentional) piracy for the hearts and wallets of would-be consumers.

While I empathize with the cultural demonetization viewpoint, it ignores too much economic context and history to hold up under the scrutiny of real life. Consuming culture is a two-way transaction for artists and audiences alike. Lofty ideals muddled with the vulgarities and economics of reality make art evocative and visceral. How can I ask an artist to put his blood down on paper if I’m not willing to open up my pocketbook in return?

Letters to WTF: Holiday Gifts for the Tube DIYer?

Q: A simple question – is it possible to purchase a kit from you? If not, are there decent kits you would recommend for a first-time tube build? My husband has built a couple of solid state preamps and power amps and is intrigued by tube ware.

A: Your husband is a lucky guy to have someone encouraging his hobby!

I don’t sell any kits for my builds at this point (though I do send out prototype PCB boards to my Patreon subscribers on occasion). I am happy to provide some recommendations for beginner-friendly tube projects and/or gift ideas, though. Some of these are PCB boards that require you to select parts (or leave your husband to do so afterwards). Many builders enjoy the process of picking out and sourcing parts, so this isn’t necessarily a bad thing  and you might include a ‘parts budget’ as part of the gift in that case. 

Tubecad.com makes some of the best documented and flexible board kits you can find for tube hobbyists.  In particular, the Aikido and CCDA designs have a great following and lots of user support on community websites like diyaudio.com:

Aikido Noval Stereo
TubeCAD Aikido (click to go to listing)
9-Pin CCDA PCB and User Guide
TubeCAD CCDA (click to go to listing)

Note the above let you add parts or order boards by themselves. Adding parts might be tricky for you to do without your husband’s input, though TubeCAD does a good job keeping the options and confusion to a minimum.

Here’s another PCB board (no kit) for a phono preamp (for turntables) that I can also recommend. The designer of this one is another well-known author on tube topics:

Valve Wizard Phono Board (click to go to listing)

Bottlehead is one company that gives you everything you need in a full kit. They have a lot of tube kit options at different price points. If your husband also listens to headphones, this company is especially well-known for their headphone amp kits (two options below, but explore the site to find more). 

Bottlehead Crack (click to go to listing)
Bottlehead Single Ended eXperimenter’s Kit (click to go to listing)

Bottlehead’s kits are pricier, but the documentation and the all-in-one nature add a lot of value for beginners. 

Lastly, Elekit is another Japanese company that does all-in-one kits. These are available through the diyAudio Store.  I don’t have personal experience with Elekit kits, but I have read a lot of good things (and the manuals I’ve seen look very well-done).

Elekit TU-8500 (click to go to listing)
Elekit TU-8100 (click to go to listing)

Hopefully you find something in your budget in the above links.  I think anything you do to show an interest in his hobby will be very well received!  

A PCL86 SET kit with chassis from the DIY Audio Store

The DIY Audio Store (part of the diyaudio.com forums) is now selling the Elekit TU-8100 PCL86 kit:

TU-8100.jpg

At only $275, this 2W output kit is about as low an entry point to all-in-one well-documented tube kits as you’re likely to find. It includes two inputs (rear and 1/8″ front) and is powered by a 12Vdc power brick. This keeps the amp small enough for even desktop usage (5.5″ square). According to the ad copy, SMD components (DC booster, etc) come pre-soldered.

The PCL86 is a 9 pin triode + pentode roughly equivalent to a 12AX7 and EL84 in a single envelope. See a datasheet here. It’s used in the Elekit in a traditional two stage cap-coupled single-ended arrangement. The output transformers are rated as a 7k primary and the circuit employs global feedback to squeeze some extra linearity out of the high gain input stage. See the Mighty Cacahuate for a similar design (no feedback and 6CG7 instead of 12AX7).

If you’re hoping to find a tube kit under the tree this year, add this one to your Christmas list. Elekit puts out some very cool products and purchasing through DIY Audio Store helps support one of our hobby’s precious resources.

I have no affiliation with Elekit or DIY Audio (other than sincere admiration).

Thomas Mayer’s new site

I’ve followed Thomas Mayer’s hobby website for a long time. He uses a tantalizing mix of high quality transformers and DHT tubes to build some beautiful audio devices. The tube of the month series is also a must-read review of odd-ball tubes and applications.

Now we can all see how much Mayer charges for his impressive tube builds. It’s about what one might expect based on the craftsmanship he clearly puts in and what the audiophile market supports in other products.

Check out vinylsavor.com here. If nothing else, browse the galleries and drool over the very Scandinavian glass, wood and metal work.

vinylsavor.png

There is now a NuTube portable amp kit

HA_KIT_All.jpg

Some recent digging around Pete Millett’s nutube.us website turned up this interesting page. What we see is a pocket size amplifier powered by AA batteries.

At first glance, it looks similar to a project you can find on this archive of Audio Mania magazine (Japan). Here’s the schematic showing the DC booster power supply:

nutube

The Nu:Tekt kit appears to use an opamp driver on the output rather than the FET combo shown above. With the exception of the small daughter board which appears to come assembled (I assume this is the booster), the kit looks to be completely through hole.

Little is revealed on Millett’s site, but I’ll be following this kit with interest!

Solid State Phase Splitters

The phase splitter is a critical step in a push pull (differential) amplifier. Because tubes don’t come in “p-types”, we feed the output devices signals that are inverted relative to one-another in order get one to push while the other pulls.

I’ve been finding solid state concertina-style phase splitters crop up here and there recently. A couple of days ago even the great Pete Millett got in on the action. Millett employs a JFET concertina splitter in his hybrid amp (a must-read, btw), but MOSFETs are also a good option for this application if you use parts with reasonable input capacitance.

Here’s a push pull schematic I’ve been marinating that illustrates the MOSFET concertina:

mosfet concertina pp

By using the MOSFET we’ve reduced the twin-triode count in a stereo push pull amp by one. The MOSFET will also let the splitter swing closer to the power rails, though in this particular case the 10BQ5 doesn’t really need a lot of voltage swing at its grid. The tubes shown are odd heater standards: 407A is 396A with a 20V heater and 10BQ5 is 6BQ5 with a 10V heater.

You can find a lengthier explanation of the RC step network between the 407A and MOSFET in Morgan Jones or buried in this diyaudio thread. In brief, the resistor divider sets the DC voltage at the gate of the MOSFET while the 0.1u cap bypasses the upper portion of the divider at AC frequencies so that we don’t lose any gain due to the divider.

Phono Preamp Heaters

Heater supplies, even with indirectly heated tubes, are a potential source of hum with high gain circuits like phono preamps. In a grounded cathode gain stage, the tube will amplify any signal it sees between the grid and the cathode. The tube doesn’t particularly care if that is an audio signal or an induced signal from some other part of the build. Indirectly heated tubes have a cathode sleeve around the filament heating it. The close geometry creates a happy little environment for coupling between the two. Eliminating this source of noise may require running heaters on DC rather than AC.

Here’s a simple schematic adapted from something Eli Duttman suggested for his modified RCA phono preamp:

12V dc heaters

This circuit (now on a PCB waiting for a phono build) uses a voltage doubler to turn a common 6.3Vac input into ~16Vdc which is then regulated to 12Vdc by a LM7812. The regulator is limited to 1.5A, but this is probably enough for any sane phono preamp’s heater demands (the pair of 12AX7 in the El Matemático require only 0.3A). This is one way of producing a DC heater supply.

I was recently discussing truly budget-oriented tube phono preamps with another builder. They proposed a $100 parts budget. The first place I’d look to start cutting costs in such a build is on the relatively pricey purpose-built power transformer needed for tube projects. In the case of a simple phono preamp like El Matemático, I’d try the following cost-cutting measures to the power supply:

  • Solid state 1N4007 rectification
  • Use a 115/230V isolation transformer like Triad N-68X in reverse (115V in, 230V out) for B+ @ $16
  • Use a 12V SMPS like Meanwell EPS-15-12 for heaters @ $7
  • Triad C-1X choke @ $10 and 220uF 350V+ caps @ $4 ea as CLC filter
  • Add RC to end of CLC filter to lower B+ and/or clean up residual ripple

We can greatly lower the cost of the B+ supply with the isolation transformer trick but it leaves us without a heater supply. Rather than a separate 6.3V or 12.6V transformer followed by a regulator circuit like the one shown above, I’d be tempted to experiment with a switch mode power supply like this Meanwell unit:

EPS15-12

The EPS15-12 supplies up to 1.25A at 12Vdc with 80mV of ripple (peak to peak). One need just supply it with mains voltage (85-264Vac). Power supplies like this switch at a very high frequency, which is why their transformers can be made so small. If that switching is audible, capacitively coupled between cathode and heater, additional filtering may be needed. Meanwell does not specify the switching frequency, but it’s very likely well above the 20hz-20khz range.

The final, potentially very affordable power supply, would look something like this:

very cheap psu

The LR8 in tube circuits

The high voltages required for many tubes rule out or complicate integrating many otherwise useful solid state parts. The LM317 and TL431 are ubiquitous regulator solutions, but they’re limited to 36-37V. Too low in most cases for a simple one-chip B+ supply.

The LR8 (datasheet here) is a lesser-known TO92 high-voltage regulator. The maximum input voltage is 450V and the minimum dropout voltage is 12V. Output voltage is set with a simple resistor divider. With just a handful of passive parts, you can use the LR8 to create a regulator for tube B+:

LR8 simple

As a little TO92 device, dissipation and current are limited of course. The circuit above might work for something like El Matemático (one per channel), but higher current applications require the addition of a pass device. In this case, a MOSFET uses the LR8 as the voltage reference on the gate, in turn setting the source voltage just a few volts lower: LR8 compound

While zeners and VR tubes also make a good gate reference in similar series regulator applications, they come in fixed values. The great thing about the LR8 is that we can set the output to any value we like, alleviating the need to keep a bunch of zeners or VR tubes on hand.

I have PCBs of the series circuit made up and will be testing in an upcoming build. In the meantime, this isn’t so complicated that it couldn’t be done on a proto board.

Western Electric 300B back in production?

300b

You may find a brand new production pair of Western Electric DHTs under your Christmas tree this year according to a recent press release that updates the release schedule from the Georgia-based company. According to WE, new 300Bs will be shipping in December of this year. You can find detailed specifications on the product page here.

Previous press releases reveal that modern manufacturing will achieve a better vacuum in the new production tubes and that cathode core material will be the same used in vintage tubes. Note that this is the core, not the emissive coating. Average lifetime is given as 40,000 hours (4.5 years of continuous playing).

Though these new production tubes will not be cheap ($1299 per pair), new old stock WE 300Bs sell for eye-watering prices online. Provided these new production tubes demonstrate a good track record, the price for made in America tubes adhering to WE’s original quality standards may not seem so exorbitant to tube enthusiasts (who are a bit exorbitant by nature).

The Western Electric brand name and trademark was revived by Western Electric Export Corporation. The current CEO is Charles Whitener, who was also a founder of Tube Depot (a Tennessee tube and parts retailer).

DIY DHT filament strategies

Having a small stash of #26 tubes and always being curious about it as a preamp tube, I’ve embarked on some preliminary research of successful implementations. There’s a huge thread on diyaudio.com, but some choice references are Ale Moglia’s iterations and Kevin Kennedy’s classic implementation.

In general, the prototypical 26 preamp is a fairly simple single tube grounded cathode gain stage. Perhaps this topology simplicity is why there is so much experimentation in the support circuits. Gyrators, current sources, and line output transformers all make an appearance as the anode loading strategy. The B+ supply is similarly diverse: SS regulators, tube regulators, VR tubes, etc. It seems the popular consensus is for fixed bias: using the filament current drop across a resistor to set the cathode current. But there are fixed bias and traditional cathode bias implementations as well.

All of the above is fairly comfortable stuff coming from the general tube world of 9 pins and octals. The filament (AKA heater) supply, on the other hand, is something new for those used to indirectly heated tubes. In indirectly heated tubes, the cathode is a sleeve surrounding the filament heating it; this mechanical separation helps prevent heater hum (50hz or 60hz AC) from entering through the cathode. In a directly heated tube, on the other hand, the filament and the cathode are one and the same.

Depending on the circuit, AC filament power with balancing resistors and/or a ‘humdinger’ pot may be enough for an acceptable hum level. With the higher Mu (8-9) of a #26 and the need to keep front end noise/hum to a minimum (because it will only be amplified by everything following it), a DC heater solution is in order. We are looking at a requirement of about 1A at 1.5V for a #26 tube. The general approaches I have found are:

A low voltage SMPS and a dropping resistor requires no explanation if you know Ohm’s Law and can find something quiet with the right ratings (here’s a good read on this topic). Voltage regulation and current sources/sinks have been covered in principle a few times in projects and general information pages as well (see links above). Mixed strategies are what have piqued my interest the most.

Kevin Kennedy’s article suggests a 7805 followed by a LDO CCS to supply #26 filaments. From what I can gather, this is the principle also behind the Ronan Regulator (which I see mentioned frequently but I can’t seem to find the ‘official’ schematic). In these strategies the voltage regulator makes a first pass at cleaning up the raw DC and absorbs some power dissipation. The constant current source follows and sets the filament current to a fixed value (in turn setting filament voltage as per Ohm’s Law). Including a CCS to limit current has a protective side-effect as well: cold filaments are otherwise eager to soak up a lot of current, potentially stressing the power supply and filament/cathode itself.

Rod Coleman also has a very interesting approach to DHT filament regulation. You can find boards/kits for sale here (no commercial interest, just admiration for the design).

coleman regulator

This circuit feeds the filament from the ‘positive’ end with a gyrator, also known as a cap multiplier in this configuration. The transistor Darlington pair sees a low-passed capacitor at its base and works to amplify this smoothed signal at its low impedance emitter (effectively making the cap seem much bigger than it really is). This doesn’t regulate voltage because the gyrator doesn’t have a fixed reference, but it does reduce ripple drastically.

The ‘negative’ end of the filament is connected to a constant current sink. This is a ring-of-two CCS design which will have a lower operating voltage requirement than a cascode CCS or many ICs. Because our current is relatively high, low dropout voltage is a benefit in reducing overall power dissipation.

The filament is fed a low ripple voltage with a CCS setting the current. It’s simple, but reports seem universally positive for Coleman’s regulator approach. Whether filament bias or cathode bias, the filament supply should be left floating (it finds ground through the bias resistor or grounded cathode).

There’s little reason to reinvent the wheel here as far as I can tell. Although I’m still casually reading, I’ll more than likely try one or more of the above approaches to powering the filaments in my upcoming #26 project. More to come on this project as parts arrive and the ideas ferment.

P.S. here’s a FET version of the same gyrator-CCS one-two punch:

FET filament reg