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This article first appeared in the November 2012 issue of hi-end hifi magazine of Germany. You can also read it in its original German version. We publish its English translation in a mutual syndication arrangement with the publishers. As is customary for our own reviews, the writer's signature at review's end shows an e-mail address should you have questions or wish to send feedback. All images contained in this review are the property of fairaudio - Ed.

Laird of the valve. Fascinating is such an inventory—not just on sheer scale but variety—with its stacked crates of Telefunken double triodes or giant Siemens transmission tubes. Here you can find nearly anything including a whiff of antique charm permeating the aisles. That’s because BTB Elektronik who specialize in electron valves of all types already pack a solid 66 years in business and some of their glass bottles can claim even more.

This vintage tube tester used type-specific hole-punched cards which today rarely sees use

Even certain valve measurement gear as the one above exudes such bygone charm. But it’s not all about yesteryear. Tubes have enjoyed a renaissance to be fashionable once again. They’ve nearly re-entered the mainstream so that valve amp aficionados no longer need to occupy the freaky fringes. But first a quick glance at the past. By 1946 Eugen Queck [framed, above] launched an eponymous engineering bureau which commissioned the production of electron valves and sold them to firms like Saba, Grundig, Nordmende et al. Success wasn’t long in coming and by the mid 50s Queck’s outfit employed some 130 people. 10 years later the German headquarters even had regional offices in Switzerland and Holland. When the emerging transistor threatened displacement and global supremacy, Queck refused to end up on the endangered species list and promptly added semi conductors and other passive electronic parts to their catalogue. By the 70s and early 80s the old valve business had seriously thinned out and whilst a large inventory remained, "much which would make your heart bleed today then ended up in the trash" explained Michael Kaim, today’s boss.

BTB valve lair all sorted, numbered and electronically captured in inventory

Eventually the time came for Queck to retire and sell his enterprise to three employees who turned the sole ownership into a GmbH whose name BTB consists of the core team’s last initials: Ballwieser, Thomanek & Bergbauer. The established business focus remained in place until the 90s when old specialties got revisited. By then the transistor market had grown too sizable and complex for the core trio with its few helpers. Back it thus was into the electron valve niche for which the inventory was still quite solid. Today’s owner and manager Michael Kaim joined by 2002 and built out said inventory partly by taking over the entire tube warehouse of RSD, the former importer of DDR/RFT valves. We visited Nürnberg to interview him.

Hello Herr Kaim. Your firm BTB Elektronik is a known player in the tube business. How many of those lovely bottles do you keep on ice in your facility?

By taking over MSF in 2002 and RSD in 2009 plus acquiring various stashes we now carry shy of one million valves which breaks down into about 4.000 different types. Certain samples are 80 years old but we also stock relatively recent additions like the JJ 5Y3 or Tung-Sol KT120.

How do you maintain any law and order at such volumes?

Our tubes are obviously EDV tagged and classified by type whereby we always know what’s available. Should something be out of stock, we always look what alternatives we might already have or can acquire as replacements. When I bought BTB Elektronik in 2002, the introduction of a high-volume suitable electronic tagging system was one of my very first tasks. Without it the day-to-day affairs of this type of business wouldn’t be possible - or at best seriously slowed down should one try to run things with a few Excel lists. Admittedly this software transition was painfully laborious. It took our entire staff four solid weeks to sort, count and enter our existing parts into the system.

Apropos tube types: There are a number of naming conventions, American, European… which one do you follow?

There are comprehensive comparator lists—nearly books in fact—which correlate the various descriptions with the technically identical valve types. But our EDV software already captures all common valves under all possible names so that upon inquiry or order, we can immediately see whether the requested type is available or its Russian, Asian or US equivalent. Admittedly there’s always some linguistic confusion based on varying lettering and language.

What are the most common naming conventions and could you explain the logic behind them?

Most common are the European, American and Russian as well as Asian systems, the latter quite similar to the Russian. Let’s stick to Europe and the most simple, an ECC83. The first letter refers to the heater where ‘E’ means 6.3V. An ‘A’ would be 4V, a ‘D’ 2V from a battery etc. The second letter describes the tube type. ‘C’ refers to a small-signal triode. ‘L’ as in EL34 would be a power pentode. That the ECC83 carries two ‘C’ is because it’s a double triode. Next comes the first number, here an ‘8’. Usually the first number references the pin configuration or socket, here an octal. The second and last number is a consecutive figure which gives the individual amplification factor or output impedance, i.e. a specific technical parameter which differs from an ECC81 or ECC82. Similar to the European system the Russian has its own logic but differs from the American where one often only knows the heater voltage from the first ciphers. Certain names like 300B contain no indicator as to specific construction details.

What types of markets does BTB serve today? Hifi and high end should be merely one of many I would think?

True, but an important sector. We actually don’t segregate by markets. We serve anyone who needs tubes, starting with the collector and ending in 100 kilowatt transmitters. One could of course rate markets by size. The most important one then becomes the musical sector, i.e. everything to do with guitar, bass and studio and recording gear. This would be followed by the hifi sector including DIY and finally industrial valves from machining to medical uses. The industry doesn’t consume the sheer quantities of musicians or hifi users but the prices for their specialty tubes are significantly higher to quickly hit four figures. And we also serve the ham-radio geeks and collectors.

How about the music market which obviously extends beyond just guitar amp & Co?

This sector also includes recording kit like valve microphones. Here we supply all manufacturers in existence. We’ll just mention AKG, Sennheiser, Microtech-Gefell and Horch. Obviously that’s a small sector since such microphones are very costly. Their makers often want New-Old-Stock valves which we can test for RoHs compliance by request. Then there’s studio gear like valve compressors; and all the kit that makes sound, from wah-wah and distortion pedals for e-guitars to all manner of effects gear. But the biggest and most important part of this sector is and remains the amplifier for guitar and bass.

A BTB service tech works over a guitar amp checking bias

Here the distortion behavior becomes vital since axe slingers only are happy deep in overdrive, correct?

True, but one has to differentiate between guitarists and the various kind of music they play. A metal freak might want truly distorted nasty sounds whilst a Blues or Jazz player wants something mellower. The one could need a very dirty bottle with lots of meat, the other merely wants to lightly augment an acoustic instruments to need another amp and valve.

Is there any overlap between musicians and hifi hobbyists? Hardly? After all, one pursues creative expression, the other high fidelity replay though…

… a high-end guy means to tune his sound as well…

… but hopefully not as dirty and mean.

(laughs): The hifi tube amp is interesting because with it you can steer the desired sound in a certain direction which goes beyond basic THD behavior to include factors like compression, damping factor and intermodulation to differ from transistor amps.

Upper right: The right valve has lost its vacuum to exhibit the milky layer

These specific traits aren’t really any strengths of tubes of course.

That depends on what you’re looking for. Obviously the output impedance of tubes is higher which means a lower damping factor for the amp. But is a high damping factor really synonymous with sound quality?

Depends on the loudspeaker…

Exactly. And often the low output impedance of solid-state amps is bought with high negative feedback which isn’t a pure bonus when it involves cascaded gain stages. Back on intermodulation, its more complex forms and many sidebands often are a direct result of multiple gain stages which occur more often in transistor than tube amps. The latter tend to exhibit higher 2nd/3rd-order THD but not the higher-order artefacts and IMD effects. And it’s also a matter of taste. With valve amps the client simply has the advantage of, within limits, tuning the final sound to taste at least when the circuitry is relatively simple.

What does ‘simple’ mean in this context?

The tube needs room to bloom. In my experience this works a lot better with minimalist circuits of no more than two gain stages and very little feedback than it does with complex layouts and high feedback. At least with the former I can far better predict what sonic effects a particular valve swap will have.

The subject of tube rolling is quite expansive. What tube types seem best suited? Due to size and glam factor, the focus tends to be on the power tubes.

Within a circuit the tube with the highest amplification factor is most important and in general sits upfront, i.e. possibly in the output stage of a CD player or phono stage or at the line input. Whatever happens upstream can’t be corrected downstream. But power tubes are important too the more so as their loads get more complex when a speaker requires more control from using heavy membranes, many crossover points or a complicated network with multiple corrective branches. With such a speaker the choice of power tubes will have a greater influence than the input or driver tubes.

In general, what tube types does one find in hifi gear?

Fundamentally there are only three types distinguished by the number of internal electrodes. The triode has three and input triodes tend to be indirectly heated whilst the most popular power triodes like 300B and 845 are directly heated. Then there are tetrodes with four electrodes often also called beam-power tetrodes which are the family of KT valves like KT66, KT77, KT88, KZ120 etc. Finally there are the pentodes like the EL34, EL84, EL156 et al. Of course there’s room for valves also in power supplies starting with the rectifiers which are softer than solid-state diodes.

BTB builds many of their own tube testers but also repairs valve amps. Lower left: A so-called Nixie tube shows numbers 0 - 9.


During load shifts tension collapses faster than with transistor diodes to cause a compression effect. This is oft exploited in guitar amps because it tailors the sound. In hifi that effect is less desirable and usually more a disadvantage but tube rectifiers are still used. And valves can also be used as voltage stabilizers.

How do you view the fundamental sonic differences between triodes on one hand and pentodes and tetrodes on the other, disregarding that the latter offer more power to be suitable for a wider variety of speakers?

Each tube based on construction and load line sounds unique but speaking in generalities a triode produces even-order harmonic artefacts which many listeners enjoy. Pentodes exhibit predominantly odd-order harmonics. Since music favors even-order relations, many listeners favor triodes for sounding ‘more natural’. But all this tends to be true in its purest form only with single-stage circuits without any negative feedback or other corrective shenanigans.

That means someone with switchable triode/pentode mode is in a very good place to adapt to various moods…

Perhaps. But the speaker too must be suited to both modes and you must remember that these types of circuits tend to be push/pull. If I switch one of those to triode, its even-order products will get cancelled in the transformer and the odd-order components are amplified. If designed properly such a circuit will exhibit very low distortion. But if a listener fancies a triode for its octave doubling, he’ll get less of it than expected (laughs). That’s the theory. In practice other factors enter which could bear well on strapped triode mode. Incidentally a beam-power tetrode in push/pull will act similarly to a pentode.

What about NOS valves built decades ago which were never used? You said that your inventory consists of such valves by about 90%?

That’s about right but to avoid misconceptions, those aren’t purely audio valves but all types including those for purely industrial apps.

Okay, but you inventory much which would seem of interest to the high-end valve lover. So what’s up with the NOS trend? I mean, really, isn’t it mostly retro? Telefunken simply looks cooler than Sovtek stamped on the glass? Or are there bona fide advantages of quality and sound? Are we really to believe that valve quality and production processes have devolved over time?

Upper right: Not for sale. BTB's oldest valve dates back to the 1920s.

The explanation is simple. In the 60s when valves enjoyed their halcyon days, the average German income was about 500 Deutsch Marks and an EL34 of the era sold for 15DM. If you transfer that relationship to 2012, an EL34 still sells for about €15 whilst the average income has come up to €3.000/month. It’s easy to see that tubes today are far more affordable. Hence the inverse is true too – price pressures on manufacturers are much higher today. Because valve production remains about 90% manual, you can’t compensate with automatization. In the past selection was much tighter and rejection ratios were far more generous. Today things make it to market which would have been trashed then. That’s why the quality of vintage valves tends to be quite high to make NOS much more than just a fascination with retro.

How do you measure quality?

We have a very varied cadre of test equipment for tubes. This begins with basic kit from Neuberger, Funke and Avo to digital measurement gear and load-line writers from Amplitrex and ends with equipment we designed ourselves which allows us to sift through even high volumes at very precise tolerances. We can obviously test for all parameters at various operating points including hiss, microphony and hum. Since we perform 100% inventory control for all current production tubes, we immediately notice quality issues. It’s not that rare that we return an entire shipment to its maker.

What NOS types do you carry?

For small signal tubes nearly all of them. With the big power tubes we only have limited stock since those wear out faster, are changed more often and thus more in demand… and restocking thus also gets slimmer.

Back to current production. You work with JJ for example. How should one envision such a collaboration?

We are in constant communications with all valve makers, be it by phone, via mail or in person. Of course such contacts don’t fall off the tree. One develops them over many years and some even turn into friendships. For the tube manufacturers we’re often a kind of market feedback provider. Many tube electronics houses are too small to develop direct contacts with the makers of their valves. They prefer to deal with us since we handle customs, prepayments and shipping fees. They pass on their wishes to us and when we get wind of a sustainable request for a particular new valve model—which the maker feels lends itself to modern production—it’s well possible that entirely new valves or reissues of old ones come to market. That’s how JJ’s KT66 evolved. We dispatched rare expensive originals to Slovakia to allow them to develop a sonic equivalent to the historical samples whilst the Chinese mostly copied this type purely on optics. With JJ we actually developed a sonic equivalent which simply looks different than the original. Other examples are the 6N30Pi (6H30p) with octal pins or the exclusive EL84T for Experience.

Legendary: Three Russian power triodes (6S19P, 6S41S, 6S33S-B), the latter employed in Russian fighter jets. BTB also winds its own transformers.

What’s in the future for BTB?

For 2013 we hope to have a fully programmed click’n’buy online shop which is a huge challenge to cleanly tie in with our existing inventory software. More interesting to the client could be the new valve types. We just finished the JJ 5751 double triode which will be mostly used in the input stages of hifi and guitar amplifiers. JJ is presently working on two other double triodes for hifi use whose names I’m not allowed to reveal yet.

Many thanks for the interview!

With pleasure.

redaktion @
BTB Elektronik Vertriebs GmbH
Knauer Strasse 8 | 90443 Nürnberg
Telephone: 0911 / 28 85 85