Make It Worth It!
In this Glass Audio special issue of audioXpress we are proud to offer two high-quality tube amplifier projects from two renowned tube experts from both sides of the Atlantic. The first project by Menno van der Veen is another amplifier designed under the auspices of the author's TubeSociety initiative. The other comes from Thomas Perazella and in this case details a remake of a famous David Berning ZOTL amplifier. Both are of remarkable quality and value to all tube/valve enthusiasts at a time when it becomes increasingly more risky (and expensive) to build your own projects, unless we already know that the results are truly exceptional.
We are also privileged to be able to share the knowledge of renowned tube audio expert and book author Peter Dieleman as he demystifies some common myths in tube circuit designs. To have original articles of this level and quality on tube design is getting to be increasingly difficult even though the enthusiasm around tubes has not diminished in any way.
A year ago in this May issue I was sounding the alarms for the dramatic supply chain constraints affecting the availability of new tubes, as the invasion of Ukraine and the sanctions imposed on Russia had a significant impact on the global supply of raw materials and packaged tubes to the audio industry. There are very few tube manufacturers left, and those remain constrained by the supply of parts and materials. A year later, those few suppliers still active have been able to re-establish barely sustainable stock levels but, as predicted, with significant price increases. So, it's not surprising that we see fewer new builds being submitted for publication.
It's increasingly not worth it to build another average amplifier when it has become painfully obvious that once we burn through existing new-old stock (NOS), it will never be possible to replace the tubes. Some might say that there are still plenty of tubes to last decades of keeping up with a fun and rewarding Hobby — and that might be true. But maybe the results of such efforts are better delivered by following designs with recognized merits.
In audioXpress we review and evaluate projects that involve tubes on a regular basis, but increasingly few are of interest for publication since they are fundamentally a review of designs that have previously been addressed and published. A word of appreciation is due to our technical editor Jan Didden for the diligence and persistence to go through that review process and have a much greater perspective of the rich history of this publication to find valuable concepts and ideas.
Alternatively, as found in this issue, you might as well pursue a rewarding build of the extraordinary high-power (300 Watt into 4 Ohm), bipolar, Class-AB, monoblock audio power amplifier that Bruce E. Gillingham concludes this month with details of the complete system, featuring an original precision Bias Controller, and its performance measurements.
And if objective, measurable audio quality is truly the goal, consider jumping directly to Class-D and the Hypex NCx500 amplifier module that Stuart Yaniger reviews. As his measurement and analysis in this issue reinforce, this is a new reference performer that just needs a power supply, wiring, and your choice of chassis. The result is so close to perfection that one would likely degrade performance to add some originality or color — maybe by combining a tube preamp stage?
If it is of any consolation for tube audio enthusiasts, neither transistors nor the latest Class-D modules are easily sourced and manufactured these days. Many of the most popular devices used in audio amplifiers have long been discontinued and are increasingly difficult to find in consistent quantities. Even from the larger semiconductor brands, it's important to know what is actually still being manufactured and what is simply available from existing stocks.
Given the remaining component supply challenges and manufacturing delays that resulted from the global pandemic, we are now seeing the products announced precisely a year ago finally becoming available. Most of the Class-D amp module manufacturers still offer six months or more lead times for volume orders.
So, whatever the chosen path, make your design truly worth it.