e: Roll Rachael Roll
Reply #13 - 06/23/20 at 06:08:32
Some great feedback regarding quality tubes...  

The beauty of a tube amp is that you can change the tubes.  You can change the tubes when they grow tired and lazy sounding over time... or you can change the tubes when you grow bored or just want to take a different seat in the music hall so that you can hear the music from a different perspective. So this leads to tube rolling which leads to brands and types... and here is some of what I know that you should know:


Current production vs. New Old Stock. In my experience the only consistently solid tubes on the market today come from Russia. Brands like Mullard, Tungsol, Electro Harmonix, Sovtek, Svetlana. The rights to these brand names have been acquired over the years by New Sensor Corp in the USA, who is predominately a tube supplier for the music industry / guitar amps. They own or partially own factories in Russia.

Decware purchases it's Russian tubes direct from Russia in bulk with the exception of the larger output tubes (EL34/KT66/KT88) which are current production branded tubes imported into the USA. All of the the Russian tubes that we purchase direct from Russia are N.O.S. Russian Military Grade tubes. Many of them have Gold grids, thick glass, high G ratings for missile use, and longer life, in some cases 10,000 hours.  These are ultra-hi-end tubes in disguise and have always been.   To hear how good these tubes are you have to install an American New Old Stock rectifier tube.

My experience with Boutique Chinese brands is mixed. The sound is good, the reliability and or consistency is ridiculous. I have been purchasing samples of these fancy tubes as they come out over the past many years and I have an entire collection of crippled tubes. Even KT88's that cost $1600 a quad drifted out of usable tolerance within days and had to be replaced.

New Old Stock is the real deal. Those who like to push the envelope of what is possible with their amplifier will often go down this path with no regrets. For one thing, the tubes not only sound better, but often last longer, in some cases like with rectifier tubes up to 10 times longer.

Rectifiers are a subject all in their own. Russian rectifiers are acceptable, everything else is a no-go from a reliability standpoint with some rare exceptions that are very pricey. My advise to all Decware amplifier owners is to find yourself a New Old Stock 5U4 or a 5R4 that has never been used and comes in it's original un-molested box. Consider the current production rectifier tube we ship with the amp the best sounding and most attractive  option that will last long enough for you to find a real N.O.S. replacement.

Finding N.O.S. tubes is easy, even on eBay there are millions. Since you only need one or two you will have more to choose from than you know what to do with.  Finding quantity of these tubes is another story. If Decware could secure reliable inventory of 1000's of N.O.S. rectifiers, it is an investment we would gladly make but in 25 years is has yet to happen. Because we can't find N.O.S. tubes in large quantities, even batches of 100 would be gone in less than 30 days, we feel there is no point in even trying.  

For the customer it is easy, just find a N.O.S. 5U4 tube on eBay that is unused, and in it's original box for $40 and it could easily last for 10 years or more and sound better the entire time.

As an amplifier designer, it is possible to create circuits that baby the rectifier tube by limiting inrush current, using smaller capacitors, running higher voltages with a choke and so on.  Correctly done, this can make a Chinese rectifier tube last the full rated 500 hours or more.  The problem with this is that it changes the sound quality of the amplifier well outside what we find acceptable.  So, we have to make a choice, do we design tube amplifiers to baby the crappie rectifier tubes being made today, or do we design amplifiers to use REAL tubes.  Of course the answer has to be REAL tubes, because we make real amps.