Joined: 04 Jun 2007
|Posted: Fri Jun 05, 2009 12:51 am Post subject: Tube Testing Standard
|Hoping to at least get the ball rolling on establishing a tube testing standard and have invited a few related audio forums to this thread.
Just posted this over at AudioKarma. Got an email asking us about the thread already in progress and the new Shuguang Treasure tubes. Here it is and I welcome any comments, advise etc. here:
I received my Amplitrex AT-1000 about 4 months ago and am getting close to finalizing how I test tubes with it and relearning what I thought I knew about tube matching. Having it has opened up some concepts for discussion and this is the first time I will be posting about it. It measures to repeatable decimals. I have no affiliation with them and paid full price (about $3k, with 211, 805 and 845 adapters). This could be the ultimate tweak for high-end tube addicts or someone should be considering basing a custom tube matching service for local tube addicts. You can program it to emulate any amp (up to 500v)
1. Tube Manufacturers (now and then) typically test and match for plate current only.
2. The scary part about 1 above is that +/- 20% is considered a good match. Somehow the fact that we are doing stereo now, never sunk in (then and now). Your prized amp will at least feature +/- 5% tolerance caps and resistors and then you throw in supposedly matched tubes that can be all over the map forcing your bias on one channel to compensate and act differently than the other channel. Common sense says this can't be a good idea.
3. They don't test for excess gas created plate current and transconductance. False energy that is not part of the audio signal.
The above is just an example of where I am going with this, there is much more including heater to cathode leakage (potential hum and premature failure) and I will post on my forum my results (just too many forums out there for this type of discussion) and invite those with more experience than I to debate in the interest of all.
These Shuguang Treasure tubes are special, you will never hear me say they are better than something else, because there is no such thing as a best tube, too much system synergy, they are much better than the stock Shuguang tubes, which were never designed for audio, as the Treasures are. The feedback has been 'wow', to put it mildly.
Shuguang has us Grant Fidelity and an England based distributor coming online soon for 'export version' distribution. We have worked with them to launch the product and have been involved in the testing (both listening and technical) process for quire a while, we are friends with the guy that has fought hard to get these tubes made over the past 3 years. He has informed us that no one else get's the premier 'for export' tubes, which are the cream of the crop and then retested and matched by us. We are already out-pacing current production, which is small runs at this point.
Grant Fidelity is promoting these tubes at our cost, assisting in getting proper distribution channels set up, offering trial purchases and more importantly establishing the test methods for Shuguang (who have millions invested in the tubes and again millions of dollars in test gear). Imagine my predicament,'throw it all out and get a pile of the AT-1000's. If they do, who needs me
Another interesting thing since getting this tester, is that customers etc are bringing their tubes over for testing (and listening) and what we are discovering is that not many people, have actually had 2 sets of the same tube for comparing what 2 sets of the same tube actually sound like. A properly matched and tested set of say EH's can sound better that an improperly matched set of 'in demand' NOS tubes.
And to finalize this little rant there still is no better tester than your system and if you are are using dual section tubes (typically driver and pre-amp) and need a pair, think quad out of 2 tubes, each section needs to matched to all 4 sections.
There is no 'best tube'. The Shuguang Treasures are new production contenders.
Come see us at FSI 2009, RM 909
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