Tubes may look the same – but test results are NOT.

In the past, most Chinese tubes (including high end tubes) are sold over internet without adequate distribution quality control. Some consumers are confused about the quality grade on the Shuguang Treasure tubes and wonder if all Premium tubes out of factory are the same, and if the factory test readings are accurate.

Below is the sample testing results for Shuguang Treasure tubes that Grant Fidelity receive from factory in 6 months of time (Jan 2009-July 2009). They are self explanatory as you can read all the testing results obtained by Grant Fidelity’s 5-spec test. 1) Listing results are listed in the order of factory matched pair or quad (shaded or unshaded in the spreadsheets). If a tube is listed as single or a quad is not complete, it means the other one(s) have failed in our first test and graded as ‘Rejects”. 2) “Rejects” are not included in the list as those tubes are reported with ‘Short’ in the tester, hence no further results can be reported. 3) KT66-Z and 2A3-Z tubes are not as popular as other models, so they are not included as we don’t have sufficient data to deem the testing results as representative.

Shuguang Treasure 300B-Z:

  • 125 Premium factory tested tubes
  • 79 Premium Grade A  – 63%
  • 46 B stock  – 37%

Test results: https://docs.google.com/fileview?id=0B06Slh1HJxoKZDI5ZTMzNjktMWRmYS00NDQ2LTkxMDMtNWI0YTFjODg3Zjhm&hl=en

Shuguang Treasure CV181-Z (6SN7):

  • 107 Premium factory tested tubes
  • 58 Premium Grade A – 54%
  • 49 B stock – 46%

Test Results: https://docs.google.com/fileview?id=0B06Slh1HJxoKM2JkMWYwOWYtYTA5ZS00NzY1LTk2YzAtZGY5YjFjZGIxMjQz&hl=en

Shuguang Treasure KT88-Z:

  • 164 Premium factory tested tubes
  • 119 Premium Grade A – 73%
  • 45 B stock – 27%

Test results: https://docs.google.com/fileview?id=0B06Slh1HJxoKYTVmYTZiN2QtMDJhNS00ZmU4LTk1NzEtMGQzZTA2ZTlkMjky&hl=en

Shuguang Treasure 6CA7-Z:

  • 99 Premium factory tested tubes
  • 61 Premium Grade A – 62%
  • 38 B stock – 38%

Test results: https://docs.google.com/fileview?id=0B06Slh1HJxoKMDYwNzU4ZmMtYTcyMS00Y2EyLTk3NmUtZTRjMTAxOTVmYjJj&hl=en

Can I hear the difference if tubes are tested different?

The answer is – it depends on the test results.

A weak (low) emission tube will last shorter time than a strong one. But you may not hear the difference when both tubes are within operating range. When a tube emission gets too low, the tube as part of the circuit is no longer operating at the optimal condition and will cause distortion in sound. It may also stress other parts of your amp causing equipment failure.

Noise / micro phonics issue on a preamplifier tube can be heard. Micro phonic is common on large power tubes but it is not important for sound quality.

Heater-to-Cathode leakage cannot be heard, but it will kill the tube faster before you know it.

Excessive gas will certainly shorten the tube life – but you cannot hear it.

A set of tubes with bad matching may cause distortion in some cases and become audible.

Do you need perfectly tested and matched tubes? Not always. You have to find the balance point yourself. Not everyone is perfectionist, but a seller should make all information known to let the buyer to make informative decision.

Why Grade A tubes only have one test card in the box?

We provide Grant Fidelity Grade A matched pair or quad of tubes – these tubes are usually packed in one box with one test card showing the ‘plate current’ reading in ‘mA’

Some customers inquire why we are not providing 2 or 4 cards showing same readings on all tubes – the reason is: we match tubes in pairs or quads to our specification. No two tubes will have 100% identical reading so we provide the average readings of all matched tubes in the package. It is misleading and untruthful to provide you 2 or 4 cards showing all same readings on all tubes because they simply DO NOT have 100% the same readings.

How is 845 like when dead?

Some forum members had a shorted tube – here is a picture of how it looks like (credit to AudiogoN member ‘amfibius’) when the event happens:

Here are some explanation from Psvane tube engineer about the event:

1. The short (lighting show you have seen) on 845 tubes is caused by residual air in the vacuum tubes act with active materials on the cathode. When active materials (electron emission coating on the cathode) become detached from the cathode under extreme heat (1000V), it will act with the residual air in the tube causing a short (lightening arc). The residual air may not be present at factory final testing when the tube leaves factory, but during shipping/handling/or usage with time, very tiny amount of air could leak into the tube, especially these large sized vacuum tubes.

2. Very few tube factory still make 845 tubes nowadays – as far as I know, only Shuguang in China and KR Audio in Europe. KR 845 tubes have quality problems too such as red plate caused by over current, so Shuguang 845 tubes have been used on most modern 845 tube amps. Shuguang made a few different design 845 tubes in the past – including a metal plate 845C. The metal plate 845C tubes were considered best sounding among all past models but the metal plate soldering cannot handle extreme heat well, so historically there have been very high percentage failure rate (nearly 50%) so the metal plate 845C tube has disappeared from the market now.

3. When a 845 tube has an internal short, it will produce crackling noise to the speakers, but such a noise (if the amp volume was not extremely high) usually is not of extreme frequency and will not damage the speakers, but it could cause panic to the users when seeing the lightening and sound at tube failure. In an event of tube short, the amp’s main fuse will be blown to protect the main transformers in less than a second, so usually the amplifier will continue operate fine and no other parts will be burnt. The tube short happens internally in the glass enclosure – the internal pressure will never be more than air pressure in the environment because tubes are vacuumed (less air pressure inside than outside even a leakage), there will never be a glass explosion happening at the event. When too much air has leaked into the tube, the silver coating inside the tube will turn grey or white indicating the tube is no longer vacuum sealed, ie not usable anymore.

4. This tube failure event is unpredictable – but it’s not to be scared. Other type of power output tubes such KT88 and 300B do not operate at as high voltage as 845 (450V vs. 900-1000V), so consumers rarely see tube failure as often with those tubes as with 845. Once a 845 has a short (light show and sound), do not use it again in other amps – such a tube should be disposed.

5. NOS RCA 845 tubes are considered the best quality on the market, but the technology then has been somehow lost with time. Shuguang is continuing research and improving on their 845 tubes, but that will take sometime to become reality.

I hope this helps 845 tube users who have been ‘shocked’ by the lighting show 🙂 Not to be scared when the lighting happens – you have just witnessed nature at work from a close distance inside a glass tube.

Happy listening.

Rachel @ Grant Fidelity

Psvane T-series ‘black bottle’ 300B-T, CV181-T and KT88-T launched

After rounds of testing and improvement over the test runs, Grant Fidelity is now ready to officially launch the Psvane T-series black bottle tubes to the market outside of the Greater China Area. It includes 300B, Kt88 and CV181 (6SN7) for the time being.

‘Psvane’ is a brand that owned by separate entity from Shuguang tube factory and the black bottle T-series is a MKII version of the original Shuguang Treasure series. In terms of sound quality, the Treasure series have been confirmed to meet many high end customers’ expectations, and the Psvane T-series is a fine tuning version of the Treasure Z-series. They are priced very similarly and if finance allows, we highly recommend customers to start their black bottle collection by owning both.

The Psvane T-series will be sold by Grant Fidelity under the same tight quality control during distribution. You may purchase either GF Grade A best quality grade, or go for the factory Premium grade to keep your budget down.

No sellers from Asia have been authorized to directly re-sell these tubes over eBay or other e-commerce website. Psvane brand owner does not guarantee or warrant the quality from these vendors.

‘Just buy the 80% emission Treasures and be done with it.’

Feedback from customer Gregg O. by email:

“The 6CA7Z’s arrived safe and sound.
I have about 5 hours on them and so far I think something special is going
on.
I have on hand a quad of NOS EL34’s from a very reputable source that have
150 hours on them..and so far the 6CA7 Treasures seem to have more fullness
and body to the sound without sacrificing detail.
I can safely say that if one wants to prevent stomach ulcers and headaches(
from banging your head against the wall) trying various NOS EL34’s…Just
buy the 80% emission Treasures and be done with it.

Be aware of fraudulent online tube seller(s)

It has been brought to attention recently that one AudiogoN member attempts to resell his Shuguang Treasure tubes by claiming they were purchased from Grant Fidelity as Grade A quality. He even further lied to a potential buyer that his tubes come in packages same as how Grant Fidelity identify Grade A tubes. However he wasn’t able to provide pictures as proof.

We have requested the seller to provide his purchase receipt from us before he claims that his tubes were from Grant Fidelity, immediately this particular seller removed his wording of tubes bought from Grant Fidelity as Grade A.

We strongly suggest consumers to use good judgement when purchasing tubes from individual sellers. If you have found anyone pretending to sell tubes from other source as from Grant Fidelity, please report to us immediately.

Please also take time to read our Test Method and Quality Control section to understand tube quality grade and protect your own interest before any purchase.

We also have compiled a list of unauthorized tube sellers – their selling status has been confirmed by factory as ‘unauthorized’ and their tubes were not purchased from factory directly.

New Grant Fidelity testing station now set up at factory

In order to further reduce the waste on unqualified tubes shipped into North America for re-testing, Grant Fidelity has recently set up a testing station right in the factory to screen the Treasure and Psvane series tubes before they leave for North America.

The test equipment used in this factory station is Amplitrex AT-1000 tube testing system, same as what we have been using in Canada for grading tubes in the past few years. Full training has been provided by Grant Fidelity to the factory personnel so that they follow exactly the same testing method and grading standard as us in Canada.

Going forward, more tube models with GF Grade A quality in the Treasure and Psvane series will be stocked in our Hong Kong warehouse to ship economically and efficiently to our worldwide customers. Some orders may be shipped out of Canada for the time being until the Hong Kong warehouse is fully stocked.

Some customers have asked us if we use our own personnel at the factory to supervise the testing process – our answer is No. We fully trust and respect our business partners and suppliers and we provide them with the right equipment and right training to ensure quality meet our worldwide customers desire for high quality. We don’t send a ‘spy’ to watch over factory’s shoulders because we firmly believe business relationship is built on trust and respect.

Small quantity of tubes will be randomly picked from time to time and ship to Canada for spot check. This is to help factory to master the testing process.

We provide same warranty as always to stand behind products we sell. Please purchase with absolute confidence.

Tube compatibility issue

Please note that due the huge variation in tube amp designs, we as a tube vendor cannot guarantee our tubes are 100% compatible to your amplifier. Each tube model description on this website includes a spec sheet link – please feel free to forward it to your amp manufacturer to confirm compatibility before you make purchase.

We cannot make recommendations on tube substitution on a particular amplifier model due to liability reasons. Your amp manufacturer or distributor is your best source of information on such a topic.

Please also check the physical measurement of the tube you are about to purchase, especially if your amp has limited space for installing tubes. Some amps have recessed chassis which could limit space available to install different tubes.

Returns due to compatibility issue listed above will be subject to 20% re-stocking fee at all circumstances.

Thank you for your understanding.