Question 1

Do I just plug them in and start playing music or let them burn in for 10 hours first?

Accepted Answer

Thank you for your question. First the quick answer...5654W tubes used in Riverstone Audio's matched tube pairs and quads have undergone extensive testing and are ready to use...so plug, play and enjoy. And now the longer answer...There are varied views on the effect of tube “burn in” on sound quality and if it is necessary. From a technical viewpoint, during initial use, there may be small changes in the electrical characteristics of a vacuum tube, including changes in cathode emission.  For a given circuit, these initial changes may influence how a tube “sounds” in a particular audio device.  For a headphone amplifier or other audio device, and depending on how a tube is used in a circuit (e.g., tube-based or hybrid circuits), detectable changes in sound quality, if any, will usually occur very early in the use cycle of a tube.  However, for some tubes, you may continue to hear subtle changes even after 10 to 20 hours of use.   Changes in electrical characteristics, which depend on the chosen operating point of a tube (e.g., plate voltage) are measureable and can be documented by monitoring a tube’s electrical parameters as a function of time.  For the 6AK5/5654 family of tubes, we find that measurable electrical properties stabilize within the first several hours of use and, in fact, for many of the 5654/6AK5/EF95 tubes we have examined, stability in measured parameters is often achieved after less than an hour of use (the rate at which the parameters stabilize during initial use depends on the chosen operating point of a tube, such as plate voltage and grid bias).At Riverstone Audio we utilize detailed screening and test procedures for our matched tube sets.  To screen out low quality tubes, and to help stabilize the electrical characteristics of the tubes used in our matched tube sets, we subject the tubes to several test cycles that incorporate an extended hold period during which key electrical parameters, such as plate and grid current are monitored for stability (drift).   As part of our QC procedure, all tested/matched tubes sets are checked for noise AND sound quality.  The sound quality test is performed using a headphone amplifier by technical staff well trained in the nuances in sound quality for various types of tubes – tubes that do not pass the electrical parameter tests, noise, or final sound quality checks are discarded.Our matched 5654W and 5670W tube sets are the most extensively screened and tested vacuum tubes available anywhere.   So..plug, play and enjoy and rest assured that the tubes are ready to use.  James at Riverstone Audio

Question 2

will this replace 6K4 i bought a headphone amp on here and it list this tube as a replacement for 6K4 so will this work

Accepted Answer

5654W tubes are not a direct substitute - however, certain hybrid circuits using the Chinese 6K4 tube are designed such that several other 7-pin pentodes can be used as replacements Note that there is also a vintage Western tube that is also refered to as a "6K4 tube:; this tube is a sub-miniature TRIODE and IS NOT a substitute for the Chinese 6K4 tube as they have much different electrical characteristics and physical connections (the vintage US-manufactured 6K4 triode has electrical leads that are soldered to a circuit).  The closest Western equivalent to a Chinese-manufactured 6K4 tube is the vintage 6BA6/EF93 pentode.  Again, as mentioned earlier, some headphone amps and tube buffers that are available on Amazon have hybrid circuits that allow using several different 7-pin pentode tubes in place of the Chinese 6K4; including 5654/6AK5/6J1 tubes. Before ordering any tube, please check directly with the amp or buffer seller to verify that your particular amp or buffer model can utilize other 7-pin pentode tubes.  Best regards, James at RIverstone Audio

Question 3

Do these riverstone audio - tested/matched pair (2 tubes) 7-pin ge jan 5654w work for my little dot mk1 + and my little dot mk ii as driver tubes ?

Accepted Answer

Yes, GE JAN 5654W tubes are excellent driver tubes for both the Little Dot mk1+ and Little Dot mk ii headphone amps.  We have several of the Little Dot amps in our workshop and have tested these tubes, and many other US as well as Russian tube brands, extensively in both the mk 1+ and mk II; when properly chosen the JAN 5654W consistently rank the highest in terms of sound quality and low noise level.   The test parameters we use during a portion of the electrical parameter testing were chosen based on the circuit requirements of the mk 1+ and mk II headphone amps. 
James at Riverstone Audio

Question 4

Do these tubes come with all the lettering intact or is the lettering worn off

Accepted Answer

We only sell vintage tubes that have good quality lettering. We inspect each tube to make certain that the lettering (tube type, manufacturer and date code) is readable on a tube - if it does not meet our requirements we simply do not sell the tube. The lettering will not always be "perfect", but it will generally be in very good condition. As background, the lettering that was used on many vintage US-manufactured tubes was often applied by silk-screen printing, which is less than ideal in regards to abrasion resistance of the lettering during shipping and routine handling. During shipping, surface abrasion, caused by movement of tubes within their boxes can damage to the print. In addition to abrasion during shipping, improper handling and cleaning of tubes can significantly degrade the quality of the 30+ year old lettering on 5654W tubes. To help preserve the lettering on the 5654W tubes we sell, we utilize thick EVA pads to prevent tubes from moving in their boxes. The EVA also helps absorb vibrations and impacts during shipping. We have gone the extra mile to provide good quality tubes, and want to make certain that the tubes you receive are protected from damage during shipment. If you ever receive tubes from Riverstone Audio that you are not completely satisfied with simply contact us for a refund or replacement.
James, RIverstone Audio

Maximum Pressure	7 Bars
Nominal Wall Thickness	1.3 mm
Material	Glass

Riverstone AudioTested/Matched Pair (2 Tubes) 7-Pin JAN 5654W Fully-Tested Vacuum Tubes - Upgrade for 6AK5 / 6J1 / 6J1P / EF95 - JAN 5654W Platinum Grade Pair

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