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

As others have done with my Dayton Audio HTA-200 hybrid tube amp, I also decided to swap out the 6K4 tubes for these or "a" pair of 5654W tubes. To test the difference I uploaded a decibel meter to my iPhone. Maintaining a consistent or fixed mid-range volume, I auditioned about 15 seconds each from a particular starting point in four different songs (Low Spark of High-Heeled Boys/Traffic 5:33, Berlin/Fenne Lily, 1:24, You and Your Friend/Dire Straits 3:00, and Hurricane Party/James McMurtry 1:35). The difference was so jaw-droppingly apparent it rendered further comparison absolutely unnecessary. My 50W/ch@8-ohm amp's volume increased like it were now a 75W/ch@8-ohm amp, EASILY half again louder with seemingly unlimited headroom. Gee, I didn't KNOW it was legal to put PLUTONIUM into a pentode vacuum tube -- like catching lightening in a (Tube-Like) bottle! These tubes are worth e-v-e-r-y s-i-n-g-l-e p-e-n-n-y of the proportionately diminutive $24 upgrade.[Two things to note/mention: (1) I found a pair of 5654W tubes for $20 (i.e., $4 less) on Amazon as well, so asked the A1 chat service, Gemini, why it might be worth spending the extra $4 when this tube's description added the words, "fully tested." They related that it was unequivocally much better to get the set marked fully tested for perhaps a half-dozen quality control reasons which completely convinced me this was the wise way to go; and (2) 6K4 tubes are triode tubes noted for warmth and emotion. Conversely, 5654W tubes like this provide a higher gain and better stability for a more clean and detailed sound. That said, maybe don't throw away your 6K4s depending on how you may feel.]

These tubes are very nice. They made a step up performance of sound quality in my phono pre-amp. I did, and always will fivevthem a warm up period of 15 minutes before use. Also, there is a lot of discussion on breaking in tubes before they achieve peak sound quality. I let mine burn in for about 50 hours of time, and they still sound as good as they did out of the box. The left and right channels on my pre-amp that feed directly into my active PreSonus 5BT speakers are very equal. The sound is very full and I recommend these for anyone with a similar setup.

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These tubes are exactly as advirtised. I have a Hitchcock TV 7 tube tester and tested these tubes when they arrived. The minimum measurement (mm) is listed at 22. Both of these tubes tested at 35.

Riverside Audio is my go-to for these tubes. I remember when tube testing kiosks were in regular stores (Sears, mid-60’s). Makes sense to match them for two channel music applications, and Riverside does this; i can’t. They come well packaged (with an “if seal is broken” notice, an “extra mile”) with documentation of the testing. What this means to me, along with my listening experience, is confidence in the brand. I paid more for a pair of 1940s vintage tubes but it wasn’t long before one burned out, leaving me with an orphan. Better to go Riverside, all of mine still work, though I can’t estimate how much time I have in them, at least a couple years in one pair. These are worth it, especially at the current price, under $20 a pair in early ‘21. What they add is an improvement in the depth of perceptible soundstage, vs. a more 2-D experience. Less potential for listening fatigue with the treble. No serious sacrifice in the details. When I have them out of my signal chain I can still enjoy the music, but then a restlessness sets in (“Audio nervosa?”), as if something’s missing. Knowing what that is means in theory is that there’s a possibility of it being all in my head — but then that’s where my ears attach. Then back in they go, and it’s “ah ...”I use them in three of those inexpensive “Chi-Fi” preamp/tube buffers that Amazon sells, in three different stereo systems, all with class D amplifiers, after many years of the same A-B amps, for something different. My first impression of class D was skewed by having it drive brand new speakers, which (seriously) benefited from a good period of break-in (believe it or not). The sound signature of all the class D I’ve heard is, to me, detail-oriented, flat across the frequency range (so far as I can tell), neutral, possibly a tad dark, which I like, after years of relative warm & creamy. But in that first combination I was reminded of the difference between early remastered CDs of rock music I had on vinyl — the analog knocked it out of the park. CDs sounded more compressed, with “digititis” leading to listening fatigue. Not so anymore.I have Riverside tubes between one of those little TDA7498 amps (32v 5 amp power supply) driving early 90s Definitive Technology DR7 speakers. One between an ICEpower 125ASX 2SE amp and Dayton Audio MK442t speakers. Even in my work-in-progress endgame (if there is such a thing) system, my sources to a Schiit Saga + and a made in Ohio VTV Hypex NCore 252MP amp, as far up the class D chain as I’ve gone, driving sweet Q-Acoustics 3050i speakers (for me the balance between two channel simplicity and enough bass to preclude a subwoofer). An issue I had was wanting to push the volume higher on certain music when using my current budget streamer, a discontinued NEXUM TuneBox TB20. The Saga has little gain. My heretical solution was to put a tube buffer back in the chain, between the Saga and the amp. Two preamps, but “Ah ... just right.” System synergy. So especially if you’re new to class D, or need a little extra volume (I set the buffers to around 11 o’clock), for not much money I found they worked for me.

Noobie to tubes but I noticed a better sound stage, more open, nice sound to vocals... When the Fosi T20 amplifier tubes were replaced with the Riverstone tubes

These are excellent driver tubes for the Little Dot mkIII headphone amplifiers. I primarily listen to jazz and classical and these tubes provide that nice tube warmth while still allowing for good resolution and separation. They’re well-matched and there’s absolutely no channel imbalance.

I was very happy with a Douk st-01 Pro. Standard tubes were 188-05. After a couple of month I noticed some hum originating from the right tube. The music was still awesome but I decided to upgrade the tubes to 5654W’s. The sound is phenomenal. I’ve never heard such clarity before. Every voice and instrument is crystal clear. $20 for the matched pair at Riverstone Audio.