If you hear that difference you are swapping damaged tubes for good ones that meet their advertised criteria. Another option is that your test bed amplifier is horribly designed so minor changes in current draw and operating points lead to audible changes.
What did the measurements tell about ube swaps you did? What was the change in operating points?
What did the measurements tell about ube swaps you did? What was the change in operating points?
No, I was referring to differences between brands, not tubes of identical manufacture. Additionally, early production models from the same brands, such as GE and RCA, often differ in construction and sound compared to later productions. I have a box of over 100 6CG7 tubes that I purchased from ESRC before Stan passed away—he used to offer excellent quantity specials.
The difference between the best 6CG7 tubes is between 0.005% and 0.037% 2nd harmonic distortion. This measurement is taken at 1000 Hz, and I’m sure it can vary across other points in the frequency spectrum.
It's important to note that not all tubes measure the same, and these measurements are typically taken only at 1000 Hz. I’m certain that a full-frequency measurement would reveal even more significant differences.
Vacuum Tube Valley Issue 11 offers great insights into these nuances.
Surely, you don't think a Sylvania 6DJ8 sounds the same as a Siemens or Telefunken, do you?
And as for the Marantz Model 9—calling it "horribly designed" would be utterly misguided.
The difference between the best 6CG7 tubes is between 0.005% and 0.037% 2nd harmonic distortion. This measurement is taken at 1000 Hz, and I’m sure it can vary across other points in the frequency spectrum.
It's important to note that not all tubes measure the same, and these measurements are typically taken only at 1000 Hz. I’m certain that a full-frequency measurement would reveal even more significant differences.
Vacuum Tube Valley Issue 11 offers great insights into these nuances.
Surely, you don't think a Sylvania 6DJ8 sounds the same as a Siemens or Telefunken, do you?
And as for the Marantz Model 9—calling it "horribly designed" would be utterly misguided.
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If I have a tube that meets all the criteria to be a 6DJ8 then it will "sound" the same as any other tube that meets these citeria. Siemens or Telefunken ECC88 and Sylvania 6DJ8 are close, but different tubes. Heater current differs, capacitances differ and a lot of other aspects as well. Compare the datasheets. Theses are not exactly the same type of tube so there is a good chance that shows up in the frequency response and distortion behaviour of an appliance using them.
What measurements @ 1kHz are you referring to? I don't know what ESRC is or who Stan was. But in 2024 nothing speaks against testing tubes with a curve tracer (the eTracer is affordable, works perfectly and the software matches to your chosen criteria).
I have had same type tubes that sounded different from others of the same type but that was rare and only in extreme cases where e.g. a 1920ies Siemens Aa or Ba with the open anodes (no box, two plates) and without metallic getter flashing but painted on non conductive getter material "sounded" ever so slightly different from their later siblings (RWN, later Siemens, Valvo) which all sound the same. All their curves match.
What measurements @ 1kHz are you referring to? I don't know what ESRC is or who Stan was. But in 2024 nothing speaks against testing tubes with a curve tracer (the eTracer is affordable, works perfectly and the software matches to your chosen criteria).
I have had same type tubes that sounded different from others of the same type but that was rare and only in extreme cases where e.g. a 1920ies Siemens Aa or Ba with the open anodes (no box, two plates) and without metallic getter flashing but painted on non conductive getter material "sounded" ever so slightly different from their later siblings (RWN, later Siemens, Valvo) which all sound the same. All their curves match.
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I looked through that link you posted. Were you linking that for the Listening to 6SN7s article on page 9? What are the "great insights into these nuances"? There is no information about how that test was conducted, there is no information about the tubes used (are they brand new? That would be an issue as emmission needs about two to four hours to stabilize) or any measurements of the appliance with these different tubes used.
The measurements can be found on pages 7 and 8. I’m not going to argue anymore—I just want a peaceful day.
Back to the original topic: it’s unfortunate that the Elekit TU-8340 no longer seems to be available. While they’re releasing the TU-8888, it’s likely to be well beyond the price range. A tube preamplifier paired with a Class D amplifier would be a more economical alternative.
Back to the original topic: it’s unfortunate that the Elekit TU-8340 no longer seems to be available. While they’re releasing the TU-8888, it’s likely to be well beyond the price range. A tube preamplifier paired with a Class D amplifier would be a more economical alternative.
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I've run tests on various output tubes in my Williamson amplifiers. The Gold Lion KT66's produced the most power before clipping--22 watts at 1% THD. Chinese TAD-branded KT66's only produced 19 watts before reaching 1% THD and clipping. The Gold Lion sounds more open and natural, the TAD more constricted, with a glare in the high-frequencies. So does the Chinese KT66 not meet the criteria for a KT66? Or is the Gold Lion an over-performer?
Various brands of 6SN7s sound drastically different in my Aikido preamp. I could twist myself into a pretzel trying to determine which NOS 6SN7's "meet the criteria" for a 6SN7, or simply accept the fact that internal structures, manufacturing standards and other differences simply produce a different tonal balance.
The criteria for what is to be considered a 6SN7 are in the datasheet. The different examples of KT66 behave different in your amplifier, which makes the appliance behave differently (as you have measured) and this goes along with a difference in sound. That makes sense and goes a lot further than that Vacuum Tube Valley article Pegasus posted.
It is very difficult, if ever possible, to separate effects of tube brand and operating point. No two tubes are exactly equal, so conclusions based on simple tube rolling, where operating points are different, cannot prove that brands are inherently different, or that certain brands have certain sonic qualities.
That said in my HK A-300 amplifiers Svetlana 6P6S sound far superior to Reflector tubes.
That said in my HK A-300 amplifiers Svetlana 6P6S sound far superior to Reflector tubes.
Well, I think we can assume that GE and Sylvania both manufactured 6SN7s to conform with the data sheet. And yet, all else being the same (testing for gm, curves and other precautions, along with the voltages one can measure in the circuit itself), they will sound different.
As for the KT66's, at 20 watts you can see different behavior, but at 1 watt or even 5 watts you cannot. But they still sound different.
Do they bias the same, and display similar voltages? Because I don't think 5 or 10 plate volts, or a couple of milliamps difference in standing current, accounts for how different two tubes can sound in the same circuit.
A300 has a unique design in which all 4 output tube cathodes are tied together and connected to ground via a string of two 12AX7 heaters, giving auto bias of about -25 V and idle current of about 35 mA per tube. This requires matched quads. Getting two quads that bias exactly the same would be pretty difficult. So no, I cannot claim that Svetlanas are generally better than Reflectors.
Also, Svetlanas have military acceptance stamp, and Reflectors are consumer grade.
Also, Svetlanas have military acceptance stamp, and Reflectors are consumer grade.
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Well, "sounding far superior" would certainly be an important criterion to me! ;-) Assuming they are NOS and operating roughly within the parameters of the circuit, it sounds like they are better tubes. Of course, longenvity, reliability and other factors are important. But I trust you when you say they sound better!
OTOH, I'm perfectly willing to grant that a lot people buy what they believe are good tubes, but have no way to properly test them or even measure their performance in the circuit. Then all bets are off, as they say. We've all seen someone say something like, "These used Telefunkens I bought are warm and syrupy," having no idea that the emissions are weak or the Gm is well below spec. So obviously, when swapping tubes, it's important to know what you have before you make a judgement call.
It is also about tradition and pride of craftsmanship. Svetlana factory was founded more than 100 years ago in St. Petersburg that was at the time technological and cultural capital of the country. Reflector is in Saratov, a remote province where people didn't care. Just look at their sloppy silkscreen.
Moscow Electro Lamp Works (MELZ/Foton) is another highly reputed manufacturer. MELZ 6N8S (equivalent of 6SN7) currently goes for about $100 apiece, while Reflector one is about $5.
Moscow Electro Lamp Works (MELZ/Foton) is another highly reputed manufacturer. MELZ 6N8S (equivalent of 6SN7) currently goes for about $100 apiece, while Reflector one is about $5.
If you change some active components in your DUT and the DUT then measures the same as before but sounds different then there is either something wrong or missing from your measurements, there is something wrong with your hearing procedure or there is something wrong with the DUT.
It depends on what kind of measurements you're talking about. Different tubes under the same conditions can display different harmonic distortion signatures. There's no mystery about this. Nobody is saying you can't find a reason for differences in sound. But it is completely dependent on the sophistication of the measurement. The measurements we depend on are only as good as the equipment we use to take the measurements. But if you tell me that our standard measurements tools can best the human ear in detecting subtle shifts in tonal balance, I won't believe you.
Our standard measurment tools better the human ear in about every aspect imaginable. By far. "sophistication of the measurement" is another story. Just doing your standard FFT business won't tell you anything about how e.g. one of the many shortcomings of tubes, microphonics, figure in. You would have to measure the tube amplifier hooked up to your analyzer and then measure again with another amplifier playing music through speakers in the same room as the DUT and see if the sound pressure shakes the grids enough to show up.
This common statement that all tubes that meet their spec will sound the same is in my opinion unproven. The specs are fairly wide, and don't say anything about distortion characteristics. And both Morgan Jones and Merlin Blencowe have shown trends for distortion for tubes from particular manufacturers versus others.