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@@Marcel-ct9wq I don't know, we don't have one here to check out.

@@marktrivette4272 they are completely different tubes, you can't compare them. But if you're talking about Sylvania 6SL7 and 6SN7, all of those tubes are similar with a warm/rich midrange and good detail, what I like to call "The Sylvania House sound". Other manufacturers not so much.

@@321CatboxWA correct we use new bases that we purchase direct from the factory (I think, Asian supply chains can be tricky). Unfortunately we don't share our suppliers information, it takes years to find good ones. If you're interested we can probably put them into the store.

@tubelab194 Nice , I am pleased that you're willing to share! I support your reason for keeping certain information close to your chest and it was kind of you to explain why even though you didn't need to. Thank you and way to be!

@@philipsecor9742 unlike 6sn7's which have at least 4 different generations (and specs that change), the 6SL7GT is basically the same tube, no matter if it was made in 1940 or 1980. So if your phono stage uses 6SL7's you can use any and all, including our rebased version, which has exactly the same internal parts (same production line, different base). The only thing to watch for is sunken sockets, which would mandate using socket saver/lifters to raise the tube up and help make sure you don't handle the rebased tube by the glass. We ship around the World, California is no problem at all (for now).

@tubelab194 Thanks for the quick reply! The tube sockets are mounted atop the circuit board within the component, so no socket savers are necessary. By the way, I love and have the same CTI Summer Jazz albums and People Make The World Go Round is my favorite track! Extra points for demoing with that track.

@@ThugStyleT pinouts are ALWAYS taken from the point of view of the designer/builder/assembler. To make this easier to program into your brain, imagine your amplifier upside down, that's the pinout used in all data sheets and if a designer has done a build layout the same is true. Now this is presuming the tubes are on top (as is normal these days). Another way of saying this is the pinout is taken from an upside down tube, looking at the key or pin end. If you are just getting started designing/building it's hard to keep this straight because the pinout becomes a mirror image of what you "think" it should be, so I suggest marking the short hand name for all the electrodes beside the socket solder lugs.

This is a great question! Let me see if I can explain it. It's a complex topic, if anyone finds any mistakes then please correct me. For the purposes of this explanation we're going to assume a cathode biased single triode operating in a simple voltage gain circuit. The first weird thing that we have to get our brains wrapped around is that the grid is sitting at or close to the same potential as ground, effectively 0 volts. In fact, designers actually install a resistor from the grid to the ground to set the potential. To ensure the potential is as close to 0v as possible. What we're doing by cathode biasing is adjusting the voltage of the cathode, relative to the voltage of the grid. This can be looked at either way. Is the grid negative in respect to the cathode? Or is the cathode positive in respect to the grid? Both are correct. So let's say we choose a cathode bias resistor that drops 10V. We now have a grid sitting between the anode which is positive in respect to both, and the cathode which is positive by 10v in respect to the grid. Unless the grid is biased so negatively in respect to the cathode that no current is flowing, with no signal on the grid we have some current flowing through the tube. This is the idle bias point and essentially means the tube is running but not doing anything. If we then apply a signal to the grid, and that signal swings negative, we lower the amount of current flowing through the tube. If it swings positive, we increase the amount of current flowing through the tube. Now remember, the grid is negative in respect to the cathode, but what happens when it isn't and the positive voltage swing approaches that 10V bias point? Well in simulations and on paper, it's mostly assumed that once the two are the same potential, current tries to flow from both of them to the anode. In practice though there are a couple of differences. The first is that unless the circuit is designed for it, there isn't much current available through the grid. So it tries to conduct, but can't. This produces clipping. The second difference is that this clipping is assumed to be hard, and only comes into place once the grid and cathode are at the exact same potential. But in reality, as the two approach the same potential, a small and increasing current starts to be drawn from the grid. Making it clip often before the grid actually reaches the same potential. All of this of course is very circuit and tube dependant. Different bias techniques, tubes, topologies, and the like will have different responses to a grid approaching and going positive. But I think the important thing to remember here is that the interactions within a tube and in the circuit driving it are complex, difficult to model, and difficult to predict. Real world experimentation and testing is the best way to test a circuit, and often the results can be surprising. A real world example would be when we were designing our GU-50 Kit Monoblock. We originally tried to use a lower current driver tube (14AF7), but we consistently had issues getting the expected swing and power output that our load lines and simulations predicted. So we tested to see if there was any current flowing through the grid of the GU-50 power tube and sure enough, we found a small current (~2mA) trying to flow as the grid approached the cathode potential. In theory, we should have been able to get the full expected swing up to 0V. But in reality we were clipping much sooner around the -2V point. This wasn't solved until we replaced our driver tube with one capable of delivering more current to the grid, the 6N6P dual triode ended up being a perfect choice.

@@johnsnowlow1883 you should be able to find complete double adapters on AliExpress and other Asian marketplace sites. The correct adapter will have the top cap wiring in place. If you want to build your own, there are 3 standard ceramic top cap connectors available today, you want the smallest one. We stock them in the store, but you can easily find them elsewhere.

@tubelab194 many thanks appreciate your tips

​​@@tubelab194hi got another question....can 6C8P and 6J5 be used as a direct drop in for 6C8C. Thanks

@@johnsnowlow1883 to determine if a tube is suitable as a drop in replacement, download both data sheets (tip: vintage data sheets are far more useful). Then start by comparing the pinout, filament voltage and filament current, max voltages, power (plate dissipation in watts) and gain (often referred to as mU). If everything mostly lines up you are good to go. A small variation of 10% is nothing to worry about, but the pinout and filament voltage need to be exactly the same.

7:57 thanks for the tips...this sharing on anode and grid is also important and useful. Thanks again

@@Pksparty2112 The prototype in development is a hybrid, with a tube driver (6N6P) and a solid state output stage operating in Class A. It's our first hybrid, so we'll see how it sounds. Note this is the only way to get an affordable kit mono block with power.

@ can’t wait

We might have a few floating around but likely not enough from the same manufacturer to even make a matched pair, never mind a quad. Sorry!

@charleslambton7836 If I need a single 6km6 I will hit you up. Thank you for letting me know. I recently came into possession of well over 1000 tubes probably closer to 2000. From the old big glass to the tiny, octal, locktal, compactron , ect . I've been sorting, testing, and learning . Your video's are a great help ! Keep up the great work guys, I appreciate your efforts. Happy 2025!

@@paulhovenga4138 wrong way around, it's not practical to go from octal to miniature 9 pin (though it can be done). But you can take a 6CG7 or 6GU7 both very close to the 6SN7 electrically and adapt them to the 6SN7. This is the wish of many owners of amps running the 12au7, which even though electrically very similar to the 6SN7, sounds very flat and meh in comparison. The better solution is to choose your tube gear, first based on the best sounding vintage types and next on the build/circuit/reputation of the manufacturer. When we design a new Kit Amp, we always start with the tubes.

Hi, thanks for letting us know. We checked the site and it appears to be working correctly on all modern browsers. I did check it against older browsers and found that on older out of date browsers there may be issues. I'd recommend making sure your browser is up to date and clearing the cache then trying again. Cheers!

@@charleslambton7836 Cleared all my cache and tried on Google and Edge. Google it comes up all scrambled and Edge comes up as page not found :( No other website I've been to does this except yours.

@@OrphanSocks are you using the correct code: tariffsale15 The code looks to be active, can you email directly if it doesn't work. valvesnmore@protonmail.com Thanks!

Yup I goofed up the code in one place, below the video, it's fixed now. Thanks for the heads up.

@@tubelab194 Thanks, that one works. The one in your description is what I typed in, so you may want to update that.

@@wh0tube i consider quality sound reproduction a serious business. Frivolous nonsensical posts will be deleted. Everyone is welcome to post intelligent thoughtful contributions, please do so in the future.

@@45calypso haha, no, not even close. The reason as I explained in #219 is the 6SN7 does a lot more in circuits than just act as a small signal voltage gain tube. Based on years of handling large lots of tubes, I'd say the most volume of tubes ever made are: #1 6sn7, #2 12au7 (modern version of 6sn7), #3 6dj8, #4 6v6 #5 6L6 #6 6sl7 (early version of 12ax7) #7 12ax7. As a high gain twin triode the 12ax7 falls into a much more specialized category. Somewhere early on the list would be the more common rectifiers, but there were many different types so no one single tube stands out. Today if you added up all the audio tube gear in use, instrument amps (guitar amps) would be a very minor portion of the total.

@@tubelab194 OK, My mistake. I thought your statement applied to the current state of tube sales.

@@revelry1969 unfortunately that's the store platform option. We can delete a listing, but then when we find stock, we need to completely rebuild a new listing. As you can imagine that would be a lot of extra work. As we move forward into an era of less availability, we'll clean up older listings for tubes that we'll probably never see again.

I notice in some sections the ones you are out of are grey. This is good. Btw, I just bought 2 6SN7 from you and they sound great! Thanks! You are the only guys I buy tubes from now on!

@@chrisblock6697 we did an entire Tube Lab on this, just Google it and you'll find it. In short the 6CG7 is the exact electrical equivalent of the 6SN7GTB and other than needing an adapter (which we stock) you are good to plug a 6CG7 into a 6SN7 socket. Also the 6GU7 is a close equivalent to the 6CG7.

@@tubelab194 Thank you for the info, I'll definitely look for the Tube Lab you did. Appreciate what you guys do!

@@STow6oj I'm not certain what you are asking? If it is about quality of construction, the better vintage manufacturers like RCA, GE, Philips, Mullard, Svetlana, RFT, Matsushita etc, built high quality long lived tubes, that operated in every electronic circuit in the World, everything from airplanes to broadcasting to home hifi and TV, so they needed to be well made or the companies would have gone bust in a few short months. Today a poorly made Russian or Chinese or Slovakian tube probably only has one of two possible uses (home audio or guitar amplifiers) so if the product fails early in service a plane isn't going to fall out of the sky or a major broadcast network go off the air (just when a football game is in the last minute of play - of course). And of course there is no longer that much competition, so of everyone is making a mediocre product, no problem!

@@danieltambasco528 Sovtek was the brand name used for export by Reflector (Saratov, Russia, now New Sensor, that makes all those reproductions that aren't) honestly there are so many better sounding vintage 12AX7/ECC83 why waste the time. My personal favorite is the Matsushita ECC83, made on mullard/Philips tooling and they look and sound very much like a vintage mullard (not the same but close, with lower noise and no microphonic issues). As far as the Sovtek construction is concerned you are almost certainly correct, but given how bad many of the tubes made in that plant sound (both vintage and modern), I wouldn't bother.

@@briancampbell7712 having handled many vintage 6550's over the years, I can verify that not only are the SED (Svetlana Electronic Devices) great sounding power tubes, but they're also better built and longer lived than the older types. Caution! I'm talking about true St.Petersburg production, lots of fakes and reissues around. I think Svetlana learned from the disaster that was the 6550b type and set out to make a much better 6550 and of course history has shown they accomplished this.

@@tubelab194 not to sure they were built better than GE 6550A or Sylvania 6550... but then again never heard those

@@alanpecherer5705 years ago I decided the only way to stay sane and provide excellent tubes was to focus on one or two manufacturers for each type we sell. Having a supply of 3 types of quality vintage GZ34 / 5AR4 is pretty amazing given how scarce they are. We never bother with rare or scarce tubes unless we used to specialize in them in the past and still have some inventory, the mullard 5AR4 is one such tube. Caution! The maximum voltage and current ratings of the 5V4 are substantially lower that the 5AR4 and is in no way a direct or even close substitute. Now that said if the amp was using a way over spec'd rectifier in the first place then down grading to a 5V4 may be acceptable, otherwise not recommended.

@@johnminassian4887 possibly, but every circuit is going to be different. Personally I dislike soft start circuits, they often compromise the power supply. One approach with all tube gear is to have the filaments on a seperate start switch. Then you start up the high voltage first and shortly after the filaments, because the tubes take a wee bit to warm up and to start conducting, you essentially have a soft start circuit. Another approach if using a tube rectifier is to observe the data sheet maximums, in particular the first capacitor (normally C1) and all of the other capacitors and related components and design for the inrush current (high voltage capacitors are no longer crazy expensive and easy to obtain - this was the main reason older equipment used soft start circuitry and it is mostly no longer valid). An even better approach for audiophile grade gear is to use solid state diodes, they're superior in every way to a tube rectifier. The exception would be instrument amps, where you might like the sound of a sagging power supply. Caution! High Voltage present, if redesigning an old schematic and want to change from tube rectification to solid state you need to redesign the whole supply, this will probably not be a big deal, but it's important to observe the different requirements of each technology. And no matter what power supply or starting circuit is used always verify and capture (on a multimeter with hold function) the actual startup surge and make certain all components are properly rated. Lastly some designs simply have too much capacitance for any curcuit to handle at least on initial startup and those circuits need a well designed bullet proof soft start circuit. Thermistors IME are not long lived devices and should not be used.