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[Anderton]

Not just to support Harmony Central, but click on this and then click on Find Out More...fascinating stuff, actually. Well, at least for Mike Rivers and me

[AlamoJoe]

So, if I supply them with the tube numbers on my Old 1967 Super Reverrb, they would be able to supply a matching set like GrooveTubes used to?

 

[MikeRivers]

Do you know who Apex is?

 

Years ago, when Aspen Pittman was working on setting up a tube factory in the US, he had a display at the NAMM show with a big tube analyzer that came out of the old Sylvania factory. He was talking about how he was going to use that in order to do quality control and matching of the tubes he made. Unfortunately the deal went bust when he found that he couldn't solve the environmental protection issues due to some nasty materials that are necessary to make tubes.

 

The multi-tube tester concept looks like something that Chris Juried deveoped for his Tube Equipment Corporation to match tubes for their Fairchild 670 compressor re-creation. He also had what's essentially a two-port vector network analyzer to QC transformers.

[philboking]

Pretty cool system.

[Phil O'Keefe]

Mike, is this Aspen's new company, or are they unaffiliated with him?

[MikeRivers]

Mike' date=' is this Aspen's new company, or are they unaffiliated with him?[/quote']

 

That's what I wanted to know myself. I was hoping Craig might know since he's more in the know than most of us know.

[bookumdano4]

I don't remember anyone trying to match tubes in 1959. I think it's nutty. Silly concept imo except for a tube-geek.. I could even say that mismatched tubes are the norm in history and the source for mojo sound (someone would buy the concept).

 

Matched tubes.... another spec-level microscoping of something on the planet that doesn't need to be microscopically-analyzed. Today's sound is already too matched, clean, 20hz-20khz, wowless, flutterless, colorless (even color is mostly colorless). If I'm looking at a lit tube, I don't CARE about the measurements of the purity of all that orange or the grids themselves. I just care if the glass is broken or the tube doesn't light up when inserted. If I have two tubes that light up, cool, close enough.

 

If the 12ax7s go out in my old VM tape machines... or in my ancient circa 1958 Zenith 80-watt behemouth stereo system, or in one of my old amps, I'll reach into my dad's huge old circa-1960 tube caddy and rummage through the dusty tube boxes and grab a replacement and throw it in. If God had meant tubes to be matched, she would've commanded entrepreneurs to market them in two-paks beginning in 1930 or whatever. Frankenstein would've turned out much better that night if those giganto tubes had been matched when the power switch was thrown. You would have had those Doublemint gum commercials on tv in the 50's along with commercials about doublematched tubes. Life magazine would've been running articles mentioning how much better "I love Lucy" looks on a tv with matched tubes inside.

 

I also don't match gasoline or check milk cartons to verify all the milk in the carton came from the same cow. I've also never tried to buy a matched set of Les Pauls. If I'm dating twin girls, not gonna try to look for a set that matches exactly. Not necessary.

 

When recording in stereo, I'm also not opposed to using an sm57 with an RE20. Matches fine enough for me in a pinch.

 

What a century. Everyone wants to dress in black, use the same loops, make stuff match, and see only clean curves on spec sheets.

 

What was the topic again?

[MikeRivers]

Today, people who use tubes are tube geeks. Audiophiles going back 50 years have bought matched output tubes for their amplifiers. But in those days, they didn't match them in the same way that the Apex folks are doing, Basically they chose a typical operating point and found tubes that drew close to the same amount of current at that bias. Many amplifiers in the glory days of Hi Fi had a balance control so that, with the help of a voltmeter, you could tweak the bias so that the tubes you had in there were a better match than without the tweak.

 

You need to understand the application, though, to understand whether matching tubes is significant. The matched tubes that people buy today are used in a push-pull output stage where one tube conducts on the positive half of the cycle and its mate conducts on the negative half of the cycle. You want a symmetrical waveform to be amplified the same in both directions. Badly mismatched tubes without enough feedback can cause non-symmetry. It's a form of distortion that we can live without. At a given amount, say, 5% THD, it sounds less pleasant than, say, 5% of just plain old even harmonic distortion.

 

If you have a preamp or a recorder that uses three 12AX7s in serial stages, there's no need to match them, though you might want to test the highest gain ones and select them for lowest noise.

 

In the case of the Fairdhild variable mu compressors (such as those re-created by Tube Equipment Corp), the signal path is balanced from input to output, and all the stages are push-pull, so it's important to match those tubes.

 

Now I'm not saying that today's matched tubes going to people with guitar amplifiers and boutique hi fi amplifiers isn't a bit of a racket. But someone's taking the time to do it, and if they think they can charge more money by doing it more accurately than necessary, well, it won't be the first time in this industry. When tubes were prevalent, it wasn't unusual to pay $5 or so extra to get two tubes "matched." Now that a single tube, without a match, can go for $75, that's $150 for a pair, and so it's not totally out of the question to charge an extra $25-50 for a matched set.

 

But if you find that your amplifier sounds better with a matched set of output tubes, it may be as much because of the quality of the tubes that the people who match them as in the matching itself. There just aren't that many tubes around any more, so people who sell them are looking for ways that they can make a profit from a smaller volume.

 

 

[Anderton]

In the days when tubes were king, people didn't think about matching tubes because the quality and consistency was much better. But there are also practical reasons for matching power amp tubes. The reason why some people think unmatched tubes sound better is because in pull-pull circuits, the better the matching, the lower the 2nd harmonic distortion...which of course, some people like. Matched tubes give a cleaner sound with more emphasis on the fundamental. There is a way around that by matching plate voltage but not transconductance; that way you can have technically "matched" tubes but with an unbalance that creates more distortion.

 

Seriously unmatched tubes have shorter lives; think of it as one "dragging down" the other. Also, mismatched tubes produce more hum, and if there's only a single bias control, you won't be able to optimize bias for both tubes.

 

Whether matching tubes matters or not depends on a variety of factors, mostly involving output stage topology. So in some cases it's audiophile urban legend translated to tubes, in others there's a valid technical and economic reason.

 

BTW Apex is part of Amplified Parts.

[Beck]

Pretty cool info. I bookmarked and saved it in my vast collection of online resources.