[Puzzles]

  Recently picked up a slightly mismatched pair of slotted Bendix 6080. The pictures weren't all that good, so I didn't catch that the top spacer in one is ceramic whereas in the other it is mica. A picture of the tops showed 6080WB 230 on one and 6080WB 244 on the other, manufactured only 14 weeks apart? So I pulled the trigger.
 
IMO, these sound extremely good and I am very pleased. However, in the back of my mind, I can't help but think: "different construction = different sound". But as I have only one of each, I have no way to effectively compare them.....

 
Don't worry, the spacers don't matter sonically. By immense luck I got a dozen of 6080WB's and while there are slight differences in sound, I don't relate that to plates or spacer arrangement.  You have two tubes that I'd assume to be the same build. These are the tubes with the usual YY WW (year, week) date code, which have slotted plates of variable shape (chamfered or on-chamfered edges; sometimes solid plates) and copper grid posts. There's a very similar build of which the date code is followed by a three-digit suffix that begins with R and ends with two numbers (e.g. 6246 R35). That build also features slotted plates (often) but steel grid posts instead of copper posts. Its sound is a little different (slightly recessed mids, a tiny little bit thinner overall). And then there's a third build with purple ceramic spacers and solid plates. Similar to the R-suffix, the date code is followed by a three digit "S"-code. It is probably the type  which is said to be the "worse" sounding type – I'd say it is just a little gentler. BTW, if the tube was branded for other parties, the R/S codes get lost. 
Now, within each of these three (or more) lines, it seems that the spacer arrangement and plate shape varies constantly. It's not even that Bendix used mica spacers from some point, it seems more like a mood thing. Anyway, you have a good pair with the same sound. 

 

[gibosi]

Thanks for sharing your knowledge of the Bendix 6080. For sure, I am very pleased with the way they sound in my amp, so will just relax and enjoy.  

 

[mikoss]

How is the Bendix vs the GEC 6080? Any major sonic differences in presentation?

 

[gibosi]

I have not had the time to compare these tubes in any detail, but my general impressions mirror what others have written. I find both to have very good detail, spatial resolution and air. However, the GEC seems to be a bit dryer, more analytical and airy. On the other hand, I find the slotted Bendix to be more similar to the 5998, with very good bass and just enough warmth to give vocals a nice fullness and good body. Both are excellent and given that I haven't had much ear-time with either, I don't have a favorite.
 
(A Glenn OTL with a Mullard GZ32 rectifier and Lorenz C3g drivers)

 

[akart]

Folks - Where can I find an excellent pair of matched RCA 6AS7G? Also, what do the numbers "X/Y, minimum A/B" mean? Should I be looking for matched tubes with these readings same or similar for both tubes?
 
As an example, here's a listing from eBay:
Tube 1 Gm: 57 / 58
Tube 2 Gm: 57/ 59
Minimum 40/40
 
How can I tell if these tubes are well matched, or not-so-well matched?
 
Thanks!

 

[MJS242]

  Folks - Where can I find an excellent pair of matched RCA 6AS7G? Also, what do the numbers "X/Y, minimum A/B" mean? Should I be looking for matched tubes with these readings same or similar for both tubes?
 
As an example, here's a listing from eBay:
Tube 1 Gm: 57 / 58
Tube 2 Gm: 57/ 59
Minimum 40/40
 
How can I tell if these tubes are well matched, or not-so-well matched?
 
Thanks!

 
A 6AS7G has two triodes (dual triode). The two values for a single tube represent measurements for each triode.  The minimum usually represents the minimum good triode value for whatever tube tester is being used (each tester is different).
 
Electrically matched tubes would have the same/similar triode measurements.
 
If you want to take the obsessiveness a step further you can also get tubes that have matching manufacturer date codes.

 

[Mechans1]

  Folks - Where can I find an excellent pair of matched RCA 6AS7G? Also, what do the numbers "X/Y, minimum A/B" mean? Should I be looking for matched tubes with these readings same or similar for both tubes?
 
As an example, here's a listing from eBay:
Tube 1 Gm: 57 / 58
Tube 2 Gm: 57/ 59
Minimum 40/40
 
How can I tell if these tubes are well matched, or not-so-well matched?
 
Thanks!

The numbers represent the health of the amplifying elements in the tube which is in the case of 6AS7Gs, are two sets of triodes. As a reminder that is an anode, a screen and a cathode times 2 in a single glass envelope. Keeping it simple the number tell you how well those individual triodes are doing their job.  The minimum number tells you that - on that tester - the a triode has to deliver a higher value to be considered "good" usable , OK etc..  It is a simple pass fail demarcation.
Sometimes sellers will also know what the new nominal value should be (on that tester) as well and report that. 
You want your tubes to be roughly the at same level to be considered "matched".  This is true for most situations where you cannot manipulate the bias current. The example you gave is a good match, you can't expect the tubes to be perfectly alike and the error built into the measurement although not given likely is +/ - 1, or more, on that meter for that tester.
There are other aspects about a tube that are considered in matching, construction is important, but beside the obvious there are other electrical parameters that are used by some experienced vendors.
One way to get good matching is to rely upon well established seller.  I just buy a couple of same testing tubes and see how they sound.  You don't always come up with winners but most of the time I have. You might have to develop a stomach for some risk. I expect there are sellers who will do matching for you and may let you return them if they aren't what you wanted.  Most don't offer that kind of security and you will most likely pay a premium for it.
I will look up a tube seller who is well established and a careful tester who sells NOS. I just can't think of his name right now.

 

[Mechans1]

I don't know if he sells 6AS7Gs but the guy I was thinking of is www.audiotubes.com  Also goes by Brent Jesse Recording.  He sells NOS tubes and is well regarded.
If you can tolerate current production then you may want to contact  Jim McShane  at McShane Design, over on Audio Asylum.  He matches very carefully upon several factors.  He has some NOS but don't know about 6AS7G.s. He is really good at what he does, I needed an octet of matched tubes and  was very happy with what I got.
Have you considered 6080s or 5998s?

 

[mikoss]

If you're ok going the eBay route, matched pairs of new old stock RCA 6AS7G tubes are sold fairly cheap and most sellers offer returns. eBay themselves have tilted the service towards buyers, so it may be inconvenient to buy tubes that have issues, but you pretty much have a satisfaction guarantee.

I've personally bought two pairs of them in the last 6 months, for around $40 per pair.

 

[rnadell]

I have a pair of the RCA's that came with my Glenn otl and while the sound quality
is acceptable they are noisy.
I purchased a pair of NOS GEC 6080's and really liked them, quiet and great detail and bass.
However after one year one blew up so I am looking for a replacement.
What about the TG Chatham's?
Also are the GEC 6as7's a good bet?
Thanks

 

[whirlwind]

  I have a pair of the RCA's that came with my Glenn otl and while the sound quality
is acceptable they are noisy.
I purchased a pair of NOS GEC 6080's and really liked them, quiet and great detail and bass.
However after one year one blew up so I am looking for a replacement.
What about the TG Chatham's?
Also are the GEC 6as7's a good bet?
Thanks

GEC 6AS7's are suppose to be wonderful....but they are pricey!

 

[mikoss]

GEC 6AS7's are suppose to be wonderful....but they are pricey!

Oh $500/tube isn't *that* pricey...

 

[gibosi]

  I have a pair of the RCA's that came with my Glenn otl and while the sound quality
is acceptable they are noisy.
I purchased a pair of NOS GEC 6080's and really liked them, quiet and great detail and bass.
However after one year one blew up so I am looking for a replacement.
What about the TG Chatham's?
Also are the GEC 6as7's a good bet?
Thanks

 
I am not sure what you mean by "TG Chatham"??
 
The following site can be useful regarding 6AS7-type output tubes:
 
http://the-key.enix.org/~krystal/review-tube-bottlehead.html
 
Unfortunately, all the pictures have been taken down, and there are some errors, for example, the Sylvania Gold Brand 6080 is most certainly not the same as the Sylvania 7236.
 
Edit: Also, the GEC, Mullard and Telefunken 6080 are three very different tubes, not at all the same. However, by and large, this is good information.

 

[akart]

Thanks Folks - lot of good information here. 
 
I have a WA2 with the stock tubes. I first want to listen to the tubes I have for a while. Then, planning to first get the RCA 6AS7Gs and then after I give them a good listen and if I want more, I might go for the TS 5998. But, to appreciate the higher costing tubes, I must first give the cheaper tubes a good listen.

 

[hdtv00]

You can get 5998's for $80-90 I wouldn't waste time hehe.