How rare or valuable are STR415s?

[justin gurnsey]

I have two matched pair of green label str415. One set is in my 1980 Mesa Mark IIA, and the other set has never been used. The set that is in my amp is original along with the preamp tubes. They sound fine and the guy I got the amp from said he had not played the amp since the mid 80's. I dont know if i should change them or keep them. I don't use this amp as much as my Mark III purple stripe or my studio 22+. I see some guys saying that they will pay a lot for str415's. I just play in my room at home, do I need tubes like this or will the str440 be good for what im doing? Sorry to be so long winded. This is the first time I have ever used some kind of forum thing.

Could anybody give any information on the pre-amp tubes that came in it.? It says positron 12ax7 on the tube.


Thank you for your time,
Justin Gurnsey
Mesa Boogie mkIIA
Mesa Boogie mkIII purple stripe
Mesa Boogie studio 22+

 

[Elpelotero]

str 415's are considered by many to be the ultimate 6l6 tube. It not only sounds great, but it lasts about 10,000 hours and can withstand heavy voltages. The price right now is about $75 per tube.

Honestly, if you have them, enjoy them! Tubes are meant to be used and played. If you enjoy them, keep using them. If you want to sell them to get some nice money and are not that picky about your tone, sell them.

 

[SixVeeSix]

Leave your tubes in there and hang on to the unused set. Worst case scenario is the NOS set will continue to go up in value. If your amp sounds good don't change it. For some weird reason I have a single STR415. I also have a lightly used pair (one pair each) of Mesa EL34s and EL84s, made in USA. I keep stuff like that, I can always sell it later. The demand is growing and the supply is shrinking, that is the cat-bird seat for sure.

 

[STUART]

The 7581a military spec Philips (6L6) is another excellent tube favourite of mine ,similar in construction to the now sought after STR 415
The STR415 was manufactured by Sylvania and sound amazing with the Mark series amps....

 

[Shep]

I just got 10 of them, they are Amazingly good tubes.. Keep them if you have a mesa..the sound is prefect..

 

[thegame]

The 7581a military spec Philips (6L6) is another excellent tube favourite of mine ,similar in construction to the now sought after STR 415
The STR415 was manufactured by Sylvania and sound amazing with the Mark series amps....

Is there an audible difference in tone between those two ?

 

[ytse_jam]

Next time we'll talk about our part in developing the great Sylvania STR 415 type 6L6 and how we're on the verge of seeing something fairly close reappear on the market

btw, what was he referring to? (taken from an article, maybe the one now included in every Mesa user manual)

 

[RR]

... The STR415 was manufactured by Sylvania and sound amazing with the Mark series amps....

In an old Guitar Player Magazine during a round table discussion, MESA Boogie representative Mark Goodman mentioned that Mark I, II (and maybe the III) circuitry was practical design around the Sylvania's 6L6s because of its rigid design. He claimed that other replacement 6L6s may not sound as good without rebiasing these amps to this 6L6s replacements.

So if you have these STR415s in your MarkII, stay with them. They'll last you for a long, long time and you will be running at most optimum performance.

As far as tone, I'm sure your amp sounds it best with these Sylvania. But if you asks me, if you use different 6L6s and have your Mark I, or II re-bias, the difference is so subtle I'm not so sure you would make a big deal about it. Of course I'm going to be flamed down by some egotistical technician claiming I don't know what I'm talking about. :?

 

[dodger916]

Next time we'll talk about our part in developing the great Sylvania STR 415 type 6L6 and how we're on the verge of seeing something fairly close reappear on the market

btw, what was he referring to? (taken from an article, maybe the one now included in every Mesa user manual)

He wrote that in 1996! I wonder what tube he was referring to as being "fairly close"?

 

[edgarallanpoe]

The 7581a military spec Philips (6L6) is another excellent tube favourite of mine ,similar in construction to the now sought after STR 415
The STR415 was manufactured by Sylvania and sound amazing with the Mark series amps....

Agreed!! The 7581A is a kick *** tube. I have a quad in my Roadking and it really opened up the clean channel. It also gave me a huge, tight, bottom end. Great tube. The GE 7581a is also a wonderful tube. Some find it to be brighter than the Phillips, and I agree. However, it adds a touch of bite to the Rec series of Boogies. YMMV, I find the Recs to be a dark sounding amp and the GE 7581a adds the top end and presence I like.

FWIW, I am using vintage Tesla 12AX7s and the tone I am getting out of my RKI is kick ***.

Is there an audible difference in tone between those two ?

Not that much. The 7581a is essentially a military version of the 6L6gc...more rugged and dependable than the average 6l6, but the Sylvania 6L6gc was far from the average 6L6GC of the time. I have some of the NOS boxes that label them as 7581a/KT66. I had a Mullard 7581 that was a relabeled GE and the Mullard was labeled KT66. While not a true KT66, the 7581a is more toward the KT66 side than the 6L6gc side. Bigger bottom end and thicker tones than the average 6L6GC....slightly thicker and bigger bottom end than the Sylvania 6l6gc.