#1
Hey all,

I currently have RCA and Sylvania power tubes in my 1979 Bassman 100. I like these tubes, but I think I'd rather keep them as backups because they appear to be dying out. Output has been decreasing. I find myself cranking the master volume to 6-6.5 whereas when I first got it, 4.5-5 was enough for gigging/practice. I think the preamp tubes are fine. V1 and V2 are legit RCA 7025s and PI is a RCA 12AT7. The amp stays clean just fine and hum is not an issue.

The volume decrease may be due to the fact that I stopped running an EQ pedal in my chain. For awhile I was obsessed with having a boost on the back and front end, but I really don't see a reason to do that anymore.

I am about 99% sure I want to get Tung-Sol 7581a tubes to squeeze out extra headroom and perhaps even have the life of the tubes elongated(?) because I'm currently running the head, which is 4 ohms, into an 8ohm cab.

I know that these amps were built during the time when tube production was going down the shitter and people often used mismatched power tubes. I'm going to buy the tubes from somewhere I can get them matched, tested before purchase and hopefully burned-in to avoid issues. There's also no bias pot in this amp (that I am aware of). Aside from this, do I need to be aware of anything?

Also would the 7581a tubes be louder than a set of 6L6 tubes?
Fender '72 Telecaster Deluxe RI
Schecter C-1 Artist II
1978 Music Man HD130
+ a bunch of neat pedals

screamy emo band
#2
First, Tung-Sol is another brand name owned by New Sensor Corp in Russia. The tubes are Sovteks.

7581a's are a version of the 6L6. If you have a power supply that will generate more power, you'll get more power from the tubes. If not, then...not. There's absolutely NO guarantee that these tubes will last longer than (or as long as) a standard 6L6. There's no guarantee that you'll "avoid issues" no matter where you buy them or how thoroughly they'll have been tested.

If you have currently failing tubes and these replace them, there's a good chance that they'll sound better (even louder) than what you have. At $30 apiece they should make you coffee as well.
#3
I'm aware that the 7581a is supposed to be a military grade 6L6. Reviews on these tubes have stated that they are indeed a high-grade 6L6, but whether or not they are truly 7581a tubes is kinda up for debate.

My thought process was that since these are rated for ~35W whereas traditional 6L6 tubes are rated for 25W that they could essentially last longer. Plus, with a 24 hour burn-in, if a tube is bad or going to fail, it's likely that it will fail in that 24 hour period. Obviously, it's almost impossible to know how long a production tube will last. I made the mistake of buying "matched" tubes without having them tested or burned-in and one tube was running almost twice as hot as the others. Burn-in could have at least shown that it was red-plating.

I have been searching for cheaper ones. The best price I can find for 4 tubes is $112.32 matched, burned-in and shipped.

Are there any other 6L6 equivalents that would increase headroom?
Fender '72 Telecaster Deluxe RI
Schecter C-1 Artist II
1978 Music Man HD130
+ a bunch of neat pedals

screamy emo band
#4
Some of these "new" tubes are simply snake oil. I have NO idea if the 7581A is one of those or not; I have no experience with it and I'm unlikely to get any in the foreseeable future.

A set of four matched, burned in (actually burned in for 24 hours first and THEN tested/matched) 6L6's from Eurotubes will run around $75 or so. And I *know* what kind of testing gear Bob uses (ask him). I'd really have to think about whether I'd want to spend half again as much for Sovteks that may or may not last any longer.
#5
A quad matched set of JJ's will run me $84.65 from Eurotubes, not a bad deal at all. I'm hesitant to buy JJ's because I always have issues with JJ's. I had Sovtek 6L6WXT+ in another amp and I thought they were way too soft, but I guess if Tung-Sol is the same company, I would probably run into the same issue if I were to buy Tung-Sol 6L6 tubes.
Fender '72 Telecaster Deluxe RI
Schecter C-1 Artist II
1978 Music Man HD130
+ a bunch of neat pedals

screamy emo band
#6
Did you check out the stock at tctubes? They have the best selection of NOS tubes that I know of.

I use JJ power tubes in everything I own.
Gilchrist custom
Yamaha SBG500
Telecasters
Randall RM100 & RM20
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Atomic Amplifire
Marshall 1960A
Boss GT-100


Cathbard Amplification
My band
#7
I'm not terribly interested in getting NOS tubes. Maybe I'd get RCA 7025's again, but I guess I might have try JJs.

Tung Sol 6L6 STR tubes are pretty inexpensive from tctubes.com. They have also peaked my interest since they're also considered to be a high-grade 6L6. $76 for a fully tested and burned-in quad. I can also pick them up from the store, which is pretty convenient.
Fender '72 Telecaster Deluxe RI
Schecter C-1 Artist II
1978 Music Man HD130
+ a bunch of neat pedals

screamy emo band