6L6 replacement?

I own a 112 RP 100 that uses 6L6GC tubes. What's the best replacement/brand for Rock and roll. My local music store had Sovtek 5881's. How are these?

Harsh.

Most of the "Soviet" 6L6 replacements are also sold and labeled as 5881. In reality, this tube is neither type and does tend to sound more "brittle" and two-dimensional than the warmer and more harmonically-complex sound of the original American 6L6.
From what I have heard, these tubes were originally designed for use in the MiG-29 fighter aircraft and then adapted to a 6L6 base wiring scheme for use in guitar amps.
They seem to work well enough but they do not in any way sound like a good-old American-made 6L6GC!
The closest thing to an old-stock American 6L6GC being currently manufactured would probably be the Groove Tubes 6L6GT, which is being mostly manufactured in California using production fixtures from the original General Electric tube plant.
I haven't personally purchased these or tried them out, but they almost have to sound better than the Soviet 6L6 imposters!
However, let me point out that a Sovtek 5881 is a TON better than not having any 6L6 type available, so I don't want to sound like I am knocking them too badly. They are cheap, they work and they are readily available. Heck, even Fender uses (or has used) them (after screening by Groove Tubes).

I bought 6L6 Groove Tubes for my 75 amp last year. I still had the original tubes from when I bought the amp new around 1981. The Groove Tubes are relatively expensive, but they really brightened up the sound and gave a much warmer sound. They are graded on a number scale from clean to hot. I got tubes on the clean end of the scale. I hadn't realized my old tubes "sounded" dull. I play bass through the 75 with a MusicMan 115RH-75 bottom and I get positive comments on the sound.

Svetlana does not mark thier tubes "5881".
The Svetlana 6L6GC is an EXCELLENT tube.
Politics should be left out of websites like this.
Whenever I read phrases like "good 'ol American",
I imagine someone who would follow the likes of George W. Bush and Rush Limbaugh over a cliff, wearing flag colors.
HERE'S what you might try reading re; the Svet 6L6GC ;http://www.victoriaamp.com/desk3.html.

It isn't political... it's generally accepted opinion!
The 6L6 is an American designed tube that powered most of the classic American guitar amps. 5881 types may work in the same socket but they are not the same internal construction and do sound different.
I didn't say Svetlana made 5881 6L6 replacements, but in the past most Soviet tubes WERE 5881 types. These tubes are haven't really been "Soviet" since 1991, they are now Russian tubes (but many of the Russian/Eastern European tubes coming into this country are still 5881 designs).
Svetlana has always enjoyed a reputation as the most knowledgeable and quality-conscious tube manufacturers anywhere, but that doesn't change anything in a 5881/6L6 comparison and THAT was the question that was asked in the first place.
Political correctness does NOT live here and where a tube comes from has no bearing on design, construction and sound quality.
There is no right or wrong about opinions and everyone has at least one!

The JJ 6l6's are very good. I have them in one of my other amps(ok, it IS a Fender Twin)and they sound great. They are stout and will take the extra voltage of the linear twins and to top it all off, they are real reasonable.

In the "old" days, a 5881 was meant to be used where the plate voltage was lower than what a 6L6 generally could handle. I have a friend who has a "blond" Fender Showman and it came from the factory with 5881 power tubes. If you use 5881s in a Twin or a Super Reverb they won't last very long because the plate voltage is too high for them. With the Russian tubes like Sovtek, you need to be careful of the 5881 model if you want them to last more than a short period. I have a preCBS Twin that LOVED the Sylvania STR tubes (and didn't like the RCA at all-even though it was originally equipped with RCA from the factory) and I use the Svetlana 6L6s now and am reasonably pleased with how they've lasted and how they sound. They sound much like the old GE tubes and are much cheaper than the GT GE tubes that someone else mentioned here. I use Svetlana in my MM 112-RP-EVM also. Very nice! One other thing, I haven't seen where anyone has mentioned KCA tubes as a good place to buy tubes. They are on the internet and I've done business with them for 3 or 4 years. They've always treated me great.

I just changed out the tubes in my 1981 RP-65 from sovtek 5881wxt to Ruby Tubes 6L6GCMSTR. Man what a change!! I had to learn the settings all over again. The clean sound I loved was more crisp and had a lot more midrange tone. The hi gain settings improved to a the point that I don't need a pedal to get crunch and break up. It is warmer and tone like that of a fender but with better hi gain like a messa boogie. My 83 Tele is brighter and sharpe. And my Les Paul is easy to dial in a warm Santana sound and a ZZ Top crunch. And also these tubes light up a lot more than the Sovteks. The back of the amp looks like a night light.

Although these posts are quite old, I'm wondering if there is any general consensus as to 6L6GC replacements, tone wise ? I have an HD150 head for bass, and am looking for clean bass power with headroom. I've been told the the Phillips 7581A is the best for this, but the Svetlana is no slouch either. Any more comments ?

I really have no opinion for BASS but the real svets(=C=) are nice, just high right now. I've heard the KT66's from JJ are nice but I have NO experience with them. I'm more of a SS guy for bass(I use a Hartke 3500 for bass when I HAVE to play bass). You COULD contact Bob at Eurotubes and ASK him about it but of course, the only tube he is going to suggest WILL be a JJ. Some guys are pissy about JJ's, some aren't. Mike.

I just looked at the tubes in my recently purchased HD 150 and noticed there were two different brands of tubes in there, namely 2 JJ 6L6GC, and two Electro Harmonix 6L6EH. I have played bass through it for a few days now, and there does'nt seem to be any issues so far, but, should I just go ahead and get a new set, just for peace of mind? Also, when I got the head, the two 6L6EH had come loose and had fallen out. I put them back in, but don't know what socket each tube was in. Is that a problem ?