Another thread on the RA100, Power tubes

I had a few power tubes I have tried in most if not all of my Mesa's except for one, The RA100.

I started off with the cold RA-100, Removed my favorite set of Mesa tubes (they are on the list, Mesa STR442) I left the preamp tubes as is. I found no point in changing anything. V1, V2 stock Mesa tube. V3 is Mesa Chinese 12AT7 (has a dryer tone to it than the JAN/Phillips 12AT7 but either will do fine, the Chinese 12AT7 just sounds better in the RA than the TC.) V4 is RFT 12AX7, V5 and V7 is Ei CV492 (similar to the Mullard long plate reissue 12AX7 but better) and the reverb is the stock Mesa JJ ECC83s tube. I also added in the Strymon BigSky and the Boss EQ-200 if I found it was needed or not.

The line up:

1. Mesa STR447 (Electro Harmonix EL34) grey bias color matched set. These are stock tubes and what I started with when I first got the RA100.
2. Mesa STR446 (TAD red-base EL34) grey bias color matched set.
3. Mesa STR450 (NOS Siemens EL34) mixed bias colors (grey and green) bought at different times.
4. Mesa STR445 (JJ 6L6GC) green bias color matched set (pulled from the Mark VII).
5. Mesa STR448 (TAD red-base 6L6GC) Grey bias color matched set.
6. Mesa STR442 (SED =C= 6L6GC) blue bias color matched set. (this is what I have been using for a few years now).

Mess STR447 review: I did not miss anything not using these tubes in the RA100 over all these years. Needed to have a baseline as this is what was shipped in the amps from the factory. Well they sounded much as I remembered them to sound, harsh, bright, and a neutral low end that was just there. Had to dial in the bass all the way to get a decent sound but I managed with the tone stack set to noon to start with. Clean channel is warm toned and will always sound this way. It did not seem to make much of a difference what power tube I was using as the clean characteristic were about the same. Lo gain was thing and anemic needing more low end dialed in, trebled dialed all the way out, and was not sure where to set the midrage. Top end brightness was most of the distraction. I guess I could get used to that. Just bright and lacking character. These tubes sound better in the Badlander or TC amps. Probably due to the plate voltage differences. 400VDC vs 450VDC (+) does make a difference. Hi gain channel was much better with the low end but still trying to tone the top end down was not easy. Had to drop the gain in order to achieve a tolerable sound. The GEQ in the loop helped a bit but just did not filter out enough. Bass dialed all the way, midrange at 3pm, treble dialed out and gain dropped to 11am. Mutli-soak saturation at -4db, well it was better as it did help in cutting out the top end. Was able to dial up the gain more. For the 50W test, I did not use the multi-soak as I wanted to hear if there was much of a difference in tube saturation. Not well noticed. GEQ in the loop helps, almost mandatory but did not do much to strip the top end. Very forward in-your face feel.

Mesa STR446 review: to keep it short it was about the same as the STR447. Just a tad bit brighter and a bit less midrange. Plate voltage again seems to thin the tube out.

Mesa STR450 review: Well this was an improvement over the STR447 tube. A little more low end and midrange, not as bright as the STR447. Sort of like the difference between skim milk and grade A dairy cream. I can get used to the NOS Siemens tube. It does have a similar character to the STR447 as I discovered that when I tried them in the TC50. This time I did not blow out any fuses. A bit bright but had more usable tone. I would not say they are epic sounding tubes. I did try the multi-soak but did not feel that magic sound I would get from my favorite tube for the RA100. Not bad though. GEQ required in the loop. I can live without the GEQ but having it helped to get close to a good sound. Not as forward sounding but still in your face a bit. This is the first time of trying the STR450 tubes. I had them for a while but never got around to running them in the RA.

Time for some 6L6GC tubes:

Mesa STR445 review: Not that is one good sounding tube, especially for the 6L6 bias. A slight drop in volume, that seems to be the common thing with an amp specifically designed for the EL34 power tube as its primary bottle. I did like them though. Lo gain and Hi gain characteristics were as close as it gets to my favorite tubes. Full bodied sound. Lo gain did not sound anemic, it actually had usable body to it. Plenty of low end and midrange thanks to the tone of the STR445 having that 6CA7 sound. Top end was on the bright side but could be dialed back with the tone stack. Did not need any GEQ in the FX loop. I did turn it on for S&G, ok fine but not needed. Felt it was taking out what I liked without it. Hi gain was just as good as the favorite tube. So when the Unobtanium runs out, the STR445 will be the tube choice I will switch too. Quite compatible with the 400VDC plate voltage, no issues with the multi-soak but could not get the magic of the unobtanium but close enough to smoke a pack of cigarettes and drink the beer I bought for the shootout. Ha. Much better, not as forward or laid back, similar feel to the best at the bottom of the list.

Mesa STR448 review: Almost similar to the STR445 but a bit different. Much thinner sound and not as rewarding as the STR445. I assume it is more related to the lower plate voltage. Also noticed more of a volume drop difference. Much like the STR440 of any bias color but not total mud fest sounding. I could get used to this tube but it was not was full bodied as I hoped it would be. Had much better results with the JP2C and the Badlander. A bit laid back with the RA100. Felt the STR445 was much better in all respects. Do not confuse these STR448 tubes with the old STR448 EL34 tubes. Those you can still find but are out of production. The STR448 tubes I tried are the TAD red-base 6L6GC tubes.

Back to the Benchmark EL34 best suited for the RA100.

Mesa STR442 review: This by far has the best tone and character I have ever heard. The low end was plentiful, midrange was evident, and the top end did not force me to run for ear plugs. This is the nirvana of utopia. The complex harmonics are full of life and that 3D effect is present. More notable with the multi-soak in use. I did not need to boost the bass, midrange or drop the treble with all controls at noon. GEQ not required but does not hurt to use it to alter the tone. Best overall balance across the sound spectrum of audible hearing range. The grind from mild to beastly is just as rewarding as ever. I would not say it is heavy metal aggressive but the RA100 comes to life with these tubes. I got lost again with the time. It was daylight when I started. I thing I burned a few hours with these tubes. That is why I saved them for last as I knew I probably would never get to trying out the other tubes. Sure there was that cool down period to wait for before handling the tubes I just ran. I have to look into getting some more of these. I should have stocked up before COVID when Mesa had inventory of them. I would say the closest to these would be the SED =C= 6L6GC or Mesa STR454 tubes. As for the Feel, it is just hard to describe. It actually pulls you to some other plane of existence. Not too forward or in laid back, it is more of a combination of both and not so 2D. The complex harmonic details of the tubes are hard to explain with words.

I've been very happily using EH 6CA7s. This is my rehearsal space amp and has been played loud on the regular for years. I just ordered my third set, I get about 400 hours per with masters usually at noon with -3db on the soak. I tried the 6CA7s originally sort of on a whim, because I liked Vintage Hi better with STR445s and Vintage Lo better with whatever it came with, probably 447s, and like you said it seemed to make no difference to the cleans. And the 6CA7s did sort of split the difference at a nice price point, so I kept using them.

The thing I find with the 6CA7s at volume is the low end is fairly tight, Vintage Lo doesn't sound thin as long as I keep the gain around or past 1:00. And with -3db on the soak, master about noon, gain about 1:30 with actives, there's really nice stuff in Vintage Hi. It makes it a little more Peavey (5150/6505) and a little less Marshall, but definitely its own thing and almost Recto-nice to play. Punchy low mids, nice definition up top, saturated but detailed, and if you have actives the volume knob is your boost pedal.

The EL34s made it a little too focused, it just sounds like a (really good) HRM, and with 6L6s I really started missing a Presence knob.