my (very subjective) tube swap-out testing

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mejoshee

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just re-tubed this weekend. been wanting to do it for a while and finally recently got a bonus @ work.

what i compared were the stock mesa 12ax7's and a set of used mesa el34's (str447). the power tubes still have a good amount of life left, not sounding flubby at all, but i thought they sound a little..."harsh" and "thin" as so many people describe. so, i set out to re-tube and review. keep in mind this review is very, very subjective, based on my own ears, playing capabilities, and set up. and of course you probably don’t need to change any tubes at all if you’re having fun the way things are. the power tubes are probably the best first step and biggest overall change, so i would do that first (and that is how i approached the test).

for the cab i used a port city os 1x12 loaded with an evm 12l. the guitar is a maple top/white korina superstrat. the pickups are dimarzio liquifire, area 58, and d sonic. all the amp settings were left the same from each tube change. the loop and solo boost were not engaged, but loop was not bypassed to use the global master, so please keep that in mind. here they were (roughly) on o’clock settings per dial:
ch1
treb—11:30
mid—1:30
bass—10
gain—11
mv—12
presence—11
90w, fat, bold, diode rect
preset eq—9:30

ch2
treb—2
mid—5 (all the way)
bass—10:30
gain—2
mv—10
presence—10
90w, crunch, diode rect
no extra eq

ch3
treb—2
mid—11
bass—10
gain—2
mv—9
presence—10:30
90w, iic+, bright, pentode
g eq—full 80, 2/3 to top of boost half 240, 1/3 from bottom 750, 1/3 from top 2200, just above the mid-point 6000

run in full power mode, global mv about 10 so this could be done @ living room volumes.

all tubes were purchased from http://tubedepot.com with certain special testing indicated below. between steps i let the tubes warm up for at least 10 min before taking them out of standby. here's what i was swapping in:
v1: mullard 12ax7, low noise & microphonics tested
v2: mullard 12ax7
v3: tung-sol ecc803s 12ax7g (gold pin), low noise & micro
v4: mullard 12ax7, low noise & micro
v5: tung-sol 12ax7
v6: tung-sol ecc803s 12ax7g (gold pin)
v7 (phase inverter): tung-sol 12ax7, matched & balanced
v8-11: matched quad tung-sol el34b (tested to mark v bias range, which happened to be 25's on this set)

step 1:
play around using the mesa tubes. using my settings i would say that they are ok. ch1 is not quite fender-y, but pretty close. closest mesa's ever gotten, imo. i try not to dial in too much treble, maybe less than about 11-12 o’clock, or the amp gets piercing in the highs; i still like the presence up about 11 o’ clock though.

ch2 is also the closest brit tone a mark series amp has gotten. i crank the mids and treb (not too much) and dial back the bass in crunch mode and you can do zep, ac/dc, lighter sabbath, all the best classic rock/metal. ch3 is a pretty close setting to john petrucci's iic+ settings, but a little modified to my tastes.

chording & arpeggios are excellent on the mark v, especially ch1. it can be spanky, punchy, and chimy depending on touch and pickup settings.

step 2:
swap to tung-sol el34b's. wow! how to describe it! clarity & definition in all channels is boosted! i believe it has something to do with a low-mid warmth that gets added, so the amp sounds more "present" and louder. the low-end is warmer yet still retains the tightness of the mark v, especially in ch3. high-end is chimy-er, more bell-like, and less harsh, yet definitely still capable of crushing distortion. overdrive is a lot fuller, with more mids and more presence, more complex harmonically, but less piercing or focused on any one unusual frequency.

the clarity of overall frequency response makes the tube sound more balanced like a 6l6 than peaky or spiky like an el34 (might) sound. these are just generalizations, of course, but i agree with http://thetubestore.com reviews of this particular tube. it doesn’t come across as the typical marshall mid-honk el34, though this isn’t a marshall, so it’s not a 1-to-1 comparison. a sovtek type tube would be a good one to try to imagine. furthermore, i didn’t intentionally try to dial out the mark and dial in the marshall so much as just dial the mark until the od sounded right for classic rock w/ my pickups. cleans and light overdrive seem to have more apparent headroom & “pop” more, not much more spanky or plucky, but definitely more “alive” sounding, very 3d.

bottom line: these tubes are a huge improvement over stock mesa el34’s. i highly recommend them, but remember what you are gaining in frequency response so you are not surprised when you apply them to your settings. you might find the bass boost to be boomy, depending on the situation, due to the strength of the tubes. they're also more affordable than the sed el34’s that everyone raves about and while i never tried those, i'm more than happy with the tung-sols.

step 3:
swap in the new 12ax7’s for each v1-7 roughly in order. i skipped 5 & 6 to go to 7, but then went back. those only affect the reverb, fx loop, and the drive stages of ch3. there was less definitive improvement to be had with the replacement of these 3 tubes than the first four (hence the discussion now). in general, they were mostly a finishing touch. i will say that i think they took out the last bits of harshness that were still present after all the other re-tubing, but that was barely perceptible to me.

v1 makes a big difference. i went off a bunch of people’s recommendations for v1 to use a less bright tube, like the tung-sol. i really like those, but since it’s the first stage for everything, it will be the most influential. mullard was a very good choice, bringing in warmth in the highs, improved clarity in chords, tighter bass, quieter operation, etc. great buy, imho. ymmv—maybe try a nos tube also, but in general i was going for a set of tubes that could be replaced with new production for little hassle.

v2 also makes a difference, but only affects ch2. even more pushing in the direction of a marshall this way. it strikes me as very brit, but not modern, harsher, diode clipped; very smooth and late 60’s marshall sound. i tried a bunch of zep riffs like “black dog,” “since i've been loving you,” “four sticks,” “dancing days.” in a word: orgasmic. well, maybe not quite, but it got close :wink:

v3 smooths out a lot of the drive characteristics for ch2 and 3, making them less harsh & gritty, more singing and sustaining. also made the amp as a whole a lot quieter in the noise floor. the hiss was diminished a lot. not sure what else to say about this except that it’s a good all-around improvement, not so much in a single channel or frequency.

v4: icing on the cake for ch3. i will also need to double check the efficacy of this tube on the reverb tone. i'm interested to find out if the tube prevents or improves any suckage issues.

step 4:
rock on!

i hope you liked my review and maybe it’ll help your choice of tubes. if you have (constructive) comments, please feel free to leave them. if you have questions on my testing, let me know.
 
I also have the Tung Sol El34b's in mine and I agree with what you have said about them.
 
excellent review!!!!!!!

i have a high gain 12AX7 mullardRI in V1 for over 7 or 8 month now... just love the smoothness and low noise that this preamp has..

the power tubes i keep switching between tungsols EL34B's and Mullard EL34's RI both work excellent for my sound...... tried SED's EL34 but didn't work for me (do not get me wrong here, SED's are amzing tubes).

again thanks for the review :wink:
 
salvatruco said:
excellent review!!!!!!!

i have a high gain 12AX7 mullardRI in V1 for over 7 or 8 month now... just love the smoothness and low noise that this preamp has..

the power tubes i keep switching between tungsols EL34B's and Mullard EL34's RI both work excellent for my sound...... tried SED's EL34 but didn't work for me (do not get me wrong here, SED's are amzing tubes).

again thanks for the review :wink:
thanks for the kind words. i just tried to say stuff i would've liked to hear sitting on the fence about changing certain tubes. i did also consider mullard el34's, but tubedepot guys were saying that the t-s would give a little bit better breakup and are more meant for guitar than the mullards, though no doubt they also sound awesome.

i guess one other thing to add is that the t-s tubes, at least the el34b's, supposedly are improving their reliability, but they're not quite there yet. i can attest to this because about 2 years ago i built a marshall 100w super lead clone and when i ordered those tubes i had difficulty getting them to stay within bias, even after the tubedepot guys burned them in and specified the bias current. they started as matched and after only a few hours of testing they were a little off. hopefully they've gotten them made better now. of course, the mesa circuit is self-biasing so that helps a lot. either way, tubedepot still accepted the tubes back for returns with (good) replacement at no cost to me, so i guess that's also a plug for them. after all that, though, i'd still get the t-s because of the tone.

and i've used sed 6l6's like i said (apples and oranges, i know), which are a huge improvement over the stock ones, or jj's, etc. so i believe that sed tubes should sound good for other applications and for other people, but i haven't tried them and basically what i was trying to say is these tung-sols are great alternatives! :D
 

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