# Tube upgrade: KT77 or E34L?



## thadood (Aug 1, 2007)

I've been browsing through eurotubes.com, reading what he has to say on the tonal characteristics of different tubes, and I must say, these two appeal the most to me. Aggressive, punchy, and with tons of depth and harmonic composition. The only problem is that I don't know which to get or if my amp is capable of running either tube.

I have a Genz Benz El Diablo, which is currently tubed with GT 6L6GC's. My El Diablo is one of the first.. it lacks the bias testing pots, which makes testing a bit tough.. last time I got it tubed (over a year ago.. and hence why I'm looking to get new tubes =p), it was by a professional.

My question is, which tubes would you go for, and since my amp lacks the bias testing pots, would a bias probe (sold on eurotubes) be a worth-while purchase?


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## cow 7 sig (Aug 1, 2007)

i dont know anything about the amp you have but i can say KT77 FTW


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## thadood (Aug 1, 2007)

I just did a bit more researching.. and I'm sold on KT77's..

plus, check this out:





KT77's in a Diablo.. it looks hot!


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## cow 7 sig (Aug 1, 2007)

and they sound hot too trust me


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## budda (Aug 1, 2007)

if your tubes are only a year old, chances are they dont need replacing yet, throwing that out there..

buy a tung sol 12AX7 for V1 first and see if you're stll hell bent on a retube lol


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## thadood (Aug 1, 2007)

My amp has become increasingly grainy. My tubes already run pretty damn hot, so their life expectancy isn't the longest, as is. I've found the highs becoming more and more annoying.. I've pretty much turned down the high end to around -10db, and I never run with the attack engaged. The amp has also become slightly more noisy and feeds back more than it used to.

I already replaced V1 pre when I retubed the power's, as well. I don't know what pre it was exactly, but it was a step up from the stock. I want to replace all three preamps, as well. I'm thinking of the JJ ECC803S's, with V1 being a balanced 803S.


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## jlagoon (Aug 2, 2007)

I have a TriAxis that runs with VHT2502.

I actually compared KT77 and EL34L, and like the EL34L better overall. The KT77, at least with my setup, is not aggressive enough with distortion, and is not chimey enough with clean sound.

Analogically, I think KT77 is like a Blaze pickup in which the high frequencies are not piercing, the mid is slightly scooped, and the bass response can give you more thump. The EL34L is a bit like Blaze Custom in which the mid is more in your face, and the bass is not as metal-thumpy-chug-chug.


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## Toshiro (Aug 2, 2007)

I can only compare the KT77s to 6L6s in my amp. I didn't get to really hear the EL34s in it, and haven't tried the E34Ls.

The KT77's, compared to 6L6s, have smoother highs, more mids(sorta "grindy"), and tight bass at about the same level.

I love them, they work perfectly for what I want.


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## Drew (Aug 2, 2007)

Actualyl, about a year of heavy use is about right for poweramp tubes. If you're playing more than 3 times a week and running your tubes hot, you could concievably replace them even more frequently than that. 

I've never played a diablo, so I can't speak for sure. However, if you've got the cash to spare, can the Diablo be run on two power tubes at half power? If so, buy two of each. Plug 'em in, and spend a few weeks dialing tones, going back and forth between the E34L's and KT77's, until you find one that you prefer overall. Then, hold onto the other for recording - you might prefer the KT77's, say, for all-around playing, but if the E43L's have the edge in one or two applications, then when you're laying tracks just swap to two E34L's for that particular part. 

I've decided that overall I prefer 6L6's in my Recto, but I'll definitely be buying a fresh set of E34L's at some point just for different tones while recording.


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## kmanick (Aug 2, 2007)

I've gone thru El34's , KT77's and 6L6's in my JSX and I've always gone back to the El34's.
at lower volumes they sound the best out of the 3 and they give me the most "chimey" tone out of all 3.
If I was gigging I would go with the KT77's, they are like a nice
blend of El34's and 6L6's and at cranked levels they sound fuller than the El34's.
It's cool to be able to go back and forth (I have a bias probe)
between the diffeent tube types to see how they sound.


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## thadood (Aug 2, 2007)

Yeah, it sounds like the KT77's are for me. I like the more complex mid characteristics of the EL34's, but they just don't have enough balls. I'm going to buy one of the bias probes from eurotubes.com when I put my order in.. it'll make it much easier for me to do it on my own. I watched his "Generic bias" video, and now I understand exactly what I have to do, which makes the whole process so much easier.


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## budda (Aug 2, 2007)

are you sure its the tubes that dont have enough balls, and not the ED? oooh the pun haha


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## thadood (Aug 2, 2007)

The amp had tons of balls when it was first retubed, haha. It's just gone a bit downhill with the ballsness over the 1.5 years since that retubing.


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## thadood (Aug 10, 2007)

Update: I ordered my tubes.

4x JJ KT77 Power tubes
1x JJ ECC83S
1x Shuguang 12AX7C 9th generation
1x Tung Sol 12AX7 balanced for V1

My other guitarist also ordered some new tubes for his 6505+:
4x JJ 6L6GC
5x JJ ECC83S
1x JJ ECC83S balanced for V1

We shall have fun! I'm also ordering a bias probe and plate voltage probe from SRS.


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## Toshiro (Aug 11, 2007)

Um, just for the sake of asking, why did you order balanced tubes for V1? The only spot I've ever seen them used is in the phase inverter slot, which is last.


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## thadood (Aug 11, 2007)

Yeah, I've just been school on that on another forum =)
So, I = wrong!


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## ohio_eric (Aug 12, 2007)

Let us know how it turns out for you. A while back there was a lot of buzz on here about kt77s. I'm interested in how it works out for you.


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## thadood (Aug 16, 2007)

Update:

I got the tubes in. The bias and plate voltage probes helped tremendously! I tested them out on the old tubes to see where the bias was set. They were at about 43-47mA, which is a bit hot. My amp should have the bias set to about 37mA given my plate voltage of 469.

Here comes the fun!
I put the KT77's in, set the tube type to EL34, and set the bias cold (near minimum). I let the amp warm up, and flicked the standby to on. The tubes were running 45 outside and 48mA inside! I turned the bias pot down as far as it could go, and now it runs at 40 and 43mA, respectively. It's a little hot, but not as bad as the 6L6's were running at previously, so they should live about the same lifetime. 

I realized what the 3mA between the two sets is:
When I got my amp retubed and biased at a local amp shop, the incompetant employee who was trying to do the bias was doing something wrong and blew the resistors for the inside tube set. They didn't have the correct ohm replacements for it, so they took 4 resistors that added up to the proper values, twisted their ends together, and soldered them in. I'm pretty sure their error values would cause a fluctuation in the proper current.

The amp has a pretty kick ass tone to it now! I accidently dropped my JJ ECC83S when I was unwrapping it, so I'm a bit pissed. Instead of keeping the no-name tube in V2, I took the input stage's tube (which the name escapes me right now), and moved it over. The sound is very punchy with my 2x12 cabinet. The grainy, nasty sound my amp was starting to produce is now gone, but now there's a slight fizz sound to the high end. There's also a "clanking" sound when my amp has both high gain and compression engaged with a lot of gain. It's noticeable when playing a note and then quickly killing the volume on the guitar. I'm going to continue playing around with it, maybe order another Tung-Sol for V1 and move the Penta tube over to V2.


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## Jerich (Aug 16, 2007)

I would love to be the one who tells you ..you did this right and that wrong but i am not..since it is your time/money and you are giving a great try good job when you mess up ,you are to blame.I have reccomended kt77's to a lot of peeps and noby is ever happy with the overall tone. The el 34's are more difined overall. but you do know High Bias'ing the tubes will give you more overall everything it just excells the longevity of the tubes life...and please man ground yourself out when messing with amps....
Penta tubes are no where as good of quality as Tung-sols. But electro-harmonix 12ax7eh's are some of the most consistant and even based tubes. with low carthode inductance as well. good luck..


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## thadood (Aug 16, 2007)

I tried one of the EH's I pulled out of my other guitarist's 6505+. I didn't dig it too much. I think I'm going to order another Tungsol for V1. If I had to describe the tone that I'm getting right now, I'd have to say "depth." I can hear a lot of detail and clarity.

I tried the amp just after replacing the power tubes (and before replacing preamp tubes), and the KT77's cleared up that grainy, nasally characteristic my amp was building with the old GT 6L6's. The preamp tubes gave me an overall warmer, deeper, more saturated tone, which was what I was going for!


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