6L6 and EL34 Tubes?

[SHRED]

I have a Mesa Boogie, Dual Rectifier, Trem-O-Verb 100W head. All stock. I bought it years ago new.

It came with 6L6's. It has a switch on the back if I were to run EL34's.

Questions:
What is the difference in tone between these types of tubes?

I play a Les Paul and love the Duane Allman type tone.

I have not played it in a while. How can I tell if the tubes are still good?

Thanks

[ProfessorGAC]

1. A Few Questions In There

EL34's are lower powered tubes. As a result, a higher input gain is needed to get to the same volume. As a result, the power tubes are driven a bit harder and they saturate more quickly. This smooths out the rough edges and increases sustain.

I have a Boogie with EL-34's and all my guitar player friends work on their tones to match what i get with the 34's. (The front end certainly has a lot to do with that, too! But, one of my friends also has a 6L6 Boogie and his full gain tone is a little harsher and "barkier" than mine.)

So, that should answer the question about tube tone. It's not a matter of better or worse, just different. A slightly overdriven power tube will always be a touch smoother, a little rounder, and the natural compression of tubes will kick in a little bit more.

On the "Tubes Still Good Question": For power tubes, there are two things you can do. First listen for a great deal of hiss. When power tubes drop off in performance, the dynamic range falls. So, to get any reasonable volume, the noise level has to be pushed up.

If the tubes are really getting bad, they can go microphonic. Just turn the amp up loud. If you can't control feedback and what's there is a high squeal instead of a smooth controlled note, the tubes are toast.

For the preamp tube (probably 12AX7's or 12AT7's), the noise level picks up A LOT when the tubes start to go. In addition, when a preamp tube goes bad the microphonics can get so bad that you should be able to just tap the tube with your fingernail. If that makes the amp make a sound, the tubes are ready to be retired.

Hope that helps.
The Professor

[SHRED]

2. Awesome

You helped make my choice.

I do want a smoother overdrive tone.

I am seriously considering getting some EL34's to replace these 6L6's.

Any place/brand I should try for?
This site has very good tubes I am told:
http://www.eurotubes.com/euro-e.htm

[Gold Metal Flake]

3. I beg to differ.

"EL34's are lower powered tubes."

No, they are not. EL34s will produce more wattage than 6L6 types. EL34s will live longer in conditions with plate voltages above 450VDC than 6L6 types. This is assuming quality tubes like American-made 6L6 and European EL34 tubes. The tubes differ in internal structure and in their operating parameters. Of those, input impedance is one. Takes a little more voltage to drive them to similar levels. If that Mesa is putting out 100 watts at clipping with 6L6 tubes, it will put out from 10 to 20 watts more with the EL34s.

The EL35 is a pentode, where the 6L6 is a beam tetrode. The EL34 likes lower plate loads than 6L6s. The EL34 requires less grid voltage than 6L6s (hence that switch on the back of that Mesa amp. They also require more heater current, so in some amps they will drag down the power trans by loading heavily the filament winding. For this reason they are a no-go in amps like the Deluxe and Princeton and old tweed Fenders and many Gibson and other old amps.

In a typical guitar amp, going from 6L6 to EL34 will give you a bit more clean wattage, and when it does break up it does so a bit more softly. You may notice a softening of the bottom as well. The bottom is usually extended further, it's just softer. In an amp like a black Fender type (pro, twin etc), you may need to replace the phase inverter tube with a 12AX7 to get enough gain, but you sometimes have to do that with 6L6s if you want a lot of drive. Black Fenders don't sound good with EL34s anyway, IMO.

What brand? The better question is: who made it? Many dealers sell the same make of tube but with differ nt labels. Assuming you don't want to sell a kidney to buy an NOS set of Mullards, you may want to try the Slovakian EL34s, like those made by Tesla. Nice and full with a long life, sounds a bit like a Mullard. Those were my favorites. The Russian tubes sold by New Sensor under the name Sovtek are OK, but I find them a bit harsh. The other Russian EL34s by Svetlana are better. The Chinese stuff was never a favorite, and not long lived. So, when you talk to a dealer, ask who made the tubes. Don't pay attention to the name silk-screened on them. Many tube tester companies sell all makes of tubes.

The US manufacturers back in the 1960s produced a beam tetrode replacement for the EL34. The 6CA7 is a more aggressive sound than the EL34, and would be like hot 6L6s. I think that a version of that tube is being made today. Groove Tubes has long been at the forefront of resurrecting production of the great audio tubes.

Dealers of all kinds promise tube matching in order to get you a pair or a quad of tubes with similar operating characteristics. Most do a good job. The MEsa matching system is similar to the Groove Tube system, and was designed by the same engineer. However, it is not as extensive, and the matched groups do not offer as many choices. The systems are both proprietary in function. Others use current draw matching or a curve tracer. Just make sure they have a good replacement warranty in case the tubes flame out early on.

If you like to play with distortion, you will like the EL34s. Don't worry about drive voltages, the Mesa has plenty. The amp has a switch on the back, but that is not enough. It's best to have the amp bias voltage set for that set of tubes by a tech. If he's good, he'll clean your pots at the same time.


EDIT Spelling

[ProfessorGAC]

4. You Are Correct. I Stand Corected

The OP wrote EL34 and i read EL84! My mistake. Everything i said was wrong with regard to the 34's. It's the 84's that are lower powered tubes and work Class A, rather than A/B. (Although there are amps that have paralleled the tubes to run them A/B.)

I had temporary dyslexia or something. Sorry about that to the OP.
The Professor

[Gold Metal Flake]

5. We stand together in Tuberhood!

I love EL84s. Four in fixed-bias A/B, ooh baby. Or cathode-biased like the Vox. The early post-Dave Reeves era Hiwatts from Sterling with EL84s, like the Lead 20 and Lead 30, were screamers. You gotta rework the PC boards, but the transformers are killer.

[ProfessorGAC]

6. Back On The Same Page

I love the 84's in my Boogie. It's the smoothest FULL saturation distortion i've ever heard. Sustain galore and almost zero rough edges on any note on the fretboard. When i'm king, this will be the amp standard!
The Professor