EL34s - how much earlier do they break up than 6L6s?

csweldon

Member
Messages
899
Hey all,
I've got a combo cab coming for my Fuchs, and I'm thinking that this might be a good time to try the swap from 6L6 to EL34. From what Im reading, the tone before power tube breakup should be more or less the same, with the 34s possibly being a bit more "complex." I also know the character of breakup will differ, with the 6L6 having a harder breakup. The question I have (obviously, it's in the title!) in an amp that can accept both tubes, how much earlier do the EL34s breakup? I've seen, "they break up earlier" to "much earlier." So, if they're both spec'd for Average distortion, and the 6L6s break up at 5, where abouts would the 34s start to grind?

Thanks TGP!
 

hogy

Member
Messages
13,732
They don't. It's the circuit, not the tubes.

Many legendary tube HiFis were based on EL34s and they were all about low distortion. Marantz 8B, Dynaco St70, etc...
 

8len8

Silver Supporting Member
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14,151
I'd just look for an amp that has great tone, not a specific tube type.
 

omfg51

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2,915
You can buy power tubes that are rated to break up earlier. Tubes are rated on a scale of 10, 1 being the earliest breakup, 10 being the latest. 5-7 is typically a mid-range or average tube break up rating, 1-4 is early break up, and 8-10 is late.

In reality, most of your driven tone (if not all of it) will be derived from your preamp, specifically the single tube in pre slot V1. 12AX7/ECC83 tubes are the earliest break up pre tubes. Then there are 12AT7's and finally, 12AU7's at the latest break up for pre tubes.

Having the proper tube in the V1 slot of you preamp will ensure that you get the dirty tone you are looking for.
 
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Custom50

Member
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8,623
Depends how many of 'em, how they test and what circuit they are in. There is no correct answer.
 

csweldon

Member
Messages
899
Thanks guys, appreciate it. Love the amp, and Andy made the bias throw large enough for me to use either. Always love to experiment, though, and was just curious to see what what the 34's would bring to the table; never had an EL34 amp before! Also heard good things about 6ca7s. I've seen a lot of 6L6 vs EL34 threads and they usually say the 34s break up early, but they're probsbly drawing conclusions based on different circuits. Guess I'll plug them in and see what happens; no harm in trying, right :)

Thanks again for the insight.
 

harpinon

Member
Messages
8,975
EL34 is still a big bottle.
The amps with those tubes tend to have cascading preamp sections which really gain up fast.
For the record...I have 13 tube amps and I tend to prefer med to higher wattage amps so I DON'T have to turn the master too high.
Power tube gain can be a bit unruly and flush the tone with excessive low mids.

Don't hate me.
 

csweldon

Member
Messages
899
EL34 is still a big bottle.
The amps with those tubes tend to have cascading preamp sections which really gain up fast.
For the record...I have 13 tube amps and I tend to prefer med to higher wattage amps so I DON'T have to turn the master too high.
Power tube gain can be a bit unruly and flush the tone with excessive low mids.

Don't hate me.
No hate here, man. That's actually something I hadn't thought of; the overdrive already sounds stellar, but probably WOULD lose something if the power tubes started adding to it! Pretty much the only sound I'm missing with my current settings is that edge of breakup clean; it's REALLY loud when I get there!

Still gonna mess with possible power tube flavors, but I think it's more time I get back to experiment with my guitar's volume control, or lowering the amp gain and goosing it with a boost for the higher distortions.

In short, thank you! I wasn't thinking about the overdrive channel and overall amp balance. Now I am :aok
 

big mike

Cathode biased
Platinum Supporting Member
Messages
13,423
Tubes don't break up. It's all about the circuit and how the circuit reacts to the tubes it has been optimized for.

Quick derail..
Remember the 90's when Marshall had to put 5881's in everything because the EL34 supply sucked royal ass?

Guess what....they sounded the same.
 

Stu Blue

Member
Messages
3,167
They don't. It's the circuit, not the tubes.

Many legendary tube HiFis were based on EL34s and they were all about low distortion. Marantz 8B, Dynaco St70, etc...
Exactly. I think people hear that EL34s as true pentodes are more easily driven and imagine a quick conversion (bias) will give them a much hairier amp.

Tubes don't break up. It's all about the circuit and how the circuit reacts to the tubes it has been optimized for.

Quick derail..
Remember the 90's when Marshall had to put 5881's in everything because the EL34 supply sucked royal ass?

Guess what....they sounded the same.
:dude I had a SF Fender Twin with EL34s... sounded/played like a Twin... side by side with a 6L6 one it was a tiny bit smoother... but could you pick it out on a double blind test?..... maybe, maybe not. About the same difference as between 6L6s from different companies maybe.
 

csweldon

Member
Messages
899
@csweldon: Maybe this will be of interest to you: http://www.secondfloortones.no/thd-flexi-50-amplifier-part2/

I test the amp with EL34's and 6L6'es, with and without master volume. I know it's a different amp, but still. Maybe the sound clips will say something?
That was actually very cool; there was a definite difference between the two; the EL34s seemed (to my ears) brighter, the 6L6 duller by comparison. Not sure what my results would be (like you said, different circuits) but the experimentation isn't unwarrented, I'd say. Thanks!


I want to thank all of you for your experience and insight; I knkw enough about amps to get the tones I love, but still have a lot to learn (and UNlearn - thanks a lot, Internet!) about the circuits themselves! Short as this thread is, I found it a good learning experience. You guys are awesome!
 

big mike

Cathode biased
Platinum Supporting Member
Messages
13,423
:dude I had a SF Fender Twin with EL34s... sounded/played like a Twin... side by side with a 6L6 one it was a tiny bit smoother... but could you pick it out on a double blind test?..... maybe, maybe not. About the same difference as between 6L6s from different companies maybe.
Bingo.
As long as the OT's rating is matched to the tube, I doubt it could be picked out. Especially live.

Now the MISMATCH of the ohm load could actually be making a bigger sound difference as you know Stu! IE dude slaps El34's in a JTM45 and doesn't compensate, it's different.
 

teemuk

Member
Messages
3,281
Characteristic curves of a EL34 pentode are slightly different than those of a beam power tetrode 6L6. In practice beam tetrodes have sharper "knees" than pentodes. Other notable differences introduced by these different tube designs are different transconductance figures (which in practice reflect as different requirements for grid drive voltage), different bias point, and different screen current draws (and its effects to harmonic distortion).

Overall we are still talking about rather small differences, which may be entirely nullified by design details such as using negative feedback, different biasing arrangements (e.g. fixed vs. cathode bias), or operating the tubes in some form of distributed loading (e.g. ultra-linear) or (gulp) in triode mode. If overall circuits and their responses are practically the same, and drive levels, plate loads and bias tweaked to match the used power tubes to the circuit they're in then the differences will be extremely subtle.

But if you A/B one amp with EL34 tubes and another, entirely different amp, with 6L6 tubes you will no doubt hear much more differences. Likewise if you just sub one tube with the other without tweaking rest of the circuit to suit the specific requirements of each tube type. But, IMO, the comparison in such cases is not really about differerent tubes per se and is therefore rather moot and no universal conclusions of specific tube characteristics can be drawn from such.

Earlier break up? As equivalent beam power tetrode and pentode tubes generate practically the very same output power the onset of "break up" largely depends on what magnitude you are driving the tubes to begin with. As is, beam power tetrodes generally have somewhat more linear characteristic curves than pentodes resulting in somewhat higher headroom than "equivalent" pentodes are cabable of (we are talking about only few watts though). In practice the result is that beam power tetrode can generate a tad more "clean" output power than an "equivalent" pentode tube but that comes with the cost of clipping onset and distortion becoming more "sudden" and "harder". So, essentially break up characteristics will be slightly different. But a lot of those very same characteristics are also very dependent on the circuit the tube gets fitted in.
 
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