6v6 vs EL84 vs EL34

[guitarmike2107]

I have seen it said a number of times on this forum and others that the 6v6 is closer to an EL34 type sound compared to an EL84 vs EL34.

Is this “nonsense” started on a forum somewhere by some guru and now people are quoting it without giving it a second thought?

If you look at the datasheets, the general shapes of the grid curves for the EL84 and EL34 are more similar compared to the EL34 vs 6V6

The 6v6 has the diode line below 30v, similar to the 6L6 which also has the diode line below ~50v

The JJ 6v6 data sheet is misleading, the curves don’t look like a normal 6v6 set of curves, To me they look like the triode set of curves, since no screen voltage is quoted.

I have linked to some datatsheets for ease of reference

http://www.r-type.org/pdfs/6v6gt.pdf
http://www.drtube.com/datasheets/el84-jj2003.pdf
http://www.drtube.com/datasheets/el34-jj2003.pdf
http://www.drtube.com/datasheets/6l6gc-jj2003.pdf

[Steve Conner]

I agree, I've always thought the 6V6 sounds like a mini 6L6 and the EL84 like a mini EL34. Beam tetrodes and pentodes make different harmonics.

6V6s can get seriously dirty, but they don't have the aggressive, almost transistor-fuzz-like distortion of an EL84. The EL84 also produces huge quantities of intermodulation which is responsible for the famous Vox "chime". The EL34 gives a bigger, cleaner sound, but it still has that edge of pentode nastiness that the beam tubes lack.

All of this is strictly IMO of course

[pdf64]

I've noticed that when overdriven, a 5E3 can sound reminiscant of a Marshall, but to draw a generalisation from wouldn't be reliable, eg with a higher plate voltage and fixed bias 6V6 sound different. But even then it's a limited comparison, eg a 5E3 can'tdo that midrangey compression that EL34s do when heavily overdriven. Pete.

[km6xz]

I've found that modern tubes have meaningless curves in their literature. Wednesday I will have my curve tracer here with me so I am going to start testing a lot of the re-branded tubes to see what they really are.
I agree, the 6V6 has a lot in common in harmonic generation with the 6L6 from the beginning, when the first metal 6l6's were released and 6v6's of the period but all bets are off when dealing with new tubes, we really do not get much information useful for engineering and after talking to people from a couple of the current brands, I strongly suspect they have no clue what their tubes spec as either.

[guitarmike2107]

Well the point I was making is that if the curves are similar then they should be harmonically closer. If your saying the curves are pile of pish well then anything goes.

You will likely still find the beam tetrodes have curves with the “diode line”, and if so the similar harmonic content comment still stands.

I have several amps here with 6v6's, el34's and El84's, they all sound different depending largely on the pre amp topology, but I dont see how anyone can claim the 6v6 are closer to the EL34 when compared to the EL84...

[Robert M. Martinelli]

Well the point I was making is that if the curves are similar then they should be harmonically closer.

Hmmm.....Maybe I'm wrong, but the curves are drawn using DC values, so, IMHO, they can give you an idea about a certain tube's linearity, (and, if the curve spacing isn't even you'll know there will be some asymmetry in the output waveform that will promote even harmonics), but they can't tell you what the EXACT harmonic content will be like....

There also are some differences with the inter-electrode capacitance(s), and that, too, has to be taken into account....

Back to the "original" question, I agree with Steve, sonically, I've always considered 6V6s as "small 6L6s" and EL84s as "small EL34s" (even though easier to overdrive and with a better top end IMHO). Also remember that AFAIK, beam tetrodes have been developed to overcome some "drawbacks" pentodes used to have, so no wonder they sound different...

JM2CW

Best regards

Bob

[guitarmike2107]

Ok so basically all your thinking agrees with what I am thinking.

I think my internet “Guru” spouting off nonsense idea been repeated by many afterwards makes the most sense.

obviously I wasn't trying to say your harmonic contect would be exactly the same, there are allot of other things that will affect that in a power amp anyway

[jpfamps]

My guess is that any comparison between EL34s and 6V6s has originated from a famous design that could employ either (Trainwreck Express).

Essentially an amp can be designed with low enough voltages to accommodate either as they have very similar bias voltage requirements.

A key feature of beam tetrodes is that the control and screen grids are wound concentrically so that the screen grid is in the "shadow" of the control grid. This reduces screen current, and thus distortion.

Thus, in my opinion, pentodes tend to have a different sound to beam tetrodes.

The JJ 6V6 curves are triode curves.

[jpfamps]

Also remember that AFAIK, beam tetrodes have been developed to overcome some "drawbacks" pentodes used to have, so no wonder they sound different...

JM2CW

Best regards

Bob

My understanding is that the beam tetrode was developed to get around the pentode patent held by Phillips.

[jrfrond]

I agree, I've always thought the 6V6 sounds like a mini 6L6 and the EL84 like a mini EL34. Beam tetrodes and pentodes make different harmonics.

6V6s can get seriously dirty, but they don't have the aggressive, almost transistor-fuzz-like distortion of an EL84. The EL84 also produces huge quantities of intermodulation which is responsible for the famous Vox "chime". The EL34 gives a bigger, cleaner sound, but it still has that edge of pentode nastiness that the beam tubes lack.

All of this is strictly IMO of course

I agree 100%.

[Chuck H]

There's another consideration that hasn't been addressed. A lot of builders like to change the power tube type only and wish to leave the rest of a circuit basically unchanged. In this scenario I would say that without regard to the actual nuances and harmonic content, but rather just 'amount of clipping', that you would almost certainly get more similar clipping levels subbing 6V6's for an EL34 design than you would subbing EL84's for an EL34 design. I think this may be where the similarity opinions started... It's also where it ends. As far as the sound goes I think they are all very different tubes and anyone who has heard each type in amps that generate predominantly power tube clipping will likely agree. When running clean the tonal differences hardly matter as much (with a nod to Steve's mention of charateristics specific to EL84's).

[Steve Conner]

That is a good point. The sonic characteristics that we all agree on are heard when you put the tubes in the amp that made them famous. So, 6V6s in a Deluxe, EL84s in a Vox AC30, EL34s in a Marshall, 6L6s in a Twin. Each power tube type has a specific level of HT voltage, drive, impedance, NFB, preamp EQ, and so on that brings out its stereotypical qualities.

It isn't clear how much of the sonic signature is a function of the tube, and how much is a function of the supporting circuitry, except I think the answer is "The tube matters somewhat less, and the circuit more, than the Internet would have you believe".

And then, it isn't clear how much of the tube's contribution comes from its harmonic generation, as opposed to its linear parameters such as gm. When the tube is used with NFB, the effects of the non-linear parameters get hopelessly mixed up with the linear ones as far as analysis is concerned, except that any differences you hear at low volume are mostly from the linear ones, because power tubes generate very little harmonics at living room volume.

The most interesting example being: The two most famous EL84 amps, the AC30 and the 18 watt Marshall, both had no NFB. So maybe the gritty, chiming sound of EL84s is really the sound of a lack of NFB.

Having said that, the 5E3 didn't have any either. I propose a blind test where we get Neil Young to play an AC30.

[Chuck H]

I think supporting circuitry is a big part of making the best of a tubes qualities (or the least of a tubes drawbacks). But those qualities (or drawbacks) are there regardless. I'll stand by my statement that they're all very different sounding tubes when overdriven. I've built amps with all four types and in many cases similar amps with the exception that I usually adjust Vp, PI output and NFB. Not to make the tubes sound like like they do in their signature circuits but just because hitting an EL84 with typical big bottle grid drive just doesn't work.

I do agree though to all the points you make and I think your assesment defined here is one of the more considered generalizations on the forces at work. Example... My current baby is an EL84 circuit. Originally I didn't want the huge brash effect of the vintage "presence" control. So I targeted a higher frequency so the control would be less brash and a little sweeter sounding. It was, sweeter wasn't better though so I eventually did open up the frequency to a more typical range AND even the clean tones sound best with the control set to at least 1/3. It usually sits between 1/2 and 3/4. So it seems that reducing NFB definitely is a part of the EL84 mojo. This from a guy who typically runs plexi type amps with the presence under 4 always. But with the EL84's less NFB just sounds "right". So good call on that.

Having said that, the 5E3 didn't have any either. I propose a blind test where we get Neil Young to play an AC30.

I actually know Neil. I mean, I've met him on several occasions. I used to sell him paint for his ranch house near Santa Cruz, Ca. when I was younger. The guy I worked with (Larry) was a huge fan so I let him make the deliveries. After awhile I swear that Neil would place orders for stuff he didn't even need just to get Larry over. I knew when I would send Larry over there that he was gone for the rest of the day. They would get baked and Neil would play studio demos for his critique. Both Neil and Larry have thanked me for instigating the relationship. I've played with Neil at house parties in that area where he just stopped in because he heard music and figured he would know a couple of people inside. He seemed to really enjoy just being a regular guy. So, it's not like I call him up to ask about personal affairs or anything, and he may not even remember me by name after some 20+ years, but I may know a few guys who can still get me in and if I mention Larry I might even talk Neil into playing through an AC30

[Robert M. Martinelli]

My understanding is that the beam tetrode was developed to get around the pentode patent held by Phillips.

You're right, I stand corrected.

(I should have said AFAICR, not AFAIK, it would have been more correct, since my memory is deserting me....)

[guitarmike2107]

Yes that is a good point in terms of drive required per valve set, but you can't drop a EL84 into a 6v6/EL34 amp anyway, So if you are building an EL84 amp then the PI would presumably be adjusted for that amp.

I have amps will those four valves fitted too, I am willing to bet the Neil Young could tell the difference between EL84’s and 6v6’v… even I can!