EL34/EL84 versus 6V6/6L6

[PRNDL]

I'm interested in the tone differences between EL34/EL84 and 6V6/6L6 output tubes.

Here's what I know so far. There are a lot of generalizations.

Amps:
6L6 - Fender Deluxe Reverb
6V6 - Fender Princeton Reverb
EL34 - Marshall 50-watt - JMP, JCM, etc
EL84 - Marshall 18-watt

EL34/EL84 are found in Marshall amps, which are well known for distortion.
6V6/6L6 are found in Fender amps, which are well known for cleans and blues.

EL84 is a 9-pin tube that gets VERY hot with normal use. It seems to take a fair beating, but people like it for its tone.

6V6/6L6 seem to be more rugged (in general) than the EL84.

6V6/6L6 originally were designed for HiFi use; whereas the EL34/EL84 were designed for general purpose use.

In general, Fender amps get incredible cleans and mild blues distortion; and Marshall amps get fantastic distortion, but it's hard to get fantastic cleans.

[octal]

I honestly think that the amplifier's topology (preamp, kind of PI circuit, amount of NFB) has more to do with the sound than the output tubes. It's definitely possible to build an extremely clean EL34 amp, for example.

EL84s are often used in non NFB circuits (the AC-30 and Marshall 18W for example) and thus tend to get dirty quickly. Plus, they are the lowest power output tubes of the list you gave.

[Chuck H]

Originally Posted by PRNDL

Here's what I know so far. There are a lot of generalizations.

Amps:
6L6 - Fender Deluxe Reverb
6V6 - Fender Princeton Reverb
EL34 - Marshall 50-watt - JMP, JCM, etc
EL84 - Marshall 18-watt

The Deluxe Reverb uses 6V6 power tubes. 6L6's were used in many Fender amps though. Probably the closest circuit for your comparison would be the Super Reverb.

Originally Posted by PRNDL

EL34/EL84 are found in Marshall amps, which are well known for distortion.
6V6/6L6 are found in Fender amps, which are well known for cleans and blues.

There are many amps that contradict this generalization. All tube types do sound different. But it is eminently possible to make dirty amps with 6V6's and 6L6's or clean amps with EL84's or EL34's and many builders do it. Probably a bigger reason for the 6 type vs. EL type reputations are the tubes Mu factors. It is easier to drive the EL type tubes into distortion so that's what those amps got used for. And the stereotype continues to represent itself in contemporary design because those are the respective roles people are familiar hearing each tube type fill. I for one think that 6V6's when overdriven sound more "Plexi" than EL84's which have a different distortion character. The popular misconceptions that a 6V6 is just a mini 6L6 or that the EL84 is a mini EL34 simply aren't true. They are all very different tubes and sound different.

Originally Posted by PRNDL

EL84 is a 9-pin tube that gets VERY hot with normal use. It seems to take a fair beating, but people like it for its tone.

6V6/6L6 seem to be more rugged (in general) than the EL84.

This is also a bit of a misnomer. If you run EL84's at their intended voltages they hold up very well. The EL84 is probably the most poorly treated tube in the guitar amp world. I mistreat them all the time with the understanding that by doing so there are other things I have to sacrifice like longer tube life. The other thing to consider is class of operation. The reason it seems that EL84's run hot is that they are typically (but certainly not always) used in class A. This runs the tubes much hotter than class AB1 which is the biasing method for most 6V6 amps.

Originally Posted by PRNDL

6V6/6L6 originally were designed for HiFi use; whereas the EL34/EL84 were designed for general purpose use.

I don't know this to be true. In fact I think the 6V6 was originally designed for low "B" supply current draw applications for car radios. The 6L6 is a "refined" tube being a "Beam" tube. But in the hayday of hi fi EL34's were used effectively in many designs. And I don't know that the EL34 was considered a "general purpose" tube. The EL84 was designed to be driven by a lower input voltage to help reduce amplification stages and therefore distortion and was used in many hi fi applications. It's also worth noting that this sort of distinction really doesn't apply to guitar amps anyway since any guitar amps "clean" sound is very likely to be over 5% THD.

Originally Posted by PRNDL

In general, Fender amps get incredible cleans and mild blues distortion; and Marshall amps get fantastic distortion, but it's hard to get fantastic cleans.

As was stated by another post. This has alot more to do with circuit design than tubes. If you build a Fender amp with EL34's and take the tubes Mu factor into acount for the design it will certainly sound more Fendery than Marshally.

I'm not just trying to be contrary. It's important to look at the big picture as see the forest for the trees. I think alot of these tube reputations have more to do with how and who used different amps more so than the tubes that were used. These reputations should apply to Fender and Marshall (and they do) and not 6 type and EL type tubes. Much of it just had to with which side of the pond you were on. And because our ears became familiar with certain tube characteristics for certain applications we continue to perpetuate the trends in current designs.

Chuck

[pdf64]

It's difficult to do direct comparisons. One of those projects I keep meaning to get around to is a single ended thing with octal and noval output sockets. Until then, my impression is that generally, 6V6s and EL34s tend to put out more top end when overdriven, with 6L6s and EL84s being a bit smoother. Along the same lines as Chuck's findings.
But like octal says, so much is in the circuit. And then there's different brands of the same tube, each with their own tone characteristics - Peter.

[mooreamps]

Originally Posted by Chuck H

I don't know this to be true. In fact I think the 6V6 was originally designed for low "B" supply current draw applications for car radios.



Chuck

The 6V6 was originally intended for mobile radio use, hense it's low filament current requirement. It was later on they were used as fly-back amplifiers for TV sets. They are much more rugged then what some of these data sheets suggest.


-g

[Chuck H]

Well, you'll notice I was careful and only said it was a fact that I thought 6V6's were designed for car radios

I wasn't too far off though. My version was probably the bastard step child of what I actually heard long ago.

That's good info. Thanks Gary.

Chuck

[BackwardsBoB]

I loves me some 6V6s. Speaking class AB, there's a bite to EL34s and EL84s that's hard to cut for a smooth jazz tone, though it can be very helpful on a crowded stage. I really like the clean of a Deluxe.

With a bias adjustment, you can run late-model and some NOS 6V6s in EL34 or 6L6 sockets (big screen resistors are a good idea), but the transformer impedance will be too low, and the low gain of the 6V6s cuts the NFB loop gain about in half, so you get smooth at low volume, but the bass turns mushy and the 6V6s go nuts when you turn things up. On the other hand, if you replace each of the larger guns with two 6V6s (heater current's still OK), things tighten up, loading and feedback are respected (approximately), and you get warm at decent volume. This is a great mod for my beloved old Carvin XT-112s, turning an attempted Boogie killer into a 35W-40W Super Deluxe.

If doubling the sockets won't work for you, swap in the 6V6s 1 for 1, double the OT impedance tap you use for feedback to increase the feedback loop gain, and halve the OT impedance tap you use for the speaker to increase the apparent plate load impedance at the tubes.

[mooreamps]

No worries. But, it a good thread for builders and designers to help them select the proper tube, for it's intended use. Clearly, it would be difficult for one amp, to be all things, to all players . . . .

-g