Tubes & Sound (12AX7 vs EL84 vs 6L6)

[nast2112]

Can someone briefly explain in a nutshell the sound difference you obtain with using different amps with these types of tube setups? IE, why would you buy one vs the other? Seems like Marshalls have the 12AX7s, Peaveys have the EL84s, Fenders 6L6s?

Thanks
Chris

[HipCat5]

First off, the 12AX7 tube is a preamp tube and its pretty much a standard in all tube amps. The preamp tube takes the incoming guitar signal and amplifies it & distorts it if desired and feeds it into the power amp section. The EL84, EL34, or 6L6 tubes are power tubes and they are different in many ways. It is true that each power tube type has its own tone color but a lot of that depends on how the tube is driven, what circuit topology its in, what plate voltage it has applied, and what the bias voltage is set to for that given plate voltage.

EL84 tubes are common in the Marshall 18 watt amps and in VOX amp designs. EL34 is a common Marshall power tube for those who want a British crunch and 6L6 tubes are in some Marshall & common in Peavey & Fender amps (for example, the Peavey 5150 runs 6L6GC tubes). You may even find some esoteric amps using 6V6 tubes (another 18 watt favorite).

If you're going to buy an amp and you're wondering about what tube type to consider, I'd suggest that you start with your ears and not with what tubes are under the hood. Also, remember that tone color is relative to each individual player. Therefore, a Peavey 5150 might sound good to one player and another might hate it. A Marshall JCM800 head might sound great to one player and another might like a modded version of the JCM800 only. It's all relative.

Keep in mind also that circuit topology makes a huge difference. Pure tube distortion sounds different than a tube amp with rectifier diodes clipping the amp to distortion (yes, some tube amps use diode clipping). Some people like diode clipping; some don't.

Most new tube amp owners want hundred watt (+) amps because they have the impression that wattage is equal to tone or power. In the tube amp world, its not necessarily true. There are a lot of 18 watt designs that will rival a 100 watt solid state amp for total output volume and they have great tone. In addition, Even the difference between a two tube "push-pull" 6L6 power section in a combo and a four tube "push-pull" 6L6 tube power section will only be the difference of a few dB in the extreme and unless you're playing arenas, you won't need that kind of power. Seek out amps based on TONE and what your ear likes to hear at LOW and HIGH SPLs.

For example, I built an 18 watt 6v6 push-pull design Marshall "JCM800-esque" clone and for total output volume, it easily drowns a club with the master vol. on "6". With all controls dimed out (10), it roars with a Marshall-esque flavor that is spiced up due to the 6v6 tubes (very unique tone). The beauty is that even with the master on "1" and at low SPLs, the topology of the circuit flavors the tone quite nicely.

FWIW, good luck on your quest.

[Prages]

I agree with everything above.

I'll also add that in my experience, EL84s tend to 'break up' or distort sooner than EL34s, and 6l6s stay cleaner longer than even EL34s. Of course, that too depends on the circuitry of the amp. There are also KT66, KT88 and several other less commonly used power tubes that change the flavor of the amp somewhat.

Also, when it comes to preamp tubes, while 12AX7s are the most common, there are also 12AU7 and 12AT7 tubes which will cause a pretty dramatic change in the amount of gain the amp has.

With the high power tubes amps (50 watts +), you're really getting most of your distortion from the preamp, so preamp tubes will make a much more dramatic difference in the tone of the amp than power tubes will. When you get down into lower wattage amps, you're more likely to push them hard enough to get the power tubes to distort. Even then, the preamp tubes still define a lot of the tone of the amp.

It's also good to note that with most amps, you can't just 'plug and play' different kinds of power tubes. Many amps even require some bias adjustment when switching between power tubes of the same type. With preamp tubes, you can generally swap between 12AX7, 12AU7 and 12AT7 without any kind of mods or adjustments.

[nast2112]

Wow. Thanks for all the info. I appreciate it.

Let me put it this way: I'm looking for something suitable for a Strat that would be good for that loose sounding blues and rock similar to say... Tom Petty. Maybe even good with a Tele for country-ish licks for kicks. Not really Marshall crunch. Also, I play here at home 99% of the time so I'm thinking 30 watts? It needs to break up at a lower volume, but maybe loud enough for a small gig if I sat in. I know I've asked about the Peavey Classic 30 amp in prior posts. They are EL84s I believe. I'm wondering if anyone thinks I would not be happy in the long run with this amp for the type of sound I'm kind of driving at as mentioned above. Or maybe there is something similar and better suited for the sound I'm talking about.

Thanks again
Chris

[Prages]

Wow. Thanks for all the info. I appreciate it.

Let me put it this way: I'm looking for something suitable for a Strat that would be good for that loose sounding blues and rock similar to say... Tom Petty. Maybe even good with a Tele for country-ish licks for kicks. Not really Marshall crunch. Also, I play here at home 99% of the time so I'm thinking 30 watts? It needs to break up at a lower volume, but maybe loud enough for a small gig if I sat in. I know I've asked about the Peavey Classic 30 amp in prior posts. They are EL84s I believe. I'm wondering if anyone thinks I would not be happy in the long run with this amp for the type of sound I'm kind of driving at as mentioned above. Or maybe there is something similar and better suited for the sound I'm talking about.

Thanks again
Chris

The Classic 30 is a great little amp. I have one, as well as a Classic 50 and a 1984 Marshall JCM 800 2203 1/2 stack. The Classic 30 gets the lion's share of my playing time. I think it would be perfect for what you're looking for. I use mine at home for practice, to record, and I gig with it too. With a speaker upgrade, the amp REALLY screams. I put a Celestion G12H30 in mine and couldn't be happier with the results.

It'll do the bluesy thing, it'll do the country thing, and if you crank the gain, it'll get you into classic rock territory and beyond. It's actually got quite a bit more gain on tap than the Marshall JCM800.

I've got a bunch of songs recorded that I used the Classic 30 on if you'd like to hear some. I tend to use the dirty channel a lot more than the clean, but I've got a few things with clean guitar parts in them.

[kevlar3000]

Here is a clip I did recently comparing 6l6 and EL34. I have both these heads, which are quite similiar to a JCM 800. On both amps, I tweaked them slightly, useing the JCM 800 warming mod, which is a google away. Simply involves a lil resistor and cap change on the input jacks. Takes the upper mid harshness away, which I think improves that amps greatly. The clips were done with a Squier Tele. An early 70s Traynor 2/12 cab, loaded with a CTS Alnico, Mic'd 7 feet back. Both amps have the master dimed and the pre right around 5. I used a Weber Mass Attenuator, set to the same volume for both clips. The
6l6 PV, is a little tighter with breakup, does not have that loose EL34 thang.. Bigger and tighter bass. The Laney is slightly looser, more round on the bass and has a bit more 'jangle' to it. I don't really like one better than the other, as they both sound real good to. They are quite close tonally....Esp when you are in the same room with them. I am a bit of an amp addict and have 18, most from the mid 60s to the early 70s. I have EL34, EL84, 6l6, 6550, 7591 powered amps. Love em all, each has a different flavor.


1986 PV VTM 120 6l6
hi-fi URL: http://www.soundclick.com/util/getpl...d=5055543&q=hi



1985 LANEY AOR 100 EL34


hi-fi URL: http://www.soundclick.com/util/getpl...d=5210690&q=hi