Musicians Roadhouse

I was wondering if anyone here can tell me from a technical point of view, at what point does the type of power tube you have in your amp matter. Let me explain. I know EL34s tend do have more mid-range and 6l6s tend to have more "headroom" and a bigger low end, but In my experience, it only seems to matter at really cranked volumes and not at "bedroom" or moderate play-at-home volumes. Just as an example, there are guys who can nail the early EVH tones with a Marshall but also guys who can nail the tones with 5150s.

The only real way to compare one amp to another is with all the controls set to 10. It is true that certain amps sound really good driven wide open and not so good using only some of the available power. Different power tubes can have a voicing effect that is like anything else with guitar player very subjective.

Guys that can really nail the early VH sound has more to do with the results of hours of practice more then the amp.

it doesn't really matter,it's more a preference thing. the overall tone is more dependent on circuit design & tone stack than the power tubes even though they add to the flavor. I prefer 6550's & 6L6 in Marshalls myself.

another thing- on average it's cheaper to retube an EL34 amp than a 6550 amp.

El34 is a pentode tube. It has a cathode, control grid, screen grid, suppressor grid, and an anode. In most typical amp designs the suppressor grid is tied to ground. The suppressor grid was added to the tetrode to make the electrons stay on the anode and not get wasted as useless dissipation by the screen grid. The suppressor grid's ground reference has the tendency to repel electrons back toward the anode's positive voltage potential.

The 6l6Gc is a beam tetrode. Instead of having a suppressor grid it utilizes a " virtual suppressor" arrangement. It has a cathode, control grid, screen grid, anode, and a beam confining plate which is tied to ground. The electrons flow through the electrical "shadow" of the control and screen grid which organizes them into thin sheets or beams. The beam confining plate focuses the electrons into even patterns aimed at the anode. This arrangement increases the tubes efficiency as more of the electrons go to the anode instead of bouncing off and dissipated by the screen grid. The 6l6GC was the last power tube ever designed and it was specifically designed to improve upon the EL34's inefficiencies.

When driven at low levels there really isn't much of a difference between the two. It is when they are driven hard that the difference becomes obvious. The EL34's reputation for being very crunchy and heavy on the mids is due to this inherent inefficiency. When driven very hard, the EL34's current requirements overwhelm the tubes ability to transfer current, especially in the lower frequencies where current transfer is the highest. This current that is unable to stay at the anode gets bounced back to the screen grid. This results in a roll off of lower frequencies and the impression that the tube is exaggerating the mids which need less current to be amplified.

The 6l6GC will appear to be much more responsive in the lower frequencies because the tubes higher efficiency puts more electrons on the anode and delivers a higher power output.

Either tube will work. It really is a matter of what you want the amp to do when driven hard. The EL34 anomaly is a much sought after tone in Marshall's older designs. It really just depends what you are looking for.

Damm...I did not know that.

Interesting!