6L6 versus EL34 compromise

[Feloniuspunk]

The specs on my Rivera Jazz Suprema 55 amp call for 5/12AX7 preamp tubes and 2/EL34 power tubes. The amp is pretty versatile and allows me to dial in pretty good sounds no matter what I plug into it.

However the sweet spots for my Telecaster and Stratocaster are different than for my Les Paul and PRS archtop; no big surprise there, always having assumed it to be the inherent sonic differences between single coil and Humbucker pickups.

My question is whether anyone has any experience using 6CA7 power tubes? I’ve read they’re supposed to be a happy medium between 6L6’s and EL34’s. I’d like to hear your feedback before springing for a pair of 6CA7’s.

I’m not trying to change the amp into something it was never intended to be but was thinking the power tube substitution might enhance the tonal depth for both type of pups. My fear is that instead of enhancing the sound it might do the opposite and rob some of the clarity and bite to all my guitars.

[skiboyny]

I put them in a friends Marshall that uses it for base. Played that amp for a week before i returned it to him sounded great for jazz. Closer to a 6l6 sound I would say. They would be a good choice.

[Hammertone]

Easy enough to call Rivera and ask - IME, they have been approachable about questions like this.

[yebdox]

Interestingly, I just had an amp shootout with a buddy, after picking up my Rivera Thirty-Twelve (30 watt version of the Fifty-Five) from a cap job. I had purchased it a couple years back on his recommendation, but it went south with a bad cap shortly after. I finally had it repaired, (plenty of other amps to play in my stash) but didn't notice that it came with 6L6s, and the local amp guru left those in, adjusted the bias, did a cap job and gave it back. My friend's identical amp still has the EL34s, and I was dismayed to find mine did not, as they originally came that way.

Anyway, we did a shootout between the 2 amps, his with a Celestion Gold, mine with a WGS Hempcone (? Whatever the model is).... Final vote for both of us was the 6L6s with the Celestion Gold.... Very versatile amp in that configuration, great cleans, almost Princeton like with that setup. (Great, now I need to spend another $300 to tweak an amp I don't really need to focus on!)

Anyway, FWIW.

[ombudsman]

It would be good to narrow down what you'd like to change to something very specific. There are many types of 6L6GC and EL34 and a few 6CA7. Each type has some broad general characteristics, and then each brand will have variations including the way they were made in different period of time, and individual tubes/pairs/quads will have their own optimal bias points.

The bias and plate current have a relationship to the overall headroom and where and how the onset of distortion (whether subtle or obvious) begins, and the amp design has a lot to do with it also. Those things aren't always easily changed, but the bias can generally be adjusted one way or another, by a knob, a small part swap, or a different tube set. It's possible that with some help from a tech you might get you what you are looking for with the existing tubes, or another set of EL34s.

The sweet spot that you're looking for with Fender pickups vs the others is a function of output and the frequency response of each pickup (but not really whether it is single or double coil as such). That is going to require some adjustment when you change guitars/pickup type no matter what power tubes you are using. One thing that you might try to simplify things is to use a pedal that has an easy to use output and eq control to allow you to quickly make that adjustment, especially if your amp control panel is complex or hard to see on a dark stage. I use a Diamond compressor for this, which has a single knob tilt EQ and an output control with a wide range.

Personally I feel there is a lot more variety of high quality EL34s available than 6L6GC, in either current production or relatively affordable NOS, so I would stick with that type even if I was looking for an exclusively clean amp (which EL34 can certainly do).

[orri]

However the sweet spots for my Telecaster and Stratocaster are different than for my Les Paul and PRS archtop;

Where are the sweet spots differenent? different settings on the knobs or have you tried both with EL34 and 6L6 and found you like one better for single coils and the other for humbuckers?


Sometimes you can make adaptions in the circuit to make it more versatile. For instance many (me included) change a coupling cap value in their tweed deluxes to make them better with humbuckers (IMHO without sacrificing how good they are for single coils)

I (and others) also feel single coil guitars can benefit greatly from a booster pedal with some amps.

With amps that have high and low impedance inputs to each channel, players can find that they prefer a ceritain input for certain guitars (while others just stick with the same input).

If you think you'll enjoy swapping output tubes (usually requires modding) you can of course give try it a try (you need to at least rebias and perhaps more mods) but I would guess it is better suited as a exploration / enjoying the journey / learning experience rather than as a solution to problem or instant upgrade.

[Greywolf]

I recently swapped out my 6l6's for Gold Lion KT77's after hearing many great reviews . They provide a cleaner , higher headroom tone. I've used 5881's over the years as well. As long as the bias is set right , they are the best I've found.