Mixing 6l6 and El34

[TheArriaga88]

Hello all! Has anybody here ever mixed el34s and 6l6s in their amps?

Is it even possible to do without damaging the amp?

Im just curious as to what effect it would have on the tone haha :shock:

any input would be greatly appreciated!

 

[gribbly]

This question is addressed in the comments here:

http://mesaboogie.com/news/2010/08/6l6-vs-el-34-feel-the-power-of-your-amps-power-section/

"Mixing the two different types of tubes (EL-34 and 6L6) is only possible in the Roadking and some Simul-Class amps – NOT the Dual or Triple Rectifier. That said, I doubt you would hear much of a difference with the mix of tubes if you could. The majority of the tone of the amp comes from the preamp and your settings. The tubes will only provide subtle differences, especially when blended like that. As romantic as it sounds to do tube blending and as much as people suggest that it’s the power tubes that make the sound of the amp, Mesa tends to find that it’s the overall design, quality of parts and the preamp which shapes the majority of what the amp sounds like. The power tubes do the job of making all that other stuff loud!"

 

[TRENCHLORD]

Definitely not a good idea.

 

[jnoel64]

I can do that with my Road King only because it was made to do that. If you want to come close to that without re-biasing sockets, try using 6CA7 tubes. EL34 bias in a big bottle design. It's like EL34s on steroids. I use the EH 6CA7s in my Vai Legacy combo and won't use anything else in that amp. I have seen many others using the same tubes in the same amp. Never had a clue that it was a popular choice. Didn't much care for them in my Dyne, though.

 

[swbo101]

There's no problem mixing them if the amp is set for that and you keep them paired appropriatly. My Mark IV can do that, but the 6L6s must be the inner pair and the EL34 the outer. You should never put one 6L6 with an EL34, if that's your question.

 

[MesaTone]

I tried the 6L6/EL34 combo in my Mark IV A. I'm getting tired of the straight 6L6 tone. I want some more mids, and no one seems to make a 'middier' 6L6. Wasn't impressed with the 6L6/EL34 combo, at lower/medium volumes there was too much mid tone, and it sure didn't sound like a boosted Marshall. I'm not a fan of JP's tone, so I figured I was headed in the wrong direction.

So, JJ came out with their 6ca7, read up on that tube, and tried a set of those in the outboard sockets. WOW! Exactly what I was looking for, throughout the volume range. I ran that tube combo through EV12L's, Delta Pro's, MC-90's and a Weber CV124F. Just perfect. Still sounds like a Mesa, but with more clear mids.

I highly recommend this combo if your amp is designed to run different tube sets. If you're running an EL34 amp and want some 6L6 clarity, I'd try a set. I just love these tubes. I emailed JJ to see if they would make a 6L6 with more mids, along the lines of the 6ca7 tone, but not too interested. I think there would be a market for a 6L6 with more mids. Oh, well.

I don't work for JJ, but I also tried one of their mid-gain 12ax7's, and am digging that tone, too. It really brought the front end of my multi-decade old MKIV to life. And I won't use any other 6V6 than the JJ. Another great innovation, I think it's a copy of the 7591 tube with 6V6 pins, sounds much better in an old Fender tweed than the 6V6's.

Peace.

 

[bandit2013]

There are some simul-class amps like the Mark IV and Mark III that will allow for integrated quads, (el34 and 6L6). Typically the primary pair (those that remain active in Class A mode) are the ones you can swap. Refer to your manual for such applications about power tubes. Most of the other amps like the Rectifier series and the Mark V should not be used with a mix of EL34 and 6L6. If there is a bias switch for EL34 or 6L6, you will cause damage to the tubes or amp if you attempt to mix the two. The Road King has a dedicated pair for EL34.

There will be a tone difference between EL34 and 6L6 when all the tubes are the same. A mix of el34/6L6 (Mark IV, Mark III) will be noticed but will sound more like EL34 than 6L6 since the 6L6 is supporting the EL34 in parallel when in class A/B mode, the 6L6 tubes will be off in Class A.

 

[swbo101]

A mix of el34/6L6 (Mark IV, Mark III) will be noticed but will sound more like EL34 than 6L6 since the 6L6 is supporting the EL34 in parallel when in class A/B mode, the 6L6 tubes will be off in Class A.

Never really thought about it, but you're right. When using a mixed quad in my Mark IV, the tonal qualities of the EL34 tend to take over more than the 6L6 in Simul-Class mode

 

[dodger916]

The outside sockets are also biased hotter.

 

[bandit2013]

That seems to be the trick with most Mesa boogie amps especially the simil-class powered ones. The primary pair has the hotter bias (generally the outer set), and the secondary will have a colder bias. For the full class A/B amps, there still is a slight bias offset but not enough to use an integrated quad unless the amp was designed to do such. When in question, refer to the manual for your amp to verify if this type of tube arrangement can be used.

Roadster, RA100, and Mark V should not be used with a mixed quad of el34 and 6L6. Early manuals did indicate the Mark V could be used in such a manner but I would advise against that (the updated manual has the statement removed). There is a way to mimic the integrated quad using el34s, use a pair of standard el34 types in the primary circuit (tubes that will be on at the 50W setting) and get a set of Tung Sol EL34B which sound very close to a 6L6 for the secondary. It is possible to mix different types of tubes within the tube family that use the same bias (pair of el34, paired with kt77, 6ca7, el34b, or other as long as the tubes are selected for your amp). You can also do the same with 6L6 tubes, for instance TAD6l6gc-str with a pair of SED6L6GC can really bring out a sinister tone. It is not the same as the simil-class circuit with the integrated quad, however, there are some interesting combinations as long as the tubes are closely matched. One point to make about the Mark V, in the class A mode at 10W setting, one of the outer tubes will be pulled in with the inner pair. Note the primary tubes are then inner pair on the Mark V.

 

[Triaxstasy]

...get a set of Tung Sol EL34B which sound very close to a 6L6...

That's the very reason I use TungSol EL34B in the outer sockets of my 2:90, paired with TungSol 6L6GC-STR in the inner sockets (which have a hint of EL34 chracteristics in their midrange).

Couldn't be any happier with the sound!

 

[swbo101]

...get a set of Tung Sol EL34B which sound very close to a 6L6...

That's the very reason I use TungSol EL34B in the outer sockets of my 2:90, paired with TungSol 6L6GC-STR in the inner sockets (which have a hint of EL34 chracteristics in their midrange).

Couldn't be any happier with the sound!

I like them too. I found them to be a suitable replacement for my SED =C=,when I run out

 

[bandit2013]

Nothing can replace the SED ~C~.

I did experiment with the Tung Sol EL34B in my Roadster. Actually I tried all of the EL34 tubes for a point of reference. Perhaps the Roadster is not the best amp for using EL34's since I like using the clean channels too and felt that the 6L6GC is the better option than the EL34.
Now that I have fresh and new V30 in a new Mesa full sized rectifier cab to match the RA100, that cabinet sounds awesome by the way. Even the Mullard EL34 are prefect tubes. So I am not too upset on St. Pettersburg halting production on their consumer products. If I can still get some TAD6L6GC for the Mark V, those tubes were very close to the SED 6L6GC to the point I would not really notice the difference. They even sounded great in the Roadster so as long as that resource is available that will work.

I have yet to try 6CA7's in the RA100 or Roadster. I have used them in the Mark V and was blown away on their tone. If the JJ tubes would have lasted more than 2 weeks before one failed (basically just shut off and intermittently would come back, may have been grid resistor since I lost one on V8 after using them). Perhaps the EH version may be better. The GL KT77 are great tubes too in the V and not too shabby in the RA100. Too much of a tone change for me to like most if any EL34 in the Roadster.

Even the Ruby EL34 sounded good but I got one that would almost red plate (or operates like a 6V6) and it did not matter what socket it was in. Those too sound similar to 6L6GC at lower volume but when pushed into saturation take on the characteristic of 6CA7.

 

[swbo101]

Nothing can replace the SED ~C~.

I found them to be a suitable replacement for my SED =C=,when I run out

I agree nothing can replace those SEDs. I guess the operative word is "suitable". lol. I like and can live with the TungSols (both EL34 & 6L6) in my Mark IV, but they are no =C=.

 

[bandit2013]

I have tried many tubes in the Mark IVb. I actually did like the Svetlana 6L6GC in that amp. They just did not work well in the Mark V which is what got me started looking for better tubes than the stock one's (basically tube that would last more than 2 months). SED's were the ticket, and they sounded great.

Give the TAD6L6GC-STR in that Mark IV if you have not done so already. That was an experience.... Mix them with SED6L6 in the secondary sockets and holy tube gain, that is outright sinister. Tried that in the Mark V but did not have the same effect...

I would also consider the Mullard EL34. I am currently using them with the RA100. I do have the TSEL34B but wanted something with a bit more bite.

 

[jnoel64]

I've always used EH 6CA7 tubes. When JJ came out with theirs, I read the reviews, and decided to stick with EH. They really do sound like an EL34 on steroids.

As for a "middy" 6L6, I've got a quad of Svetlana 6L6s in my old Carvin X100B. I had to do a double check to be sure they really were 6L6 tubes, because the midrange response was so strong, I thought for sure I had EL34s in the amp. I can't praise them enough, and they've lasted just as long and strong as any other power tubes I've tried.

I tried the 6L6/EL34 combo in my Mark IV A. I'm getting tired of the straight 6L6 tone. I want some more mids, and no one seems to make a 'middier' 6L6. Wasn't impressed with the 6L6/EL34 combo, at lower/medium volumes there was too much mid tone, and it sure didn't sound like a boosted Marshall. I'm not a fan of JP's tone, so I figured I was headed in the wrong direction.

So, JJ came out with their 6ca7, read up on that tube, and tried a set of those in the outboard sockets. WOW! Exactly what I was looking for, throughout the volume range. I ran that tube combo through EV12L's, Delta Pro's, MC-90's and a Weber Cali/Silver Bell mix. Just perfect. Still sounds like a Mesa, but with more clear mids.

I highly recommend this combo if your amp is designed to run different tube sets. If you're running an EL34 amp and want some 6L6 clarity, I'd try a set. I just love these tubes. I emailed JJ to see if they would make a 6L6 with more mids, along the lines of the 6ca7 tone, but not too interested. I think there would be a market for a 6L6 with more mids. Oh, well.

I don't work for JJ, but I also tried one of their mid-gain 12ax7's, and am digging that tone, too. It really brought the front end of my multi-decade old MKIV to life. And I won't use any other 6V6 than the JJ. Another great innovation, I think it's a copy of the 7591 tube with 6V6 pins, sounds much better in an old Fender tweed than the 6V6's.

Peace.

 

[domct203]

............ For the full class A/B amps, there still is a slight bias offset but not enough to use an integrated quad unless the amp was designed to do such.........

Very interesting, I've never come across that (an intentional offset in the bias voltage for each side of the sine wave), either in an (Class AB) amp I've worked on, or schematic I've seen.

Any more info on this?

Dom

 

[bandit2013]

I can only reflect on the Mark V schematic since I do not have one for the other amps.

The outer tube pair has a -47V bias compared to the inner pair which is -43V (this is assuming the schematic is correct and not missing details) Bias source voltage -51v for 6L6 tube and -39 for EL34 tube.

Typical for a Simul-Class type amp where the one pair of tubes is biased hotter than the other pair. This is accomplished though a voltage divider network of resistors on the control grid of the tubes. For 6l6, source is -51V, passes though 220k resistor, 180k resistor and grounded though a 2.2M. The outer pair has control grid bias of (-51)*(2.2M + 180K)/(220K +180k +2.2M) = -46.6v, inner pair: (-51)*(2.2M)/(220k + 180k + 2.2M) = -43V. Note that there is a series resistor of 2.2k to the control grid on the hot biased tube vs the cold biased tube (having the higher -voltage).

As for the Mark IVb, the bias on the inner tubes is -52v and outer pair is -47v. Source voltage is -57V and replace the 180K resistor value with 220K in the equations above. One would almost think you could run EL34 without using the bias switch set for EL34. However I would not recommend this.

I have not seen any A/B schematics to compare too. My apologies if I stated something incorrect.