Running full power mode with EL-34's

Hey guys, I have a question. On the Mark V I read somewhere that when you run EL-34's you have to keep in variac power, I thought I read this in the manual but I was just reading through again and I don't see it..

So, I figured I would ask. If I install EL-34 tubes and set the bias selector for them do I have to stay in variac power mode or can I run at full power?

Thank you.

Page 43 of the downloadable manual, under the Bias Select section. Worded by lawyers IMHO. It states Variac "will reduce the strain on EL34 tubes", but leaves that up to you to interpret.

Monstercastle said:

Page 43 of the downloadable manual, under the Bias Select section. Worded by lawyers IMHO. It states Variac "will reduce the strain on EL34 tubes", but leaves that up to you to interpret.

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Ok, thank you. That is how I interpreted it. I distinctly remember reading something that said to NEVER (in bold letters) run EL34's in full power mode. Then the manual said something different.. Strange..

The bold letters you may be thinking of might be the always flip the switch to match the tubes in use phrase. It's in the manual multiple times. Here's the thread where I first heard to run the amp in variac with EL34's. http://forum.grailtone.com/viewtopic.php?f=4&t=71074&start=15

I ran on full power all the time, even with EL-34, KT-77 and did not have an issue.... Thanks for the advice... if it was that important, it would have been noted on the back along with the bias setting notice... :evil: Chalk that up to an oops.... (this is where the poo smiley would be a necessity) :|


There have been many amendments in the manual. First run of the manual, there was a section that said you can run an integrated quad (6L6 and EL34) at the same time like you could with the Mark III and Mark IV. With the Mark IV amplifier, you could even use 6V6 but would be required to use tweed (variac) power only. Do not attempt to use a 6V6 tube in the Mark V!!!!!!. So much for information supplied with the manual..... what was once written is not cast in stone as mistakes do happen and as a result of customer service and issues resulting in poor performance due to what is in print when you first bought your amp. Now I have to dig up the original manual that came with my Mark V just for kicks and see what is in print vs online. Also there was no mention on how to compare the IIC+ mode or Mark IV mode to the actual amps. Perhaps get rid of the generic stuff and stick that into another manual on its own and keep information specific to the product in the user manual. :shock: Have you read the JP-2C manual yet? I had to filter out all the information how to compare the JP-2C to the original Mark IIC+ and basically lost interest in reading though it.... JP-2C was easier to figure out than it was to read the manual.

In the Getting Started section:

When using the BIAS SELECT switch on the Rear Panel to accommodate the use of EL34 Power Tubes, ALWAYS switch to
VARIAC POWER (switch down) on the main Front Panel POWER switch and operate the amplifier in this power mode until
swapping back to 6L6 Power Tubes. This will ensure uninterrupted performance and avoid running the EL34s over their rated
safe operating voltage.

Thanks!

Authorized Boogie said:

In the Getting Started section:

When using the BIAS SELECT switch on the Rear Panel to accommodate the use of EL34 Power Tubes, ALWAYS switch to
VARIAC POWER (switch down) on the main Front Panel POWER switch and operate the amplifier in this power mode until
swapping back to 6L6 Power Tubes. This will ensure uninterrupted performance and avoid running the EL34s over their rated
safe operating voltage.

Thanks!

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Ah, hah! I knew I read it somewhere.

So, in getting started it says to ALWAYS run in variac and on page 43 it says it's "better" to run in variac.. hmm.

Authorized Boogie said:

In the Getting Started section:

When using the BIAS SELECT switch on the Rear Panel to accommodate the use of EL34 Power Tubes, ALWAYS switch to
VARIAC POWER (switch down) on the main Front Panel POWER switch and operate the amplifier in this power mode until
swapping back to 6L6 Power Tubes. This will ensure uninterrupted performance and avoid running the EL34s over their rated
safe operating voltage.

Thanks!

Click to expand...

This was added recently. The thread I linked was before this was in the manual. But it's in there now, lol :lol:

I am not doubting your statement as I am sure the manuals have been updated since I had bought my Mark V. No upset here as it always is a learning experience when it comes to tube amps. I am glad that updates are made as it is a sign of progress and better customer service. Thumbs up for that.... And thank you on your behalf with your post. 8)

Here is what I found on page 43 in the manual, printed 10/05/2010, I compared that to what I had downloaded from Mesa, dated 9/11/2013 and both are the same..... I will have to check for an update on the user manuals for all of my amps as it is good idea to have up to date information..... When I sold my Mark III I gave all of the original documentation that came with the amp as well as a downloaded version which had some differences with it.

SamuelJ86 said:

The bold letters you may be thinking of might be the always flip the switch to match the tubes in use phrase. It's in the manual multiple times. Here's the thread where I first heard to run the amp in variac with EL34's. http://forum.grailtone.com/viewtopic.php?f=4&t=71074&start=15

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This thread was where I discovered full power for EL34's was a no no. I've stuck to variac with EL34's for over a year now, sometimes running at very high volumes with no issue's at all, touch wood. I'd stick to variac especially after re-reading through that thread.

I am good with that. Only amp I run EL34 with is the RA100.

Wayno said:

I'd stick to variac especially after re-reading through that thread.

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Yep, think I'll do that. I'm not running 34's I was really just curious because I knew I had seen it both ways..

Chiliphil1 said:

Wayno said:

I'd stick to variac especially after re-reading through that thread.

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Yep, think I'll do that. I'm not running 34's I was really just curious because I knew I had seen it both ways..

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Cool beans, I can recommend EL34's though. They sound great to my ears in the Mark V. Defo worth an audition if you have the chance. They're not for everyone, but work for me.

I've run EL34's full power for several years now with no problems. Variac is too grainy and less power and tightness for my ears especially on clean and fat. Surprisingly i can get great cleans with EL34's if i have the gain at about 11:00 and the master at about 2:00. I like to run Extreme in Triode, and Variac makes it too saggy.

I got acceptable cleans with EL34's. The driven sounds are much better with EL34's, however the clean sounds sold this amp to me. If I want driven EL34 sounds, I've amps that do just that.
Mesa are safeguarding themselves with the Variac thing. EL34's. Probably a combination of Mesa's penchant for running the power section cold and the EL34's need for lower plate voltage, to do just that efficiently. Than the 6L6. Though I have to say, the Mark 5 knocks out something like 450v plate voltage in full power and 370 or 380v in Variac. I've never seen an EL34 using Marshall knock out less than 465v.
So I suspect something to be going on with the bias resistor switch that happens when you switch to EL34's on the back of the amp. That needs a lesser plate voltage of Variac to sound right. Though for the life of me I can't think what it could possibly be.

Anyone ever try KT-77s in the V? I love them in my Peavey but thats a whole other animal.

I've been running mine at volume with 34's for a few years with no problem. Often in high power. But the bias is usually highest on the clean settings which I don't use all that much.

jdgebha said:

Anyone ever try KT-77s in the V? I love them in my Peavey but thats a whole other animal.

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I still have a quad of Gold Lion KT77. Used them for about 8 months at full power without any issue. Those sounded killer. I may have to drop then in again. I have not been able to get the crunch mode the same since going back to 6L6. Come to think of it I was also running EVs at the time. I tried them in my other amps (RA100) but did not sound as good as it seemed there was too much headroom. When I bought them I specifically stated they would be used in the Mark V. I have not tried the JJ version but I did try the 6CA7 JJ tube. Those sounded killer too but they did not last more than 2 weeks of use, one tube basically shut down, did not red plate or anything. Perhaps an internal issue. I killed two others in my Mark IV. That was an instant death since they went into arc mode. I did try them before in that amp but that was prior to loosing the one tube.

For those of you running El-34's or KT-77's in full power mode in their mark V with no red plating issues: what brands are you using ?
I would like to try a different taste in my mark V and I'd like to run at full power; of course I know what the manual says about it but if some of you were able to do it I'd like it too.
I live in Italy by the way, so european dealers are preferred.
Thank you in advance for your answeres.

I've been using the same set of Mesa branded EL34's for almost 10 years. I use an attenuator as well so the master is always at 11 O'clock at the least. Now I'm not gigging, so I probably play once a week on average for 30 minutes to an hour.