Who is running EL34s in their V:90s?

[bandit2013]

I really liked the winged =c= EL34s I had in my first mark V 15ish years ago. Just running 6L6s in the one I just got at the moment though. Sounding really good so I'm not in a rush to experiment.

Out of curiosity... how serious is the manual update about ONLY using variac mode with EL34s? I had my old one before they updated the manual to say this. I never had any issues using regular power mode pretty heavily for the 2 or so years I had the amp. Anecdotally never heard of any issues from anyone else either (and =C= EL34s were a pretty popular pairing with the Mark V at the time as I recall)

This is from the online manual,

NOTE: 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.

 

[spawnofthesith]

This is from the online manual,

NOTE: 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.

Right, I was just curious if that was added to the manual as more of a "cover our *****" and proceed with caution because the tunes will wear quicker type of thing, or if it's seriously putting the amp at risk to run full power with 34s

 

[MarkV User]

Well it's good you have a fallback configuration.

TBH I am a bit puzzled with this only cause so many have a V and do not appear to have an issue with the presence (me included). For sure some folks don't find the V a good solution. for their needs. Totally get that. Now @bandit2013 gets a pass... as his V certainly exhibits other strange behavior issues, probably mistreated in it's adolescent years by Randall or Doug . BTW, I'm not disagreeing with what you hear or your modifications just curious as to why?

That said presence is one of the more defining features in an amp. Case in point my Stiletto, after adding the simple Depth Mod to the presence circuit it was a game changer. It provided the capability to enhance the bass response of the presence which allowed it to be much more frequency balanced. So I for one get how a change to that would be a big deal. TBH I wasn't really aware of how complicated Mesa had made the presence on the V anyway.

Hopefully I'll get a chance to do the el34 test on my V this week.

Ok, I have two different theories, not necessarily exclusive. First idea is that the presence thing is down to component selection. Either the spread on those caps in the feedback loop or the resonant frequency and inductance of the capacitors. It doesn’t even have to be a change of parts. Manufacturing batches could be different, etc. I never did analyze the circuit or simulate it or even measure the phase shifts carefully to validate the idea.

But I saw a big part of the problem go away when I removed all the switched options in the presence circuit. Now my amp looks very much like a Mark III presence circuit in all modes. But.. the problem can still happen.

Second theory is that my C90 speaker was bad and that was responsible for most of the problem. That speaker really was defective and it only came out clearly in testing. It had some nasty bright resonances starting at low power. The presence circuit feeds the negative speaker compliance error back and then cuts out part if that feedback to boost presence. But a weird enough speaker compliance error could boost instead of cut. When I put in the BN12-300S the amp became ear safe. By the time I changed it for the 300W EVM 12L I’d already gain stages the amp and at the moment of the speaker change that amp became a glorious thing. But the problem can still happen e.g. if the tube bias is too hot.

The real cause could be something different. It is possible to figure it out, but I think just installing bias adjustments will be my next move. That and restoring some of the Channel 3 gain. By the way… some of the problems are connected. My amp has the ringing problem worse when it is biased too hot. Bandit’s troubles also started with bias that was way too hot and was burning his tubes…

I have heard glorious Mark V amps on YouTube. I know they are out there. My amp never sounded like those but now it is something very different and also great. If it was easier to work on I would experiment with the presence circuit and fix it. But it is not worth the trouble and risk. Better to run 5881s, always in Variac mode, and experiment with the maintenance friendly amps.

 

[MarkV User]

Right, I was just curious if that was added to the manual as more of a "cover our *****" and proceed with caution because the tunes will wear quicker type of thing, or if it's seriously putting the amp at risk to run full power with 34s

I think it is a real concern because when I put in EL34s in Variac mode they seem to run a little hot. I didn’t measure the bias current but could if you were interested.

 

[bandit2013]

It could be a CYA thing, more so due to the reliability issues with EL34 being an issue. It is not the plate voltage that does them in, it is the screen voltage. Depends on the tubes. In a different post, I got this answer... I do recall reading something similar.


I'm sure the issue of EL34's not getting a vote of confidence from Boogie is because of the variety of "inferior" tubes available in today's market. The days of robust, high current, durable EL34's definitely are in the past. As a disclaimer, Boogie just wants to CYA should you want to run in the EL34 mode. The same issues occur in some vintage era Marshalls. This was one of the reasons they were shipping US (domestic) versions of their 100W amps in the early 70's with 6550's and not EL34's. The 6550's were tolerant of higher plate voltages and better at withstanding mechanical failures.

 

[woodbutcher65]

I happen to be fortunate enough to have a few Sylvania 6CA7s (STR-416 if Mesa branded) that are still quite good, healthy tubes. IF I were to put them in my Mk V, with these tubes I should not NEED to use the Variac power mode. Correct? Because they can handle the voltage!

 

[MarkV User]

I happen to be fortunate enough to have a few Sylvania 6CA7s (STR-416 if Mesa branded) that are still quite good, healthy tubes. IF I were to put them in my Mk V, with these tubes I should not NEED to use the Variac power mode. Correct? Because they can handle the voltage!

Don’t do it blind at least. You can get a tube bias tester that will interpose a connector and let you measure the bias current being applied to your tubes. Infer the range that is reasonable for that tube. I suspect one issue with Mark V amps may be that the actual bias voltage and current for a particular tube varies more than it should between amplifiers. That would go a long way to explaining the diversity of results people get. I’ve come to think it is a bit nuts to shoot blind the way we do with the Mesa amps. I want to add external bias test points and two different bias pots for the two pairs of tubes.

 

[woodbutcher65]

No worries. I'm an experienced amp tech and quite well equipped, with tube testers and everything needed to service, troubleshoot, and repair just about anything that uses electricity.

 

[MarkV User]

Oh, you are more experienced than I am then. You should be able to figure out how to test it safely if there is anything resembling a spec you can rely on or if you index the measured rails and bias on the Mark V against an amp contemporary with those tubes manufacturing date. I find it a bit confusing that all the old tube amps ran hotter than the absolute max ratings on the tube data sheets. But there is a yardstick at least.

 

[woodbutcher65]

No, the amps didn't exceed the tube max specs, IF you were using the RECOMMENDED tube types. If you can FIND the elusive PhilipS/ECG/Sylvania datasheets for the 7581A, 7027A, STR387, STR415, or 6L6GC tubes, you'll find that the amps made for them may push close to the max ratings but won't exceed them. That'd be a really bad engineering decision that would result in amps that can't be used, due to a lack of tubes that can survive in them.

However, there are certainly some tubes that you just can't run in your 80s Mesa Mark II amp. They won't last long, if they even survive long enough to check the bias on them.

Giving credit where it's due, Sovtek (Reflektor factory and its various brand names) have now been in business making power and preamp tubes for several continuous decades and they've learned how to make excellent reliable tubes. Sovteks today are a much better, more reliable tube with more consistent out of the box performance than they ever were in the 90s or 00s. But still, check their ratings and don't put them in amps that exceed them.

I'm hanging on to a very lightly used quad of STR415s specifically so I have tubes I can trust in a Mark II. At the moment I don't own a Mark II. But I will again.

 

[rarebitusa]

Well appreciated those who chimed in, finally had a chance to try the el34s out. Initial take is... I do like what they bring. Is it earth shattering... hmmm no, but it definitely does provide a nice el34 vibe to the amp, no doubt.

The sparkle on Ch 1 Fat Clean was pretty sweet. Ch 2 Crunch, which I run with tube rect had a nice bright snap to it. Ch 3 was also good with heavy rhythm but for single note work there is where to me the push of the 6L6s benefit. As expected they're less dense/fat/stiff with more sag vs the 6L6s (441s outer, 440s inner pair). It does give the V a different character and it's an easy swap. If I didn't have a Badlander and a Stiletto already leaving them in there may have been a serious consideration. But swapped back in the 6L6s for now. Later I'd like to tra some other cab/speaker arrangements, for this session it was the WB G12-65 1x12 at moderate volumes.

Gotta give it up for the V:90, in some ways it's an amp tweakers dream. Maybe not every feature it has is a clear winner but damn it's fun to screw around with if that kinda thing floats your boat.

 

[tbonesullivan]

I think part of it may be the STR450 Siemens tubes they use are known to have issues with plate voltages over 450 Volts. They definitely don't want people dropping that kind of change and having their tubes get nuked.

As stated before, there are many "classic" amp designs (like the Vox AC30) that really will smoke modern production tubes. They only reason that they didn't smoke the old tubes is because they were made so conservatively, so it didn't matter when so many makers went over the tube design specs. This is especially true with cathode followers in the preamp, where often the heater to plate voltage exceeds the spec sheet.

 

[MarkV User]

This is a little late and off topic maybe, but it comes up as a consequence of this thread.

Being busy and lazy I left the EL34s in my Mark V for the last few weeks. The horrible brightness was not that hard to tame by turning down presence in this case. And I felt I should spend time with them. Anyway I knew I liked the JJ 5881s in the center best and that I was unhappy with Mesa 6L6GC tubes in the much cooler outer positions, before I made the swap. Then I was reading the blog on Eurotubes a few nights ago and he suggested JJ 6V6S tubes for the cooler positions in another Mark series amp with 6L6 bias. I had some and tried it. 5881s in the middle, 6V6 on the outside. And I really love this. If the tubes last I’ll keep it this way forever. I’m only running variac mode so far and the amp feels just right. Not too cool or hot.

 

[sherrillsml]

This is a little late and off topic maybe, but it comes up as a consequence of this thread.

Being busy and lazy I left the EL34s in my Mark V for the last few weeks. The horrible brightness was not that hard to tame by turning down presence in this case. And I felt I should spend time with them. Anyway I knew I liked the JJ 5881s in the center best and that I was unhappy with Mesa 6L6GC tubes in the much cooler outer positions, before I made the swap. Then I was reading the blog on Eurotubes a few nights ago and he suggested JJ 6V6S tubes for the cooler positions in another Mark series amp with 6L6 bias. I had some and tried it. 5881s in the middle, 6V6 on the outside. And I really love this. If the tubes last I’ll keep it this way forever. I’m only running variac mode so far and the amp feels just right. Not too cool or hot.

Hey dude I am very interested in buying the tubes and trying this. I bought my V new in 2010 and it has the icepick some others have experienced. The closest I have come to make my amp useable is running a AT7 in V4 and SED EL34s for the outputs. Could you describe to me what the 5881/6V6 combo you are using does for the overall sound and what channels/modes benefit by this? Thanks!

 

[MarkV User]

I spent

Hey dude I am very interested in buying the tubes and trying this. I bought my V new in 2010 and it has the icepick some others have experienced. The closest I have come to make my amp useable is running a AT7 in V4 and SED EL34s for the outputs. Could you describe to me what the 5881/6V6 combo you are using does for the overall sound and what channels/modes benefit by this? Thanks!

Hi! I spent a huge amount of effort to get my Mark V sounding how I want it and I'll he happy to help.

This power tube change is really great but it is not the first or most important thing.

Priorities are: 1 If you have the combo, change speaker to EVM 12L black label 300W, regardless of what kind of music you play with this amp. Then 2, select preamp tubes to optimize gain stages. Then 3 check power tube bias and 4, power tube changes. Possibly also 5, modify feedback loop. And stop that process as early as you are happy with the results. No matter how you cut it the process will take money and time. You will learn a lot about the amp.

There is a thread "Mark V:90 combo speaker change" where you can read the whole process I went through in lots of detail. But I will also write a summary of the amp tuning procedures for you and other people some time in the next few weeks. Feel free to use me as a resource. I would not have succeeded with my own project except for the kindness and help of other people here.

I'll describe the tube change more soon also.

 

[rarebitusa]

1 If you have the combo, change speaker to EVM 12L black label 300W, regardless of what kind of music you play with this amp.

Just seconding the opinion... with a V:90 and IIC+, which are my reference points, find the EVM is a great fit. It's flat response really reveals the amps inherent character. It's certainly not a fit for any amp but with a Mark it floats my boat. Interesting tidbit is when I was up at Mesa talking to Mike B about the IIC+ and speakers, he said they do all their testing with the EVM, in his opinion it was the best speaker for it.

On the same topic... a speaker swap would be the first part of the rig I'd go after, the biggest bang for the buck in ones tone quest.

 

[MarkV User]

Just seconding the opinion... with a V:90 and IIC+, which are my reference points, find the EVM is a great fit. It's flat response really reveals the amps inherent character. It's certainly not a fit for any amp but with a Mark it floats my boat. Interesting tidbit is when I was up at Mesa talking to Mike B about the IIC+ and speakers, he said they do all their testing with the EVM, in his opinion it was the best speaker for it.

On the same topic... a speaker swap would be the first part of the rig I'd go after, the biggest bang for the buck in ones tone quest.

Yes, the speaker was such a huge change and it was the biggest for me too. To be clear, the speaker change is not because it filters the spectrum of sounds that can be reproduced. In any tube amp with speaker feedback for presence, etc, the speaker heavily influces what the amp power section puts out. It is partly amplifying the speaker position error. The MarkV is a particularly strong case of this because of diabolical things they did in that feedback loop. In this one very special case you don't need to be thoughtful about it or listen to things online. Just buy that particular one and put it in, then see what else is still wrong.

 

[MarkV User]

Hey dude I am very interested in buying the tubes and trying this. I bought my V new in 2010 and it has the icepick some others have experienced. The closest I have come to make my amp useable is running a AT7 in V4 and SED EL34s for the outputs. Could you describe to me what the 5881/6V6 combo you are using does for the overall sound and what channels/modes benefit by this? Thanks!

Hi Sherrill,

I've been slow to write more because I'm grabbing time here and there. But I just came from a long session of playing the Mark V this morning and it's a good time to respond to your direct question about the sound of the 5881s and 6V6s.

First, I never loved the 6L6GC tubes that came with my amp, and they made that high frequency problem worse. Switching power tubes is not enough to correct the icepick problem, but it helps. As my amp was originally configured turning down the presence only corrected the icepick at the extreme lower end of the range, where it also deadened the whole amp--not what I wanted. The changes that helped most with the icepick were the speaker change and the preamp tube changes.

At some point I blew up a 6L6GC tube and swapped in a pair of 5881s. The brand may not matter much. The Tung Sol 5881 tubes and the JJ 5881 tubes worked great. How hot the particular tube are does matter. You will be using variac mode only with the bias switch in the 6L6 position, and it works best if you get slightly warmer tubes--5881s that expect a lower bias current. The 5881s belong in the inner positions which are biased warmer and driven harder.

The 6V6 tubes you want are probably JJ 6V6S tubes, which can take the higher voltage and current. They go in the outer two positions, and the amp should only be used in Variac mode.

Now in 45 watt mode you get a certain tone--a nice 5881 tone from the inner pair of tubes. It is a lot warmer than 6L6GC tubes, far brighter and smoother than EL34 tubes, and it is possible to get some breakup at higher volumes. In 90W mode you switch in the outer pair of 6V6 tubes. You will hear additional top end, a real chiming/singing quality, and much more significant power tube distortion. I am playing in my house where I live alone, and I play loud but not super loud, and I haven't tried it at high volumes. Turning the volume all the way up might blow up the 6V6 tubes.

As far as the sound.... I am playing channels 1/Tweed, 2/MarkI, and 3/IIC+. I've revoiced these channels and channel 3 is currently reduced gain in my amp. But the sounds I'm getting are like 1970s lead sounds. They are not huge and beautiful like an old Marshall, but they are tighter, super grainy, chaotic, crisp, distorted and beautiful. The distortion is not a static kind of distortion like I get with EL34s in the MarkV or a controlled buzzing like a Mesa Rectifier. It is a ripping kind of distortion. It is not like anything else, but it reminds me of a JCM800 (though without the utter hugeness of that) and it is also like putting a really great distortion pedal in front of an old Fender Deluxe. That is just a very approximate comparision. A lot of the wonderful things about those two amps come from the configuration of the power rails, and there is no way to get that on the Mark V without reconfiguring the power supply.

I feel like this combination of tubes is delivering the real promise of simulclass for me. Because there is sweet and mostly clean tube tone from the inner two tubes and breakup from the outer pair. So the clarity and beauty of the power amp sound is surprisingly good. This is sort of what I imagined when I heard about the feature originally.

If you like the sound of this, the tubes are a modest investment to try. If you play at home and/or record then this is probably the endpoint. If you play out and need higher volumes then I would suggest adding independent bias pots for the inner and outer tubes (either you or the amp tech can do this) and getting the 6V6s set up where they will be comfortably warm at the level you like, at the range of volumes you want to use. You can even make it so the normal vs variac setting is useful again. E.g. play in normal bias for low volume home/recording and variac bias for louder/live use. I haven't done these things, but I have been feeling the need for bias pots and test points on the back of the amp..

 

[sherrillsml]

I spent

Hi! I spent a huge amount of effort to get my Mark V sounding how I want it and I'll he happy to help.

This power tube change is really great but it is not the first or most important thing.

Priorities are: 1 If you have the combo, change speaker to EVM 12L black label 300W, regardless of what kind of music you play with this amp. Then 2, select preamp tubes to optimize gain stages. Then 3 check power tube bias and 4, power tube changes. Possibly also 5, modify feedback loop. And stop that process as early as you are happy with the results. No matter how you cut it the process will take money and time. You will learn a lot about the amp.

There is a thread "Mark V:90 combo speaker change" where you can read the whole process I went through in lots of detail. But I will also write a summary of the amp tuning procedures for you and other people some time in the next few weeks. Feel free to use me as a resource. I would not have succeeded with my own project except for the kindness and help of other people here.

I'll describe the tube change more soon also.

Thanks again! I look forward to when you have time to detail your changes so that I and others here may finally have resolution to some or all of the issues with the V.

 

[sherrillsml]

Hi Sherrill,

I've been slow to write more because I'm grabbing time here and there. But I just came from a long session of playing the Mark V this morning and it's a good time to respond to your direct question about the sound of the 5881s and 6V6s.

First, I never loved the 6L6GC tubes that came with my amp, and they made that high frequency problem worse. Switching power tubes is not enough to correct the icepick problem, but it helps. As my amp was originally configured turning down the presence only corrected the icepick at the extreme lower end of the range, where it also deadened the whole amp--not what I wanted. The changes that helped most with the icepick were the speaker change and the preamp tube changes.

At some point I blew up a 6L6GC tube and swapped in a pair of 5881s. The brand may not matter much. The Tung Sol 5881 tubes and the JJ 5881 tubes worked great. How hot the particular tube are does matter. You will be using variac mode only with the bias switch in the 6L6 position, and it works best if you get slightly warmer tubes--5881s that expect a lower bias current. The 5881s belong in the inner positions which are biased warmer and driven harder.

The 6V6 tubes you want are probably JJ 6V6S tubes, which can take the higher voltage and current. They go in the outer two positions, and the amp should only be used in Variac mode.

Now in 45 watt mode you get a certain tone--a nice 5881 tone from the inner pair of tubes. It is a lot warmer than 6L6GC tubes, far brighter and smoother than EL34 tubes, and it is possible to get some breakup at higher volumes. In 90W mode you switch in the outer pair of 6V6 tubes. You will hear additional top end, a real chiming/singing quality, and much more significant power tube distortion. I am playing in my house where I live alone, and I play loud but not super loud, and I haven't tried it at high volumes. Turning the volume all the way up might blow up the 6V6 tubes.

As far as the sound.... I am playing channels 1/Tweed, 2/MarkI, and 3/IIC+. I've revoiced these channels and channel 3 is currently reduced gain in my amp. But the sounds I'm getting are like 1970s lead sounds. They are not huge and beautiful like an old Marshall, but they are tighter, super grainy, chaotic, crisp, distorted and beautiful. The distortion is not a static kind of distortion like I get with EL34s in the MarkV or a controlled buzzing like a Mesa Rectifier. It is a ripping kind of distortion. It is not like anything else, but it reminds me of a JCM800 (though without the utter hugeness of that) and it is also like putting a really great distortion pedal in front of an old Fender Deluxe. That is just a very approximate comparision. A lot of the wonderful things about those two amps come from the configuration of the power rails, and there is no way to get that on the Mark V without reconfiguring the power supply.

I feel like this combination of tubes is delivering the real promise of simulclass for me. Because there is sweet and mostly clean tube tone from the inner two tubes and breakup from the outer pair. So the clarity and beauty of the power amp sound is surprisingly good. This is sort of what I imagined when I heard about the feature originally.

If you like the sound of this, the tubes are a modest investment to try. If you play at home and/or record then this is probably the endpoint. If you play out and need higher volumes then I would suggest adding independent bias pots for the inner and outer tubes (either you or the amp tech can do this) and getting the 6V6s set up where they will be comfortably warm at the level you like, at the range of volumes you want to use. You can even make it so the normal vs variac setting is useful again. E.g. play in normal bias for low volume home/recording and variac bias for louder/live use. I haven't done these things, but I have been feeling the need for bias pots and test points on the back of the amp..

Great info and I really appreciate it! I agree the JJ 6V6s would probably be the best to handle the voltages. Also as you referenced EL34s do rob much of the chime on the clean settings so I am looking forward to trying your power tube changes. Besides the speaker change you recommended some preamp tube changes, so when you have time I am very interested in those and lastly the negative feedback modification(s) if you feel like that is worth it. Currently between my 50 year old Super Reverb and my Marshall JCM800 2203 I have a lot of bases covered but my Mesa S.O.B. that I purchased in 1980 blows the doors off of my particular Mark V and that is just a waste.