EL34's in Heartbreaker: "Tweed" or "Hi" Voltage Setting

Mesa opines in their user Manual that it is recommended that the amp be used in "Tweed" voltage setting when using EL34's due to the "less sturdy" EL34's available 'today'.

'Today' was 15 years ago.

I just bought a single pair of "Yellow" (earlier breakup) Mesa STR 447 EL34's.

Can I shoot them with full plate voltage and not worry about frying them?

What has been the general experience with the tone and attributes of the STR 447?

Anybody know exactly the make and model that this tube is selected from? There are rumors they are ElectroHarmonix.

I have run them in mine with no problems now off and on since 2000 in full power setting (really don't like the tweed setting) with no problems, but I really prefer the 6L6 types as the majority of the tone in mine comes from the preamp section anyways - the 6's just seem more versatile. YMMV

Tommy_G said:

Mesa opines in their user Manual that it is recommended that the amp be used in "Tweed" voltage setting when using EL34's due to the "less sturdy" EL34's available 'today'.

'Today' was 15 years ago ...

Click to expand...

In early December I had spoken with Marcus at Mesa about this very thing. Today was 15 years ago. I have been using the green Mesa rating EL34 Power Tubes with Full power, Vacuum rectifier (manual did recommend a 5U4G if only using 2 x EL34 tubes BUT I liked using 4 x EL34 tubes so stuck with the 5AR4), and three went south on me. He did say that the Red rating Mesa EL34 power tubes with Tweed & Tube Recto settings would be safest (maybe), but after about 15 minutes of "whatcha think"(s) on my part it came down to using 6L6 power tubes as the best bet. Kinda sad since I did like the EL34 sound over the 6L6 sound I had A/B(d) against in my HB.

I am having some service work and an upgrade done to make sure the EL34 tubes didn't take anything else out when they blew the HB's fuse. And I did put in 4 fuses which blew immediately. I'll have a seperate thread concerning this once I get it back and have played it for a few weeks.

Dennis

jpdennis said:

Tommy_G said:

Mesa opines in their user Manual that it is recommended that the amp be used in "Tweed" voltage setting when using EL34's due to the "less sturdy" EL34's available 'today'.

'Today' was 15 years ago ...

Click to expand...

In early December I had spoken with Marcus at Mesa about this very thing. Today was 15 years ago. I have been using the green Mesa rating EL34 Power Tubes with Full power, Vacuum rectifier (manual did recommend a 5U4G if only using 2 x EL34 tubes BUT I liked using 4 x EL34 tubes so stuck with the 5AR4), and three went south on me. He did say that the Red rating Mesa EL34 power tubes with Tweed & Tube Recto settings would be safest (maybe), but after about 15 minutes of "whatcha think"(s) on my part it came down to using 6L6 power tubes as the best bet. Kinda sad since I did like the EL34 sound over the 6L6 sound I had A/B(d) against in my HB.

I am having some service work and an upgrade done to make sure the EL34 tubes didn't take anything else out when they blew the HB's fuse. And I did put in 4 fuses which blew immediately. I'll have a seperate thread concerning this once I get it back and have played it for a few weeks.

Dennis

Click to expand...

So what you're saying is: Run on Tweed voltage.....Correct?

I'm not disappointed with my choice of a Yellow and Tweed Setting so far.

I'm going to write a review in a new thread, after I get a bit more experienced and opinionated with it.

jpdennis said:

Tommy_G said:

Mesa opines in their user Manual that it is recommended that the amp be used in "Tweed" voltage setting when using EL34's due to the "less sturdy" EL34's available 'today'.

'Today' was 15 years ago ...

Click to expand...

In early December I had spoken with Marcus at Mesa about this very thing. Today was 15 years ago. I have been using the green Mesa rating EL34 Power Tubes with Full power, Vacuum rectifier (manual did recommend a 5U4G if only using 2 x EL34 tubes BUT I liked using 4 x EL34 tubes so stuck with the 5AR4), and three went south on me. He did say that the Red rating Mesa EL34 power tubes with Tweed & Tube Recto settings would be safest (maybe), but after about 15 minutes of "whatcha think"(s) on my part it came down to using 6L6 power tubes as the best bet. Kinda sad since I did like the EL34 sound over the 6L6 sound I had A/B(d) against in my HB.

I am having some service work and an upgrade done to make sure the EL34 tubes didn't take anything else out when they blew the HB's fuse. And I did put in 4 fuses which blew immediately. I'll have a seperate thread concerning this once I get it back and have played it for a few weeks.

Dennis

Click to expand...

I would also check that rectifier tube - will take out the mains fuse when it goes bad. has happened to me more than once!

@Tommy_G

Yes, run Tweed with Rectifier tube with the EL34 power tubes. I think Yellow & Red are close enough to be a good match in that configuration. Are you going to run in full power or half power? Just wondering how the 5U4G recto in 1/2 power would compare to the 5AR4 in full power using the configuration you are in.

@thunda1216

Oh ya! I have heard the story of a bad recto taking out more then just the power tubes. I have two brand new 5AR4 rectifier tubes as well as an old stock in box Amperex Holland/Bugle 5AR4. I talked to my tech to see if he could put in a spring loaded retainer for the recto replacing the bear trap one since the Amperex has the metal base.

Dennis

You dont know how Im dying to flick the switch to full power....just to taste it....

Never had a problem running EL 34's at full power.
I don't do it alot but it has been tried.
Mine went in for service a while back and I had
everything tested.Everything worked with all settings
for 6L6,EL34 and 6v6 as I use the amp with all the tube
options.Also had them try all the tubes with GZ34 and 5U4GB.
So far so good.

The EL34's I got are Mesa STR 447's they sound fantastic!
I was told these were Sovtek tubes.Not my favorites but in the HB
the sound is amazing.Got the Mesa 6v6's also Sovteks.Winged =C=
6L6's that came with the amp sound fine too.

Going to replace preamp tubes soon any suggestions?

Tommy_G said:

You dont know how Im dying to flick the switch to full power....just to taste it....

Click to expand...

I did that once with Bold - OMG!!!!!

As an update I was at Mesa today and spoke with Rich. He said his feedback from the techs is that the HB eats Rectifier tubes and you should run in Solid State Rect with 6L6 tubes. On the other hand, Monsta-Tone has said he successfully uses some type of "circuited" Recto tube substitute that still gives the sag of a tube - http://www.webervst.com/ccap.html . However, ...

I have invested in the Mercury Magnetics output, power, and choke transformers and they are in at my tech's shop right now. I called him on the road after leaving Mesa and asked him to check with the techs at Mesa since he has the back-channel that I do not have. I told him to let them know I have the blackface HB which is version 2. And if the Rectos are a problem is there some "hoodoo voodoo" Mesa does to fix it or is it to suggest using the 6L6 in SS mode. If the later then does Mercury magnetics have a cure or know about this. Seems strange to have an amp which is documetned as having various "features" which will not work AND keep the amp stable.

I will post in a seperate thread when I get the "facts" which may be several weeks.

Dennis

Does OMG mean that you blew the tubes? Or should I try it....or is the risk to the pair of EL's unnacceptable?

I'm probably going to call Mesa tommorrow. The EL34's are biased at about -29V on the Tweed Setting/Tube Rect, and would hit about -37V on hi voltage, which is spec for an EL34, I think (but probably depends on plate voltage....). I also want to find out what version I own. Bought used, can't remember what I did with the hangtags. Is there anyplace else I can find the serial # without pulling the cabinet off?



Let me know how your mods turn out. I think I'm going to changeout that honking capicitors across the power tubes with something more in the Bassman or JTM size range.

This amp still produces too much low [edit: frequency] energy. May decrease some cathode bypass resistors too.

Tommy_G said:

Quote #1 - Does OMG mean that you blew the tubes? Or should I try it....or is the risk to the pair of EL's unnacceptable? ...

Quote #2 - This amp still produces too much low energy ...

Click to expand...

In regards to #1 - Only try this with 6L6 tubes. I put it on Hi voltage power, 100 Watt, SS recto, & bold! It was extremely "BOLD" if you get my meaning. In your face and melted my face kinda sound!

In regards to #2 - ??? could you clarify?

Thanks

Dennis

the clarification on #2 is basically an extension of #1:

You call it "melt your face"....I call it "shellshock". The punch of the low freqs coming from this amp will rearrange your innards, to be sure.

There must've been an inside joke at mesa on the Heartbreaker..Its not that its breaking your heart from sweetness, its that its blowing your heart apart from sonic punch....Haha. I wouldn't call it a "sweet" amp by any means. I would call it a military weapon....called the HEARTBREAKER!

hearing what I mean.

Tommy_G said:

... I would call it a military weapon....called the HEARTBREAKER!

hearing what I mean ...

Click to expand...

Oh ya! "I Like, It I Love It, I Want More Of It" :arrow: Shouted to the cadence of field boots on a cold, windy, wet march!!

Dennis

jpdennis said:

Tommy_G said:

... I would call it a military weapon....called the HEARTBREAKER!

hearing what I mean ...

Click to expand...

Oh ya! "I Like, It I Love It, I Want More Of It" :arrow: Shouted to the cadence of field boots on a cold, windy, wet march!!

Dennis

Click to expand...

Haha

Tweeked said:

Never had a problem running EL 34's at full power.
I don't do it alot but it has been tried.
Mine went in for service a while back and I had
everything tested.Everything worked with all settings
for 6L6,EL34 and 6v6 as I use the amp with all the tube
options.Also had them try all the tubes with GZ34 and 5U4GB.
So far so good.

The EL34's I got are Mesa STR 447's they sound fantastic!
I was told these were Sovtek tubes.Not my favorites but in the HB
the sound is amazing.Got the Mesa 6v6's also Sovteks.Winged =C=
6L6's that came with the amp sound fine too.

Going to replace preamp tubes soon any suggestions?

Click to expand...

Hey thanks for your input, and Thunda, too!

I'm going to try the 2xEL's on Hi Voltage tommorrow. Mine are 447's and agree they sound fantastic with one proviso: the PI has to work with the tubes, or else there will be incoherency in the lows, especially with high gain setting and palm muting.

The first PI I tried, the power tubes sounded fuzzy below the low G string. The second PI trial, it was clear the whole way through, but I think the LPS is so weak that it was distorting before the Power Tubes. I'm kindof thinking that a 12AY7 may be the ticket for a PI to keep the PI as clean as possible to really let the power amps push through with minimal PI interference. But need to test.

So, in terms of new tubes, find the one that sounds the best in the PI...first. I've got about 15 tubes that I'm going to circulate through until I find "the one". (finger's crossed).

In terms of the first valve stage which sets the fundamental tone in that chain...I have noted that speakers and tubes need to walk hand in hand, particularly for edge of breakup gain settings. If you have a British style with speaker breakup, you can go with a more sterile tube and you won't overdo it.

So, with my Greenback-ish speaker:

LOVE: I'm really loving a NOS RCA Short Greyplate ($20)....not everyone's first choice in Fenderesque preamps... but seems to work excellent with this speaker in conjunction with 6L6's. (Never like it at all with the stock MC90). Classic country spank and modern sizzle if you want it. With EL34's, I'm finding that the way that power tube compresses and overdrives is so different than a 6L6, that I'll have to figure out how to pick preamp tubes all over again. I'll be swapping my inventory through V1 to see what brings out the right stuff.

LUST: I'm still trying to find the right combination, but currently run a Groovetubes Gold 12ax7 C (eg. Chinese) followed by a Raytheon Blackplate for the creamy smooth clipping that tube delivers in the cathode follower position. Not 100% happy, so, give me a few weeks to hone in on it. It works good on the Low Gain setting, but the High Gain setting needs something different but I can't quite put my finger on it.

Tommy_G said:

... I'm going to try the 2xEL's on Hi Voltage tommorrow ...

Click to expand...

So you are going to use the power source in "FULL NORMAL" position & the watt switch in 60 WATTS. Are you going to use Rectifier Select in Silicon Diode mode or Vacuum Tube mode? And if Vacuum Tube mode will you be using a 5U4G rectifier as the manual suggests?

Dennis

Yes, 60W mode. Normal Power (eg. 458V on plates), 5AR4 Tube Rectifier.

Maybe I'll call Mesa first.

Geez, the Stilletto these STR447's came out of runs 450V plate, and Silicon Rectifier.

I found a NOS GE 5AR4 rectifier tube a few years ago. It seems pretty bulletproof. Has less sag than the chinese version, but it even *looks* heavy duty. Maybe you should seek out one for yourself. So far it has out lasted three import versions.

I talked to boogie and the general advice is that the rectifier seems to be only sized enuf for 4x6L6's, and EL34's "for some unknown reason" make the rectifier so it doesn't work properly.....ah....o...k.....

On reading some internet heresy about EL34's, they actually consume quite a bit more current (power) than 6L6's , so that's probably the reason the rectifier blows. ITs only sized for the lower draw of 6L6's.

However, with only 2xEL34's there should be wayyyy adequate capacity in the stock 5ar4 rectifier. And since I'm after smooth clean power amp breakup, EL34's are the way to go.

Based on the "advice" in the manual that says that EL34's aren't made as sturdy as they used to be, a reasonable person would come to believe that boogies were having problems with the EL's blowing up. But no, they are having problems with the Rectifiers when EL's are used. Just a tad bit of bait and switch misinfo there I think.

I'm putting er up to full voltage. That gets the bias voltage up to where its supposed to be (assuming MB used the correct resistors and tolerances), -37V so the tubes run in the proper range. Power tubes don't last very long if they're not in the correct bias range. You get something like 50% of the life for every 10% off on bias voltage. That said, the 'correct bias' changes with plate current, but that relationship is allegedly non-linear. So 20% lower plate voltage may mean quite a variation from the proper bias voltage at that level. Some of that info I got from guitarampblueprinting. Thanks Myles.

By further reasoning, the tweed switch is most likely to change the bias and plate voltage so it sits in the proper range for 6v6's, I'm now certain.

Whatever the manual says, it smells to me this EL34 vs. Rectifier issues is an exercise in confusion for a small error in design.