Mesa Boogie Heartbreaker tubes (EL34, 5881, etc)

Any heartbreaker fans here? I am looking for tube choices for this amp. I am having a hard time decoding what it is mesa is selling in their tube sets (like what the tube manufacturer and series actually is).

I've heard that the EL34 winged C is a great match for this amp, but which mesa tube is that? Or is there a simple mod to add a bias pot to this amp? Is EL34 really the best way to go?

Also, I have a matched NOS quad of tung sol 5881 from 1947, but I don't even see anywhere that I can use those. I know the tweed voltage is 384 (I measured the plate voltages when I had the amp chassis out) and the normal is 452 on my amp.

I got the amp used (traded a guitar for it) and it had a broken lust channel, which I easily fixed (presence pot was open), so now it's just about dialing in the tone.

So many heartbreaker questions!

I hooked up an SRS tube bias shunt and the 6L6GC are reading 22.5ma at 450V and 16.5ma at 384V.

WTH? There's no way Mesa would bias this amp that cold is there? That's crazy.

EDIT: So in the tweed variac mode, I get 384V plate voltage, and flipping to the EL34 bias position (versus the 6l6GC setting) I am running 53ma which is real close. Did Mesa wire this switch backwards by chance?

I found the schematics, and metered it out. The switch is in right, at least it matches the schematic, and the voltages from the bias circuit are as they note... all of which seems to indicate that boogie biases the amp way too cool in 6L6 mode, and just barely in usable range in EL34 with EL34 tubes. I guess that's why everybody likes the EL34 tubes better.

Anybody with some insight into this with the HB?

Hi Mike, I don't have the Heartbreaker.
However I've read time after time about Mesa amps being biassed cold for 6L6's. Then hot for EL34's. I've a post a few down from this wondering about valve tolerances in my MK5. Where Authorised Boogie offer the advice of going with cooler EL34's.

I can see two reasons for that. One that Mesa amps all seem to be preamp focused. The power amp playing little in the sound from the speaker. The other being that perhaps the cold 6L6/ Hot EL34 bias thing is just a way to simply cram it all in. 22ma is terribly cold, around 40%. You're biassed at less than 30% on Variac/Tweed.
I think I'd be taking the amp to get looked at. I wouldn't be messing around putting a bias pot in. Or worrying about Svetlana EL34's. I'm a lifelong Marshall user. The only reason I learnt to bias an amp was because of the bias drift Randall Smith talks about as to the reason he goes fixed bias. A friend of mine works stripping out old RAF bases of electronic equipment. I've been through valve after valve in my 800's. Which rely a lot more on the power amp for their sound than my MK5. I don't hear that much difference between a 50's Mullard El34 and a modern JJ or EH. I do with the ECC83's. I certainly wouldn't contemplate paying £30 per valve for modern production valves. When you can pick up NOS Tungsram for £40 each.

Nicklotsaguitars said:

I can see two reasons for that. One that Mesa amps all seem to be preamp focused. The power amp playing little in the sound from the speaker. The other being that perhaps the cold 6L6/ Hot EL34 bias thing is just a way to simply cram it all in. 22ma is terribly cold, around 40%. You're biassed at less than 30% on Variac/Tweed.

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I'd guess it's option two: "... a way to simply cram it all in".

Nicklotsaguitars said:

The only reason I learnt to bias an amp was because of the bias drift Randall Smith talks about as to the reason he goes fixed bias.

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He's a snake-oil salesman. A fixed bias power amp merely means there's a bias voltage applied. As opposed to a self-biased amp, which means there is no bias voltage applied. What he's done is set two bias points, neither of which is great, but both work, and then polluted the terminology calling his bias voltage points "fixed." Yikes. Better description would be "Preset bias voltages for 6l6 & EL34 tube types".

However I think you're right in the end, either way the boogie sounds good, so he built his sound around the cold power amp. Go figure.

Meanwhile my amp has two bad screen resistors on V11 - all the others meter out at about 500 ohms, and those two are 31 ohms, one of them even looks cooked. Which indicates to me this amp had a bad power tube in it at one time. I'll call a service tech but without warranty on the amp I can only guess it won't be cheap; I'll probably fix it myself and give another go.

Digging around in one of my bins, I had a NOS 5881 Sylvania quad (I have no idea how or why!), and they were bundled together with "matched" marked to them from Antique Electronics.

Putting them in the amp, in tweed variac mode with the 5AR4 tube rectifier selected, at 369V plates, with bias switch set to EL34, I am reading 35.4 +/-1ma on each tube.

That's usable!

5881 = 25W dissipation.

25W/369V = 0.0677506775067751A

0.0677506775067751 x 1000 = 67.75mA

35.4mA / 67.75mA = 52%

50% is actually pretty safe to run, and miles better than I was doing with the 6L6!

Sanity check anybody?

Amp is back together (minus the back panel on the combo) and man it sounds freaking sublime.

I am so totally stoked!

In general, Mesa's thing has been to create the gain in the preamp and for the power amp to color the sound, but not really create the distortion. One of the things that separates a Mark sound from a JCM sound is that a JCM has to be cranked and pushed with a pedal to breakup, but the Mark can do it at lower volume, since the preamp is doing all the work.

This concept carried over to the Rectos and are part of what separates it from being just a SLO clone. The phase inverter in the Dual Rectifiers and amps made after it tend to be a little bit spongy and the 6L6 modes are cold to be deep and glassy. The relative loss in headroom in the P.I. makes it fry the peaks a little when the negative feedback loop is disengaged for Modern or Clean, but the power tubes remain pretty flat. I would say that the P.I. is purposely designed to be inefficient and unbalanced, precisely because of the cold power tube bias.

There are 3 capacitors that cut a bunch of the treble out from the power amp, where the P.I. feeds the power tubes, to keep the response deep, but also stable from oscillation in the highs from all of the content that is being created in the preamp. They also allow the NFB to cut in and out without stability issues.

With the negative feedback engaged, the P.I. and the power tubes are both very clean and adding some fat and compression. While the whole signal down into the sub-bass frequencies is being flattened, the highs sound like they take a bigger hit, due to those capacitors that are filtering out treble.

It is apparent it was designed with the ethos of using the preamp and not the power amp to cut heads. Considering the popularity on this site for the Vintage mode, I'd say it wasn't a bad idea, though I personally prefer Modern and Raw.

If you want to hear what the power amp contributes, plug the FX Send into a line level device and monitor it. It's much sharper than what comes out of a speaker and Modern and Vintage are pretty much exact. Run into another amp, it sounds like a totally different thing altogether.

I've got a Heartbreaker as well; manufactured in 1998. I'm at least the fourth owner, but I don't understand why anyone would give this thing up. Mine is somewhat of an odd bird. It's been modified by Andy Turner of Thomas Ampworks and has (essentially) the JCM800 circuit in the Lust channel, a more Fender-y clean channel, an upgraded reverb, and a solo boost. You could play practically any style with this thing.

I'm trying to decide what to use when re-tubing it, especially since it can use a variety of tube types. The mods that were done to this thing also include a bias pot. Has anyone struck gold with some non-Mesa tubes that they'd be willing to recommend? Right now it's got Mesa 6L6's in it, but I want to see what it can really do.

I'm new to the forums and just really starting to dig in - thanks!

scott_l said:

I've got a Heartbreaker as well; manufactured in 1998. I'm at least the fourth owner, but I don't understand why anyone would give this thing up. Mine is somewhat of an odd bird. It's been modified by Andy Turner of Thomas Ampworks and has (essentially) the JCM800 circuit in the Lust channel, a more Fender-y clean channel, an upgraded reverb, and a solo boost. You could play practically any style with this thing.

I'm trying to decide what to use when re-tubing it, especially since it can use a variety of tube types. The mods that were done to this thing also include a bias pot. Has anyone struck gold with some non-Mesa tubes that they'd be willing to recommend? Right now it's got Mesa 6L6's in it, but I want to see what it can really do.

I'm new to the forums and just really starting to dig in - thanks!

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Hi Scott!

Like you I don't understand why these amps are available for sale, especially for so cheap. Probably the best deal in any amp out there.

I played with the 5881 tubes for a bit, but really wanted to try the cooler EL34 option. Talking to Eurotubes, I expressed some of my concerns to Mike there, and he recommended some cooler KT77 tubes (like an EL34) that would retain some of the openness of the 6L6GC, but work well with the bias of the EL34 setting on the amp. I am glad I did, it sounds amazing, and has a bit more headroom than the 5881, and I can use it safely on all settings.

I'd call Eurotubes if I were you; great company and product, and he is knowledgeable about the Heartbreaker.

Mike