Single, Dual, Triple Recto all marketing?

[LockStock]

My amp tech, a certified Mesa Boogie repair shop owner, tells me that the rectifier series of amps have their rectifier tubes wired in parallel. Therefore, power is never doubly or triply rectified. Those other tubes are simply backups in case the main tube fails.

Anyone else surprised by this?

I LOVE my Tremoverb and my IIC+. I love Mesa Boogie. Just a bit shocked at this.

 

[lookslikemeband]

I don't know how the DR is wired - but common sense implies with a Triple only having 2 rectifiers, that it is, in fact a 150 watt Dual Recto.

 

[lailer75]

i believe the name "dual" rectifier refers to the fact it ha 2 forms of rectification, "single" because it only has 1 form of rectification. the triple who knows, but it kicks major a$$ though :twisted:

 

[mikey383]

i believe the name "dual" rectifier refers to the fact it ha 2 forms of rectification, "single" because it only has 1 form of rectification. the triple who knows, but it kicks major a$$ though :twisted:

Exactly. The original Mesa ad from 1992 states "Dual switchable rectifiers", aka - solid state or tube rectifiers. The single - well, it only has solid state rectification.

The other rectifier tubes aren't "backups" per se. You need one rectifier tube per pair of power tubes. Just because they are wired in parallel doesn't mean anything other than they are sharing the load between all of the power tubes.

 

[sixtonoize]

You don' really need one rectifier per pair of power tubes. Just look at the Heartbreaker. It just gives the power section more headroom, so that there's less sag.

 

[zeeman]

I don't know how the DR is wired - but common sense implies with a Triple only having 2 rectifiers, that it is, in fact a 150 watt Dual Recto.

As Boomhauer would say it..

Yeah man, I tell ya what, man, that dang ol’ Triple Reckifier has three dang ol’ reckifier tubes.

zeeman

 

[LockStock]

Right, dual rectifiers have two rectifier tubes, and triple rectifiers have three tubes.

Seems there's a lot of confusion.

But I will clarify - per my amp tech, and per the schematic he showed me, the rectifer tubes are NOT dedicated to any power tubes, so that one rectifer for each set of two tubes is not correct. One rectifier of the two (or three in a triple) is for all 4 power tubes in a dual rec, and for all 6 in a triple - the other rectifer tubes are simply backups.

That third rectifier tube in a triple recto apparently is there only if not one but two rectifier tubes fail during a show. Incredibly unlikely.

 

[mikey383]

They may not be dedicated to a certain set of power tubes, but since they are wired in parallel, then they are sharing the load of all four power tubes...not really a backup, per se. It's not like there's only one rectifier running at a time, and if it quits the other takes over. They both run constantly and share the duties. If both tubes have equal resistance, they will equally share the load. I'm not saying you are wrong, I'm just elaborating on that statement.

As for the statement of needing one rectifier tube pet pair of tubes, let me clarify what I meant. If you have all four power tubes installed in a DR, you will have both rectifiers installed. If you pull a pair of tubes to lower the wattage, you also remove one rectifier tube.

 

[LockStock]

They may not be dedicated to a certain set of power tubes, but since they are wired in parallel, then they are sharing the load of all four power tubes...not really a backup, per se. It's not like there's only one rectifier running at a time, and if it quits the other takes over. They both run constantly and share the duties. If both tubes have equal resistance, they will equally share the load. I'm not saying you are wrong, I'm just elaborating on that statement.

As for the statement of needing one rectifier tube pet pair of tubes, let me clarify what I meant. If you have all four power tubes installed in a DR, you will have both rectifiers installed. If you pull a pair of tubes to lower the wattage, you also remove one rectifier tube.

This is directly opposite to what my amp tech, who is Mesa certified and also has his own amp line, says. I don't know enough to know. But he says because they are parallel all rectifiers are NOT being used, and he is the one telling me that the others are truly just backups. I'm not saying you're wrong and I'm right. Just I'm getting two very different opinions. Can anyone else chime in here?

 

[Demoncleaner]

I'm just gonna clarify what it means to be in parallel. If you have just one tube in a loop all the current in that loop is passing through that one tube. If there are two tubes parallel in a loop all current in that loop is broken up according to the resistance of each tube. If the tubes are the same they will have 1/2 of the loops total current running through each. Likewise if there are 3 equal tubes they will have 1/3 of the loops total current running through each tube. Therefore, if you have 2 tubes, you can drive the whole loop twice as hard and stress the tubes the same as having one in circuit with half the current. Likewise with 3 tubes, you stress them the same as the other configurations with 3 times the current. I'd assume that is why you have 50 watts for a single, 100 for a dual, and 150 for a triple.

TLDR version:
All tubes are being used, you can just multiply the amount of current going through the circuit by the number of tubes and stress each tube the same in all configurations.

 

[msi]

And to even further elaborate, the rectifier tubes can only provide so much current before the voltage they supply starts to drop. This is the "sag" that everyone talks about. With four power tubes and only one dedicated rectifier the current the power tubes pull will stress the rectifier tube. It will try to supply the current, but when it can't it will at some point fail. So the second tube is added so that rather than having all current from all four tubes going through one rectifier tube, the two rectifier tubes each share half the current from the four power tubes. Or each of the three rectifier tubes share a third of the current for the six power tubes in the triple.

 

[mikey383]

Lockstock, it's possible you are misunderstanding what he was trying to say. I don't know. They can't be double or triple rectified, meaning that the voltage would pass through two, or three rectifiers in a row. That would put the rectifiers being in series. But in parallel, they all would share the load. That's just simple electrical theory.

Look at the rectifiers being wired in parallel the same as two speakers being wired in parallel. Both speakers work and share the load equally, and if one quits, the other still works but takes over the entire load.

 

[mikey383]

Update:

I just checked out the schematics. They are indeed wired in parallel, and they both lead to the power section. There's no way that one would be running at a time, and if it fails the other takes over. They are sharing the load equally.


Check it out - http://www.freeinfosociety.com/electronics/schemview.php?id=507 - scroll about halfway down to the power supply schematic.

 

[LockStock]

Cool, thanks all. So it's not just all marketing.

I guess this is a way to have the Dual and Triple rectifiers exhibit less sag then?

 

[sbalderrama]

Rectifiers convert AC to DC. You can't put it through a bunch in series and somehow get "even more DC", so "triple rectifying" in that context would make no sense. As others mentioned, they are in parallel to share the load. My electrical knowledge stops with some circuit theory classes I took way back, but unless they are switched out, it is impossible for them to NOT be sharing the load in parallel.

And having them simply as "backups" would make no sense either, as no other tubes in the amp get backups and no amp manufacturer would do something like that for "marketing" that causes the cost of manufacture to go up that much.

Contrary to what some seem to think, Everything Mesa does in their amps seems to have a specific purpose and thought behind it. As you said, more power tubes require more tube rectifiers to keep sag from getting out of control. I imagine that one rectifier and 6 power tubes would be pretty unusable, unless your entire sound comes from note bloom. Unless you are pushing the power section near max anway, you probably arn't experiencing much if any sag. At low volumes, it may be that 1 rectifier has enough headroom to handle 6 tubes, until you start cranking it.

 

[mikey383]

I guess this is a way to have the Dual and Triple rectifiers exhibit less sag then?

Correct. If you look at the Heartbreaker, it uses one 5AR4 rectifier tube for 4 6L6 power tubes. Though the 5AR4 is a little stiffer than the Rectifier's 5U4, the load of all 4 power tubes will cause a substantial amount of sag, more noticable than 2 5U4s.

To elaborate on the statement of double or triply rectified, the purpose of a rectifier is to convert your wall's AC current into DC current which the amp uses. Once you pass through one rectifier, there's no need to pass the rectified current through another rectifier, because it's already converted into DC, and the other rectifier tube will not work properly with DC voltage at it's input.

Usually if a rectifier tube fails, it will take out the fuse with it, so a backup really wouldn't be effective in that case. But if it does fail and the fuse doesn't blow, you could run on the remaining rectifier for the rest of your set.

 

[Bchewdown]

So will my TRIPLE RECTIFIER run on 2 rectifier tubes?!?!?!