dual rec set to 50 watts...diode mode..is it really 50 watts

[bsideexperiment]

A while ago, i pulled the correct tubes to make the Dual rec 50 watts...however!, it just occurred to me that i play in diode mode and since i'm not using the rectifier tubes...is it really playing at 50 watts?? or is it working as if i never pulled any tubes.

I'm also kind of worried because i connected the 8-16 ohm jack from the back of my amp to the 4ohm jack in the back of the cab...actually i could be wrong...it could have been opposite...i'm trying to do this by memory ..all i know is i followed what i read was the safe way from one of the forum threads. some how i cut the ohms in half so i could run it in 50 watts. Anyways....if it holds true that the amp was really running in 100 watts the whole time did i damage something?

how should i connect the amp to the cab?

on another note..i've been noticing that my sound has become more muddy and boomy. i know there are so many variables that could make this happen (ie tubes, etc), but if i connected the amp to the cab incorrectly ...does that degrade the sound in any way?

help put me at ease, or tell me what i need to do so that i dont' damage anything!

 

[bsideexperiment]

can anyone give me anyyy insight?

 

[MrMarkIII]

The mode of rectification doesn't affect the final output power.
All a rectifier does is take the A/C coming out of the wall and change it into D/C. Amps work on D/C, like flashlights.
As a rule of thumb, when removing power tubes to halve the power, the impedance of the speaker should be doubled.
So, if the cab (or the combo's internal speaker) is eight ohms,
plug it into the four ohm jack in back of the amp.
If all you had was an eight ohm speaker output on your amp,
it would be best to use a 16 ohm speaker.
Amp small number, speaker big number.

 

[bsideexperiment]

ok..so let me get this straight..sorry, but i just want to clarify...

is it correct to assume that in diode mode i could hypothetically take out all the power tube and run it safely....in other words, does it bypass using the power tubes all together?

and if that's true, then while being in diode mode in order to cut it to 50 watts all i would need to do is pull one of the two rect tubes...

or am i completely getting this wrong... :shock:

 

[nomad100hd]

dude your so lost! diode mode is not a solid state power amp, but .... the method in which A/C power is converted to D/C power. If you pull all the power tubes than you'd have no power at all! The only reason to pull one rectifier tube is to maintain the level of sag you had with 4 power tubes when only using 2 power tubes.

 

[Ellero]

On diode mode it's bypassing the REC tubes. Power tubes are always in use.

 

[bsideexperiment]

wow....thanks for the help...i feel like an idiot...but i'm sure as h#$$ happy you guys took the time to explain this to me...

now knowing this i have a question...are their differences in tone if i switched from 6l6s to el34s and set to diode mode...
or is there a more noticable difference if i had switched from 6l6 to el34 in vacuum tube mode

 

[ANIMATED SUSPENSION]

It doesn't mention anything about doubling the impedance in the manual. So don't do it !!! Just pull the centre two tubes and one of the rectifier tubes like it says. I'd try using the correct impedance i.e 8 ohm -> 8 ohm or whatever. Although most mismatches are safe, the tone and feel of the amp changes, this may be why the amp sounds boomy. 8 ohm/16 ohm -> 4 ohm mismatches are NOT safe and will damage your amp ! I hope you didn't do that !! The impedance of the cab can be higher than the amp within reason, but not lower is the rule.

 

[Sustain]

mesa engineering told me that it is not a half power = double impedance straight conversion, but its a close rule of thumb.

Best bet is to consider it halved impedance. What this means is its not really halved, but it is fairly close to it, thereby always giving you a mismatch (albeit less of a straight up mismatch, and even straight up mismatches can be "safe" so this is even more safe).

diode or not, you will hear a difference in el34 vs 6L6's.

 

[bsideexperiment]

so the general concensus is to connect the 8/16ohm jack from the amp to the 8 ohm jack in the speaker when run at fifty watts...and that will make it sound less boomy...

 

[kb7010]

I just called Mesa on this.. the proper way to go about this.. again as per Mesa

you can pull 2 inside .. or two outside tubes.. then you must pull ONE Recto tube.. now it is at 1/2 the power of the amp..( but not really at 50 watts.. if that makes since..??? ) after you do that you MUST change the way you plug into a cabinet..

ie: have a 16 ohm cab.. amp now MUST be plugged in as to think it is a 8 ohm cab..

got a 8 ohm cab.. run amp at 4 ohms.. etc.

ALSO... you CAN NOT run two cabinets..!!!! period.. unless you put it all back to stock.. ie: put all three tubes back in.. but then you are at full power again...

again.. this IS AS PER MESA..!!!!! not my info.. call them and they will tell you SAME thing.. if not.. PLEASE send me a PM or e-mail.. as I don't want to cook my amp or a cabinet..!!!!!!


EDIT: I forgot one IMPORTANT THING... he ( Mesa ) also told me.. change things alittle at a time.. so make a diagram of the way you are happy with your tone NOW..!! pull tubes.. then try one thing ONLY per night.. don't like tone..??? set it back.. ie: spongy mode.. tube mode.. you get the point..

if not .. send me a PM or e-mail.. and I WILL explain in more detail..

 

[clutch71]

wow....thanks for the help...i feel like an idiot...but i'm sure as h#$$ happy you guys took the time to explain this to me...

now knowing this i have a question...are their differences in tone if i switched from 6l6s to el34s and set to diode mode...
or is there a more noticable difference if i had switched from 6l6 to el34 in vacuum tube mode

Did you actually put EL34's in? This isn't a magic switch that makes the tubes sound like one or the other. It is only to be used with the particular tubes you choose ie 6L6 or El34's.

 

[mikey383]

you can pull 2 inside .. or two outside tubes.. then you must pull ONE Recto tube

I'm calling bullshit on the must part.

The only reason to pull a rectifier tube is for the sag. If it's left in, the tone will be tighter because of the decreased load on the rectifiers. If you used diodes, then there is no reason to pull a rectifier either. Or, you can pull both of them.

Been running 2 power tubes with 2 rectifier tubes for 2 years now with no adverse effects.

 

[StoneOfFire]

look son,
you sound like youre gonna damage something so pay close attention

your amp has three types of tubes.

first there is the preamp,
a set of five small tubes

next there is a set of four power tubes
the amp comes with 6L6 tubes from the factory.
mine said 6L6GC on the four tubes
IF you take them out and replace them with EL-34 (or el34 type..) tubes
THEN you are supposed to change your bias switch from 6L6 to EL-34

last, there is a set of two rectifier tubes that are about the size of the powertubes. the ones that came in my amp were much fatter, bulb shaped, and the ones that are in there now are shaped slimmer like the power tubes, only smaller. stock should read 5UG or something like that.

if you are set to vacuum tube,
you will use pre > power > recs
if you are set to silicon diode,
you will use pre > power > silicon diodes



i am using TWO KT77 tubes (similar to EL-34)
so i set my bias to EL-34
and i run BOTH GZ34 rectifier tubes
i dont pull one to match pulling two power tubes
sounds real shitty in a good way.
what could go wrong?
i run 8ohms out to the cabs 16ohm in.

i dont run four KT77s.. not even when im with the drummer..
this thing is SO LOUD

 

[Leng]

I've wanted to run my recto like that for so long, but have never heard consistent instructions from multiple people on how it's done. And as the instructions contradict each other, the people giving them say the others' instructions can cause damage.

So I've never ran my recto with 3 tubes pulled, for fear of toasting my beautiful baby. Would be nice though, if sometime everyone agrees.

 

[bsideexperiment]

that's just it....i'm confused on pulling one or keeping both rec tubes in.
someone said mesa says you MUST pull one rec tube out when playing in fifty watts. i guess that's what i have been doing and i'll stick to it....however, is there a noticeable difference in tone/sound if i would keep both in?

 

[mikey383]

that's just it....i'm confused on pulling one or keeping both rec tubes in.
someone said mesa says you MUST pull one rec tube out when playing in fifty watts. i guess that's what i have been doing and i'll stick to it....however, is there a noticeable difference in tone/sound if i would keep both in?

Try it and see how you like it. It's not going to damage anything by keeping both in.

The reason behind pulling a rectifier tube is this:

When using all 4 power tubes, the rectifier tubes exhibit a certain amount of "sag" to them from working to rectify enough current to feed all 4 tubes. They are wired in parallel, so they split the load of 4 tubes equally between the 2 of them.

Now, pull 2 power tubes. In order to exhibit the same amount of sag, you pull one rectifier tube as well. Otherwise, with both rec tubes running, they won't have to work nearly as hard to rectify current, and the tone will be tighter. They won't sag from a heavy load like they will with 4 power tubes.

It's up to you whether you want to pull a rectifier tube or not. There is no harm in pulling one, or not pulling one. The tonal change is the only difference.

As for how to pull tubes, here you go. I can't make this any clearer:

1 - Pull either the 2 inner or 2 outer power tubes.
2 - Change fuse size to half of current fuse rating. (you're running half the power)
3 - Speaker cabinets now go to the jack with half their rating...I.E. - an 8 ohm cab goes to the 4 ohm jack on the amp. 16 ohm goes to 8 ohms. 4 ohm cabinets should not be used.
4 - If you use diodes, you're done. If you use the tube rectifiers, decide if you like one rec tube, or both. If you like the tone with one, pull one rec tube. If you like the tone with both, keep them both in.

5 - Done. Enjoy.

 

[nomad100hd]

Why you "missmatch" the speaker jack with 2 tubes pulled.

The impedance is translated threw a transformer, when you pull 2 tubes the impedance on the tube side of the transformer is doubled so to keep the same balance double the impedance of the speaker side. aka put an 8Ω in the 4Ω jack.

As far as tube amps liking an 8Ω speaker in the 4Ω jack better than a 4Ω in the 8Ω... do some research tubes prefer a short to an open. It's tube theory can't argue with text book theory that's been proven time and time again. Some amps are even designed with a speaker jack that shorts when nothing is plugged in, this puts less strain on the OT and more on the tubes.

 

[kb7010]

you can pull 2 inside .. or two outside tubes.. then you must pull ONE Recto tube

I'm calling bullshit on the must part.

The only reason to pull a rectifier tube is for the sag. If it's left in, the tone will be tighter because of the decreased load on the rectifiers. If you used diodes, then there is no reason to pull a rectifier either. Or, you can pull both of them.

Been running 2 power tubes with 2 rectifier tubes for 2 years now with no adverse effects.

once again..
I am just telling you what " Mark " at Mesa Boogie told me..!!!!

in fact look on page # 13 of your owners manual.. it says.. ( word for word .. even in bold and caps as I have done )

" NOTE: On the Dual Solo Head it is possible to run two 6L6 or EL34 tubes pulling the two center tubes, leaving far left and far right tubes intact. This procedure reduces the power by approximately 50%. Remove one of the Rectifier tubes if you are using the TUBE RECTIFIER setting to assure a correct match "

the part worded TUBE RECTIFIER is why I even called Mesa to make 100% sure as I was unsure of the wording.. but if you are happy with yours .. and not having a problem.. I MIGHT try your way.. but I am going to call Mesa once again on Monday as to be 110% sure.. as I don't want to smoke my amp..!!!!! THAT IS NOT A SLAM.. SO PLEASE DON'T TAKE IT AS SUCH..!!! again... I am just telling you what Mark at Mesa Boogie told ME..!!!!! as per a phone call I had with the man.. I even asked.. are you sure as it doesn't say that word for word in MY owners manual.. ????? esp. if you do such " mod " ( if one would call it that ..??? ) why the manual wouldn't tell you to reduce the ohms as I explained before..

" well I think I would know " where his exact words..!!!!

again... my amp is a 3 channel Dual Rectifier model..!!!!


Rex

 

[mikey383]

The key words there are "to assure a correct match."

I'll explain again. With 4 power tubes, the 2 tube rectifiers will produce a certain amount of sag. This is due to the load that 4 tubes put on the rectifiers.

Now, you pull two power tubes. The load on the rectifiers is cut in half. To keep the same amount of sag (assure a correct match), you pull one rectifier tube. If you don't pull one, there won't be as much sag. This is comparable to installing GZ34 rectifiers in your amp.

You will do no harm to your amp by pulling 2 power tubes and leaving both rectifier tubes intact. In fact, the life of the rectifier tubes may be lengthened because they won't be working as hard.

It's not easy to fully explain the fundamentals of it, but trust me, you won't fry your amp by leaving both of them in.