Difference in Mark III Colosseum & Standard Mark III?

[dandan]

Aside from the deafing wattage is there any difference in the 2?

saying both are "reds" or "blues" ?

 

[timv]

I put pictures on my yahoo page of a standard blue stripe mark 3 next to a coliseum blue stripe mark 3. Here they are: http://photos.yahoo.com/tvogelin Click on the mark 3 coliseum folder.

 

[Boogiebabies]

First off, it is a Simul-Class K series. The output and power transformers are enormous in comparison to the standard Simul MK III. The iron and stack size on the K series are bigger than you will ever see on any Mesa amp. That thing will have power, attack and clarity above and beyond any amp of its day, and even most today. There are obvious changes in the filter caps in the power section as it is needed. That is one scary amp!!!!

On the preamp side, I can assume that there is no change. The K series does use one less 30uf 500V filter cap on the preamp circuit. You would have to sit there and blueprint every resistor and cap to see if there are any other changes. I did not see a limiter circuit on the K. It must be the loudest amp you have ever heard.

A very nice clean example of Mesa decadence.

 

[timv]

I just got the coliseum in the mail on friday and got a chance to check it all out. It came with newer boogie str440 tubes in it, it was retubed at the boogie store in la. I checked the idle bias on the tubes and they were extremely high which seemed strange to me because I spoke to mike b. this week and he mentioned that they were biased pretty cold. The B+ voltage is about 507 and the 4 standard tubes were at about 40ma, the 2 triode tubes were at 54ma and 58ma!!! R117 was not installed on the amp. I ended up changing a few resistors in the bias circuit to get the negative voltage higher. I put in a set of JJ tubes from eurotubes that were mesa rated, 4 6L6's and 2 E34L's and they biased up great right away. The 4 6L6's are at 30ma and the E34l's are at about 40ma. I wonder if the newer mesa tubes bias hotter than there older ones? I think this would of originally shipped with the str415, sylvania tubes. Any thoughts???

 

[Boogiebabies]

I just got the coliseum in the mail on friday and got a chance to check it all out. It came with newer boogie str440 tubes in it, it was retubed at the boogie store in la. I checked the idle bias on the tubes and they were extremely high which seemed strange to me because I spoke to mike b. this week and he mentioned that they were biased pretty cold. The B+ voltage is about 507 and the 4 standard tubes were at about 40ma, the 2 triode tubes were at 54ma and 58ma!!! R117 was not installed on the amp. I ended up changing a few resistors in the bias circuit to get the negative voltage higher. I put in a set of JJ tubes from eurotubes that were mesa rated, 4 6L6's and 2 E34L's and they biased up great right away. The 4 6L6's are at 30ma and the E34l's are at about 40ma. I wonder if the newer mesa tubes bias hotter than there older ones? I think this would of originally shipped with the str415, sylvania tubes. Any thoughts???

At 507 volts, the 6L6's @ 75% MPD is 44ma, so 40 is perfect. The simul sockets are hot. All you need to do is run a cooler color code of Mesa tube and you will be fine. The Simul sockets are always biased hotter from the factory. They always seem to get a cold set of Mesa EL34's to bias either cold or right on. The STR-415's were not even graded by color.

 

[timv]

Thanks for the input. I thought the chinese str440's were only rated for 25 watts not 30 like other more robust 6L6's? I think I will stick with the JJ's but bias them up a bit. I added a adjustment pot so can easily adjust the bias. I need to recheck my B+ with the lower current anyway, it may have gone up a bit. Thanks for the help.

 

[Boogiebabies]

The 440's are Ruby 6L6GCMSTR's. They are a 30 watt tube. At 40ma and 507 plate volts I would say that that amp PT probably puts out 520 volts.
If you put less of a load on it, the 507 volts is bound to go up.

 

[MesieBooga]

okay tech dudes... enough... :lol: HOW DOES IT SOUND?!!!!

 

[timv]

I actually did turn the current up a bit. It is now 35ma for the 6L6's and about 40ma for the EL34's. The B+ did go up to about 517 with this setup. I am sticking with the JJ's for now but have the mesa tubes to play around with. How it sounds? I can't really give a fair review right now because I haven't been able to crank it yet, first it seems to have more low end then my standard mark III did. I'm sure cranked it will sound really good. I have already did the R2 mod and added adjustable bias. It is so much easier to add things in the longer chassis. The holes were already there to add pots to.

 

[dandan]

how do you even put that amp at volume 3 without it being deafing loud? : O


Can someone help me with this question please? : )

how do 4 mesa 6l6 str 440's compare to 2 6L6 2 EL34's in my Mark III C++(used to be blue stripe)?


ive been told by John at Mesa Hollywood that he recommends just 4 straight 6L6 440s.

It also sounded like Mike B prefered 4 6L6's when i talked to him.

he said adding 2 el34's add a little bit more growl to it.

Im really going for somewhat of a "john sykes" like tone. So what do yall recommend?