Tubes for a IIC+

[MesieBooga]

Hi guys! I'm new to the board.

I'm looking for tubes for my IIC+. I noticed the manual from Mesa says to use STR415's.
Anyone see these NOS around? :lol:

 

[JazzRules]

Hi guys! I'm new to the board.

I'm looking for tubes for my IIC+. I noticed the manual from Mesa says to use STR415's.
Anyone see these NOS around? :lol:

I bought a matched pair of Philips NOS 7581As for my IIC+, from KCA NOS TUbes.

Someone here said such "35 watt tubes" "wouldn't bias correctly" as they would run a cold 18 mA of bias current. According to Mike at KCA-NOS, the actual bias was about 32 mA.

They sound good to me. Very clean tube.


I had a pair of new GT 6L6GEs in the Mark IIC+, but I moved them to my Mark IV.

 

[MesieBooga]

Hi guys! I'm new to the board.

I'm looking for tubes for my IIC+. I noticed the manual from Mesa says to use STR415's.
Anyone see these NOS around? :lol:

I bought a matched pair of Philips NOS 7581As for my IIC+, from KCA NOS TUbes.

Someone here said such "35 watt tubes" "wouldn't bias correctly" as they would run a cold 18 mA of bias current. According to Mike at KCA-NOS, the actual bias was about 32 mA.

They sound good to me. Very clean tube.


I had a pair of new GT 6L6GEs in the Mark IIC+, but I moved them to my Mark IV.

Didn't you like the GT's in the IIC+? What kind of tone are you going for?

 

[Joey707]

NOS 7581's will work as will the NOS Phillips 6L6's. Phillips made the STR 415 for Mesa. You can also use some of the current Mesa 6L6's. The STR 430's and the STR 454's will work. However, you should call Mesa and ask them what tube color code will work in your amp. If you get the correct color code for your amp the fixed bias will work correctly and you'll be a happy camper.

 

[JazzRules]

Hi guys! I'm new to the board.

I'm looking for tubes for my IIC+. I noticed the manual from Mesa says to use STR415's.
Anyone see these NOS around? :lol:

I bought a matched pair of Philips NOS 7581As for my IIC+, from KCA NOS TUbes.

Someone here said such "35 watt tubes" "wouldn't bias correctly" as they would run a cold 18 mA of bias current. According to Mike at KCA-NOS, the actual bias was about 32 mA.

They sound good to me. Very clean tube.


I had a pair of new GT 6L6GEs in the Mark IIC+, but I moved them to my Mark IV.

Didn't you like the GT's in the IIC+? What kind of tone are you going for?

The GT 6L6GEs sounded fine it the IIC+. They sound good in the Mark IV too.

Being a jazz and fusion guy, I go for the sweetest distortion possible. I still love the vintage Carlton-Ford-Santana-Holdsworth-Ritenour sound. That to me is "Boogie".

 

[MesieBooga]

When I was a kid we always though Mesa Boogies were "Mushy". aka great lead tone = muddy rhythm. :lol:

I called Mesa today and they sold me some STR440's. The 454's are "Out of Stock".

 

[Boogiebabies]

Hi guys! I'm new to the board.

I'm looking for tubes for my IIC+. I noticed the manual from Mesa says to use STR415's.
Anyone see these NOS around? :lol:

I bought a matched pair of Philips NOS 7581As for my IIC+, from KCA NOS TUbes.

Someone here said such "35 watt tubes" "wouldn't bias correctly" as they would run a cold 18 mA of bias current. According to Mike at KCA-NOS, the actual bias was about 32 mA.

They sound good to me. Very clean tube.


The 32ma is the natural plate current the tube drew during testing. Now when you put a bias meter on your amp and tell me what they draw in a IIC+, you can then stop talking out of your arse.

 

[Boogiebabies]

Hi guys! I'm new to the board.

I'm looking for tubes for my IIC+. I noticed the manual from Mesa says to use STR415's.
Anyone see these NOS around? :lol:

I bought a matched pair of Philips NOS 7581As for my IIC+, from KCA NOS TUbes.

Someone here said such "35 watt tubes" "wouldn't bias correctly" as they would run a cold 18 mA of bias current. According to Mike at KCA-NOS, the actual bias was about 32 mA.

They sound good to me. Very clean tube.


I had a pair of new GT 6L6GEs in the Mark IIC+, but I moved them to my Mark IV.

Didn't you like the GT's in the IIC+? What kind of tone are you going for?

I just threw in a set of NOS Phillips 7581A's matched to 1ma. They are rated a natural plate current at 48ma. In a 7/84 IIC+ with Simul Class these tubes drew 30ma of bias at 480 plate volts. This works out to around 42% of Max Plate Dissipation. The factory bias is set to -56 volts. This amp
has -57 volts at pin 3 of each 6L6. A general rule is to try to bias tube to around 75% of max plate dissipation. This is to ensure that the tube is out of crossover and is idling around where is should. I generally try to do 60-75% of MPD and test by ear. If you have a scope. have at it. In a IIC+ the tube would have to draw 54ma to be at 75% MPD. A set of 7581A's with a natural current draw of 32ma I could only make an inference to the fact that they are only biased at around 30% MPD. Maybe more, maybe less. The point is, if I am going to drop some goofy coin on NOS I am going to be sure that the amp runs the tube somewhere near where is should. The dela with Boogie's is to find an tube with enought natural current draw to get you to 40-50-60-70%. I am not the type of amp guy that would blow $ 190.00 on a quad and be at 30% MPD or less trying to convince myself that they are the second coming. The same goes for an amp with a bias pot. It your tubes draw a low natural plate current and you dont have a wide sweep on your trim pot, the tubes will run only as hot or cold as the sweep on the bias pot allows. Adversely, if you buy a tube with a very high drawing natural plate current, even the bottom of the bias pot may have you cooking the tube beyond its MPD. It is not likely with the Phillips 7581A. It is a monster tube that can take a severe beating and still last 10,000 hours.

Caveat Emptor. With low NOS tube supplies, dealers are going to sell what they can and let you deal with the aftermath. I am sure the dealer is reputable, but did he have a bias meter and a IIC+ in front of him. Yes, the tube draws a 32ma plate current on what????

 

[JazzRules]

I bought a matched pair of Philips NOS 7581As for my IIC+, from KCA NOS TUbes.

Someone here said such "35 watt tubes" "wouldn't bias correctly" as they would run a cold 18 mA of bias current. According to Mike at KCA-NOS, the actual bias was about 32 mA.

They sound good to me. Very clean tube.


I had a pair of new GT 6L6GEs in the Mark IIC+, but I moved them to my Mark IV.

Didn't you like the GT's in the IIC+? What kind of tone are you going for?

I just threw in a set of NOS Phillips 7581A's matched to 1ma. They are rated a natural plate current at 48ma. In a 7/84 IIC+ with Simul Class these tubes drew 30ma of bias at 480 plate volts. This works out to around 42% of Max Plate Dissipation. The factory bias is set to -56 volts. This amp
has -57 volts at pin 3 of each 6L6. A general rule is to try to bias tube to around 75% of max plate dissipation. This is to ensure that the tube is out of crossover and is idling around where is should. I generally try to do 60-75% of MPD and test by ear. If you have a scope. have at it. In a IIC+ the tube would have to draw 54ma to be at 75% MPD. A set of 7581A's with a natural current draw of 32ma I could only make an inference to the fact that they are only biased at around 30% MPD. Maybe more, maybe less. The point is, if I am going to drop some goofy coin on NOS I am going to be sure that the amp runs the tube somewhere near where is should. The dela with Boogie's is to find an tube with enought natural current draw to get you to 40-50-60-70%. I am not the type of amp guy that would blow $ 190.00 on a quad and be at 30% MPD or less trying to convince myself that they are the second coming. The same goes for an amp with a bias pot. It your tubes draw a low natural plate current and you dont have a wide sweep on your trim pot, the tubes will run only as hot or cold as the sweep on the bias pot allows. Adversely, if you buy a tube with a very high drawing natural plate current, even the bottom of the bias pot may have you cooking the tube beyond its MPD. It is not likely with the Phillips 7581A. It is a monster tube that can take a severe beating and still last 10,000 hours.

Caveat Emptor. With low NOS tube supplies, dealers are going to sell what they can and let you deal with the aftermath. I am sure the dealer is reputable, but did he have a bias meter and a IIC+ in front of him. Yes, the tube draws a 32ma plate current on what????

That's nice. I don't have a Simul-Class Mark IIC+ however, just a 60 watt model.

I can tell you the Philips 7581As sound at least as good as the GT 6L6GE with a GT "rating" of 7.

 

[Boogiebabies]

Didn't you like the GT's in the IIC+? What kind of tone are you going for?

I just threw in a set of NOS Phillips 7581A's matched to 1ma. They are rated a natural plate current at 48ma. In a 7/84 IIC+ with Simul Class these tubes drew 30ma of bias at 480 plate volts. This works out to around 42% of Max Plate Dissipation. The factory bias is set to -56 volts. This amp
has -57 volts at pin 3 of each 6L6. A general rule is to try to bias tube to around 75% of max plate dissipation. This is to ensure that the tube is out of crossover and is idling around where is should. I generally try to do 60-75% of MPD and test by ear. If you have a scope. have at it. In a IIC+ the tube would have to draw 54ma to be at 75% MPD. A set of 7581A's with a natural current draw of 32ma I could only make an inference to the fact that they are only biased at around 30% MPD. Maybe more, maybe less. The point is, if I am going to drop some goofy coin on NOS I am going to be sure that the amp runs the tube somewhere near where is should. The dela with Boogie's is to find an tube with enought natural current draw to get you to 40-50-60-70%. I am not the type of amp guy that would blow $ 190.00 on a quad and be at 30% MPD or less trying to convince myself that they are the second coming. The same goes for an amp with a bias pot. It your tubes draw a low natural plate current and you dont have a wide sweep on your trim pot, the tubes will run only as hot or cold as the sweep on the bias pot allows. Adversely, if you buy a tube with a very high drawing natural plate current, even the bottom of the bias pot may have you cooking the tube beyond its MPD. It is not likely with the Phillips 7581A. It is a monster tube that can take a severe beating and still last 10,000 hours.

Caveat Emptor. With low NOS tube supplies, dealers are going to sell what they can and let you deal with the aftermath. I am sure the dealer is reputable, but did he have a bias meter and a IIC+ in front of him. Yes, the tube draws a 32ma plate current on what????

That's nice. I don't have a Simul-Class Mark IIC+ however, just a 60 watt model.

I can tell you the Philips 7581As sound at least as good as the GT 6L6GE with a GT "rating" of 7.

The ultimate moral of the whole saga still boils down to the fact that the tubes sound good to you. Even at 32ma the 7581A's do sound better than 99% of the currently available 6L6's.

 

[axwielding1]

Well, I've heard from a reliable source that Mesa in fact does have str415's still available, green labels and light blue labels, at the factory at least... He had alot of work done to his Mark IIc+, and had them install the 415's as well...
Big bucks though, I think $150 a pair?!? But those old sylvannias sound excellent, and last a long time at the Boogie's fixed bias...
I ended up replacing my 415's with 2 454's and 2 442's, they both sound excellent. I also have GT12AX7M's in V1-2 &3, and moved the Spax7 into V4 (reverb) This sounds great to me, and I have yet to see a problem with the GT's...I love what they did for the mids, not barky or as pronounced, but very complex with great harmonics..Really a nice tube.
The spax7 for a reverb driver was a great move for me.. Added a great deal to the reverb, and absolutely silent!I like the reverb in my mark III, but as stated, there isn't much, just enough to let it breath, but the spax7 added more reverb somehow, and a fuller quality..
ax. :twisted:

 

[MesieBooga]

Mesa sent me some STR440's. I got them Fri and brought them along to the gig. I put them in only to take them out and put back in the STR454's and STR430's I already had in the amp. (dialed in)
I'll have to put then in again at home to compare...