MesieBooga said: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 said:MesieBooga said: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 said:JazzRules said:MesieBooga said: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?
JazzRules said:MesieBooga said:
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".
JazzRules said:MesieBooga said: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:
MesieBooga said:JazzRules said:MesieBooga said: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?
Boogiebabies said:MesieBooga said:JazzRules said: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 said:Boogiebabies said:MesieBooga said: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.
Enter your email address to join:
