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Build a Bass amp? Tube Q:


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9/30/2000 1:49 AM
JaySG
 Build a Bass amp? Tube Q:
Guitar amps galore here. What about bass amps? I've previously owned a V-4B and an HD-130. I found that ~100W was good power level. Can I get that from a pair of KT-88s or 6550s with an Ultralinear OT? I'd like to keep it simple.
  
9/30/2000 3:24 AM
Ray Ivers
Jay,  
 
Yes, you can - even more with the KT88's. How about a Marshall Major (200 watts, four KT88's, ultralinear circuit); does that sound interesting?  
 
Ray Ivers
  
9/30/2000 3:41 AM
JaySG
even more !?!? How's the support on transformers. Would I be looking at Hammond for all the iron?
  
9/30/2000 1:42 PM
Ray Ivers
Jay,  
 
Yes, I think the Hammond 1650R would be a good ouput transformer choice for 6550 / KT88 tubes. You could also use the 1650T with a pair of KT90's, by mismatching the secondary (8 ohm tap for a 16 ohm cab, etc.) to get a 3,800 ohm primary load impedance. Believe it or not, the KT90's like it even lower; my data sheet indicates a 3K primary load for 850 plate volts, 165 watts out from one pair! I don't know what voltages you're looking at, but Hammond makes a bunch of trannies, and were pretty cool on the phone about custom-winding ("what do you need?") although I never got around to taking them up on it. I would think that 150 watts would not be unreasonable for a pair of KT88's run at or near maximum voltages (this is for loud/clean, not heavy power-amp overdrive).  
 
A 12BH7 would make a pretty good driver tube for loud/clean usage.  
 
Ray
  
10/3/2000 12:39 AM
dpcoyle
I got about 60 watts out of 2 6550's into the 60 watt UL Hammond xfmr and was very happy with it for practice. For clubs I would think two pair a minimum, and the 120 W xfmr.  
I use my crown CE 2000 with a tube preamp at gigs cause the show has to go on, and I'm not rich enough to bring two 300W tube amps.  
Also, IMO a 6SN7 is another good choice for a driver.  
Dan
  

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