31
Bass Amps & Effects / Re: Mesa 400 tube recommendations
« on: December 28, 2014, 04:45:36 PM »Change the driver tube from a 12AX7 to a 12AU7 if you find you need more headroom. It will lower the overall gain of the amp a bit, but that trade will give you more useable volume and headroom. I'd also go with 6550's or KT88's, whichever you can find the cheapest. Mesa output sections are designed for lots of distortion and "dirty" power and tend to be a bit muddy but their preamps are very bright and high gain. Any of the big beam tetrodes, 6550's/KT88's, are going to have lower plate impedance which will shift the tonal balance even further towards lows, but in the case of the Mesa amps, it increases low-end extension and rolls off the highs just barely inside the range of human hearing. The 400 was designed around GE 6550A's, which is what all modern 6550's copy. It's a 200 watt amp, but it's good sounding 200 watt amp. I'm using a 400+ right now with a 12AU7 driver and while it will never have the punch of a beefier tube amp, it is a nice flavor tonally that cannot be derived any other way.
Basically, Randall Smith took what he had learned about making guitar amps and translated it directly to bass amps. There's an interview with him in the new Bass Gear magazine about his design philosophy that confirms everything I have been speculating about Mesa's tube bass amp design philosophy for years. They're not my favorite, but they are distinctive.
Thanks for weighing in - I was hoping you would... I'm leaning towards a set of JJ KT88s from eurotubes, and having my amp guy bias them properly - although eurotubes state that their tube sets are a direct match for my amp, and no re-biasing is necessary... Any thoughts on that???
I was already planning on trying the 12AU7 driver tube swap... Also, agreed that my 400 is quite bright - rolling off some highs will not be a bad thing for me... While the 400 isn't quite as powerful as an SVT-II(my other tube amp choice), it's much lighter - and I tend to prefer the Mesa sound over the Ampeg sound - so far, I'm fairly happy with my purchase...
- georgestrings