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VTL MB-450 "Generations"

I read the following in a 'goner's virtual system (from a 2004 Sterophile review).

"Since Chip Stern's update on VTL's second-generation MB-450 Signature back in October 2002, the amplifier has undergone further changes and improvements. It now features a completely redesigned input stage that incorporates advances made during the development of VTL's mighty Siegfried monoblocks."

This implies to me that there are at least 3 "generations" of this amp.
1 - When first introduced
2 - Available at the time of Oct. 2002 review
3 - Sometime before April 2004 when above line was printed
(they have a new version on the way but I won't count that)

Does anyone know how you could tell what "Generation" you had, serial number? other markings? Can you get a 1G or 2G upgraded to a 3G? If anyone is "in" on the nuances of the MB-450's life I would be interested in learning more.

Thanks for your input.
128x128bmcleod
zaikesman
3,017 posts
 
Bmcleod: That's interesting, Bea Lam told me (albeit a couple of years ago) that the "Super Balanced" input couldn't be upgraded to because it involved replacing the monolithic circuit board of the older amps completely, and wouldn't be worth the cost for what she described as a fairly minor change sonically speaking. I think you might be right that less than enthusiastic reports could be due to connection to single-ended preamps. The "Tube Saver" upgrade for $500 has to be the external soft-start modules, that's what they cost per pair.
peter_s
1,313 posts
 
I recently spoke with Bea, as I am about to purchase a pair of 1997 MB-450's that have been upgraded with infinicaps, the tube saver circuit, and balanced inputs (in addition to the RCA's). The tube saver circuit is not the soft start, but a current limiting circuit that kicks in when the tubes are driven to clipping (I believe). These amps also reportedly have 600v ceramic fuses (not sure if this was an upgrade or stock). They use the older, box chassis rather than the sloped backed chassis, which are easier to deal with when tilting back. Bea said she doesn't know anything about a "resistor upgrade" - it was the fuse change that offered the additional protection. Anyone else know anything about a resistor upgrade on the 450's and when it would have occurred?
theduker's avatar
theduker
53 posts
 
the resistor upgrade was a change in valuation in screen resistors done with the lowering of the B+ voltage. A rolling update approximately 2001-2 or so.
theduker's avatar
theduker
53 posts
 
I spoke too soon about the resistor upgrade, there was a resistor change to the resistors on the capacitors, going from a parallel to a series configuration, so that if one failed, the big power supply/mains caps don't explode. This I paid to do on my MB-300s, it was cheap and a good insurance move... My 450s had it already...
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