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VTL 450 mystery - please help


Hello Folks:

I am now the very proud owner of the VTL MB-450 monoblock. They were built in 1998 and upgraded with every available option in 2003. The seller has an impeccable reputation and I trust him. With that said, something very very upsetting is happening that I could use some advice on.

The first night that I used them, I brought them over to a friends home who has a new PS Audio Premier power conditioner and we plugged both of the amps in and listed for a few hours with no problems. Late that night, after I left, one of the amps B+ fuses blew out.

When I went over to run some tests, we found that both amps tube bias readings are about dead-on and while we were working on one of them with no signal, the other fuse in the other monoblock also blew and I thought I observed one of the tubes near the front of the unit glow unusually bright just before that happened.

The preamp that my friend has is passive, built by Creek and was not muted. The home also has one dedicated power line and one older power line that the other unit was running through.

Bea at VTL told me that sometimes power conditioners inhibit the amount of current that these amp's need to function. She also recommended that I buy a new set of tubes.

Can anyone help?!!

Thanks.

D.H.
danhirsh
theduker's avatar
theduker
53 posts
 
Just so people know, there is a rolling update on these amplifiers that lowers the voltages and makes them more "friendly" to modern production tubes. Local dealers can do this, Mine in Minneapolis did... I have lots of VTLs and have had occasional problems with tubes failing, but only when they were old and weak,
theduker's avatar
theduker
53 posts
 
Also I have had the MB300 and the MB450 and what you need to know is that the updated, fat ceramic fuses used in the newer Signature series are better than the skinny ones in the older series, like the MB300. That being said, the only time I had a fuse go over on the mb300 is when they were played on led zeppelin late night. The fat fuses don't seem to blow unless tubes are bad. This holds true in my system for both the MB-450 and the Wotan. I will update my MB-300 eventually to the fat ceramic fuses.
kosandr
6 posts
 
Hello, my friend overseas has two MB450 Signature III and just had two 6550 blown. A last one blown along with fuse. Local dealer overseas told him to use ONLY the VTL supplied tubes and asking way too much money (300% profit for sure).
The US VLT guys are not helpful at all. Is this a true that VTL only tubes supposed to be used or I can use any good ones?
Many Thanks!
jwm
918 posts
 
Danhirsh, I have a Amplitrex 1000 tube tester. The best in the business. If you want I would be willing to test all your tubes and send them back to you. Jeff
vegasears
1,173 posts
 
I previously owned VTL 300 Deluxe MB’s for many years. I had them fully upgraded in the early part of this Century. I took the amps to VTL myself and was given at tour of the factory. I met and have talked to the owners many times over the years. Truly, stand up people.

Once I tried plugging the 300’s into a PS Audio PPP and they sounded anemic and recessed and quickly plugged the amps back into my dedicated 20 amp outlet and they sounded normal again.

My advise is to buy a set of tubes from VTL and establish a business relationship with them. While you are getting to know the amps you may have questions and they have the answers. Every time I’ve called with questions. The first question from Bea’s is “Where did you get the tubes?” It helps to answer “From You!” Yes, you will pay a little more but you will be a customer.

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