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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
jc51373
519 posts
 
I have an st-85 as a loaner while my st-150 is being built at VTL..Whenever I put this little guy in triode mode it does exactly what is described in this thread. I saw a glow in one of the tubes on the respective channel of that fuse then the fuse blows (.5 A).

I have this amp plugged directly into the wall on a dedicated cirucit, not a power conditioner. I have never plugged my amps into a PC and wouldn't anymore than would put my fridge on a PC. Prior to this little amp I had a Krell FPB 400cx plugged into the same cirucit, never a problem. I suspect the amp needs new tubes and it is about the same generation of the ones described here.

Hopefully my new amp will not have this issue, that would be disappointing.
ozzy62's avatar
ozzy62
2,920 posts
 
Yep, plugging a tube amp of that magnitude into a power conditioner is a sure fire way to ask for trouble. At the very least, the sound will suffer greatly. And that's reason enough for me to plug 'em straight into the wall.

Oz
nrostov
199 posts
 
Hey Oz/JC51373,

I have to respectfully disagree with you. I plug both my VTL's into my Shunyata Hydra 8 and have dramatically better sound than when I plug them into the wall. Now I have to say that plugging them into a Shunyata is like going straight to the wall except you get surge protection and noise free power.

Justin
jc51373
519 posts
 
Do you have a line dedicted to your system?

If it works for you by all means go for it, I just wouldn't try it. Maybe Shunyata is the exception...I still would not do it.
nrostov
199 posts
 
No I don't. When I got my Shunyata I a/b'ed with the wall outlet. There was a dramatic(and I am talking night and day difference here) increase in dynamics when I plugged my amps into the Shunyata Hydra 8.
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