Reliability issues with VTL amps/pre-amps

I have two pair of VTL 750's, meaning I have 48 6550 tubes to contend with.

I have lost tubes and with that the large fuse behind the screw plug on the rear of the amp. No damage to the unit other than fuse and I'm into my 5th year with these.

I think VTL amps are among the most reliable and best sounding of all the big amps. If you want to keep them reliable be sure bias is right and tubes are suitable. I don't know about your ST-85, but the VTL 450, 750 and 1250 all run very reliably with Wing C 6550.

Hi. I am in my 7th or 8th year using my VTL MB450s (and I bought them used). They continue to be fine. Because I do not get enough hours on mine, I may not have the problems others have had, but so far, other than a couple of blown tubes after 4-5yrs, I have not had any issues. I use mine in triode almost exclusively.

I own VTL 125 mono block amps that are 11 years old never a blown tube . I had a on / off switch go bad a few years ago sent to VTL for repair and has worked great ever since . My amps get use just about every day for the past 11 years I like em and they sound great . Marc

I've owned a pair of older VTL 300s for at least a dozen years. While they have had little use in the past couple of years they have been very reliable. They had one part failure which VTL replaced for free even though I was not the original owner.

I agree they are among the best sounding and most reliable of the big tube amps.

If you look at VTL schematics you will see they are very simple and intrinsically reliable, operating the output tubes at low current. However they use a high anode voltage and the choice of output tubes is critical - if you take Albert Porter recommendation of Wing C 6550 you will have no problems!
Many cheap 6550 can not withstand these high voltages. Also, when tubes became tired replace them - do not wait until they break!