Audio Research vt100mkll question

Hi Guys,
I managed to talk to Leonard who advised that there could be some perminant damage due to the use of the wrong valves, so weeping, with a screwdriver in hand I took the cover off the VT100 and found that the valves were in-fact 6922's not the 6h30's as i'd been advised by the previous owner. So kind of good news there. I suspect that the valves in situ are the original factory supplied valves and hence 5 years or so old and that the previous owner was trying to "up sell" this amp by claiming a recent upgrade etc.(not so good).

I've just bought a matched octet of jj electronics ECC88 so I'm going to replace these and bias up the amp this weekend. Looking forward to it.

After that I'm going to replace the 6550's with a matched octet of jj electronic KT88's which leonard has confirmed will work fine.

I'll let you know how I go.

i really like this amp and have heard it sound great in a well balanced system...

btw, you might find the jj e88's a little lacking in resolution....

Borg

I think it is important to note again that the VT100 MKII requires input tubes with closely matched tolerances. You may encounter problems with arcing of the output tubes with a loss of the bias resistors if the tubes are not properly pre-selected.

Still, the previous owner may at some point have used the 6h30 tube (or done something else equally stupid) and damaged the amp. I'd be very suspicious. I recommend that you send it to ARC -- or someone familiar with the amp -- to make sure everything is OK. Otherwise, you'll always wonder if you're hearing the amp as it should sound. And it really is a superb amplifier.

Thanks for all your advise guys.

Just to let you know that the person who supplied my tubes has matched/supplied them up in relationship to their use in the circuit described in the schematic that Leonard sent me(together with the original biasing instructions).

I'm going to do the job this weekend, I'll let you know how I go. Thanks for your interest and comments.

Myron.