Audio Research vt100mkll question

Yes, be careful, the bias scheme for the 6922 is involved.

Go Here: http://mycollins.net/audio/artube1.html

very good article on this.

Cheers,

Ron

Thanks again guys. I tried to talk to Leornard this morning but he's not in untill Tues. :-) I'll give him a call tonight.

Any thougts on the single ended operation without the balanced jumper pins ?? Should I perhaps be thinking that connections have beed internally modded as the single ended inputs work without the jumpers in place ??

I really hope its not been internally modified and that everything is as it should be.

Thanks agian,
Myron.

I am currently using an ARC VT100 mkII in my system. The 6H30 tubes are used in the VT100 mkIII amp. As mentioned previously, you need a set (8) 6922 tubes. Upscale audio sells the 6H23 (NOS 6922) with the required tolerance/balance that are necessary for the VT100 MKII. Poorly selected input tubes will cause your 6550C output tubes to arc and take out the bias resistor.

The above article by Collins is excellent in providing guidance in setting the bias of your amp correctly.

Myron: Please tell us. What did Leonard say?

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.