ARC VT100MK1 owners help...

The MkI is not as highly regarded as the MKII due to it's too small power supply.

Maybe this will help, Audio Review website has 29 reviews from owners of this amp.

http://www.audioreview.com/mfr/audio-research/MPR_589crx.aspx

Re-tubing this amp can be a bit of a chore.

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

Nice amps.......

I owned the Mk-I. I liked it.
Traded to the Mk-III. I liked it too.
The Mk-I has one bias trim screw per side.
The Mk-III has two bias trim screws per side and 6H30 input tubes.
Two screws per side allows for finer biasing.

I use solid state amps now.
I think solid state does a better job in a power amp application.

Tubes are still the way to go in a pre-amp, however.

Thanks for the info men,very helpful,Bob

The Mk1 was raved about when it came out. It didn't have "too small a power supply" for it's size, but when it comes to power supplys, bigger is always better. So it was increased in the mk2. I have not owned a mk1, but I did own a mk2, mk3, and now a Ref 110. I am sure you would be happy with it. It is more difficult to bias than the mk3's because the input tubes have to be biased, whereas starting with the mk3's they used jfet inputs. But it is not a real problem, and can be performed in a about 20 minutes. Mk1's are quite a bit cheaper used than mk2's or mk3's. There are a couple of VT200's listed now, and those are really nice amps also, with power to drive anything.