Audio Research VT 100 MK III vs. VS55

I just changed my VS55 to a VT 100 MK III(needed more power). Of course it was a general upgrade and at the same time it differed in a way I didnt expected. Listening to the VS55 it was very easy to the "se" and point out the instruments and vocals in space. The VT 100 dont behave in that manner. Instead the soundstage is much more open and wide and the vocals/instr are there but hard to say where. But still music presented in a fantastic way.

Is this a property of tha amp or an interaction effect? I use a ARC LS 17 and Eminent Technology LFT-8b speakers.
I've had a lot of Audio Research equipment over the years and I have had the same expereinces. When you compare their balanced inputs vs. single ended, the balanced almost always sound better. My theory is that ARC designs their circuits originally as balanced and adds the SE to that design. If you looks at the specs between balanced and SE, there is sometimes a difference in S/N ratio between the two inputs ratings. Check out for more info,
It sounds like the amp may be due for a re-tube. I try and tell people that no one ever sells a used amp with new tubes in it. If the amp sounds a bit diffuse,smeared, it might be time.
I have a VT100 mk3 and it images very well. I am using it with a Ref5, and feel in now way that it is limiting the performance of the preamp. I have owned a Ref110 previously, sold it, and really don't miss it with the mk3 around... It is completely silent in use, very transparent, and very "musical". I love it. Perhaps you need a retube on yours?
I am using an old VT100 mk II with a new LS17 and the sound was a bit “soft” or “closed” in the beginning. But it turned out, that the old tubes had a lot of hours on them and after changing both input- and output tubes in the VT100, the sound changed (after running the tubes in) and now I am very happy with the soundstaging. I find the LS17 and the VT100 mk II to interact well and I guess using the mk III should not be that different.

My loudspeakers do not provide at very broad soundstage, but it is deep and with a clear definition of instruments and voices. It is quite revealing and changes in cabling and source is quite “visible”. I use the 8 ohm tap and balanced cabling.
The only difference is some minor changes with circuit topology with the mkIII. The mkIII's front end is much easier to set up.