Richard, in your original post, you mentioned upgrade, am assuming you mean upgrade from Mk1 to Mk2 or Mk3?
If that is the case, you would be better off selling your amp and buying a Mk2 or Mk3 on the used market. You would never get the return on the money spent upgrading your Mk1 to a Mk2 or 3.
I have both a Mk1 and Mk2. Have heard the Mk3, but do not own one.
The newer ARC gear seems to have less of that tube sound.
would suggest the following with your Mk1 amp; try a set of Shuguang Nature sound KT-88s in the amp you currently have and bias the amp for the tubes. Think you'll be surprised at the sonic improvement over the stock ARC tubes.
best
If that is the case, you would be better off selling your amp and buying a Mk2 or Mk3 on the used market. You would never get the return on the money spent upgrading your Mk1 to a Mk2 or 3.
I have both a Mk1 and Mk2. Have heard the Mk3, but do not own one.
The newer ARC gear seems to have less of that tube sound.
would suggest the following with your Mk1 amp; try a set of Shuguang Nature sound KT-88s in the amp you currently have and bias the amp for the tubes. Think you'll be surprised at the sonic improvement over the stock ARC tubes.
best