Yes, indeed, the materials AND the execution...the care and skill used in the assembly.
'Vacuum Tube Valley' tested 6550s/KT88s/90s in issue 19 and indicated the Ei KT90 the Best Value of the group. (The original Tung-Sol 6550 was voted the Best 6550 and the Genalex KT88 the Best KT88.) The KT90 'was liked by all the reviewers and many considered sonic characteristecs on par with the Tung-Sol 6550.' The '90s are only $70 per bias-matched pair at the Tube Depot, http://store.tubedepot.com/6550kt88.html . I sure like mine in a c-j Premier Eleven-A, as did the previous owner.
'Vacuum Tube Valley' tested 6550s/KT88s/90s in issue 19 and indicated the Ei KT90 the Best Value of the group. (The original Tung-Sol 6550 was voted the Best 6550 and the Genalex KT88 the Best KT88.) The KT90 'was liked by all the reviewers and many considered sonic characteristecs on par with the Tung-Sol 6550.' The '90s are only $70 per bias-matched pair at the Tube Depot, http://store.tubedepot.com/6550kt88.html . I sure like mine in a c-j Premier Eleven-A, as did the previous owner.