ARC Ref 3: Tung-Sol 6550 in power supply?

Just to add that my ARC Ref3 time counter shows 3674 hours and today I tested the original 6550 tube : transconductance was 5200 micromhos - this means the tube is still perfect!

ARC says you easily get 5000 + hours before retubing is necessary

I have been using the NOS 6550 TungSol Black Plate without any single issue for the past 6 months or so, and so do my two friends.

My guess is that the problem is not 6550 related.

Hi Elberoth,

You were spot on. Problem was related with the combination of ARC socket and pins of 1957 6550. Issue is now solved.

Cheers Broederen.

I thought that I would resurrect this topic perhaps with a little more pertinence to the later Ref 5SE and in particular with regard to comment made by Ethannn back in 08

" 07-13-08: Ethannnn
I would recommend the (blue label) GEC KT88 for this pre."

I would appreciate any further actual user expearience with regard to substituting 6550 with a KT88 in this circuit, given that they are very close in specification.

I did make inquiries with ARC only to received the standard

" We do not recommend , you will comply "

response .

I fully appreciate that there would be no economic incentive for this consideration by ARC , however that is not quite the same as ~

" Whilst we would not warranty support or be liable in instance of this substitution please find attached our considered opinion on a technical/circuit basis alone "