My answer applies to all types of tubes, but for the sake of clarity my examples will refer only to Mullard EL34. This is one of the most popular tubes ever made and of all I've ever owned (hundreds), only a handful were purchased new. Many of the Dynaco stereo 70 amps in operation today still have their original Mullard EL34 output tubes on board and working perfectly.
These tubes do eventually wear out but old, conservative tube biasing circuits plus the extreme quality of Mullard leaves many of these EL34's alive and testing 80% or more of brand new.
Most of the Mullard EL34's I own were bought for $55.00 to $75.00 each (in large quantity). New stock in original boxes can go for hundreds of dollars a pair. Many times the price is driven up by a collector or avid tube nut, a person not necessarily buying only for performance reasons.
So, the question comes down to: How many tubes do you require, what are you willing to invest in tubes (considering value of the piece they're going in) and how long do you intend owning this after the investment?
When it came to tubing the EL34's in the power supply of my Aesthetix Io and Callisto, I bought the most premium NOS available to insure maximum possible performance. In my Aesthetix this is justified as I have no intention of switching brands and this equipment cost multiple times my investment in these super premium tubes.
If I bought a used Wolcott Presence stereo amp for the bedroom and wanted great sounding tubes, no way would I shell out for original boxed Mullards. Good used tubes beat the stock to death and at a price I can justify.
These tubes do eventually wear out but old, conservative tube biasing circuits plus the extreme quality of Mullard leaves many of these EL34's alive and testing 80% or more of brand new.
Most of the Mullard EL34's I own were bought for $55.00 to $75.00 each (in large quantity). New stock in original boxes can go for hundreds of dollars a pair. Many times the price is driven up by a collector or avid tube nut, a person not necessarily buying only for performance reasons.
So, the question comes down to: How many tubes do you require, what are you willing to invest in tubes (considering value of the piece they're going in) and how long do you intend owning this after the investment?
When it came to tubing the EL34's in the power supply of my Aesthetix Io and Callisto, I bought the most premium NOS available to insure maximum possible performance. In my Aesthetix this is justified as I have no intention of switching brands and this equipment cost multiple times my investment in these super premium tubes.
If I bought a used Wolcott Presence stereo amp for the bedroom and wanted great sounding tubes, no way would I shell out for original boxed Mullards. Good used tubes beat the stock to death and at a price I can justify.