CV4004 are long life Valves. When supplied with very good measurements, these are proven to be very secure Valves that have a very long usage life.
Note: Measurements shown in relation to Factory Spec' are the only description worth taking on board, I have received verbal descriptions and in nearly all cases they are proven to be very unreliable, causing Seller/ Vendor friction when Valves are wanted to be returned.
Caveat Emptor is ones friend when purchasing Valves.
It could be a case where a 1000hrs are used by the latest owner of the Valves, the Valves are still presenting a very good measurement, this can result in more monies being remunerated than the original purchase.
This is one of the fuels that stoke the Vintage Valve Market and one I know that has benefitted my choices made for Vintage Mullard Valves.
Alternatively at a later date, an Amp' can be brought in for demo' purposes as a Amp' replacement, that has the same Valves used in the Circuit. This indirectly means that Valves already purchased with a recognised high end sonic quality, can be immediately used on the New Amp' to assist with the assessment. If the New Amp is the preferred Amp' the earlier amp' used can be considered for being sold on with original supplied Valves in place.
