I have heard changes generated in a Phonostage as a result of the design put in place for the Phonostage > Power Amp Interface.
I have referenced this experience within other Threads on the Gon.
In a nut shell the Wire used as the Signal Path in the umbilical is PC Triple C.
The Cable Terminations were exchanged from the Manufacturers to Low Eddy RCA Connectors. The Phonostage Chassis Input / Output RCA's were exchanges from a Solid Copper RCA Connector to a Solid Copper Low Eddy RCA Connector being the dame brand as used on Cables.
There are other control measures in use that can be read about within other Threads.
The outcome being the Low Eddy Interfaces, where the assessment has been of the End Sound being produced, has substantially surpassed the Pure Copper Chassis RCA and Manufacturers RCA option.
I have now learnt that investing in this area, is as important as investing in the Circuit.
In the case of the H'man, the circuit already in use may be discovered to be more that adequate when an Interface between downstream devices is addressed.
Swapping out Valves can be costly, I know the types which are needed and have been demo'd a large selection of iptions from the 50' - 70's.
I know the cost of the 60's Vintage ECC 83 Valves and getting the selection correct for a Phonostage can for the unsupported be extremely costly.
I have bought Vintage Valves for owned Phonostages of which one design has a circuit that used the ECC 83 Valve Type.
Each Valve when received to be used in a Phonostage has been checked for being near prime as an example. Valves selected for committing to a purchase are almost identical in their measurements taken on each Valve Half and across each Valve selected to be used.
A Quad set of perfectly matched Vintage Valves or more recent production Valves, expected to be supplied is a Fantasy. As a buyer it is not even a guarantee to get the correct circuit match of Valves if substantial monies are parted with to a very very trust worthy seller.
When without a support to be able to investigate what is purchased, the buying comes with an extremely high risk for the not achieving a matched circuit.
I own Valve Hybrid - Valve Input / Out and SS Phon's, I take the first amplification, adding gain, to the Cartridges sent signal in a way that is very very focused on what is the best basics that I can put in place for the circuit.
I now have a new objective, which is what is the very best basics I can put in place for the interface between required umbilical's and other devices.