Hello to all!
I'd like to use high quality NOS tubes on a Luxman CL-38uSE preamplifier.
This has 5x ECC802S on the line stage and I always defeat the tone controls with the dedicated switch on the front.
My question is: if I don't use tone controls do I have to change all 5 tubes the same in the line section?

Maybe I can save money and keep the stock tubes on tone control section if the signal it's bypassed there when defeated, but I'm ignorant about block diagrams and even watching it and my amp I'm not sure what to do.
In a phone conversation with the importer I've received a vague answer that "generally" they use all 5 tubes regardless since tone controls are not done with tubes, but they're not totally sure, they need to ask the manufacturer. Unfortunately after a few months no answer and they don't seem interested in helping me after a few more phone calls.
So I'm here to seek advice from such expert forum members.
Attached the block diagram and a picture of the internal so you can help me choose the right valves to change and maybe suggest me the right position of those in the real life picture to avoid errors.


Hope someone could help me.
Thank you very much!

P.S. I have a recently purchased MaxiPreAmp II tube tester to select them.

 

Does the pre-amplifier have a problem? Does it not meet its specification? I don't understand why you want to replace any of the tubes.
My philosophy is "If it works, don't fix it".

 

2 High-End Quad-Op-Amps will fix the whole thing.

It's impossible to know what's inside of the generic "Boxes" in the Schematic.

I wouldn't change any of the Tubes unless one of them develops a problem with "Microphonics",
actually all Tubes have problems with Microphonics, it's just a matter of the degree of the problem.

Changing Tubes will not alter the Fidelity of the Amplifier in any way.

Tubes are cool and kinda interesting, but they certainly have their draw-backs.
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