GoodSoundClub - Romy the Cat's Audio Site

In the Forum: Analog Playback
In the Thread: The LCR RIAA correctors

Post Subject: The BS about the “matched pairs” of NOS.Posted by Romy the Cat on: 11/13/2009

I do not know here to start. I absolutely assertively insist that under normal circumstances it is absolutely imposable to buy matched pairs of NOS tubes, particularly the high Mu tubes. When sellers advertised the “matched pairs” I just discard the claim and if they insist that their tubes as matched then I just abandon the deal and walk away. It is possible match tubes but it would happen ONLY if the seller has personal relationship with you, a large pool of the tubes, time to do it, knowledge and erumpent to do it (a regular tube tester will NOT do it) and has a very specific knowledge HOW your tube is used in your circuit. Even that will not be an assurance for proper matching for shitty (from noise perspective) high Mu triodes. They all age differently and matching according to the plate impedance, cathode emission, noise, gain at the given curst NOT might not be how those tubes will behaves in 3 month. It is not to mention that the tunes like 417A will have different noise contingent upon where they are located and what kind sockets are used. They are very finicky. This is one of the reasons why I am a bit afraid of high gain triodes WE style.

You see, when the tube become to do the oscillation things then this it is not good but this “not good” might manifest itself in a very different ways. It is good when the tube burns your tweeter. Yes I do consider it good as you know that the tube is oscillating. The bigger problems happens when the tube is oscillating and you knave no knowledge about it. You are not keeping a fast scope all time on you phonostage and you might not know that the 417A went berserk. In many cases the fact of oscillation is not directly auditable but has impact to many other auditable properties. So, I would like the tube to have the oscillation or not but would like it do not develop it after it was chosen to work in my phonostage. I remember what when I used Lamm LP2 with two stages of 417A I each month had a center image of a leading instrument moved to right of left side. In my case it was not oscillation/noise but gain change but I know the people who had the same spontaneous oscillations with LP2 and 417A. I found it very unreliable and frankly speaking annoying. I do not hear the Lamm LP2 user even complain about it - ether they have not problem or they do not understand what they hear. I vote for the last one….

The Cat

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