Where are we getting tubes and blank rack cases in the USA these days?

ruffrecords said:

Well I was looking for low noise and microphonics ECC883/12AX7 tubes. I have a Lindos test set with a built in speaker so you can hear the noise and listen to microphonics as you tap the tube with a pencil. You can hear loose grid wires vibrating and the pings as the tube heats up and cools down.I tested dozens of NOS and current production tubes this way. The NOS tubes were very inconsistent with very few samples having low enough noise and microphonics for my purposes. I found the most consistently low noise/microphonic tube is the current production Sovtek 12AX7WB.

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I feel like NOS 12AX7s are practically "over."

It's such a popular tube type that the available stock has been picked over and sorted through so many times (before the remainder is then in turn picked over and sorted through) that what's left probably isn't really a representative sample any longer.

I also get the feeling that that there are many, many tubes being sold as NOS just because they test "strong" on an emissions tester.

And of course there are old counterfeits that aren't very good. Very early in my DIY days I bought an entire lot of NOS "Amperex Bugle Boy" 12AX7s. They were lackluster older made-in-USSR tubes with counterfeit labels.

(..actually, I like your ramblings..)

Hi

Reading the book below a long time ago took about all my illusions about measuring valves and NOS values. The manufacturing tolerances in Ia and more have always been up to as high as 40% and a lot of issues cannot be measured. I use a roetest with audio-extension, just to make sure, the valve is not absolutely out of specs. But I don't care about NOS. OS and working fine in the given application is good enough and saves money. Takes some time though.
This might be a very subjective feeling, but I sometimes tend to miss other qualities in very low noise and very low microphonic valves - super high gain stages are noise critical and (apart from mic pre's) sometimes rather a poor design.             

http://tubebooks.org/Books/Atwood/Tomer%201960%20Getting%20the%20Most%20Out%20of%20Vacuum%20Tubes.pdf

Hope the link works - it's a pleasure to read

Thank you - that book is a real treasure of information!

Added to "META - Tech Library (Recommended Books)"

/Jakob E.

gyraf said:

(..actually, I like your ramblings..)

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Mine? 
As a case study in clinical psychology or?


  Cheers Jakob.