Fake valves

[spendorman]

Here is the card that came with my Langrex order

Langrex by A60man, on Flickr

[anthonyTD]

The one main thing you have to establish, where either fake valves, or semiconductors are concerned is; are they actualy the same "electricaly" as the device they are pretending to be ?
For example, there were a lot of a well know make of ECC88/E88CC's being sold as the real deal years ago, [when everyone and his dog seemed to be building equipment using them] on physical inspection,they looked to be the real deal, however; after thorough testing, they turned out to be a variable mu version!!!
A...

[Mixc]

Hi what would the effect of "variable mu" be if the ecc88 was installed?

[anthonyTD]

In Audio aplications, the diffrence between fixed, and variable mu triodes is not always obvious, however; one should not be substituted for the other, especialy in radio, or test equipment aplications, as the affect of the diffrence in grid spacing character [which is the main diffrence between each type] can be considerable.

Hi what would the effect of "variable mu" be if the ecc88 was installed?

[spendorman]

Stumbled across this, long, but interesting

https://www.youtube.com/watch?v=BXAjspPLzRQ