Cryogenic and long plate valves tubes

There are offers of Cryogenic and long plate valves tubes in the marketplace. What is this all about?
There are  long plate versus short plate preamp valves and matching of valves. Some can be mighty expensive so it is worth the time to look at these options and see if it is real value for money or just another marketing angle to make you part with your money
Here is my view on  these variants.
Cryogenically treated ( “Cryo” )  Valves
This is where the valve is supposedly placed in very very cold liquid nitrogen and left there for a number of hours, and then removed and brough back to room temperature. The metal crystals in the plate are supposed to align themselves and then this results in better tonal quality.
I have some concerns  with this claimed improvement in sound. First of all in the case of an ECC83 pre-amp valve, the pins come straight out of the glass vacuum envelope.  Glass and metal will surely contract at different rates and so there is the real possibility of a reduction in the vaccum in the valve as small amounts of atmospheric gas get into the valve. This could either reduce the valve life and /or its performance ( probably for the worse)
Aligning the metallic crystals in the valve elements , may happen , but valves have a heater inside and run at high temperatures.
Surely, the alighment of the crystals can only be temporary because as the valve is switched on and off, it is temperature cycled to hot and back to room temperature again.
The key to the performance of any electronic component is the data on the data sheet showing its gain characteristics for a cryo treated valve and I would like to compare the data of a valve before and after treatment so we can see EXACTLY what characteristics have changed. I would also like to see the same cryo treated valve characteristics after, say 10 hours of normal usage so we can compare the chacteristics of the valve from before it was was treated. This would give us hard evidence on the benefits of cryo treated valves.  I have never seen such hard evidence so my conclusion is that this is all marketing hype and a way to charge more for the same thing.
A final thought is that if the effect is due to the alighnemt of the plate crystals then why not just heat them up and use a magnet ?
Long Plate and Short Plate Valves
Agian this can be proven by looking at the electrical characteristics.  I would guess that it could have some influence.  I am concerned though that the larger the plate and grid is in the valve, then the less physically robust, it is to microphonics. It is more metal and bigger so probably will be more affected by bass notes than smaller plated cousins.  More metal also means that  even in this tiny world of the innards of valves, that there is more mass and needs better anchoring than lighter small plate valves.
I took a look at two modern ECC83S types and in particular I had a look at the short plate ECC83S and the ECC803S from JJ Elctronics. Aside from any black magic on the “sound” , I had a look at the data sheets of both and here is a quick guide to long plate and short place versions. Both are pin compatible.

This is just a key summary. at higher voltages and with a 100KΩ load and running with 400 volts there are differences in the cathode resistor value need so plugging the long plate version into an amp designed to use the ECC83 short plate will have differences because some of the surrounding component values may be wrong for vintage long plate valves  The ECC803S from JJ is tolerant to be inserting in an ECC83S socket.  One thing that is never shown on modern valve data sheets is the frequency response. The two different construction types have different capacitance values and I am sure they will therefore have different frequency responses which of course means they will have audio differences.
However, as the long plate is basically a bit beefier it will allow you to get a different sound. Folks report that the ECC803S has better base and mid response.
So, long plates and short plates I think have nothing to do with the sound. The  real answer is that they are valves with slightly different specifications.  Modern valve data sheets show this up clearly.
However, there is nothing magic about the valves being vintage. It is purely due to the slightly different specifications of the two types of construction.
So my conclusion is to have fun trying a long plate ECC8o3 in a short plate ECC83 socket and see if the sound suits you.  I am working on  my own amp design and I will optimise the circuit it for long plate and see if I like what I hear. I am also going to try the JJ 12AY7 as this is basically like an ECC83 but with slightly lower gain.  This might give an amp a bit more headroom and could be good if you like a nice clean sound
One point to notice is that long plate data sheets claim better microphonics than short plate so that might be a reason its own to use long plate right at the inputs of the amp. Personally , I believe that the ECC803S  might be more likely to have microphonics. I am awaiting a batch  of JJ ECC803S arriving as part of another large order and I am going to try this out and see what the results are. I will write it up here and add to this blog
Gold Pins
Some valves are sold with gold pins. Standard metal pins on valves corrode with time and make poorer contact.  I live by the sea and the salt air does create oxidation on the valves in my amp and I have to un-plug and re-insert them after every winter ( storms and easterly winds make for more salt in the air).
So if you live by the sea or gig on cruise ships then gold pins are for you 🙂
Conclusion
“Cryo” valves seem to be in the same category as alien abduction theories and old wives tales.  When writing this blog and doing some research, I have come to the conclusion is that there is real merit in the long plate versus short plate pre-amp valves. However, it is not related to being vintage, it is purely due to the different construction which I am sure will have a different audio response = different sound.
If you are by the sea or on a cruise ship then gold pins on your valves might be a benefit !
One final daft thought I had was that a valve needs a high quality vacuum in the glass bottle to ensure best operation. I just wonder if modern vales/ tubes have a better or poorer vacuum than the vintage valves and I wonder how this affects the sound?