6L6GC-HARMA RETRO CRYO MESA SELECT Click on image(s) above to view larger

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Harma Deep Cryogenic treated valves offers improvements to the sonic character of the valves and results in sound characteristics only normally found in very expensive NOS valves such as Mullards. The process involves taking the vacuum tubes and freezing them down to -312 Fahrenheit and soaking these for a minimum of 12 hours. Then the temperature is held at this low level for 24 hours. The vacuum tubes are then slowly brought up to normal levels over the next 12 hours.

Metals respond very well to deep cryogenic process. The reasons are as follows, during the cooling or solidification phase of the manufacturing process, molecules are trapped in a haphazard pattern. This is down to stress caused in the bending and welding of the anode plate material. This random placement causes obstacles for electrons and when encountered this interference can cause noise, slow down electron flow and sound deterioration affecting the quality of the sound of the vacuum tube. .

At very cold temperatures (below -312 Fahrenheit), the molecules will align in a more uniform, compact structure through the removal of kinetic energy. When the material is returned to ambient temperature, this new uniform, compact pattern is maintained, Thus changing the structure of the nickel permanently. This process makes a permanent change and the benefits do not deteriorate over time or upon return to operating temperature, it changes the whole way the vacuum tube performs.

The biggest benefits I have found have been a dramatic improvement in the sound quality. The bass response has been clearer with reduction in microphonics and clear more transparent highs. Cryogenic treatment has now become a way for a modern valve to produce a sound quality that approaches the iconic originals.
Mesa Select for use in Mesa Boogies

The Harma 6L6GC Retro Cryo Mesa Select is a re issue of the famous Sylvania STR 387 that was produced for Fender in the early 1970s.This was one of the most famous 6L6GC and sought after for it balanced and clear sound. The valve features thick mica spacers and internal bracing which reduces vibrations and microphonics making it an excellent choice is Mesa amplifiers.

This valve is specially selected to run in Mesa Boogies fixed bias arrangement and will work in all Boogies that use 6L6GC. These output valves have also been specially burst tested under real working conditions to ensure the utmost reliability.
The Harma Retro 6L6GC Cryo is for the player that wants a modern edged Hi gain sound with a balanced and detailed response. In the design of the valve it has an extended treble response in order to spice up old vintage amps and also cater for the modern high gain sound. This is why many Boogie owners have made this 6L6GC their number one choice.

The Cryo treated version offers more clarity, cleaner more defined bass and a musical sparkle in the top end than the standard version. The Harma Cryo 6L6GC Retro offers new old stock sound quality with a modern price tag and is the ideal upgrade for all 6L6GC powered amplifiers. These we have dual matched which means they are matched on anode current and gain and are available in matched pairs and quads and sextets only.
We do not have any singles.

Ideal to upgrade you're Boogie over the Chinese STR 440 that all Boogies are now shipped with.



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