EL84-HARMA RETRO CRYO EL84-HARMA RETRO CRYO 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.
The Harma EL84 Retro Cryo is a recreation of the famous Mullard EL84 and follows the original design and electrical specification of original Mullard valve.

The Harma EL84 Retro Cryo has a number of special features such as gold plated grid wire with carbonized screen grids. The anode plates follow the original Philips Mullard design and uses a tri-alloy plate structure which gives exceptional heat transfer characteristics and sound quality.

Close attention has been paid in the manufacturing process to the original Mullard specifications. The valve has gold plated grids with special attention given to the windings to reduce the likelihood of the valve arcing. The plates have been coated with the dark grey/black material as per the Mullard to further enhance the valves heat transfer and eliminate red plating. This you can see in our 2nd picture with the Harma EL84 on the left and the Mullard EL84 on the right.
The Glass Envelope is made of thick 22mm glass to prevent microphonics when used in guitar combos.

The Cryo treatment gives the EL84 Retro the sonic improvement to sound that Cryogenic treatment can only bring to the valve. The EL84 Retro Cryo has a smoother distortion with more detail and clarity. The valve has more bite and better focus in the bass end and they produce a musical sound that is only attainable by using very expensive new old stock valves Mullard EL84

The Harma EL84 Retro Cryo has a deep well defined tight bass that produces the classic Mullard Style slam in the bottom end. The midrange performance has been tweaked to provide warm clear detail tone at low volumes with clear articulation and smooth even distortion when the amplifier is cranked. Special attention has been given to the top end of this valve giving touch sensitive bite without any hardness. This is a Musical and dynamic sounding EL84 that provides the instant vintage tone.

All EL84 Harma Retro Cryo are burst tested on the rig Built for The Queen Guitarist Brian May.
The valve undergoes full drive testing under the most extreme conditions with a series of timed signals that replicate the stress that a valve will encounter in real working conditions. This is designed to ensure the ultimate reliability in a class A operation.

The valves are then dual matched on anode current and gain. Please note that we do not supply these in single items we can only supply these in matched pairs, quads etc.



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