GZ34/5AR4-HARMA RETRO CRYO Click on image(s) above to view larger

All prices contained on this page are exclusive of VAT. This is currently charged at 20% and is payable by the UK only.

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.
This is a special cryogenically treated version that offers the highest performance.

The Harma GZ34 Retro Cryo design is based on Mullard's famous military GZ34/ CV1377.The Harma GZ34 Retro uses Mullard's compact serrated double anode design that is carbonised for greater radiation efficiency with a double support structure for the getter. This has a number of advantages and the biggest being that its design is resilient to shock and vibration, making it an ideal choice in Vox AC30s.The Harma Retro GZ34 also provides correct rectification and works well in early Vox AC30 with no reduction in B+ voltage unlike many of the modern GZ34 on the market. At last we have a real alternative to the famous Mullard GZ34/CV1377.

All Harma rectifier valves undergo testing under real working condition and the voltage drop is measured between each plate and the cathode. This ensures correct conformity to design parameters under working conditions.



Facebook Twitter Follow us on Instagram