Harma Valves / 5U4GB-HARMA RETRO

5U4GB-HARMA RETRO 5U4GB-HARMA RETRO Click on image(s) above to view larger
£16.00

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Harma valves consist of a selected range of valves that are chosen after meeting stringent standards for sound quality and reliability. These valves are sourced from current production as well as some of the finest Nos valves available. Unlike our competitors no Harma valves, past or present has been made in China. Harma valves represent the finest available items of their type available.

Harma valves are tested using a range of custom designed and built test rigs which are unique to Watford valves.These unique tests are not offered by any other valve supplier in the world.

All Harma pre amp valves undergo the drive rating system; the valve undergoes a series of through tests under full operational conditions. This involves a controlled burn in process to ensure perfect stability and correct ageing. A shock and vibration test, microphoney, hum, and a balance and symmetry test.

All Harma output valves undergo our own unique real world burst testing. No other supplier tests valves this way. The burst testing process involves a series of varying timed electrical signal bursts. This runs the valves under the same stress conditions that they will meet in your amplifier especially when overdriven. All out put valves are then dual matched by us on anode current and gain. This will ensure that you get the best selected valves available anywhere in the world.
The Harma 5U4GB Retro is designed on the military grade Philips Sylvania 5U4GB that was used extensively in audio and commercial electronics in the 1960’s.

The Harma 5U4GB is fully interchangeable with a 5U4G and has the dual advantage of standing approx. 90mm tall excluding the base with straight sides which allows fitting in small enclosures.

The design features high grade nickel formed in two large box anode plates which are pleated together with internal supports, just like the original USA design. The valve is also internally braced to prevent vibration in guitar amplifier applications. The Harma 5U4GB Retro have proved to be long lasting in demanding applications such as Mesa Boogie Single, Dual and Triple rectifier’s amplifiers and work very well in all Fender amplifiers such as the reissue Bassman 1959.

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.

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