Harma Valves / 12BH7A-HARMA RETRO

12BH7A-HARMA RETRO 12BH7A-HARMA RETRO Click on image(s) above to view larger
£16.00

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A test report is available click here to view

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 12BH7A Retro design is based on the original U.S.A made General Electric 12BH7A. It has a number of features which make this the ideal choice for any high end application.

It uses the thick 3 rib ladder plate anode design combined with a welded anode plate with a double supported getter. It uses a thicker glass envelope to reduce microphonics. This combination of the best rugged mechanical design and top sonic performance add up to give you the best tonal quality coupled with the highest reliability. This is a great choice for vintage Ampeg SVT´s, modern Marshalls and the Blackstar HT-5 as well as high-end aplications such as the Conrad Jonson amplifiers.

All Harma preamp valves are Dynamically Drive tested under real working condition have passed the following tests:

Gain (db) Drive Tested)
Transconductance (gm) Drive Tested
Output Drive Tested
Noise 1 (signal to noise)
Noise 2 (Aural)
Microphonics Test 1(Ambient)
Microphonic Test 2 (Shock)
Cathode Test
Grid Leakage Test

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