6550A-HARMA RETRO MARSHALL VBA 400 OCTET 6550A-HARMA RETRO MARSHALL VBA 400 OCTET Click on image(s) above to view larger

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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.
This is a specially selected set of 8 output valves for the Marshall VBA 400 bass head.

The Harma 6550A Retro is designed on the classic General Electric 6550A that is regarded as one of the best 6550A types made.

The valve uses special thick mica with internal bracing and spacing supports with full length anode heat wings to aid cooling capacity and provide improved heat transfer. The plate is constructed out of high temperature laminated alloy with an industrial grade glass envelope to prevent microphoney. The control grid wire is made of gold with a special coated screen grid to improve reliability.

The combination of these features supply a deep solid bass response with even balance a great high frequency detail. This valve supplies an exceptional midrange clarity and punch and is equally at home in any touring Amplifier or studio set up that require 6550 valves.

The warm sonic signature of the Harma 6550A Retro coupled with its midrange punch and bass fluidness make this the ideal choice to power your Marshall

All Harma 6550A Retro valves are burst tested on a special valve testing rig. 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. This vigorously testing and dual matching provides a specially selected set of 8 off 6550A Harma Retro identically matched for use in the Marshall VBA 400 bass amps.

8 x 6550A Harma Retro in a specially selected octet for the VBA 400



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