In the late 1950 's Siemens introduced an EL34 which was the first to claim a plate voltage capability of 800 volts.The Siemens Valve very quickly became popular with amplifier manufacturers for its crisp distorted sound and even response.

Harma EL34-RETRO [To Order]
The Harma EL34 RETRO offers a unique combination of the famous Mullard bottom end response and the Siemens ease of distortion with 800 plate Volt capacity .The block grid construction provides smoother output and eliminates odd order harmonics. The result is a very touch sensitive valve with a balanced crisp compressed overdrive. This valve is ideally suited to Blues players looking for that MULLARD sound.
This valve is also available in a specially tested and CRYOGENICALLY treated version.

In 1959 the British Marconi-Osram Valve company Introduced a beam Tetrode design known as the K.T 77. Their Version of a super high power EL34.
The ratings claimed a maximum plate voltage of 850 Volts with 70 watts a pair in AB1 operation. One tough customer.

In the 70 's many Marshall owners fitted the KT77 to beef up the sound, The Burman amplifiers of Newcastle fitted these as standard.

Harma E34L-STR [To Order]
The Harma E34L takes the same KT77 plate structure and places it into a pentode design. The valve has the highest plate dissipation of any pentode EL34, Rated at 30 watts. This is achieved by the use of a special plate material. The valve also benefits from gold wound grids which improves sonic performance. The glass envelope is made from special heavy grade glass. This not only allows the valve to handle high temperatures but also helps to prevent breakages when on the road. The Harma S.T.R E34L has a wide dynamic frequency response with a fat overdriven sound and has become the choice of many British Guitarists.

This valve is also available in a specially tested and CRYOGENICALLY treated version
[CLICK HERE FOR TEST REPORTS]

Full Drive Testing Rig
This led to the development of FULL DRIVE TESTING which is only available from Watford Valves.
This system was developed to recreate the operational conditions and stress that the valves needed to endure in Brians Vox.
Two common types of fault quickly emerged, control grid failure which can cause excessive cathode current, which in turn can cause extensive damage to the amplifier.
We found the more dangerous short circuits, such as screen grid, suppresser grid and screen to control grids were occurring also under heavy use.
We test all these parameters under full driven conditions in a full class A cathode biased test circuit. Each valve is driven by a series of electrical pulses, which replicate the same stress levels as the valve will encounter in operational conditions. The pulses are specially timed to replicate a single note and also a sustained power chord. Only the best valves will survive this test, therefore we are confident in supplying the best tested valves available anywhere in the world, for use in Vox AC30's . This service is available also on new old stock EL84 at extra cost.

EL84 Matching [To Order]
We found that under these conditions by Matching the A.C gain under full load it would give us the following advantages.

• Improved tone and sustain by elimination of phase cancellation which occurs in incorrectly or unmatched valves.
• Increased reliability as the valves are tested under full operating conditions in class A cathode biased circuit we can supply sets which are of the same operational characteristics and therefore work in a uniformed fashion.
• No valve is working harder than another thus not over stressing the output transformer.
  We offer three valves tested in this way to Provide Vox owners the world over totally tested valve especially for their amplifiers.

Harma EL84-STR [To Order]
A high gain valve with a tight deep bass. The top end is very clean and bright and gives a large sound stage when overdriven. Due to its higher gain this tube will distort sooner than our E84L or EL84 VINTAGE and is a firm favorite with rock players. The HARMA STR EL84 is burst tested on the rig built for The Queen Guitarist Brian May. The valve undergoes full drive testing under the most extreme conditions in a class 'A' cathode bias rig. The valves are gain selected to provide the maximum early distortion in a Vox AC30 or Matchless with the ultimate reliability.

This valve is also available in a specially tested and CRYOGENICALLY treated version

Harma E84L/7189A [To Order]

The Harma E84L is a high quality special application military valve. The valve has rugged construction and thick glass which reduces microphonics and rattle in all guitar combos. The valve has a coated anode which makes it stable and able to stand high voltages. The valve produces the maximum clean headroom out of any current EL84 providing a rich warm overdrive sound when distorted
[CLICK HERE FOR TEST REPORTS]

This valve is also available in a specially tested and CRYOGENICALLY treated version

Harma E84L/7189A burst tested [To Order]
The HARMA E84L is burst tested on the rig built for The Queen Guitarist Brian May. The valve undergoes full drive testing under the most extreme conditions in a class 'A' cathode bias rig .to ensure maximum reliability. These are the valves that we supply to the WE WILL ROCK YOU stage shows worldwide.

This valve is also available in a specially tested and CRYOGENICALLY treated version

Harma EL84 VINTAGE [To Order]
The Harma Vintage EL84 provides the highest harmonic mid-range response of any EL84. The high sustain and warm treble make them ideal choice for blues players or those wishing to smooth out a modern amplifier.
The valves have been burst tested under extreme conditions on our rig built for Brian May to ensure high gain and maximum reliability. Image-

This valve is also available in a specially tested and CRYOGENICALLY treated version

The design brief was to produce a valve that could hang upside down and be resistant to microphonics. The microphonic effect is greater in guitar combos due to the position of the speaker relative to the valves.
The valve can pick up the sound transmitting through the speaker and re amplify it. This in turn can ruin your sound. Thus the special design valve made by Sylvania was used in Fender amplifiers from the early 70's and the term Special Tube Request was born.

Harma S.T.R 6L6GC [To Order]
The Harma S.T.R 6L6 has been greatly influenced by the great valves of yesteryear. It takes the large plate structure of the RCA 6L6GC and the internal supports of the Sylvania 6L6GC/STR387 to provide a uniquely sounding valve. Each valve is specially tested for micrphony in a circuit which is designed to recreate the operational conditions the valve encounters in every day use. This ensures perfect operation in all combo's, standard or high gain.

As with the The S.T.R E34L the valve is made from special grade heavy glass. This prevents microphonics and also prevents breakages when on the road. The valve has special alloy in the plate material and has gold plated Control grids. This improves plate dissipation of up to 30 Watts, thus improving reliability.

Finally our special high plate testing and grading insures that this valve will sound good in vintage or modern amps.

This valve is also available in a specially tested and CRYOGENICALLY treated version

HARMA 6L6GC - Retro [To Order]
Based on the classic Sylvania STR 387 that was used by Fender from 1974 until the closure of the Sylvania plant. The valve features a thicker glass envelope and rugged plate construction to eliminate microphonics & mechanical noise. The retro provides that big clean fender sound and has an extended treble response for glassy highs. The valve is ideally suited to both modern boogies high gain and vintage amps.

Harma 6L6WGC/5881 [To Order]
The Harma 5881 is a military long life valve that has become the industry standard.
The valve was used by BOOGIE (STR 425} and MARSHALL in the 1980S. The valve has a nice sonic clarity with a tight bottom end. It has the small button base making it ideal for those restricted height applications The valve is still favored by many hard rock and metal players. We have supplied these to many hire companies and British rock giants IRON MAIDEN.

This valve is also available in a specially tested and CRYOGENICALLY treated version
[CLICK HERE FOR TEST REPORTS]

The closing of the 1950s saw demand still increasing for products and designers demanding greater power output. It was inevitable that the popularity of this valve would diminish due to its low power output. The final development came in 1959 when G.E introduced the 7408 for the audio market. This was not very successful and led to many companies winding down production over the next decade.

Harma 6V6GT [To Order]
The Harma 6V6GT takes its design from the famous R.C.A 6V6 of the 1950s.
The anode plate structure is the single cylindrical ribbed plate. The valves are also tested at high plate voltages which make them ideal for use with vintage guitar amps. The sound of these closely resembles the old R.C.A valves and they will provide and instant up grade for any modern amp.

Harma 6V6GT-STR [To Order]
The most important new design since the 1960s. The Harma takes the RCA design and uses the large plate structure and grid technology of the Harma 6L6GC and places it in one package.
The valve provides a smooth clear distortion with ultra tight bass. The valve will handle the high plate voltage of 450 volts in old Fender Deluxes and will provide unique vintage tone in modern high gain amplifiers.

Two years later in 1957 M.O.V of England struck back with the launch of the now famous K.T.88, later marketed under the G.E.C name in England and Genalex in the United States. The Valve had higher ratings than the Tung-Sol. 800 VDC pate, a screen of 600 VDC and plate dissipation of 42 watts.
These valves have become some of the most sought after valves of all time. The Tung-Sol for its rich tonal balance, bullet proof reliability and famous St 'coke' bottle shape, the M.O.V K.T 88 for it's unsurpassed musicality, warmth and sonic perfection.

In the 70'S the General Electric Company based in Owensborough Kentucky introduced the 6550A. This valve shared the same dissipation value as the K.T 88 of 42 watts but had lower plate and screen current values of 660 and 440 respectively.
This valve has immense sound staging with pronounced fat mid range response and is the only valve that gives the AMPEG S.V.T its snarling growl.
Harma S.T.R 6550 Superior Grade
The valve has been developed for use in AMPEG S.V.T's and owners of high power audio amplifiers.

Harma S.T.R 6550 Superior Grade [To Order]
The plate construction and internal bracing is reminiscent of the Tung-Sol with the 800 VDC plate capacity of K.T.88. The fat mids and forward in your face sound of the G.E wrapped in the famous St 'Coke' bottle shape of the Tung-Sol makes this 6550 as distinctive as its legendary predecessor.
Each Harma S.T.R 6550 is checked for stability and under goes a controlled burn in at 500 plate 500 screen. The valve undergoes checks for cathode heater insulation and gas.
Bias voltage is then moved six times with stability checked and then finally matched on anode current and g/M.
[CLICK HERE FOR TEST REPORTS]

Harma 12BH7A [To Order]
This valve provides the drive to the output stage of the classic AMPEG S.V.T amps made up until 1988. It is also found in Hammonds, Leslie and Macintosh made in the late 60's. With no American production for over a decade this valve has become extremely rare.
The Harma 12BH7A is based on a proven American design and is tested for use in all applications.

Harma 12DW7/7247 [To Order]
A dissimilar double triode which is half a 12AU7 and Half a 12AX7.
The valve was used for its low impedance drive characteristics as a cathode follower in many classic AMPEG amps including the legendary S.V.T.
We have found that converting your S.V.T circuit to accept 12AX7 will affect the sound, therefore we've included this valve in our catalogue to maintain that S.V.T when all the New old stock valves have run out.

Harma GZ32 [To Order]
The Harma GZ32 is a smaller and more compact version of the Mullard and retains the classic shouldered shape which complements the look of the Q.U.A.D 11 amplifier. Each valve is individually tested and selected for use in Q.U.A.D amplifiers.

Harma GZ34-STR [To Order]
The Mullard GZ34 is the longest lasting, highest capacity and best sounding GZ34 ever made. The Harma GZ34-STR takes its design form the early MULLARD long plate GZ34. It is aimed at the professional musician who requires the ultimate in performance and reliability.
Each valve is individually tested to ensure conformity to specification for use in vintage Fender, Marshall and Vox amplifiers.

Philips put its' famous research and development department to work with one aim, to develop the best ECC83/12AX7 type ever made. With careful attention to the control grid windings and improving the cathode materials by the early 1950's the famous Mullard ( a British Company bought by Philips in 1926) ECC83 was born. Needless to say total market domination followed and has remained ever since.

The American companies needed to find an answer to the ECC83. They introduced the 7025 which was simply a 12AX7 with a coiled heater to reduce hum.
History shows us that this was not very successful in denting Philips strong hold on the market but produced a great guitar valve.
Fender, one of the world’s biggest amplifier companies in the world found that musicians wanted the 12AX7 distortion character which was higher than the ECC83 Mullard but did not like the extra hum that the 12AX7 produced. The Americans introduced the 7025 which has an extra hum canceling filament and was selected for low noise as a super 12AX7. Therefore many Fender guitar amps have a 7025 in the critical position. This, however, did not even dent the Mullards sales.

We currently offer two types of ECC83/12AX7 which are uniquely tested and gain selected.
We also offer CRYOGENIC treated versions of our ECC83/12AX7 types.

Our own unique custom test rig is a culmination of our work with some of the U.K leading artists and musicians. 50 valves are racked up and are subjected to a controlled burn in. They are subjected to the same stress and operating conditions that they meet in your amplifier. Each triode is tested for noise, balance, hum and subjected to a shock and vibration test designed to excite the valve, enabling us to select for low microphony.

This service is available on our Valves as well as Harma.

We then drive test each triode digitally because as musicians we want the ones that give us the maximum tone. The system is very accurate, for example valves that have read balanced output on an A.V.O 163 machine in drive conditions have had unequal outputs.
Therefore the valve carries a three digit code per triode which represents the drive rating in real working conditions.

CLIENTS INCLUDE ERIC CLAPTON, BRIAN MAY, PETER GABRIEL, MANIC STREET PREACHERS, OASIS, SISTERS OF MERCY AND BEN MATTHEW'S OF THUNDER HAVE BENEFITED FROM OUR SPECIALLY TESTED VALVES

Harma ECC83-STR [To Order]
The Harma STR ECC83 is a recreation of the famous Telefunken ECC803S.
The valve has a frame grid construction which eliminates microphonics. The grids are all gold plated as the original Telefunken The valve is the most neutral and has the warmest vintage tone of all the current production ECC83/12AX7 types. This makes it a great choice for clear Fender sounds or warming up a harsh amp. The tubes are all tested for low noise, low microphoney and are drive tested for gain. The ECC83-STR has a drive rating of between 229 to 249.
This valve is also available in a specially tested and CRYOGENICALLY treated version.

Harma ECC83/7025 DRIVE TESTED DR250 [To Order]
The Harma ECC83/7025 is based on the ladder plate design made famous by Mullard.
The valve features a spiral filament which will reduce hum irrespective of whether the heaters are connected for A.C or D.C.
A true high gain valve that provides low noise, low microphoney. These selected valves all measure up to the 7025 specification and can be fitted in the most demanding positions. Each part of the triode will have a rating of between 250 to 270 on our rating system. Providing you with a valve that will give you that singing sustain.

This valve is also available in a specially tested and CRYOGENICALLY treated version

Harma ECC83/7025 DRIVE TESTED DR270 [To Order]
The Harma ECC83/7025 is the highest gain Version. The valve will have a drive rating of above 270. These are aimed at the musician that wants every last ounce of gain with the lowest noise.

This valve is also available in a specially tested and CRYOGENICALLY treated version

This is a LOW GAIN low amplification double triode. The valve is internally rugidised to military Specification.
The tube has a lower amplification of 70 mu as opposed to a 100 mu of a ECC83/12AX7.

This makes it harder for the valve to distort and therefore an ideal choice when the best clean sound is required due to its top end detail and clarity. These are a great choice for taming down that hard Hi gain sound. They are also a superb audio tube providing sharper imaging and detail than standard ECC83/12AX7 types. This valve has a drive rating of between 170 to 200.
[CLICK HERE FOR TEST REPORTS]