"Watford Valves, ... with the aid of its custom-built test rigs, puts the valves under ’real working’ conditions which is the equivalent of a hellish week with the US Navy Seals"
Ben Bartlett, Guitarist, Feb. 2001

Watford Valves "runs them through more checks than any other facility in the world"
Dave Hunter, Guitar Magazine, Nov 1999.

THE X-FACTOR
Watford Valves research into testing techniques has developed test rigs which test the characteristics relevant to toady's musician. We introduced Full drive testing, burst testing & High plate volt testing.
Watford Valves are the first company to introduce Cryogenic treatment on an established brand. To read more about the Harma Cryogenic range and this revolutionary treatment select the Cryogenic section from our products menu.

We also offer our own brand the HARMA Diamond superior grade valve range, these are specially selected and tested to meet the needs of the modern working musician. The valves performance, tone and reliability are major selection parameters.

Pre-amp and small signal valves selection service
If you buy selected valves from Watford Valves you can be sure that the valves have been thoroughly tested to meet original manufactures specification. Guitar signal valves such as 12AX7 will be further tested for noise, microphonics and drive tested to ensure uniform output with valves coming in position matched sets. Audio valves will also undergo a distortion test to provide the maximum clean power.

Drive tested ECC83/12AX7 types for the musician
The pre-amp valves are a vital link in achieving great sound from your amp.
The old adage of garbage in, garbage out is true yet no one until now offers any sort of rating service. In our tests we found that valves even with the same current and transconductane (g/m) readings would amplify the signal quite differently in the same circuit.

Watford valves have therefore developed a drive rating system especially for musicians. This will enable them to choose either a valve which has a high gain rating to provide maximum drive to the output valves or a valve which will take longer to distort and provide a cleaner sound.
The valves under goes a series of tests at full operational conditions. Firstly a controlled burn in process to ensure perfect stability.
They then under go a shock and vibration test, microphony, hum and balance test before being drive tested.
The rating system runs from 150 to 300 digital points. The higher the rating the greater the gain. The beauty of this system is that we can provide sets of valves that have uniformed output and gain thus eliminating valves of different or low output to give you maximum tone.
We term the Driver valve to be the valve which runs the distortion channel normally the first valve in a Marshall super lead head. The balanced valve being the phase inverter which supplies the signal to the output valve.
Here is a chart which will help you in choosing the valve most suitable to your Musical style.

We know you will hear the difference as our clients such as AC/DC, Brian May, Eric Clapton, Oasis, Radiohead, Manic Street Preachers, Joe Satriani, Sisters of Mercy, Thunder and Peter Gabriel will all testify as they have used our custom selection service.

Output Valves Matching
We offer free matching on output valves on 6L6GC, 6V6GT, 5881, 6550, 7027A,7591A , EL34, EL84, KT66, KT77 & KT88.
Standard matching is done via our digital valve test rig with all valves matched on anode current ( plate current) and g/M ( Transconductance) in real working conditions. This rig is one of the most accurate available today as it can match valves to 1 % accuracy on both parameters.
All matching and testing is done with fully regulated supply voltage at 240v.

We offer high plate volt testing, typically 500 vdc 500 screen which selects the strongest valves for today's professional music hire and touring musicians. The valve undergoes a controlled burn in process and each valve is additionally tested for cathode-heater insulation, heater continuity, gas and six shifts in bias voltage to ensure perfect curve tracking and matching via quiescent current method. If you require valves tested this way then please contact us for a quotation. All HARMA output valves are tested this way.

Warranty- No Quibble satisfaction Guaranteed!
All small signal valves and output valves carry a 90 day warranty except HARMA diamond valves which carry 6 months warranty from the date of purchase. We warranty sweep valves for 14 days from date of purchase.
If valves are to be returned then you need to obtain a return authorization number from us without this we cannot process your claim.
Exchanges/refunds are subject to shipping charges and we reserve the right to charge a re stocking fee of 25% on correctly supplied items.
When replacing output valves it is essential that the bias voltage is checked by a qualified technician. This includes amplifiers with user adjustable bias indication lights. Output valves cannot be changed without correct monitoring as it is not the same as changing a light bulb. We cannot accept liability for valves which are operated out side the manufacturer’s operational limits, breakages, valve failure due to incorrect bias voltage or component failure. We are not liable for any consequential loss or damage to individual or equipment.

Biasing your amplifier
This is absolutely vital when changing your output valves if you wish to get the best sound and longest valve life.

Biasing simply sets the operational level of your amplifiers output valves. The reason that the English call vacuum tubes valves is simple. The grid bias setting on your amplifier affects the current flowing from the plates of the valve, increasing the negative grid bias. This means that less current flows through the valve. By decreasing the negative grid bias more current will flow through the valve. Increasing or decreasing the negative grid bias of the amplifier allows the technician to regulate the amount of current flowing hence the term 'Valve'.

Why is this important? If you have too much current flowing through your valves you will run them and your amp hot. This will result in burning the valve out and risks amplifier and/or transformer damage.

Symptoms of this are normally red spots appearing on the plate of the valves.

If your amp is running with not enough current flow then your amp will not have enough time to correctly amplify the signal. This will normally result in a horrible un-musical distortion which is hard on the ear. Sometimes humming and crackles can also be heard.

Guitar amplifiers contain lethal voltages which can cause personal injury or death. Do not attempt to carry out any modification or adjustments yourself. Always refer your amplifier to a qualified technician. All valves are fitted at your own risk.

See our Biased Information article in

February 2001 p139
Article by Derek Rocco
Biased Information

Ordering and Contact Details
We ship items all across the world and our web site is linked to our sales office where your order can be processed quickly and goods dispatched promptly.

If you have any enquiries that are not answered by our website please contact us by any of the means below.

Payment terms
All prices contained in this website are exclusive of V.A.T. currently at 17.5% and are payable by EU countries only. All orders are pre paid, we accept cash, most major credit cards and telegraphic transfer (T.T.). We do not make any additional charges for credit cards, however all T.T. must have our bank charge of £10 added to the order. The client is responsible for all charges when using the T.T method.

Shipping
We offer insured Special delivery within the UK and World wide shipping to most main international centres via UPS. We will quote shipping rates only if requested on receipt of your order. UK shipping charges are a minimum of £4.00 plus VAT

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