Why use valve amps?
Valve amps in our opinion sound so much better than solid-state for the majority of guitar styles, the only people who will tell you differently are solid-state amp builders! Oh and maybe jazz guitarists!

What are valve amps?
Valve amplifiers are those amplifying devices which use electronic components called "Vacuum Tubes" or "Electronic Valves" for amplification in the circuit instead of solid state devices such as transistors, FETs, ICs etc.

What's the difference?
Both of them will amplify your sound but in very different ways. Without going into too much detail, valves amplify sound especially instrument (guitar) sounds, in a way which is pleasing to our ears and brain due to certain factors like the way a note decays giving longer sustain, natural compression, midrange emphasis, compressed soft clipping when overdriven, preservation of harmonic content etc.

Why do tube amps cost so much?
Quality doesn't come cheap! The cost of parts in a valve amplifier alone is a lot more than those used in a solid-state amp and the labour required to manufacture tube amps, especially hand wired ones involves many more man-hours and that all adds to the cost.

The best valve amps tend to be made in countries where the labour rate is higher than say the Far East, although we are now seeing more Far Eastern built valve amps coming on the market, i.e. HiWatt, Sound City etc.

Can’t we get the same sound from a modelling amp?
The best maker of modelling amps has just released a version with a valve output stage, so what does that tell you?

Modelling amps are great, they are mostly light, reasonably priced and they do a lot to encourage people to take up the guitar and I have had several myself over the years.

The bottom line is that they haven’t made one yet that is as good as a valve amp.

Will a valve-powered pedal help get the same sound as an all valve amp?
Not unless you drive a valve amp with it!

If you are driving a solid-state amp you will still have a Solid-state output stage, which does not overdrive and distort in the same way a valve output stage does, FET’s (field effect transistors) are closer to the sound of valves, but being close is not good enough for most of us.

Putting a solid-state pedal in front of a valve amp on the other hand does sound good, it can boost the signal and overdrive the pre-amp which will in turn drive the output harder and that can sound great.

Why does a 50-watt Tube Amp sound louder than a 50-watt solid state?
In the beginning amplifiers were not required to distort, guitarists needed a louder sound, but clean. Your local 1950’s big band leader would have blown a fuse if the guitarist in his band took the lead break in the foxtrot with the sound Hendrix had for purple haze!

When Rock and Roll came along guitarists found themselves becoming the lead instrument rather than playing in the background. They had to be louder for lead breaks and they found that the lower-powered amps of the day were clipping and distorting. But as the sound was quite pleasing this was a desirable by-product of a happy accident.

Guitar amps were from then were made to drive the valves into the clipping region and this is where we get the valve overdrive. A JTM 45 for example was designed to give 30 Watts before any clipping of the signal occurred, but a good well set-up example will easily drive the loudspeaker beyond 45 Watts. Marketing ploys by solid-state builders these days will often state maximum power rather than output power before clipping, which is why an 18-Watt valve amp can sound louder than a 50-Watt solid-state amp.

Another reason is the efficiency of the loudspeaker and how it reacts with the device that is driving it, if you drive your car up a 25% hill in top gear the engine will struggle, get hot and lose performance, if you then go down the other side (still 25%) in 1st gear with your foot hard to the floor you will get the same effect i.e. inefficiency, a mismatch and overheating.

This is the same with amplifiers, if you have an efficient match between amp and speaker it will be louder.

What do all these different valves do?
Pre-amp Valves in guitar amps are commonly the 12AX7 also known as ECC83 (ECC83 is the English name for this valve, 12AX7 the American), lower gain valves such as the 12AU7/ECC82 or 12AT7/ECC81 are also used in some amps like Fender. Other rare varieties like EF86 are used in matchless and VOX amplifiers among others, (these can have microphonic problems, as they are very high gain valves) and the 6SL7 and 6SN7 were used in Ampeg.

Power amp valves in common use are EL84, E34L, EL34, KT66, 6L6, 6550, 6V6, 5881 each with their own unique sound and output power limit.

EL84 and 6V6 are low power tubes a pair of which can give around 15 to 18 watts at clipping and more when driven, a quad is used in 30-watt amps.

EL34, 6L6, KT66, 5881, etc. will give around 50 watts of power from a pair and 100 watts from a quad.

EL84 is well known for it’s bright chimey sounds and is used in the EVA 2061, VOX AC30, Marshall 2061 and several of the boutique AC30 clones.

6V6 has a bigger bottom end than EL84 and is used in lower powered Fenders and EVA TMB’s.

EL34 is associated with Marshall Amps and is a big part of their sound, EVA use a single EL 34 in the 10-Watt high gain amp.

6L6 have a tighter bottom end than EL34s; they are fairly clean sounding tubes that don't easily distort without a large pre-amp signal.

KT66 are extremely expensive for good ones and NOS (new old stock) KT66 are getting very rare. They are known to be the best sounding valves for Guitar Amps, and have a very powerful sound. Both Jimi and Eric had these valves in their Marshalls.

Is point to point (P2P) better than PCB?
As far as EVA is concerned, yes. PCB (printed circuit boards) have their place in the world of guitar amplifiers and we would not rule out using a PCB in our amps should a need arise. But we feel that P2P is the best solution for EVA for the following reasons: 

We are a small company and PCB design is expensive and if a design is modified you have to scrap all the boards that you currently have in stock. With P2P you just add another turret or change the routing of a component...easy.

You get less dry joints as the amp ages with P2P

Repairs are easier and neater with P2P.

It looks better... A lot better.

How long will my valves last?
If you don’t take them out of the packaging they will last forever!
Pre-amp valves can last for decades as they are less stressed than the output valves.
Power-amp valves on the other hand are designed to work hard in getting your sound and may typically last 1 to 3 years if you are using your amp 4-5 hours a week. It all depends on the design of the amp, how much use it gets and how loud you play.

EL84’s tend to need replacing sooner than say KT66’s. Our amps work the valves hard to get that great sound, so don’t expect the valves to last forever, there is a cost to owning a real valve amp and that is it will need servicing every couple of years.

That said if you play quiet jazz the service interval goes up …………… JAZZ??

How do I know when my valves need replacing?
You can use a highly accurate and specialised piece of expensive equipment that is ideally suited for this task …………. YOUR EARS!

You will notice that there will be degradation in your sound either pops, crackles, flabbiness in the bass, loss of the highs or just a dullness to the sound.

This is the time to take you amp to your favourite Ampguy for a service and re-valve/re-bias.

Why do some amps have a Standby Switch?
A Stand-By Switch on a valve amp allows the user to let the valves heat up to their operating temperature before applying the H.T.

If you apply HT before the valves are hot enough to allow the cathode to emit electrons material will be stripped from the cathode and decrease the life of the valves. This does not apply to amps that have valve rectifiers, the rectifier will take time to heat up and the HT comes up gradually.

What sequence should I use to turn my valve amp on and off?
With both mains and standby in the off position you plug the amp into the mains supply and more importantly plug the amp into a loud speaker of the correct impedance.

Switch on the mains switch.

Wait at least 2 minutes and turn on the standby switch.

Your amp is ready to use.

When taking short breaks, switch off the standby switch

To turn the amp off, switch off the mains switch, and then switch off the standby.

This will bleed away any residual HT voltage.

I hope that you have found this both useful and informative.