Step inside any high street electronics retailer and the chances are that all of the speaker systems and consumer amplifiers that you find are based on transistors (except Rapallo). Yet among enthusiasts and hi-fi customers, the valve amplifier is still incredibly popular and desirable.
To the untrained eye, valve amplifiers are a thing of marvel – glowing bulbs of stunning beautiful light, they seem more like something out of Dr. Frankenstein’s laboratory than a piece of hi-fi equipment. The wow factor when they are warmed up and a a great “look at this” for when the mates are over.
The scientific principle behind valves was a by-product of unrelated experimentation by Thomas Edison. Having just invented the light bulb, Edison found that they were blackening from the inside, so he experimented with placing electrode in his bulbs. Inadvertently he created the principle behind the valve without realizing its potential applications!
John Fleming, a British physicist, was the man who created the initial diode valve as we know it – and this design has led on to the triode, pentode and ultralinear designs we see today.
When the transistor became prominent and the commonplace technology used in amplifiers, it was heralded as the successor to valves for the following reasons. Firstly, transistors were significantly cheaper to manufacture than vacuum tubes, resulting in the potential for a price cut to the end user.
The transistor was, and is, more efficient. This means that a transistor can be considerably smaller than a similarly powered valve, and therefore so can the amplifier. Valves tend to give off quite a lot of heat due to the inefficiency of Class A operation, while transistors typically give off less. Solid state amplifiers are typically much more powerful than similar valve models, which is why tiny pocket-sized amplifiers like the below Pro-Ject Amp Box are able to conjure 20W, while a valve amplifier would need to be at least 10 times bigger!
Transistors allow for tiny pocket-sized Class D amplifiers like the Pro-Ject Amp Box to exist and to work so well.
Solid state amplifiers are suitable with a much wider range of speakers thanks to their increased power, which makes these amps more versatile. People who like their music loud or their bass very deep will prefer the transistor over the valve for their amplifier.
Transistors are also considerably more durable and resistant than a valve. Valve amplifiers are somewhat fragile and any significant bumps, knocks and shocks can result in a cracked or broken valve.
Transistors in summary: smaller, more cost-effective, more durable, more powerful sound
With the ability to make amplifiers smaller, cheaper and cheaper to run in terms of electricity and maintenance, it is no wonder that the mass market took to transistor topologies rather than valves. Why then, you might ask, would anyone opt for a valve amplifier over a transistor design, in light of all these drawbacks?
While it is certainly true that a valve has a shorter lifespan than a transistor, valves are readily replaceable and many valve amplifier manufacturers seek to make such replacements simple. Auto biasing systems to ensure switching valves is plug and play. Transistors can be replaced, but this is a much more significant repair task and will often require sending off your amplifier to a specialist unless you are a dab hand with a soldering iron!
Replacement valves like the stunning Tung Sol KT150 are available and offer different choices for the HiFi audiophile. Kind of like tuning your car and adding extras.
Despite all of the nuances of valve amplifier ownership, they are still incredibly popular among hi-fi enthusiasts and audiophiles who are more than happy to put up with these tradeoffs in order to attain the major selling point of valve amplifiers – the sound.
Any valve fan will use phrases like “warm”, “rich”, “sweet” and “dynamic”. Valve amplifiers have a certain sonic magic to their presentation which, when paired with the right kit they can take your music out of the mundane and make listening to your record collection a completely different experience. Soundstage and imaging can be almost tangible with vast holographic projections conjuring the image of a real orchestra or band physically in your living room, all audible in their own space. Mid-range and vocals are rich and emphatic, while higher end frequencies are sweet and clear.
From a technical point of view, valves are favorable as they are highly linear without negative feedback, they offer a wider dynamic range and clipping is smoother than transistors which results in a more musical tone. Crossover distortion is minimized as valves operate in Class A or Class AB. Some transistor amplifiers are able to operate in Class A, such as Luxman amplifiers, and these models are famed for offering a sound more similar to valve designs than typical transistor amps.
It may seem counter-intuitive, but the way in which a valve amplifier portrays silence is one of the favorable aspects of its sonic traits. Silence with many valve amps is described as “inky black”, and the spaces between notes is emphasized, adding a greater sense of authority to the sound and a much more realistic and holographic soundstage thanks to the notes themselves being more defined due to the emphasis placed by the silences.
Valves in summary: sweet and open tone, “inky black” silences, rich and dynamic soundstage, oh and gorgeous to look at at night, the ooooo factor!!
The Valve vs. The Transistor
Some transistor amplifiers, notably Japanese manufacturer Luxman, operate in Class A, just like valves. This results in a tone which is much more akin to valve amplification than transistors – sweet tone with a big holographic soundstage. To some this presents an ideal compromise between lifespan, durability and valve-like sound quality
Is the Luxman L-590AX MKII Solid State Class A Amplifier the perfect compromise? Maybe, but there are other manufacturers who seek to compromise by utilizing hybrid designs – a combination of valve and transistor. Magnat Audio use valves for the first stage of amplification, and solid state transistors for the output stage. This results in an impressive compromise between power and tonality.
It may seem like transistors are only favoured for practical reasons, yet sonically they can perform as well. Hi-Fi press awards are dominated by transistor-based amplifiers, which are more common and also more suitable for the typical consumer. Amplifiers like the Arcam SA10 offer a lot more than most equivalently-priced valve amplifiers can – insight, musicality and real control over a wide range of speakers. It is the cost effective nature of transistors that makes this possible at this price point, and this is why the entry level and even mid-level price points are dominated by solid state amps.
There are a range of limitations which make transistor designs ideal and more suitable than valves for many users. The first is budget. As discussed, transistors can be more cost-effective, so those with a limited budget may get more bang for their buck by opting for a transistor amplifier. Another reason people may opt for a transistor amp is if they do not want the increased level of maintenance required for valve amp ownership. Those who want to install their hi-fi, enjoy their music and forget about it may not want the hassle of replacing valves.
Free of budget and practical limitations, and in an ideal world, many enthusiasts would opt for valve amplification.
However, unfortunately we do not live in such a world (most of us that is!), and for many, the transistor is still the best choice, the best compromise between sound quality and practicality. As with most things in hi-fi the decision is ultimately based on what is most suitable for you, and we are always on hand to advise if you are unsure!
We are always happy to offer a demonstration of valve amplifiers vs solid state amplifiers, and urge you to try both to see what is right for you!
Read more technical articles from the Rapallo Team
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