Comment from BluesBaby's designer
(More like a rant!)
Analogue Transistor Amplifiers… Isn’t It Time To Get Up To Date?
Transistor amplifiers have had their share of problems with regard to poor design and resultant slaggings; and I want to explain what has been done to bring transistor amp design to a point where they can compete with the tone of tube amps. I also want to highlight how current perceptions of transistor amplifiers are very out of date and causing players to overlook some truly amazing products.
Right from the begining, transistor amplifiers got off to a bad start, for a number of reasons which no longer exist. But really, I want to expose how peoples’ perceptions need to be brought up to date, as modern advances in analogue transistor amplifier design become available to the market.
Presented below is a rather interesting, but slightly illogical, example of how guitarists view two items of everyday gear made using similar technology - distortion pedals and transistor guitar amplifiers.
Guitar players will happily spend £200 on an analogue ‘boutique’ transistor based distortion pedal and see it as essential tone creating kit! But to spend £200 on a transistor guitar amplifier is much less likely to happen! True?
Those pedals provide electric guitars with a huge variety of tone colours, dynamics, distortion depths and styles. Brilliant… they make perfect sense. Players may even have several in their arsenal! So, generally seen to be good, therefore acceptable; despite the fact they’re made using transistors.
They are promoted to their best light by influential guitar gods and journalists appearing in adverts, talking on forums, magazines and blogs, etc. And, as a result, everyone has them… therefore they form part of the ‘being a guitarist’ culture we want to fit into. Players see other musicians using them, so naturally they feel totally comfortable with the idea of using transistor pedals to achieve their tonal goals. And again, they’re undaunted by the fact that those pedals have transistors in them… totally acceptable… a normalised situation. You’re not part of the clan unless you have one!
Put simply, transistor pedals are the backbone of rock guitar tone... like it or not!
But hang on… aren’t transistors those nasty thingies that add loads of odd harmonics, fizzy distortion, have a lack of warmth and generally impart an all-round bad tone to guitar sounds! Or do pedals employ some kind of special ‘distortion pedal only’ transistors that make nice warm cuddly tones? To be honest, I’m often told by ‘tube tone hounds’ that transistors are hopeless for amplifying guitars! So, which is right?
Frankly, this is an illogical attitude, as demonstrated by the use of transistors with great results in pedals! It should follow, that they’re capable of some brilliant tonal and reliability contributions to the world of electric guitar amplification too. Just as they clearly contribute to boutique distortion pedals… so what’s the difference?
Do we guitar players ever see pedals as being basically the same as amplifiers? I mean, we all know they’re ‘electronics’, but is our mental picture of their innards showing that they use the same type of components that transistor amplifiers have in them. Well, shock horror… they do use largely the same parts! But I suspect, because pedals look different, they are perceived as different in players’ minds. But, they’re not really. You see… you can serve soup in a cup, a mug, a bowl, on a soup plate or even in a bloody great bucket… but it’s still the same soup!
Logic always rules. Because distortion pedals generally use the same chips and components as transistor guitar amplifiers, this would imply that if transistors were truly rubbish at amplifying guitars, NONE OF THE DISTORTION PEDALS WOULD BE ANY USE EITHER!
Hypothetically speaking, it seems like if a transistor was to escape from a distortion pedal, squeeze its way down the guitar lead and end up inside a guitar amp; it mysteriously becomes defective at amplifying guitars! Huh… surely nobody would think that... would they?!
So, by simple deduction (my Dear Watson), if it’s NOT the actual transistors that’s the problem, is it possible that it’s the way they’ve been used in the past that has caused all this animosity?
Well, that idea is right on the money, as it happens. Musician's acceptance of transistor pedals, but not transistor amplifiers points to something wrong with the way we were designing transistor amplifiers over the years! And there is one vital difference between valve and transistor amplifiers. It’s not rocket science, but it can make a huge difference in tone between them. And it lies with how the power transistors drive the speakers. Without going into deep technical ramblings, I shall attempt to explain those differences as simply as possible.
You see, valve amplifiers have an ‘output transformer’ which creates a speaker driving method which is known in the audio engineering world as ‘constant current’ drive. Traditionally, transistor amplifiers drive their speakers by a method called ‘constant voltage’. The output transformer method of the valve amp works in that the voltage across the speaker rises or reduces dependent upon the impedance of the speaker attached to it. This results in a warmer low end and a brighter ‘chime’ to the top end tone. It’s like the transformer creates variable gain governed by the speaker’s impedance!
Factoid: a speaker’s impedance is NOT fixed, it varies with frequency. This is why a speaker is rated NOMINALLY at 4, 8 or 15/16 ohms.
Usually, there is not an output transformer in a transistor amplifier. This means that the power transistors’ ‘constant voltage’ drive method DOES NOT create this kind of ‘variable gain’ in the power amp, so that the lovely warm bottom end and chime in the highs is NOT produced.
Well that’s true for the old transistor amp designs. But most modern transistor guitar amps are equipped with ‘constant current’ drive… so they exhibit the same low end warmth and treble ‘chime’ characteristics of a valve amp with an output transformer driving the speakers!
The lack of 'constant current' drive in tranny amps is the reason behind why guitarists have, over the years, accused them of sounding 'cold'. This was right... but is no longer the case!
But what about those amps with a disgusting distortion tone? Well simply, you have to write those amps off to iffy designs concocted by designers who didn’t have much of a clue! After all, we use pedals which create wonderful distortion sounds… and they’re designed by people who DO know what they’re doing with transistors. So why blame the transistors for poor amp tone?
OK, if transistors can ‘do it’ in pedals, then there’s absolutely no reason why they can’t be made to 'do it' in amplifiers just as well! The idea that transistors can't sound good in a guitar amp is a crazy notion. Especially as we all know very well that they work just fine in a distortion pedal. If they didn't, then no one would buy those pedals!
Guitarists are not silly, they have good hearing and can easily detect when something is not right with an amp tone. But poor tranny amp tone has led to guitarists assuming that, because they cannot not see any valves in the amp, it must be the 'transistors' causing the inferior tone. Although, in electronics, the differences you can 'see' are rarely the real reason for what you can hear!
A great big red herring really, which has become like the 'rolling stone that's gathered way too much moss'; or in this case, collected too much misinformation! And as I said earlier, there has been no one seriously designing transistor amplifiers that could produce the quality of tone that could counter that reasoning.
Not only that, a collection of 'tube nerds' invented a raft of unproven reasons as to why transistor amps stinck! They were all entirely wrong - it was the missing 'constant current drive' that was causing the tone to be 'not quite right'. Along with a shed load of God-damn dreadful tranny amp designs thrown into the market place aimed at young metal players who like their guitars to sound like chain saws!
So, ALL ALONG, it was NOT the transistors’ causing the problem… it was how they were being used in the circuitry which was the real culprit?
Yes, the exact point I have been leading up to!
Far too much credit is given to technology and the components' quality for great guitar tone! When really, it's the amp designer's knowledge which creates the final sound you hear.
Ever since guitar amps first came onto the market, manufacturers have tried to make them ever cheaper. And in doing so, they have made many of the vital components perform worse and with shorter life expectancy. This lowering of quality impacted on the tone of amplifiers in many ways. Those components now had 'defects' which influenced the sound you heard. And, as if by some great stroke of luck, many of those amplifier defects had a positive effect on the amplifier's tone when played too loudly. In the guitar amp design world we refer to these as 'beneficial defects'. Over the years, we designers have learned how to use those defects for the advantage of guitar players. Learning how those defects are created has enabled speaker designers to make available a myriad of different sounding speakers that break up nicely under stress!
Whilst being driven hard by the amplifier, guitar speakers are 'excited' to generate 'harmonic tones' (edge) which do not come from the amplifier itself! Each speaker available on the market has an individual voice based on its own set of deliberately planted 'beneficial defects'. So, if you have ever thought that all 12" guitar speakers are the same, you are seriously mistaken. In fact, a simple speaker swap in your amp can bring a far bigger change to your tone than changing tubes or fitting new pickups into your guitar... and for a lot less money!
Even back in the nineteen fifties and sixties, all tube amps were designed around pre-existing components. With the designer's influence, some amps sounded good and have become iconic models… others did not sound so good and have faded from memory. It's important to understand that a 'human being' designs amplifiers; and their skills alone with regard to how they use those components is what determines whether it will still be popular and have any value in the future or not. Not the just the components or the badge attached to that amplifier. Without human intervention, components alone cannot create a sound... or work at all!
Perfect quality components retro-fitted to guitar amps will create a boring and sterile sounding amp... just leave it as it was designed!
Award-Session guitar amps employ ‘constant current’ speaker drive to help achieve the scintillating tones our amps are known for. But, although vital, this factor alone is not enough. Award-Session combines this with our signature design attitude. Connecting these with our forty-plus years of design knowledge and other novel techniques enables Award-Session to nail classic guitar tones. All this gives our products a unique place in the guitar amp world.
It seems there’s a lack of manufacturers interested in building transistor amplifiers that are seriously capable of providing musicians with those ‘old school’ tones. ‘Old school tone' will always be the right starting point for players to build from and develop their own tone.
To be perfectly honest, there’s not really that much difference between a valve and transistor amplifier anyway… apart from the fact that transistors work as soon as you turn them on!
From the perspective of real life, a transistor guitar amp’s circuitry operates very much like any valve amp! The power transistors are 'biased' class AB… They heat up to 100° Celsius… They have 'negative feedback'… all just like valve amps! The preamp is 'high impedance' circuitry... Its power supply voltage dips when you turn it up loud... just as a valve amp's does! No one has ever explained this before, so it should be a revelation to players. Is it not any wonder guitarists fear transistor amplifiers when they are presented with such a highly negative picture all the time? They just need to know more of the truth and none of misconceptions banded around out of ignorance!
The 'two technologies are more similar than you have been led to believe‘ idea is not generally known by shop sales personnel either, so guitarists are never likely to learn of this. I don’t know if a shop owner is at all bothered… their job is to sell you what you think you want. And a shop preferring you to buy a more expensive valve amp is probably very high on their wish list!
Let’s not forget that guitarists are already thinking they must have a valve amp, in order to be accepted amongst their peers. So, a very strong pressure upon any player to own a valve amp does exist!
I’ve heard comments like… “Your puny little transistor amp doesn’t sound like my 2 x 12” valve combo!” Well, of course it won’t! That puny little tranny amp is squeezed into a small box with a big speaker in it! Who would expect it to sound like it was housed in a big 2 x 12” Twin Reverb style cabinet? Who on earth would make such a stupid unfair comparison? Well, it happens all the time! All guitarists should know that a large 2 x 12” speaker cabinet will sound much bigger than the small tranny amp box! But it’s not the transistors’ fault that ‘lil amp sounds the way it does! It may be armed with a really cheap naff speaker as well!
Further, other clever people have steered us all away from transistors to keep us on the treadmill of regular expensive valve replacements and repairing heat damaged amplifiers. It’s been very easy for them without any opposition from designers like me. All in all, the tubes vs transistors debate has been a very one-sided conversation!
There is a common perception that a transistor amp should cost much less than a valve amp. That is true to a point. But a well-designed transistor amplifier will use higher quality components than the transistor amps you are used to seeing in your local music shop, so will cost appreciably more. It will be built more solidly. Like having all its pots and jack sockets securely attached to the front panel with nuts; or its cabinet made from birch ply or pine – basically, to build levels many 'affordable' valve amps don’t always have!
The power transformer will be more highly rated to provide a much longer service life – and perhaps radiate 70% less hum into your single coil guitar pickups - very useful! It is likely to be built on a high quality glass fibre printed circuit board (PCB). It’s just not practical to build a transistor amp by hard wired techniques. Besides, there wouldn't be any benefit from attempting it either. A PCB can make amplifiers perform almost identically to each other, one after another. PCBs also enable high gain amps to operate with much more stability… in fact; it just wouldn’t be possible to make one without using PCBs… the same situation for a high gain valve amp too.
I regularly see Session amplifiers made in 1981, where the glass fibre PCBs are still in top condition. We have never had to write-off an amp because the PCB failed!
It is an absolute that transistor amplifiers get very bad press, by default. However, unlike in the past, there are now more designers around who really can produce wonderfully designed transistor guitar amps that hammer loudly on the doors of the tube camps. Of course, the tranny amps I refer to are not those ‘big-brand’ budget amplifiers that are dressed up to look like a vintage ‘black face’ amp or something. No, these are small builder produced, mainly in America and the UK, but built up to a quality rather than down to a price.
Times have moved on. Award-Session’s conceptually ‘new-school’ analogue transistor amps available now deliver a decidedly ‘old school’ tone… and with a lot less bother than their thermionic brethren!
We often see very experienced guitarists playing through our BluesBaby amp at local jams... and they have absolutely NO idea they are TUBELESS! Transistor guitar amps rightfully share centre stage... at last!
Have fun…
Stewart Ward – Guitar amp designer (valve & transistor) since 1967 - Session Amplifiers & Award-Session Electronic Products
PS: To be a designer of any kind of product, that person has to think outside the box to a very large degree. And this does mean, sadly, that he may disagree with the commonly held beliefs that many of his potential customers may hold. Whilst I am an active musician with an outrageous passion for electric guitar, I do work with science and proven facts... not romantics!
So, I'm sorry if anything said above upsets you or sounds 'in your mind' like a load of bull! I fully expect people to hate me for what I say and accuse me of being a heretic. Because of this rather dangerous lifestyle, I fully expect to be burnt at the stake eventually! lol
