They don’t make ’em like that any more: tone controls
Until the 90s, hi-fi preamplifiers and integrated amplifiers always had bass and treble controls. Many also had a ‘loudness’ switch which, essentially, put the bass and treble controls on steroids. Even portable audio equipment usually had these controls; they were ubiquitous across the entire hi-fi industry, from the cheap, throwaway plastic boxes to the sell-a-kidney, sleek, brushed-metal behemoths that enthusiasts salivated over.
Thirty years on, almost no top-quality hi-fi equipment has these controls. I’ve found, to my amazement, that many younger people don’t even know what they’re for. My Leak 130, I’m pleased to say, is a new-ish integrated amplifier which does have bass and treble adjustments but, sadly, no loudness switch.
Strangely, it seems that the more expensive an amplifier is, the fewer features it has. The Leak 130/230 amplifiers are almost unique in their price bracket, in having features that were universal thirty years ago, like a phono preamp for vinyl turntables. Leak, however, specifically caters for the nostalgic: its products even look like they did in the 70s. So they’re hardly representative of the market.
What tone controls do (or did)
Tone controls boosted or cut frequencies in the bass and treble range. There never was much consistency about what frequencies constituted ‘bass’ and ‘treble’, beyond bass being ‘low-ish’ and treble being ‘high-ish’. The Leak 130 has a bass adjustment that centres at about 50Hz, and a treble about 50kHz. Of course, human hearing doesn’t extend to 50kHz – we’re firmly in bat territory here. But the frequency cut-off is relatively smooth, so both bass and treble controls affect a rather wide range of frequencies. In practice, the bass will have some discernible effect on all frequencies up to about 500Hz, and the treble all frequencies down to about 1.5kHz.
Almost all bass/treble controls on commercial hi-fi equipment were based on the notorious Baxendall circuit which, astonishingly, dates from 1950. This circuit requires, in addition to a measure of amplification, only a handful or resistors and capacitors, along with potentiometers to form the controls themselves. Apart from its simplicity and low cost, the Baxendall circuit was a good fit to the way human hearing actually works – a point I’ll return to later.
Simpler than the Baxendall base/treble circuit was the ‘loudness’ control, which just boosted the bass and treble frequencies by a fixed amount. Many amplifiers had both bass/treble controls and loudness, operating at the same frequencies. So switching on the ‘loudness’ just made the bass and treble controls more emphatic.
In the 80s there was a brief fad for more sophisticated ‘graphic equalizers’ which, these days, are often simulated in software. These devices operated on a larger number of narrower frequency bands allowing, in principle, subtler adjustments in the tonal response. In practice, they were fiddly to adjust, and needed constant tweaking, and the simple Baxendall bass/treble control has dominated tone controls right up until the present day.
Why we need tone controls
Even among hi-fi enthusiasts, there’s debate about the purpose tone controls serve, if any. Some, of course, argue that they serve no purpose, that they’re a gimmick. Rather than adjusting your equipment, the hi-fi snobs say, you should adjust your ears, and learn to like your music the same way the studio engineers do. There’s a terrible misconception behind this argument, which I’ll come to in due course.
Among people who allow that tone controls have some utility, a common suggestion is that they’re needed to compensate for differences between speakers and listening environments. After all, few of us listen to music in recording studios, or using the same loudspeakers that the studios do.
While I’m sure this is a reasonable explanation, I don’t think it’s the only one, or even the most important. After all, it doesn’t explain why we have specifically ‘bass’ and ‘treble’, and leave out all the other potential frequency bands.
A cynical answer to that question, perhaps, is that a simple bass/treble control can be implemented with only the modest Baxendall circuit, while control of multiple frequency bands is more complex. So the answer might simply come down to cost.
It isn’t the only explanation, though. The real reason we need tone controls is because of the characteristics of human hearing.
The human ear is sensitive to frequencies between about 20Hz and 20kHz – at least in our youth. But it isn’t equally responsive to all frequencies in this range: our hearing is particularly sensitive to the frequencies made by other humans and animals (except those pesky bats). It isn’t hard to think of evolutionary reasons for this but, whatever the explanation, our hearing tends be most acute at frequencies between about 500Hz and 1.5kHz – what we might call the ‘midrange’ frequencies.
This fact by itself doesn’t call for tone controls – studio engineers are well aware of these oddities of auditory perception, and adjust for them. The real problem is that our peculiar frequency sensitivity depends on volume.
The louder music is, the more sensitive we become to frequencies below about 500Hz and above about 1.5kHz. Our sensitivity to midrange frequencies doesn’t change with volume all that much. What this means is that to perceive music as tonally similar at different volume levels, we must boost the bass and treble by differing amounts as volume decreases.
This isn’t something that can be adjusted out in the recording studio. In theory, an amplifier using modern electronic techniques can compensate for it, and some designs even attempt to do so. In such amplifiers, the volume control not only affects the amplitude of the sound, but also the frequency balance. The problem with such approaches to tonal compensation is that they can’t easily deal with the different sensitivities of different loudspeakers, or even how close the listener is sitting to them. In addition, the volume-dependent sensitivity of human hearing differs from one person to the next.
In short, we need tone controls, not just because we have different equipment, not just because we have different tastes, but because the frequency response of the human ear depends on volume. We need a simple way to adjust the tonal balance for different listening levels.
This explains why a simple bass/treble adjustment works better than a complicated graphic equalizer, and why Baxendall-type circuits remain popular: we need to tweak the tone controls rapidly according to volume. Even the simple ‘loudness’ control was effective in practice: we just switched it on when listening to music quietly in the background, and switched it off when listening properly at higher volumes. Of course, what ‘quietly’ amounts to differs from one person to the next, and the loudness control was always a blunt instrument.
Where did the tone controls go?
Serious hi-fi equipment started to drop tone controls in the 90s, and consumer products soon followed. A perception arose that, if you were a real hi-fi purist, you didn’t ‘need’ tone controls. That was never true, even if you listened using the same equipment and in the same environment as the studio engineers; it could only possibly have been true if you’d listened at exactly the same volume. Still, the idea took hold in the hi-fi world, in the same way that balanced headphones and ‘oxygen free copper’ cables took hold. These things offer no benefits – they’re just snake oil – but certain things just seem to capture the imagination.
The demise of tone controls coincides approximately with the mass-market adoption of audio CDs. Perhaps tone controls came to be seen as relics of a bygone age: something we needed because vinyl records were so imperfect, but which CDs would render obsolete.
Whatever the reason, the sentiment suited manufacturers, because dropping the tone controls allowed a modest cost saving. To be fair, a poorly-implemented, cheap tone control could interfere with sound quality. Analog potentiometers, in particular, can generate a lot of noise when they start to wear out. These days, the few good-quality amplifiers that still have tone controls usually have a switch to bypass them completely, to avoid any problems of this sort.
It wasn’t just the cost of the electronic components that gave manufacturers a reason to dump the tone controls: the extra tooling needed to drill and label the case of the equipment also added to the cost.
In short, tone controls faded away because manufacturers capitalized on one of the many misperceptions that plagued the hi-fi community (and continue to do so). If a hi-fi manufacturer can save a few pounds per unit while at the same time promoting the idea that its offerings are ‘more serious’ than its competitors’, why wouldn’t it?
The loser, as always, is the consumer. In this case, though, the consumer was at least partially to blame. The market for top-end hi-fi equipment is a comparatively small one – a market where consumer preference can still influence product development. If buyers had turned up their noses at the ridiculous affectation of dropping the tone controls, manufacturers probably wouldn’t have been able to continue with it. That remains the case today, as the market for high-end hi-fi equipment is still a niche one. The problem is that so few amplifiers now have tone controls, that people under fifty don’t realize they’re missing out.
