Warmth - what is it? How do you get it? The digital emulation of warmth
TV dinners are, as you doubtless know, best warmed through in the oven. Putting in the microwave might take less time, but it's never quite the same. One could wonder whether warmth is best achieved by using original valve equipment and analogue tape recorders, or whether there might be a more convenient means of achieving much the same effect. Valves are easier to deal with since there is a wide variety of equipment on the market that incorporates a valve or two into its design.
It has been said quite often that putting one valve into an otherwise completely transistorized or IC design is not the proper way to do it. I beg to differ. If the object was to recreate as closely as possible the sound of a piece of technology of a bygone era then yes, it is appropriate to model the original right down to the power supply as every component contributes to the overall sound. If the object is simply to provide a means of attaining warmth, then this can be done with a single valve.
But merely having a valve doesn't mean that the equipment will sound good.
Far from it - if the design engineer has grown up with transistors and integrated circuits, what guarantee is there that his first stab at a valve circuit will be any good? And design engineers, it has to be said, are sometimes prone to analyse systems into their most basic elements before attempting to imitate them. So because a valve can be used to produce a bit of even-order distortion, it is too easy to say a bit of even-order distortion is all that is required. It's like making an Indian meal with curry powder - the basic flavour is there but with none of the subtlety of the careful selection of spices.
It's the same with tape emulators. There is more to analogue tape than harmonic distortion and soft saturation, but does the emulator go so far as to add flutter noise? Unless it is a digital system it's difficult to see how it can, and even in a digital tape emulator one has to wonder whether the subtleties of a well used analogue recorder with dirty heads, worn bearings and frayed edges on the gaps of the record and playback heads will be perfectly reproduced, as they all contribute to the sound. Even dropouts contribute to the sound of analogue tape and if they are not emulated then the imitation just isn't going to sound like the real thing.
But hang on a minute - why should it sound like the real thing? If we take the wealth of classic equipment as we have as indicators of what warmth consists of, then we don't have to model their idiosyncrasies slavishly, or provide a mock front panel display on a TDM plug-in. It would be far better to provide controls for even-order distortion (which we know to be desirable, and maybe digital technology can separate it from the odd order distortion that always seems to accompany it), perhaps even extending to control over individual harmonics.
Controls could also be provided for noise, modulation noise, flutter, with sub-parameters for the frequency balance of the noise, the granularity of the modulation noise, the irregularity or otherwise of the flutter. All of these are certainly possible and much of the research material is there in secondhand audio dealers' warehouses.
The conclusion is that we have a pretty good idea of what warmth is already, but genuine warmth isn't always easy to find and often turns into harshness all too easily. But warmth can mean so much more than just using old equipment. With digital technology we are surely now able to go beyond what the old equipment had to offer and achieve warmth in new, exciting and possibly even better ways.