Back in the day, it somewhat made sense that polyphonic synthesizers were expensive, since the electronics itself was expensive. Today, if you have a few weekends time, you can rather easily design your own custom analog polyphonic synthesizer in e.g. Eurorack format, manufacture it for something around 30-50€ (e.g. using some Chinese PCB manufacturer + their SMT assembly service), and the resulting module will outperform modern commercially available modules that cost multiple times more (think of a factor of 10x for the price difference).
It's even crazier if you look at digital synthesizers or samplers. Remember the E-MU Emulator from 1981, which cost more than $8000 when it was released? Today, a cheap 5€ microcontroller together with a 2€ DAC will give you more of everything already (more polyphony, more RAM, higher sample rate, more resolution per sample, stereo output instead of mono, …).
The trouble comes when it absolutely will not, because the sound of the 'vintage digital gear' is heavily influenced by the primitive DACS and typically non-miniaturized circuitry putting out a relatively low-bit sound with some serious beef to it.
This does not apply to the Teenage Engineering… except to the extent that they've specced it out with fancy internal parts. They may well be avoiding jellybean op-amps etc. and producing unusually high quality analog stages. It IS possible to do that: I think Make Noise does it very well, and from what little I know about the Teenage Engineering thing, I wouldn't be surprised if they were performing on a very high level even though there's nothing retro about any of it.
I'd love to see someone do a seriously overkill Pi DAC/ADC hat. What you're saying is not exactly untrue… just that the people habitually saying these things are also the farthest from being able to MAKE it be as true as they think. The Teenage Engineerings of the world are more likely to be able to deliver the goods.
> The trouble comes when it absolutely will not, because the sound of the 'vintage digital gear' is heavily influenced by the primitive DACS and typically non-miniaturized circuitry putting out a relatively low-bit sound with some serious beef to it.
The real question is if you want to accurately clone "vintage gear" or if you want to have something modern which is only somewhat "inspired" by "vintage gear". If you really want to create an accurate clone, sure, this is hard and potentially not that cheap, since it might require multiple hardware revisions before you're satisfied with the result. But if you only want to build something similar, which obviously won't sound exactly the same as the "vintage gear", then it's cheap and easy to do. Also keep in mind that you totally can get e.g. 8bit DACs or 12bit DACs if you really want. Even with "variable sample rate", like what some old digital samplers did. If you then play around with different interpolation algorithms, because modern microcontrollers are fast enough to allow you to do this, you'll get a sound that's surprisingly similar to "vintage digital gear". Sure, it won't be e.g. an E-MU Emulator, but does it really have to be one?
Interestingly it's still possible to do this. I'd cite the Behringer D, which has managed to get surprisingly close to the Minimoog; I've owned and disassembled a Behringer D.
At least with the one I had, it was designed in such a way that it continued to use the primitive electronic parts found in a real Minimoog, and key components such as rotary switches were designed to be similar to what the original device would have. The modern assumption is that all these things can be redesigned to handle barely the energy required by the waveform being passed: microminiaturized SMD components you'd get in cellphones, on microscopic traces. Behringer used some of the SMD components, but sourced others to be more like what you'd get in the old gear: wildly, wildly overspecced, so the waveform wold go through a switch that could pass two or three amps of current.
I've also seen a guitar compressor (from a different company, but you know Behringer is just as capable of making one this way, or taking their earlier designs and optimizing for cost once it's established), which was clearly designed like a cellphone. It was a flyspeck of a circuit, rather beautiful to look at in its tininess and elegance: I tried to play bass guitar through it and had to get rid of it as it sounded simply awful, taking away all of the instrument's tone. Not all of this was due to coupling capacitors designed to be as small as possible, though some of it was. Some of it was the sheer miniaturization of all components. This is never found in the 'vintage gear' or the modern stuff that matches it.
You can never design audio gear around only the bare limits of what is 'meant to be there'. It's a trap, there's a lot of success to be had in excess capacity to carry tone and sound. Interestingly, it's still really cheap and easy to go the 'vintage design' way, even if you're also using microcontrollers and SMD and all…
It's even crazier if you look at digital synthesizers or samplers. Remember the E-MU Emulator from 1981, which cost more than $8000 when it was released? Today, a cheap 5€ microcontroller together with a 2€ DAC will give you more of everything already (more polyphony, more RAM, higher sample rate, more resolution per sample, stereo output instead of mono, …).