Temperature-compensated resonance ( was Re: [sdiy] RE: [AH] Parametric EQ)

[cheater cheater]

Tom,
> Aww, c'mon! Who ever bothered having a temperature-compensated resonance
> control anyway? Certainly no synth I own has one. You're lucky if you get a
> tempco in the filter *cutoff*, let alone the resonance.

This only shows the sad state synth designs are in. Most high quality
equalizers have tempco Q.

> One thing I'm really learning about synth building is that you can often get
> away with a lot less than you think you need. It's amazing, but the human
> ear really isn't "hi-fi" at all. I thought I needed 16-bit parameter values
> for everything, but 12 will do, and often 8 is enough.

The way I think of this is that I can't figure out all ways that
people will be using my synth/eq/computer program/other invention,
therefore I shouldn't compromise where *I* think that *I* don't need
the accuracy. I usually go and ask experts, I'm definitely not the
best expert in the use of anything I created.

D.

On Mon, Feb 22, 2010 at 15:36, Tom Wiltshire <tom at electricdruid.net> wrote:
>
> On 22 Feb 2010, at 09:49, cheater cheater wrote:
>
>> Tom,
>>>
>>> Anyway, if there was a DAC controlling it, I'd still save the hardware
>>> and
>>> use a lookup table to linearize the resonance response. But that's just
>>> me.
>>
>> But a LUT is not temperature dependant, and will probably not work
>> that well with resonance settings which can be really delicate around
>> the generative point.
>
> Aww, c'mon! Who ever bothered having a temperature-compensated resonance
> control anyway? Certainly no synth I own has one. You're lucky if you get a
> tempco in the filter *cutoff*, let alone the resonance.
>
> The nearest I can think of is something like the Oberheim Xpander, which
> calibrated the resonance control as part of its full auto-tune. But even
> that doesn't avoid the temperature dependence  - it just ensures that you
> get the same response as you got at whatever temperature you were at last
> time you tuned it. If you take it outside from a warm room, it'll still
> drift out, but you're only an auto-tune away from having it right again.
>
> It's true that you're going to need a fair bit of DAC resolution, since
> you're trying to linearize an exponential curve, but my recent experience
> with the pan law suggests that 12-bit would do it.
> A practical example is the Korg Polysix which uses SSM2044 filters ( which
> need an inverse-log pot to linearize the resonance control ), but seems to
> manage to have a reasonable resonance response. It only uses an 8-bit DAC,
> and I suspect there's a LUT involved there.
>
> One thing I'm really learning about synth building is that you can often get
> away with a lot less than you think you need. It's amazing, but the human
> ear really isn't "hi-fi" at all. I thought I needed 16-bit parameter values
> for everything, but 12 will do, and often 8 is enough.
>
> Regards,
> Tom
>
>
>
>
>