![]() ![]() I.e, you can feed the number directly to a linear numeric oscillator. If you set the variable and fixed frequencies correctly you can get a pretty linear response in the exponential domain. If you are using the offset heterodyning approach you might be able to use that to do your linearization. Inertial delay isn't as easily perceived IMO. 10ms of transport delay should be OK, and 10x this inertial delay (100Hz) should probably be OK too. I used to have a inertial target of 1kHz (1ms) but I now think that's overkill. The Theremini bandwidth is something like 2Hz which is way too low. I think 100Hz or even a little lower is probably OK, though I haven't experimented with this much. Assuming you don't have significant throughput times (transport) you're then talking bandwidth. Though they can be decoupled too - particularly in digital systems that do batch data processing. There's latency (transport delay) and there's bandwidth (inertial delay), and they are generally related - particularly in a first-order filter. I hate how my Theremini reacts on hand movements." "BTW, does someone know what is max latency value which still allows to play vibrato? I hope 1ms is good enough. One technique for longer distances would be to track the distance in SW and apply more filtering to longer distances. If you think about it, it's pretty amazing that physics allows this. This is a reasonable goal, and very similar to my own. "My goal is to achieve pitch antenna sensitivity at least 1/100 semitones with hand far from antenna (~80cm)." IMO this is diminishing returns, so probably not worth it as higher voltages generally aren't present around digital circuitry. A higher supply voltage could help you process a larger oscillator swing, and so give you somewhat better internal SNR in that stage if all other things are equal. "Can I have some benefits from increasing oscillator voltage to 5/9/12 Volts?" The 3.3V oscillator supply should be independently regulated from the digital stuff. "Is it ok to use pitch antenna oscillator powered by 3.3V? Any problems with noise expected?" - Bugginsģ.3V should be OK if you use high Q to get the voltage swing at the antenna high enough (some tens of volts minimum). If you aren't averse to using a plate antenna, this is one way to multiply the sensitivity several times right at the source.Īnd I would highly recommend using a software CIC filter to kill mains hum and low pass filter the data. So much of it, as you understand, comes down to SNR, so you need as many significant digits of data as possible as cleanly as possible. Hi Buggins! It sounds like you are dealing with many of the same issues as I am over on the Digital Theremin thread. I hate how my Theremini reacts on hand movements. By averaging more values (increased measurement interval), better precision may be achieved, in cost of bigger latency.īTW, does someone know what is max latency value which still allows to play vibrato? I hope 1ms is good enough. But after applying of linearization formula sensitivity for low notes is expected to be reduced a lot (not sure how much). W/o linearization, sensitivity is about 1/100 halftones when measured for 0.5.1ms period (pitch hand position measurement latency 0.5.1ms). ![]() With signal from heterodine in range 2.10KHz for working hand location range, it should be possible to have about 13 meaningful bits to be used for pitch value. Frequency measure is based on hardware timer, and measurement precision is not affected by delays in interrupt processing. It can provide reference frequencies for using in D-trigger based heterodine. MCU is able to measure number of 60Mhz pulses per input signal period. There is a sound board, and audio library which allows to implement low latency solution. ![]() For 44100 Hz output, it may perform 1000-2000 floating point operations to calculate single sample value. It's enough for precise digital sound processing. It has hardware floating point support (1-2 cycles per floating point addition or multiplication). I'm using Teensy 3.6 ARM based MCU board with 180Mhz clock, 192K of RAM and 1Mb of flash. My goal is to achieve pitch antenna sensitivity at least 1/100 semitones with hand far from antenna (~80cm). Is it ok to use pitch antenna oscillator powered by 3.3V? Any problems with noise expected?Ĭan I have some benefits from increasing oscillator voltage to 5/9/12 Volts? ![]()
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