TEENSY-Synth EXTRA: Do we need the Audio Board?
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- เผยแพร่เมื่อ 6 ม.ค. 2021
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In this series we are learning how to build an awesome DIY Synth with a Teensy 3.2 Microcontroller!
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The ringing on the edges of the 'real' DAC is due to the bandlimiting a high quality DAC provides. It is a feature, not a bug. It prevents aliasing.
Thanks Hans! Good info
@@NotesAndVolts and that means that 12 bit guy will give you aliasing artefacts when spectrum goes higher than sampling rate.
Basically high order chebby filter on the output, can be had in one dual opamp and some resistors + capacitors ;-)
a spectrum analysis would be a good way to see any aliasing.
I'm super excited for these. I just started the teensy synth project. I'm hoping to create some instruments for/with my students in rural Maine. Love this channel, keep up the magic!
Thank you very much Gregory!
Great update on a super project. Good to see you again
Thanks faramoftae!
Great Video Man, really enlightening !
It's actually very cool that you still have your vintage breadboard. Especially since Radio Shack has bitten the dust.
I know, right?
you are a great teacher Dave, really thank you for all!!!
Thank you very much Carlo!
The vintage Radio Shack breadboard is Awesome! Very Cool 👍.
Yes! Thank you Andrew :)
Thanks Dave!
Hey Dave, thanks for posting this! I'll definitely be building one. One question though, is it possible to make it programmable?
Heck Yeah! love your videos!
Glad you like them calzar!
Where has the teensy been all my life? It will probably take me till next summer to get one. Once I do, I’m coming back here.
See you then.
Great Stuff.
God Bless.
I have wired up the older version of your Teensy Synth on the breadboard and thought it was really fun. I haven't (luckily) committed it to a final hardware piece yet, tho. So glad this video came out! Maybe I'll have to commit to a finished project now LOL
That's great Demag!
@@NotesAndVolts my ideas tend to suffer from "feature creep" and I could totally envision a voltage-controlled version of the teensy synth that could interface with a modular, etc.....
What would be super useful is a Teensy 3.2 “generic” Eurorack module that can be configured by s/w. I know some commercial modules are done this way, but use less diy accessible processors.
The most "generic" module I found is Music Thing Modular‘s Radio Music. Which is built around the Teensy and is open to custom firmwares.
Peter, I actually built a couple of these from the open source files, and you are right. But Dave’s approach using the Teensy GUI tool and Pure Data would make experimentation easier, I think. He could eliminate the SD card, add some pots for CV, switch for filter type, etc. A 12HP voice for the price of a Teensy 3.2 would be kinda nice.
I also still have my Radio Shack bread board but mine still has the power supply connector posts in the 3 holes!
I took them out for some reason a long time ago and I don't know where they went LoL
thank you!
You're welcome!
Can the Teensy generate a stable midi clock? If so, can you give some hints as to what it would take to make a midi clock with audible click/metronome sound that can be used with headphones?
Hi! Great stuff.. Can you add some polyphonic to it?
FYI, I've learned that the DAC output pins on the T3.6 are not AC coupled and have ~ 1 VDC offset voltage. If the LFO offsets are used to compensate, then the signal starts clipping @ 0 VDC, instead of having a +/- 3 Volts P-P range. IOW, they only output 0 to +3 VDC signals.
The last week I try to answer this question and your video comes now. Thanks!
Edit: The difference caused by the opamp and the passes (frequency filter) on the audioshield, which make the sound "round" for our ear. The 12 bit ADC hasn't any of these luxery electronics and it ihas more accuracy on the oscilloscope.
Great info! Thanks
I think there is a filter in the audio board. You did not filter the output of the DAC, which is why you see those high-freq components. Anyway, this is a good video - thanks!
Thanks for the info Alessandro!
The HF components of the 12 bit wave are likely very high in, or above, the audio spectrum, and pretty low in amplitude. There's a good chance the amplifier/speaker won't reproduce it. But if it's a concern, it would probably take only a *very* simple RC low pass filter to effectively remove those harmonics. The ringing is interesting, though. Perhaps the analog circuitry on the audio board isn't as good for hi fi as one might wish? Perhaps reproducing prerecorded audio at less than full amplitude makes the ringing less of a concern?
@@SuperShecky the "ringing" comes from the band limiting. When you leave out higher order harmonics of the infinite series, thats just the way the curve looks. There are some nice animations of fourier series of saw waves on yt e.g. on Greg Martins channel. :-)
Thanks for this really interesting video.
I can't wait to see the new synth in action without an audio board. Maybe with a Teensy 4.1?
Unfortunately the chips used for the Teensy 4.x do not have a built in DAC.
Thanks Jorg!
There is no DAC in Teensy 4.x. NXP did not include that function in the version of the chip used by PJRC. I am experimenting with the PT8211.
Hi Dave, very interesting video! Useful as a step by step guide! What would have been great to hear an example of a range not sounds of different pitches and timbre's. Or playback of samples, both melodic and percussive (bass drum, cymbals) to A/B sounds our ears are used to distinguishing quality from. A low bit rate mp3 of a crash cymbal sounds terrible vs a mp3 at higher bit rate. It might be more obvious if there is a difference, and how much difference, at different frequencies and types of sound. This leaves me still wondering if there is a reason to cough up the extra cash for the audio board. But I really appreciate the way to covered the process of wiring and coding the two versions. That was really great. Thanks!
Nice Teensy audio demo. Keen to build the Teensy synth with Teensy 4.0, have you worked with that newer version?
Not yet. I still need to get my hands on a Teensy 4.
The Teensy audio board has a 2.2 uF series capacitor on the line out signals whereas you used a 10 uF series capacitor on the DAC output of the bare Teensy. I wonder whether the two output signals would look more similar if you used a 2.2 uF series capacitor on the DAC output of the bare Teensy.
Really interesting video. Super! :-D
Thanks iFaber! Good to see you
What I’d love to see built is a synth with more than one teensy in it, perhaps 4 and breakout all the outputs to have an 8 output synth that way each teensy could run a slightly different or drastically different synth patch then mix them and post process each on its own, but share common things like midi I/o and power, teensy is so small I’d think the overall size could still be pretty compact. The more complicated idea I have is to have a way to set each of the teensy synths to a separate midi channel to create multitimbral capabilities as well but have a way to switch modes back to having them all listen to one channel, without needing to reprogram and flash the devices. Any thoughts?
That would be an awesome project! You could definately switch the modes as you described without reprogramming. You would just need to have some sort of user interface to select like a display or button combination.
Trying it on the Teensy LC now, I sometimes get reboots when I touch the ADC pin with the oscilloscope. Did you experience something like this?
Also would you advise connecting it to other gear as is or add a transistor or buffer stage in between?
Hi Peter. I'm not sure this will work on the LC. The Teensy audio library specs say it's for models 3.x and above.
@@NotesAndVolts You are right about the Audio Library, that's why I am directly talking to the DAC using an IntervalTimer and making my own osc objects.
Works fine for now.
I am more concerned about the electrical connection, e.g. impedences, loads on the DAC pin.
Thanks for your videos by the way. Got hooked by the Teensy Synth series.
what do you need 16 bit for?! i dont get it.
So my take away here, since it is all I can Find about the Teensy, is that it is only good for audio projects?
There's no ringing on the audio board's waveform, it's band-limited. Which is very desirable for audio signals that are supposed to be played by a speaker! Not so good for low-frequency signals like CV
Where do I get an enclosure like that, or is I a custom job?
It's a Hammond 1590DD box. You can see the process here: th-cam.com/video/n6PceuBUDh4/w-d-xo.html
Might be neat to record and sync the two tracks (maybe program in a pop & a pause at the start to help) and then reverse the phase on one to cancel out anything but the differences.
(Glen Fricker did that during his comparisons between tube brands.)
how much is savings?
So one of the reasons the teensy got popular is because it has DAC "audio out", then someone made a synth with a teensy and completely ignored said DAC "audio out"?
miss you bro thanks for new video and please make drum machine like tr8 or something like that
Thanks Mulk!
Compraring them side by side is pretty useless... only a few people can differ between bit depths and sample rates. the problems come when editing the audio in the digital domain. since 16 bit has a pretty low SNR, 12 bit can in fact increase the noise level.
Compraring them side by side is pretty useless... only a few people can differ between bit depths and sample rates. the problems come when editing the audio in the digital domain. since 16 bit has a pretty low SNR, 12 bit can in fact increase the noise level.