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 Forum index » DIY Hardware and Software » Arduino
BassMaster 85
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JovianPyx



Joined: Nov 20, 2007
Posts: 1824
Location: West Red Spot, Jupiter
Audio files: 218

PostPosted: Mon Dec 17, 2018 5:48 am    Post subject: Reply with quote  Mark this post and the followings unread

Very cool!

How does the filter sound?

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Hammer



Joined: Mar 13, 2018
Posts: 70
Location: Russia, Zhukovsky
Audio files: 23

PostPosted: Mon Dec 17, 2018 8:00 am    Post subject: Reply with quote  Mark this post and the followings unread

It have very strange form of resonance. I think it will sound different with different MOSFETs.


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JovianPyx



Joined: Nov 20, 2007
Posts: 1824
Location: West Red Spot, Jupiter
Audio files: 218

PostPosted: Mon Dec 17, 2018 9:28 am    Post subject: Reply with quote  Mark this post and the followings unread

MOSFETs (at least those in 4069ub and 4007) have an odd relationship between gate voltage and output. Using a 4007 or 4069 as a linear amplifier, gain is highest when the gate voltage is halfway between the rails and goes lower as the gate voltage approaches either rail. This can allow it to round out a triangle input, but I've no idea what harmonics are added/subtracted. The WASP filter uses 4069 as a distortion element which gives the WASP filter its crunch.
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Hammer



Joined: Mar 13, 2018
Posts: 70
Location: Russia, Zhukovsky
Audio files: 23

PostPosted: Mon Dec 17, 2018 11:07 am    Post subject: Reply with quote  Mark this post and the followings unread

JovianPyx wrote:
gain is highest when the gate voltage is halfway between the rails and goes lower as the gate voltage approaches either rail


Yes, I know it, and I like it)

I've use this circuit to test MOSFETs:

Posted Image, might have been reduced in size. Click Image to view fullscreen.

With 100k stereo pot it sounds better:


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JovianPyx



Joined: Nov 20, 2007
Posts: 1824
Location: West Red Spot, Jupiter
Audio files: 218

PostPosted: Mon Dec 17, 2018 3:36 pm    Post subject: Reply with quote  Mark this post and the followings unread

wow caps rated in mF - takes me way back. When I was a kid, I looked for TVs to scavenge on the curb on trash day. These were vacuum tube TVs. The caps were in mF or mmF which one doesn't see much these days.
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Hammer



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PostPosted: Wed Dec 19, 2018 3:51 pm    Post subject: Reply with quote  Mark this post and the followings unread

I found this very interesting module: http://www.stgsoundlabs.com/products/digital_attenuators_mu.htm

This is digital pot based VCA. To get rid of clicks these guys make the switch of digital pot at the zero crossings of the input signal.

It remains now to understand whether the microprocessor has enough speed for zero crossing detection.

Or just to send a signal from the first ATtiny85 when PWM is 127.
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Hammer



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PostPosted: Thu Jan 10, 2019 4:11 pm    Post subject: Reply with quote  Mark this post and the followings unread

Vactrols lost during shipment Sad

But I got in the mail 100k digital potentiometers X9C104. 4069 SVF with this potentiometers sounds clean. But the resonance is too weak.. Will try with low pass gate.


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Hammer



Joined: Mar 13, 2018
Posts: 70
Location: Russia, Zhukovsky
Audio files: 23

PostPosted: Sun Jan 13, 2019 10:33 am    Post subject: Reply with quote  Mark this post and the followings unread

Still messing with flters...

But I've made some 5V digital VCA.

TL431 used as 2,5V comparator. In this curcuit envelope is exponentional. But if you will make inverting amp with digital pot. in feedback loop, envelope will be linear.

If you will use CD4069 as inverting amp with digital pot. in feedback loop, envelope will be also linear, but shape of signal may be distorted. For example, triangle wave will look like lines bended into arches.

Pot. can switch in non zero crossing point, and I don't know why, maybe because of TL431 is not the best decision. Maybe it's breadboard feature.

That's why I used the 470 pF capacitor. It removes the peaks from switching. Two oscillograms, with and without capacitor. Code also included.


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5V digital VCA
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Hammer



Joined: Mar 13, 2018
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Location: Russia, Zhukovsky
Audio files: 23

PostPosted: Mon Jan 21, 2019 3:53 pm    Post subject: Reply with quote  Mark this post and the followings unread

And after one more month I got my vtl5c1 vactrols)))

And they are so slow... It's not necessary to use second ATTiny85 for PWM, i'ts sounds very intuitive if just change a length of note. Very clean and tasteful sound! I like it a lot!


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Hammer



Joined: Mar 13, 2018
Posts: 70
Location: Russia, Zhukovsky
Audio files: 23

PostPosted: Thu Jan 31, 2019 2:05 am    Post subject: Reply with quote  Mark this post and the followings unread

Now I can make single sided PCBs:
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Hammer



Joined: Mar 13, 2018
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Location: Russia, Zhukovsky
Audio files: 23

PostPosted: Wed Feb 27, 2019 11:51 am    Post subject: Reply with quote  Mark this post and the followings unread

Trying to etch a pcb. New circuit design and new code coming soon)


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