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 Forum index » DIY Hardware and Software » Les Hall's Projects including eChucK
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Cfish



Joined: Feb 24, 2016
Posts: 451
Location: Indiana

PostPosted: Mon Dec 26, 2016 5:06 pm    Post subject: Reply with quote  Mark this post and the followings unread

Looking good Les. I have started doing some VCA tests on the single transistor VCA.

It would be a very easy module build. But it is pretty noisy. May try to send you a sample audio of it tomorrow after work.

Am about exhausted after work today.

I have been toying with etching for a while. This would be a good first project to try it out on.

If we had solder board versions mapped out and available for each module, that could be nice. What do you think?

I really need to learn to use the computer to map boards anyway.
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Stream Operator


Joined: Oct 13, 2007
Posts: 6171
Location: San Antonio, Tx, USA
Audio files: 267

PostPosted: Mon Dec 26, 2016 10:51 pm    Post subject: Reply with quote  Mark this post and the followings unread

AlanP wrote:
Ahhhh, now I see what you are driving at Smile

This is a very, very clever way of working around the problem of not being able to solder in your living situation, Les Smile


Thank you for chiming in on this thread - yes, I am nothing if not clever! I have since figured (well, re-figured) out that I can get a "cold" soldering iron for this purpose. It is very safe. Still, this is worth doing if only for the exercise of doing it! I figure some customers will want this, and we can offer our flagship model, the VCO, in solder and non-solder versions.

Les

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Cfish



Joined: Feb 24, 2016
Posts: 451
Location: Indiana

PostPosted: Tue Dec 27, 2016 6:22 am    Post subject: Reply with quote  Mark this post and the followings unread

I should be ready to try my hand at etching VCO boards this weekend.

Will document the method I came up with in a video.

Really didn't want to buy anything new just to try it. So we will see
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Cfish



Joined: Feb 24, 2016
Posts: 451
Location: Indiana

PostPosted: Wed Dec 28, 2016 5:36 am    Post subject: Reply with quote  Mark this post and the followings unread

I have always wanted to see if I could make the best VCO possible from a UJT saw core.

This is just concept and needs work. But temperature compensation, and the use of the opamp in place of the single FET to minimize interference,
were things I always wanted to try.

Still needs volt per octave adjustment, and some thought put to some resistor values

If you ask why???

I have always had a soft spot in my heart for the UJT.

My first early sound projects were built around it.

If anyone sees obvious problems, please let me know.


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Cfish



Joined: Feb 24, 2016
Posts: 451
Location: Indiana

PostPosted: Wed Dec 28, 2016 5:53 am    Post subject: Reply with quote  Mark this post and the followings unread

Could switch to a TL074

Ad a comparator and get PWM with the extra 2 opamps.

Never tried PWM from a saw wave.

I can't think of a reason that it wouldn't work ok. Shifting the comparator reference voltage would change the puls width.

???????? Any thoughts anyone??????

I like the simple EFM version, but it has a lot of limitations

I have never seen anyone use a UJT core on a VCO of any quality.

May be a good reason for that. May not.
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Cfish



Joined: Feb 24, 2016
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Location: Indiana

PostPosted: Wed Dec 28, 2016 6:12 am    Post subject: Reply with quote  Mark this post and the followings unread

Just came to the realization that the little UJTs I like and the woman I loved both have a little saw shaped heartbeat.

Coincidence??? Probably not 😜
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Stream Operator


Joined: Oct 13, 2007
Posts: 6171
Location: San Antonio, Tx, USA
Audio files: 267

PostPosted: Wed Dec 28, 2016 7:38 pm    Post subject: Reply with quote  Mark this post and the followings unread

Funny, funny...
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Cfish



Joined: Feb 24, 2016
Posts: 451
Location: Indiana

PostPosted: Wed Dec 28, 2016 8:49 pm    Post subject: Reply with quote  Mark this post and the followings unread

So I commented earlier about not seeing a vco schematic with good temperature compensation using a UJT core.

Turns out there is a guy over on muffs working on one too.

LOL what's the odds of 2 guys trying to perfect a vco using outdated UJT transistors at the same time?

I don't feel so alone in the world.
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Stream Operator


Joined: Oct 13, 2007
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Location: San Antonio, Tx, USA
Audio files: 267

PostPosted: Thu Dec 29, 2016 12:53 am    Post subject: Reply with quote  Mark this post and the followings unread

Are you comparing notes with him?

Les

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Cfish



Joined: Feb 24, 2016
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Location: Indiana

PostPosted: Thu Dec 29, 2016 5:41 am    Post subject: Reply with quote  Mark this post and the followings unread

No Les, I actually made a conscious decision not to read beyond the beginning of his poste.

I would like to see where that section of working with the VCO design goes for me.

Then compare end results with his end results.

Will be interesting to see how similar the end results are.

As they say, there is more than one way to skin a cat.

I'm not a cat lover, so I prefer the straight forward get it done and ccck it method. LOL.
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Cfish



Joined: Feb 24, 2016
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Location: Indiana

PostPosted: Fri Dec 30, 2016 11:29 pm    Post subject: Reply with quote  Mark this post and the followings unread

So we got a functional envelope generator up and running that fits the current project profile.

Is about as simple as it gets.

I'm sure someone has done it this way before, but I have never seen it.

Will fill in final values once I'm done fine tuning.


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