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 Forum index » DIY Hardware and Software » Thomas Henry designs
Electronic Drum Cookbook: some questions
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Silesius



Joined: Feb 12, 2010
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Location: Berlin

PostPosted: Sat Feb 18, 2012 7:20 am    Post subject: Electronic Drum Cookbook: some questions Reply with quote  Mark this post and the followings unread

Hi, I've just bought the Electronic Drum Cookbook from Mr. Henry, and I must say it's a fantastic piece of synth knowledge; the level of complexity is perfect for the learning stage where I am now.

Now I want to begin building and experimenting with the circuits, but I've found a couple of problems. The main VCO explained in the book is based around the lm/ne 566 chip, which is very difficult to find and very expensive. So my question is if there's another chip I could use for this application. Anybody has built that circuit with another ic?

Other circuits use the ca3080, not so difficult to find; I have some ca3080's and this chip won't be a problem, specially because lately I've been using the lm13700 as a replacement for the 3080 and it has worked in a couple of filters I made. Must I assume it will work in the majority of the cases?

And my last problem is with the lm741 opamp. This one is very common. The problem here is not where to find them but where to connect it. I mean, all the schematics in the book show how to connect the ic's to the power rails, as you would expect. But this is not happening with the lm741. I'm not sure if I must connect the 4th pin of the chip [the negative one] to -12 or to ground. All the schematics where the 741 appears don't show this information. Anybody knows the reason for that? Maybe it's something I don't see [I am still a beginner].

So now I've got the book, and I'm eager to start with something, but I need to solve this small doubts before. Any ideas?
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Cynosure
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PostPosted: Sat Feb 18, 2012 9:50 am    Post subject: Reply with quote  Mark this post and the followings unread

I don't know about the 566, but I can help with the other things.

LM13700: Just ignore the extra pins that the 3080 doesn't have and it is will work identical to the 3080.

LM741: Pin 4 should be lower than whatever you have connected to pin 2 or 3. This is how you would wire it up in most cases:

Pin 7: V+
Pin 2 or 3 (depends if it is inverting or non-inverting): 0V (Ground)
Pin 4: -V
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Silesius



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PostPosted: Sat Feb 18, 2012 11:29 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks a lot for the answers; that really makes sense [about the 741]. And it's nice to hear that one can easily replace a ca3080. That makes "Making Music with the 3080 OTA" much more interesting for me.

I'm very happy with the book, so I'm planning to purchase "An Analog Synthesizer for the 21st Century" as well. Does anybody know if this one uses the 566 a lot?
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jumunius



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PostPosted: Sat Feb 18, 2012 1:17 pm    Post subject: Reply with quote  Mark this post and the followings unread

For what it's worth, all the pinouts for ICs used in the book appear in section 5.1, p 44.

One thing to note about Analog Synth for the 21st Century -- it's just schematics, it lacks the detailed descriptions given in the Electronic Drum Cookbook. I was a little disappointed about that, but so it goes.

I'm not sure offhand if it uses 566s, but there is a wide variety of chips used in the book.

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Silesius



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PostPosted: Sat Feb 18, 2012 5:55 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
For what it's worth, all the pinouts for ICs used in the book appear in section 5.1, p 44.

Yes, but if you look at the schematics, there's no indications about where to connect pins 4&7 of the lm741. That's what confuses me. Of course, pin 7 should go to +v, but I'm not able to see if I should connect pin 4 to ground or -v. But I think Cynosure is right and pin 4 goes to -v.

And about the book: that's very disapponting. I thought "An analog synth for the 21st century" would be written in the same style as the Drum Cookbook. That's what it makes the latter so good imo. It's great to have all the information you need in the same place, with clear explanations and a logical disposition. That's very good for learning. If it's "just" a collection of schematics then it's not so appealing to me. Sad

All I know about synth diy comes from hours and hours of web browsing, looking here and there, reading hundreds of threads without finding what you're looking for, or finding contradictions, etc...

That's why I find the Drum Cookbook so interesting. It gives you a global perspective about the matter. I think there's a lack of resources like this.
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jumunius



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PostPosted: Sat Feb 18, 2012 6:52 pm    Post subject: Reply with quote  Mark this post and the followings unread

Silesius wrote:
Yes, but if you look at the schematics, there's no indications about where to connect pins 4&7 of the lm741. That's what confuses me. Of course, pin 7 should go to +v, but I'm not able to see if I should connect pin 4 to ground or -v.


It can be confusing at first, but I think it's very common for schematics to reference the power connections separate from the main schematic itself. Perhaps because they aren't a particularly unique part of the functioning of the circuit, it's a little cleaner to represent the circuit that way. In many projects TH will put that info in a corner of his schematic. In this book he lumps it all into the pinout section.

Quote:
That's why I find the Drum Cookbook so interesting. It gives you a global perspective about the matter. I think there's a lack of resources like this.


Agreed, I was a bit disappointed in this regard too. If you also purchase various DIY projects using pre-printed PCBs, you will find some designers are generally very good at describing the functioning of a circuit. That's a great way to learn too, and very useful for troubleshooting, which should not be overlooked. In general Thomas Henry's stuff is well documented in that regard -- he approaches everything with a sort of professorial tone. Boards like the Bass++, MPS, etc, can be quite worthwhile to build if you are learning.

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Cynosure
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PostPosted: Sat Feb 18, 2012 8:49 pm    Post subject: Reply with quote  Mark this post and the followings unread

I was confused about the opamp pinouts at first too. Diagrams and schematics can add to the confusion because everything is labelled differently depending on who made the schematic; Vdd, Vss, /\, \/, +, -, 0, lines shortening in length, what looks like the letter E on its side...

And then add to that the fact that some of the opamp inputs are also labelled + or -.
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richardc64



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PostPosted: Tue Feb 28, 2012 5:11 am    Post subject: Reply with quote  Mark this post and the followings unread

Cynosure wrote:
...everything is labelled differently depending on who made the schematic; Vdd, Vss, /\, \/, +, -, 0, lines shortening in length, what looks like the letter E on its side...


Bloody annoying. Of Vdd and Vss, who remembers which is which? Wish they'd standardize on +V and -V.

In general, if the power connections are omitted in an op amp schematic, power is assumed to be dual-supply; +V and -V. The "less positive" power pin would connect to ground only in a single-supply situation.

Never thought of the tipped over and skewed symbol as a sideways E, but I suppose that makes sense to those who call the common-to-everything point "Earth" instead of "Ground."

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wmonk



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PostPosted: Tue Feb 28, 2012 6:10 am    Post subject: Reply with quote  Mark this post and the followings unread

What is used on the datasheet is dependent of the type of transistor used in the IC. If bipolar junction transistors (BJTs) are used, you see Vcc for positive, and Vee for negative supply. If field-effect transistors (FETs) are used, its Vdd for positive, and Vss for negative supply.
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CJ Miller



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PostPosted: Tue Mar 13, 2012 7:16 pm    Post subject: Reply with quote  Mark this post and the followings unread

Following Mr. Henry's articles and books through the years, I see that he likes using certain chips for certain jobs, typically parts that are easy to find at the time of writing. The Electronic Drum Cookbook I think was from the 1990s, so it represents the parts which were around then. I never thought that 566s would become "rare" stuff like CEM and SSMs... there are probably tens of thousands squirreled away in warehouses.

Anyway, the recipes are IMO still useful. I substitute LM13600 OTAs for the 3080. Half the price, and I get two of them, no complaints here. As for the 566, it is just used because it is a cheap linear VCO which was readily available at the time. If you look at the pinouts you can substitute an 8038 or one of the Exar ICs. Or even just use a basic 555 or 741 based single chip VCO. The same ideas apply.
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