ETI/Powertran/Elrad vocoder

[Magnus Danielson]

From: Hallvard Tangeraas <hall at oslo.online.no>
Subject: Re: ETI/Powertran/Elrad vocoder
Date: Sun, 18 Jun 2000 18:35:55 +0200

> 
> At 03:54 +0200  18-06-2000, Magnus Danielson wrote:
> 
> >> I've had a friend scan the PCB/component placement as well as the
> >> circuit and plan to colour-code the connection points and upload to a
> >> web page, so we can take it from there.
> >
> >Ah. This input board really needs a good workthrough it seems.
> 
> Yeah -a completely new design if you ask me!

Yeah ;)

> >So, I'd say that the schematic is incorrect here. It is the only
> >sensible solution to this inconsistency.
> 
> So it seems.
> I've tried to follow the circuit, but it's pretty complicated I'm
> ashamed to say due to the circuit being pretty small as well.
> Maybe I'm just a bit too impatient, after having been patient for so
> long with it, having put the project away for quite a while, and now I
> want to complete it (just like you do).

It is a bit confusing.

> >> This time I have fresh PCBs, and I'm going to figure out the
> >> connections *before* soldering!
> >
> >Wise man. If you been really smart however, you would have figured it
> >out and redone the PCB Layout, but then naturally you fall into the
> >trapp that the documentation (with it's faults!) does not document
> >your PCB Layout but another, so you really have to document this new
> >layout better than the previous one.
> 
> The problem here is that it's a pain to etch PCBs without professional
> equipment. I got most of the boards made by other people as I didn't
> want any half/too much etched circuits for this big project. Too many
> things can go wrong.
> If I had the equipment for it myself I would probably have redone the circuit.
> The input amp that you had working -is it a completely remade PCB?

Nope, just did some rewiring.

> Perhaps, if you have the PCB layout as an image file I could try to
> look around if someone has the equipment to etch me a couple, then take
> it from there, and finally include this and some documentation for
> others asking.

No image files except what you and Anders has brought up. No scanner
in sight either.

> >> But why not just look at the modified PCB and compare it with the
> >> other one?
> >
> >Been there... however, the other nigth I found some connection that
> >was not correct. I don't recall what it was thought. Anyway, carefully
> >checking it up should make it apparent.
> 
> Yup, a lot of patience is also needed ;-)

Yeah, don't forget to buy a big bag of patience at your next round at
the supermarket. Have another lollipop while you are at it.

> >> As far as I can remember, someone scanned the whole project and made it
> >> available on the web. If I succeed in completing mine I want to add
> >> information about these input amps and other things that can be
> >> misunderstood easily.
> >
> >This someone is Anders Sponton. He also built most part of one, but he
> >sold it to me before he got to finish it. So I am sitting here with
> >the vocoder and the original copies that he scanned.
> 
> Aha. I know I have the URL somewhere.
> I've also been in touch with others having built it and told me about
> certain modification that will make it even better. I don't know the
> details, but provided that the email addresses still work I might be
> able to get in touch with them.
> But first I just want to make it work "out of the box" before I ruin it
> with modifications ;-)

Love to hear more about those.

> By the way, I've been told that it's a very good sounding vocoder, so
> this sounds promising!

So they say.

> I have lots of ideas for the actual design, and will incorporate an
> effects processor as well (someone else on the net helped me design one
> such unit, based on the fact that I wanted the really fat sounding
> "ensemble" effect of the Roland vocoder I used to have).
> I also didn't like the rather old fashioned design of the original unit
> featured in the magazine and will make it more modern looking.
> As for the LED bargraphs -I've used special stackable LEDs, and
> inserted an option on those boards for either "bar" or "dot" mode.
> 
> 
> Anyway..... I'll look into what you've written here and compare it with
> the circuit diagram/PCB, but as it's all too easy to misunderstand
> things I've made a web page available with the scanned PCB and circuit
> diagram along with my notes on it.

Great!

> For the PCB I've colour coded some of the connection points, but I'm
> still puzzled. Perhaps you could look it over, maybe even download the
> single .HTML document and two images to your computer, then colour code
> the rest so I'm sure it'll be correct.
> 
> 1) one colour for the potmeters
> 2) one colour for the ground points that have to be connected together
> (i.e. the potmeter frame)
> 3) one colour for the two jacks
> 
> Then you could mail me the edited image. I don't think the list will be
> too happy to receive attachements.

No, they usually are not happy, but passing URLs is another game ;)

> Perhaps we should even take this discussion off the list as it seems
> we're the only ones involved (anyone else built this vocoder, or even
> reading this?).
> We can get back later when we're done and can present a completed
> project with all documentation. What do you think?

Well, unless someone screems I think we can keep it up. I for one find
it interesting to read about other peoples debug sessions, there are
things to pick up. We don't contribute to many emails anyway.

> The URL to the page with illustrations etc. is:
> 
>     http://lightning.prohosting.com/~hall/temp/vocoder/eti_amp.html

Please check the updated version at:

http://home.swipnet.se/cfmd/synths/schematics/eti_amp.html

I hope that the added picture helps to remove some questions.

I also learned the hard way that I need to spend some more time with
GIMP.

Cheers,
Magnus