ETI/Powertran/Elrad vocoder

[Hallvard Tangeraas]

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!


>> I'm going through every component, and have covered a few
>> connection points, but I'm still confused. I need some help.
>> Do you have all the diagrams there?
>> (it's a little hard to explain if you don't ;-)
>
>Yeap! And I have it "in flesh", that is, I have the input boards
>stuffed with components.

Good.

 [......]
>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).



>> 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?

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.


>> 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 ;-)


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

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.
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.
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?

The URL to the page with illustrations etc. is:

    http://lightning.prohosting.com/~hall/temp/vocoder/eti_amp.html


Hallvard
--
Hyperlink Launchpad: <http://www.crosswinds.net/~hall/>
Atari Launchpad    : <http://launchpad.atari.org>
Notator/Creator SL : <http://www.crosswinds.net/~notator/>