DIY - Elektor Vocoder - General Build Thread

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shogeki
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Post by shogeki » Mon Feb 11, 2019 1:39 pm

I have yet to start the build but was wondering if anyone would be interested in group-ordering some CA3080s from Rochester Electronics. Thonk has them for ~$4.44 a piece which is pretty high (but normal for retail) and they are not located in the US.

Since the Vocoder needs 14 (?) of them, it shouldn't be too hard to get enough people to get an order going. I can front the money and contact them if needed.

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Fitchie
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Post by Fitchie » Mon Feb 11, 2019 4:02 pm

shogeki wrote:Since the Vocoder needs 14 (?) of them, it shouldn't be too hard to get enough people to get an order going. I can front the money and contact them if needed.
You need only 12 CA3080's:
  • 8 x BPF
    1 x LPF
    1 x HPF
    2 x Switching interface

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Fitchie
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Post by Fitchie » Mon Feb 11, 2019 4:22 pm

jbdiver wrote:Line 16 in Noise Generator: quantity should be 3 - 0.1uF film capacitors
This is the only error I could remember offhand. I'll check again later.
Thanks for the feedback, updated BOM available here:
http://vocoder.eu/bom.html

shogeki
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Post by shogeki » Wed Feb 13, 2019 11:31 am

Fitchie wrote:
shogeki wrote:Since the Vocoder needs 14 (?) of them, it shouldn't be too hard to get enough people to get an order going. I can front the money and contact them if needed.
You need only 12 CA3080's:
  • 8 x BPF
    1 x LPF
    1 x HPF
    2 x Switching interface
Thank you for the precision!

Does anyone has a recommended sources for CA3080's in the US?

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elmegil
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Post by elmegil » Wed Feb 13, 2019 12:32 pm

I suspect anyone talking about 14 or 15 3080's is padding their total so they can switch out any that are problematic, or that fail due to build errors or otherwise. I know I got more than I specifically needed for this project :)

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elmegil
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Post by elmegil » Sun Mar 03, 2019 10:35 pm

Any update on those filter calibration revisions?

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jbdiver
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Post by jbdiver » Tue Mar 05, 2019 9:40 pm

Image

I'm finally getting to the assembly stage of this project. All the boards are built and need to be wired to the front panel. Power supply tests were fine.

The frontpanel wire connections to the solder pins on the boards don't feel real solid to me. Maybe that's expected? The pins are 1mm and the crimp connectors are the same so I don't know why they feel kind of loose.

Also, I had to figure out how to mount the pots to the frontpanel so that the knobs would be relatively flush with the panel. My solution was to buy a bunch of hex nut fasteners so that I could adjust the pot mounting depth in the frontpanel holes.[/img]

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elmegil
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Post by elmegil » Tue Mar 05, 2019 10:41 pm

jbdiver wrote:The frontpanel wire connections to the solder pins on the boards don't feel real solid to me. Maybe that's expected? The pins are 1mm and the crimp connectors are the same so I don't know why they feel kind of loose.
Huh, that's odd. The ones I got don't seem loose....

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Fitchie
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Post by Fitchie » Mon Mar 11, 2019 1:51 am

All,


To adjust the LM741 bias exactly to 0,00 mV on the low pass filter (IC11) and high pass filter (IC7), there is a minor modification on both PCB's required.


Low pass filter:
  • - Cut the trace (red cross on the picture) between R200 and C38 (component side of the PCB)
    - Wire bridge R200 and R95 (green connection on the picture)

    Image

    Instructions also here:
    http://vocoder.eu/low-pass-filter.html
High pass filter:
  • - Cut the trace (red cross on the picture) between R201 and IC7 (component side of the PCB)
    - Wire bridge R201 and R55 (green connection on the picture)

    Image

    Instructions also here:
    http://vocoder.eu/high-pass-filter.html

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Fitchie
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Post by Fitchie » Mon Mar 11, 2019 1:54 am

elmegil wrote:Any update on those filter calibration revisions?
  • Hi Elmegil,

    I just published a minor patch for the low pass and high pass filter, next ting on my to-do list is to update the filter calibration procedures.
    Please give me some days...

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elmegil
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Post by elmegil » Mon Mar 11, 2019 9:27 am

Fitchie wrote:
elmegil wrote:Any update on those filter calibration revisions?
  • Hi Elmegil,

    I just published a minor patch for the low pass and high pass filter, next ting on my to-do list is to update the filter calibration procedures.
    Please give me some days...
Thank you for the update :-D

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Fitchie
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Post by Fitchie » Sun Mar 17, 2019 11:24 am

All,

I was asked in which order the vocoder can best be built, so please here you are:
Succes !
:tu:

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Vlado
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3,5mm socket

Post by Vlado » Sat Mar 23, 2019 6:28 am

Hello,

quick question:

From another project I have 3,5mm audio sockets that have switching functionality. Meaning, if nothing is plugged in, contacts are shortcut. When you plug in the jack, the contact is opened.

Can i use these for the vocoder?

Best regards

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jbdiver
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Post by jbdiver » Sat Mar 30, 2019 3:33 pm

I finally had time to work on this project again and I began testing the input-output card today. I don't own a signal generator so I had to come up with an alternative. After thinking about it for awhile I realized that I actually own a big signal generator. :razz:

Image

I tried to follow the build instructions, but I don't get an opportunity to do this kind of calibration work much. I think I dialed in a ~440hz sine wave at around 770mV RMS:

Image

Finally, I adjusted the trim pot so that the voice and carrier signals (as measured at A & B) were almost identical. Is this the sort of result I would expect to see?

Image

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Fitchie
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Re: 3,5mm socket

Post by Fitchie » Sun Mar 31, 2019 2:46 am

Vlado wrote:From another project I have 3,5mm audio sockets that have switching functionality. Meaning, if nothing is plugged in, contacts are shortcut. When you plug in the jack, the contact is opened.

Can i use these for the vocoder?
Yes you can.
Actually it's recommended to use connectors with a build in switch, so that by default the input & output from a filter unit are passed along.

Wiring instrcuctions:
http://www.vocoder.eu/vocoder-wiring-instructions.pdf

Connector pinout:
Image

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Fitchie
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Post by Fitchie » Sun Mar 31, 2019 2:49 am

jbdiver wrote: Finally, I adjusted the trim pot so that the voice and carrier signals (as measured at A & B) were almost identical. Is this the sort of result I would expect to see?

Image
Perfect !
Your speech input has been calibrated for using line levels now.

PS: I like your scope (using the same one). :love:

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jbdiver
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Post by jbdiver » Sun Mar 31, 2019 6:33 pm

I'm starting to look at the filter adjustment and I have a couple questions.

Why does the high pass filter have two adjustment pots while the other filters only have one?

For the DC bias voltage adjustment, the instructions suggest that a 500Hz sinewave with a DC offset is a suitable test signal. How much DC offset voltage should be used?

Does it matter what the front panel pots are set to when performing these filter adjustment tests?

Thanks!

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Fitchie
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Post by Fitchie » Tue Apr 02, 2019 3:42 pm

jbdiver wrote:Why does the high pass filter have two adjustment pots while the other filters only have one?
One potentiometer is to adjust the level of the high pass filter, identical as for all other band filters and low pass filter.
The second potentiometer (P17) is used to mix the 'unvocoded' high pass speech signal to the output. This mixture results in a better intelligibility and is only available on the high pass filter.
jbdiver wrote:For the DC bias voltage adjustment, the instructions suggest that a 500Hz sinewave with a DC offset is a suitable test signal. How much DC offset voltage should be used?
Peuk voltage is maximum 10 V.
jbdiver wrote:Does it matter what the front panel pots are set to when performing these filter adjustment tests?
Either do not connect the pots as described in the adjustment procedures:
http://vocoder.eu/filter-adjustment.html

Either do connect the pots and turn them to minimum, except for the filter you want to adjust.

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yan6
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Post by yan6 » Thu Apr 11, 2019 11:45 am

Fitchie wrote:
Image
I am a bit confused, is this done on just P1 of the filter boards (10 in total) or on P1, P5 & P9 (30 in total)

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Fitchie
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Post by Fitchie » Fri Apr 12, 2019 12:13 am

yan6 wrote:I am a bit confused, is this done on just P1 of the filter boards (10 in total) or on P1, P5 & P9 (30 in total)
8 x on the band filter boards:
P1

1 x on the high pass filter board:
P5

1 x on the low pass filter board:
P9

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yan6
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Post by yan6 » Thu Apr 18, 2019 9:03 am

I'm just getting to the filter adjustment but cant see any signal at the output of the vocoder.

I'm using a signal generator and a scope. I have the signal generator being injected on the speech input, a 500hz sine 1.3vpk-pk and offset by 2v DC.

I have dummy jacks in the speech and carrier input to break the ground connections

I don't have the filter pots or jacks connected and have the P11 to output jumpered

I have the backplane I-J & G-H jumpered.

I'm monitoring at the master output jack and don't see anything :hmm:

Any suggestions :despair:

Edit: also tried adding a noise signal from the second channel of the signal generator to the carrier input, but still nothing
Last edited by yan6 on Thu Apr 18, 2019 9:13 am, edited 1 time in total.

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Fitchie
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Post by Fitchie » Thu Apr 18, 2019 9:10 am

yan6 wrote:I'm monitoring at the master output jack and don't see anything :hmm:
Did you already adjust the input/output module?
http://vocoder.eu/io-module-adjustment.html

And did you patch the filter boards?
http://vocoder.eu/band-pass-filter.html

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yan6
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Post by yan6 » Thu Apr 18, 2019 9:15 am

Yes I was able to adjust the input output module and I place the 12K on all filter boards and made the trace cuts to the LP & HP boards.

also tried adding a noise signal from the second channel of the signal generator to the carrier input, but still nothing

Edit: I tried plugging in a different filter board (3900Hz instead of the LPF) and got a square wave output that I was able to bring down to near zero

Edit2: all band pass board I was able to adjust down to near 0. I had to lower the injection frequency on the lower band boards (from 500Hz down)

The high pass and low pass board don't have any output

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Fitchie
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Post by Fitchie » Fri Apr 19, 2019 12:26 am

yan6 wrote:Edit: I tried plugging in a different filter board (3900Hz instead of the LPF) and got a square wave output that I was able to bring down to near zero

Edit2: all band pass board I was able to adjust down to near 0. I had to lower the injection frequency on the lower band boards (from 500Hz down)
Excellent !
I'll update the adjustment instructions with regard to the suggested frequency.
yan6 wrote:The high pass and low pass board don't have any output
OK, let's do some trouble shooting here.
Please can you check the patch on both LP & HP filters ?

High pass filter:

Image
  • Cut the trace (red cross on the picture) between R201 and IC7 (component side of the PCB).
    Wire bridge R201 and R55 (green connection on the picture).
Low pass filter:

Image
  • Cut the trace (red cross on the picture) between R200 and C38 (component side of the PCB).
    Wire bridge R200 and R95 (green connection on the picture).
And did you add the 12K resistor under P5 and P9 ?

http://vocoder.eu/high-pass-filter.html
http://vocoder.eu/low-pass-filter.html

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yan6
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Post by yan6 » Fri Apr 19, 2019 12:23 pm

All of the listed mods are done, please see the attached photos and double check if they were done correctly

Image

Image

Image

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