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 Forum index » DIY Hardware and Software » Jürgen Haible designs
Bringing the Vocoder to life
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zthee



Joined: Feb 20, 2008
Posts: 413
Location: Stockholm

PostPosted: Tue Nov 08, 2011 2:22 am    Post subject: Reply with quote  Mark this post and the followings unread

Sound wrote:
Zthee, I noticed that at maximum mic gain the voiced/unvoiced section works better. And this will have a very easy solution, like increase R2302 (voiced/unvoiced schematics page.


Sounds like a great starting point!

I'll experiment some on this.

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Sound



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PostPosted: Wed Nov 09, 2011 10:10 am    Post subject: Reply with quote  Mark this post and the followings unread

jhaible wrote:
Sound wrote:

However could anybody explain me what is doing U2104A? A virtual ground?

A "dirty GND buffer". Provides a GND node for the LED, while keeping the LED current away from the GND plane.
Sound wrote:
What is its function on the bridge rectifier?

Full wave rectifier for the LED, and contributing to the limiter threshold (in combination with the LEDs' own drop voltages.)
JH.


OK , understood. Thankyou.

Quote:
Quote:

On "Speech Input Amplifier" schematics, R2129 should be tied from Led D2109 to the node D2106/D205 instead to the node D2108/D2107.

Right. Drawing error in schematics, but should be ok on PCB.

Yes, PCB is OK.
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Sound



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PostPosted: Wed Nov 09, 2011 10:14 am    Post subject: Reply with quote  Mark this post and the followings unread

zthee wrote:


While at it I tested the mic input section as well. And it works as it should. I also got a reply from JH about the resistor values - it's basically pick and choose to suit your needs.

I think I'm gonna go with the same as the FS-1A which means:
RG0 = Open (Nothing in it)
RG1 = Jumper
RG2 = 10R
And use a 5K rev. log pot as gain control.


I'm using the chip THAT1510 instead the SSM2019 which are fully compatible.

I noticed that turning the gain potentiometer to its maximum, So Rg=10, thus 60dB gain, the preamp was unstable.
Does it happens to you?

So, following That 1510's data-sheet I added a capacitor in series with Rg and now preamp is stable. Actually with the capacitor in series you can make Rg much more little.

Looking That 1510's data-sheet I suggest:
RG0 = Open
RG1 = 5 Ohm (This is 66dB gain)
RG2 = Capacitor 6800uF 10V
Potentiometer Gain Control = 10K rev. log (this is +6dB) (wired as variable resistor)
So the control will be from +6dB to +66dB.

There are interesting readings regarding the preamp:
-THAT corporation Design Note 138 "Configuring Gain With The THAT 1510 and 1512"
-THAT 1510 Data-sheet.
-Analogue Devices AN-242 Application Note.

Quote:

Then we have the limiter section. I haven't quite figured it out - but I figured that putting a 22K at RG3 should make sense? That would mean unity gain if the vactrol is not active? And I guess that RLIM needs to be adjusted according to what signal levels you choose to operate within? Which means experimenting with different values...


RG3 could be used to give +6dB of extra gain to the preamp instead of the unity gain (0dB) .
But it interacts with Vactrol resistance... so it has to be studied together with RLIM... Since both resistors seem to affect threshold and ratio, it would be useful to define which threshold we desire, and if we can/want attenuate the ratio in order to use it more as a compressor than a limiter.
Opinions?

Quote:
Voiced/Unvoiced section

I report that with the previous suggested values for the preamp plus RG3=43K (+72dB). (Limiter is still bypassed and untested). Voiced/Unvoiced section is working fine as it is.

Note: New test showed up that it works fine for ssssss and shhhhh. For ffffff works fine if you talk indirectly to the microphone. Talking directly to it, turns both led ON.
Also is remarkable that touching some sensitive parts of the preamp section results in switching comparator state. So it will need a test with all components correctly placed.

Last edited by Sound on Wed Nov 09, 2011 10:22 am; edited 1 time in total
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Sound



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PostPosted: Wed Nov 09, 2011 10:21 am    Post subject: Reply with quote  Mark this post and the followings unread

zthee wrote:
Sound wrote:
Zthee, I noticed that at maximum mic gain the voiced/unvoiced section works better. And this will have a very easy solution, like increase R2302 (voiced/unvoiced schematics page.


Sounds like a great starting point!

I'll experiment some on this.

I didnt notice improvement increasing R2302, did you?
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Sound



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PostPosted: Sun Nov 13, 2011 6:38 am    Post subject: Reply with quote  Mark this post and the followings unread

About the Slew/Freeze Section,

What is supposed to do the Frze/Accu switch?

What "Accumalate" means to do?

Im trying (Front Panel Switch) (Freeze) and it "freezes" independently of the position of Frze/Accu switch
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jhaible



Joined: May 25, 2007
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PostPosted: Sun Nov 13, 2011 7:07 am    Post subject: Reply with quote  Mark this post and the followings unread

Sound wrote:
About the Slew/Freeze Section,

What is supposed to do the Frze/Accu switch?

What "Accumalate" means to do?

Im trying (Front Panel Switch) (Freeze) and it "freezes" independently of the position of Frze/Accu switch



Freeze means, the spectrum is frozen.

Accumulate means, a certain spectrum is frozen, but can be added upon.
So if Channel 5 has a level of 0.3 when accumulate is switched on, an lower input level for channel 5 will not make it go lower, but a higher level (like 0.5),will make it rise to 0.5.

No idea if it will be as usefull as I thought it might be, but it was easy to implement, and my be worth to ty out.

JH.

_________________
"I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f)
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Sound



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PostPosted: Mon Nov 14, 2011 7:11 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:

Freeze means, the spectrum is frozen.

Accumulate means, a certain spectrum is frozen, but can be added upon.
So if Channel 5 has a level of 0.3 when accumulate is switched on, an lower input level for channel 5 will not make it go lower, but a higher level (like 0.5),will make it rise to 0.5.

No idea if it will be as usefull as I thought it might be, but it was easy to implement, and my be worth to ty out.

JH.


OK, It seems interesting.

Quote:
(5) The silence bridging / filterbank part is untested. I have tested that a CV will bring up a channel volume, of course, but I never wired a bank of 21 potentiometers for this.


I tested this section and it does work fine.
I connected the PS (Pause Stuffing Bus) output to ALL the filter channels at connector PB (e.j. PB6 for channel 6), in the squared pin (Filterbank CV or external channel CV input).

All controls are working OK.

To add potentiometers just will set the individual levels.

I think I will put all the potentiometers on the front panel or maybe one for each two channels like Sennheiser Vocoder does.
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Sound



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PostPosted: Wed Nov 16, 2011 8:40 am    Post subject: Reply with quote  Mark this post and the followings unread

About Preamp Section: Optional Values RG3 and RLIM.

To decide these values is to decide levels.
So, I made a little research about levels on all the Vocoder.

First, on all channels at rectifier output (e.j. U0403B for channel 5) the maximum value is about 3.2V~3.4V.
It means that no matter how big the wave is at preamp output, the maximum peak envelope is ~3.4V.

Second, In the other end, the maximum output wave from the preamplifier (U2101) without distort is about 20Vp-p, so a peak of 10V.

Now we need to decide levels of both, limited and unlimited signals.

What do you think about this criteria:
For the Limited Signal, when preamp output (U2101)=10Vp, Rectifier output (e.j. U0503B for channel 5)=~3.4V
For Unlimited Signal , when preamp output (U2101)=10Vp, Rectifier output=~(3.4*2)V

The idea is that for Limited Signal, preamplifier's maximum signal output equals at rectifier's maximum envelope peak output.
This means that, at maximum preamplifier's output, first harmonic, will be "unity" and other harmonics envelopes will have a proportion to it.
Unlimited signal, preamp at its maximum output, First harmonic will clip, so other harmonic's envelopes will be enhanced.
This would be achieved with RG3=11KΩ and RLIM=100Ω

Obviously it is not needed that max preamp output equals maximum envelope. It would be OK for maximum dynamics, which maybe don't have importance here. We can also play with Gain and Sp_LEV controls.
Opinions?

Other point to consider is to increase Zener Values (e.j. D0503 for channel 5). To test it means unsolder/solder Zener, so, do you think it is worth look for in this direction?

Edited:(rectifier output)

Last edited by Sound on Wed Nov 16, 2011 11:30 am; edited 1 time in total
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jhaible



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PostPosted: Wed Nov 16, 2011 9:25 am    Post subject: Reply with quote  Mark this post and the followings unread

Don't increase zener voltage. This will kill the OTA inputs.

JH.

_________________
"I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f)
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Sound



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PostPosted: Thu Nov 17, 2011 8:59 am    Post subject: Reply with quote  Mark this post and the followings unread

OK.

About Preamp Section: Optional Values RG3 and RLIM.

RG3=22K
RLIM=6.2K
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keithwin



Joined: Jul 20, 2007
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PostPosted: Mon Nov 21, 2011 6:25 am    Post subject: Reply with quote  Mark this post and the followings unread

Just about to start stuffing resistors, is the screen printed overlay accurate for values?
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Sound



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PostPosted: Tue Nov 22, 2011 1:51 pm    Post subject: Reply with quote  Mark this post and the followings unread

keithwin wrote:
Just about to start stuffing resistors, is the screen printed overlay accurate for values?


Yes, they are the correct values, but the things that must be tuned.
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keithwin



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PostPosted: Tue Nov 22, 2011 3:02 pm    Post subject: Reply with quote  Mark this post and the followings unread

Got that about values to be determined, just wanted to be sure about the rest. Thanks for the response Smile. X
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Sound



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PostPosted: Wed Nov 23, 2011 7:17 am    Post subject: Reply with quote  Mark this post and the followings unread

The Living Vocoder is working.
As a summary, I suggest:

Synthesis Input and Compander
Levels:
R2610 (Potentiometer on front panel)
R2612=39K (to add 6dB of extra gain)
R2659 (Switch ExcMode and S_Mode OFF and Ns_Mode ON and adjust the trimmer R2659 for 1.23VRMS at U2606B output. Pin 7) (R2659 could also be on the front panel)
R2645=20K
R2649=7.5K
R2654=10K*
R2655=1.8K*
C2626=47nF*
R2657=20K
R2656=JUMPER
*PCB's Layout says 100K, 18K and 4n7 respectively. Schematics say the suggested values.

Switches:
C2622=100n
C2623=100n
C2624=100n
(These values attenuate “pops” when switching, these are noticeable when unvoiced signal turns on Ns_mode Switch for example.)

Posted Image, might have been reduced in size. Click Image to view fullscreen.

Voiced/Unvoiced Detector
Filter's Cutoff Frequency:
I placed high-pass filter cutoff at 5000Hz and low-pass filter cutoff at 2000Hz.
R2311=33K
R2312=150K
R2309=56K
R2310=24K

Instability Preamp Protection:
Noise or high frequency oscillations in the preamp section will turn ON the unvoiced section.
To achieve protection to this, I considered to use the channel 17 analysis output instead of the high pass-filter, or convert the high-pass filter in a band-pass filter. However I found a more easy solution:
Place a 470pF capacitor in parallel with R2302 and
R2303=JUMPER

Posted Image, might have been reduced in size. Click Image to view fullscreen.

Speech Input Amplifier
I noticed instabilities in this section.

TONE Network:
U2102A's inverting input has long trace and also it is the center leg of the TONE potentiometer. It will be recommendable take special care of this when assembling the Vocoder to the front panel, like to use a short length and coaxial cable (shell grounded).

A tested and working solution is to place a 100pF capacitor parallel to R2120.

An extreme solution could be bypass the tone section. In this case: do not place all components related (Blue labels on the attached picture) and C2111=JUMPER, R2117=20K, TONE 5 pin connector (pin 2 to 3)=JUMPER, R2120=20K with a paralleled 220pF capacitor. This is by now untested.

Preamplifier:
I'm using the chip THAT1510 instead the SSM2019.
My suggested values are R2101=10R, R2102=10R, R2103=1K, R2104=1K, RG0=OPEN, RG1=5R, RG2=Capacitor Electrolytic 10V 3300uF (will cut about 10Hz).

Limiter:
RLIM =6K
RG3=22K

Posted Image, might have been reduced in size. Click Image to view fullscreen.
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Paradigm X



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PostPosted: Wed Nov 23, 2011 11:18 am    Post subject: Reply with quote  Mark this post and the followings unread

vids/audio please!!

some proper geniuses here. Very impressive.

Nice one

Ben
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SubG (deactivated)



Joined: Oct 09, 2009
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PostPosted: Sat Dec 03, 2011 2:38 am    Post subject: Reply with quote  Mark this post and the followings unread

WANTED TO BUY, JH VOCODER PCB,bare,partly or full populated.

Send your offer via PM plz
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keithwin



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PostPosted: Mon Dec 12, 2011 2:28 am    Post subject: Reply with quote  Mark this post and the followings unread

Would love to see/hear some examples of the completed vocoder, stuffing resistors on mine right now but this thread seems to have ground to a halt. How are you all doing? Sounds recommendations seem great but I see no comments or discussion at all. Let's keep Jurgens legacy Living Smile
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/mr



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PostPosted: Wed Dec 14, 2011 4:17 am    Post subject: Reply with quote  Mark this post and the followings unread

20*20 Ghielmetti matrix on eBay, might be useful for Vokoder builders. Smile
Only 19 pins though, and I'm not sure which type...

http://www.ebay.de/itm/ws/eBayISAPI.dll?ViewItemnext&item=170747775985.html

Great research, Sound! I'm excited like a working Living Vocoder.
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/mr



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PostPosted: Wed Jan 25, 2012 12:56 pm    Post subject: Reply with quote  Mark this post and the followings unread

In order to minimize the size (and heat) of the vocoder, I'm considering the possibility of using a switched-mode power supply instead of a transformer. Something like these devices:

http://www.tracopower.com/products/ac-dc-power-supplies/encapsulated-modules/

It would then probably be a +/-15 V supply, regulated down to +/-12 V with the linear regulators on the Living Vocoder pcb in order to get rid of the switch ripple. The supply would sit very near the vocoder circuitry though, practically on the free lab area in the corner of the pcb.

Can anybody recommend for or against such switching supplies with analogue audio? Would it be a sensible idea at all, or would I regret that I tried?
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keithwin



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PostPosted: Tue Jan 31, 2012 3:18 pm    Post subject: Reply with quote  Mark this post and the followings unread

RSUM = 5K6?

Have I missed something?

Cheers
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diablojoy



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PostPosted: Tue Jan 31, 2012 4:51 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
In order to minimize the size (and heat) of the vocoder, I'm considering the possibility of using a switched-mode power supply instead of a transformer. Something like these devices:

http://www.tracopower.com/products/ac-dc-power-supplies/encapsulated-modules/

It would then probably be a +/-15 V supply, regulated down to +/-12 V with the linear regulators on the Living Vocoder pcb in order to get rid of the switch ripple. The supply would sit very near the vocoder circuitry though, practically on the free lab area in the corner of the pcb.



I would think it to be OK as long as the switching supply was adequately
shielded ie : fully enclosed in a properly grounded metal case
modern switching supplies switching rates are well above audio
so there should not be much of an issue from that
with that aside since you are thinking of going down this route would not +/- 18v regulated down to +/-15v be better?
jurgens designs usually asked for 18v to the onboard regs though i must confess i havent looked up what he specified with this project

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/mr



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PostPosted: Tue Jan 31, 2012 5:03 pm    Post subject: Reply with quote  Mark this post and the followings unread

diablojoy wrote:
with that aside since you are thinking of going down this route would not +/- 18v regulated down to +/-15v be better?
jurgens designs usually asked for 18v to the onboard regs though i must confess i havent looked up what he specified with this project

15 VAC from the transformer, +/-12 V after regulators.
However, wise people on the SDIY list adviced against using further linear regulation of the switching-mode power, since the high-frequent noise will reach through it. So I guess it makes more sense with only SMPSU if at all.
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keithwin



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PostPosted: Sat Feb 04, 2012 2:09 am    Post subject: RSUM Reply with quote  Mark this post and the followings unread

What are people using for the RSUM in the Synthesis Input and Compander section? 5k6?

Anyone got any demos yet, I'm plodding on slowly and expenses Smile
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frenchyinmunich



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PostPosted: Thu Mar 08, 2012 1:58 pm    Post subject: Vocoder improvement Reply with quote  Mark this post and the followings unread

Hello Sound,

What is the status of your Vocoder.
It seems that you succeeded to get it working.
Any picture?

Thanks,

f
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zthee



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PostPosted: Wed May 02, 2012 6:15 am    Post subject: Reply with quote  Mark this post and the followings unread

I've almost implemented all the changes suggested by Sound. Hopefully I'll have it all up and running in a week or so.
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