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jhulk wrote:


Further along in those posts others warn they had to revert to the 100k/18k values because levels were too high. Sockets.

There's a lot of good information in the e-m threads... wish they had an 'all' pages button.



from jhulk on muffwiggler:

As a summary, I suggest:

Synthesis Input and Compander
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)
*PCB's Layout says 100K, 18K and 4n7 respectively. Schematics say the suggested values.

(These values attenuate “pops” when switching, these are noticeable when unvoiced signal turns on Ns_mode Switch for example.)

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Voiced/Unvoiced Detector
Filter's Cutoff Frequency:
I placed high-pass filter cutoff at 5000Hz and low-pass filter cutoff at 2000Hz.

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

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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.

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).


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this is what was recommended for tuning the pcb
and some one asked about the values for resistors on the pcb values if they were correct and the answer was yes apart from the tuning values above







This explains at least a part of the wiring: rt=300

"Zthee: What's throwing me off is this
*) Connect patchbay outout to cw end of 5k audio taper potentiometer.
Connect wiper to middle pin of connector.
Connect ccw end of Pot to GND.

Right now the middle pin is labled patchbay output: And I'm supposed to connect that to CW end, and then I'm supposed to connect the wiper to the middle pin! "

"From the PCB viewpoint, the lowest pin is the analyzing filter output, and the middle pin is the envelope detector input.

But if you look at the matrix as a module, that can (optionally) be inserted at this break point, the matrix' input signal will come from the lowest pin of the PCB, and the matrix' output will go to the middle pin.

And if you look at channel potentiometer(s) as another (optional) module, the matrix output will go to the potentiometer's "input" (cw end), and the potentiometer's "output" (wiper) then goes to the env detector input (middle pin on PCB).