PCBs for Thomas Henry's X-4046 VCO

tehskull · Posted: Wed Jul 13, 2011 4:46 pm Post subject:

Finished mine last night. Working on calibrating it now. I have only been doing DIY synths for about 3 months. This is my 4th completed module. Calibrating is going OK so far. When the VCO gets into higher octaves, it cuts off. Powering it off then on brings it back once the frequency is turned back down. Not sure if this is a characteristic of my 4046 or not (which is a motorola). The HF trimpot is set to maximum resistance per Thomas's calibration instructions. I am going to continue calibrating with tools now. However if anyone has any input it would be gratetfully appreciated. So far I am very happy with it. A very big thanks to Matthias and Thomas for this great project.

Thanks!

Andrew

IMG_0480.JPG

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Completed X-4046 VCO

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IMG_0479.JPG

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Completed X-4046 VCO & MFOS 1v\oct calibrator

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2.6 MB

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fonik · Posted: Wed Jul 13, 2011 11:43 pm Post subject:

Bogus Noise · Joined: Jun 03, 2009 Posts: 65 Location: Sheffield

Ah, nice one! Sending a reply to your PM now. Smile

fonik · Posted: Thu Jul 14, 2011 1:40 am Post subject:

loopcycle · Joined: Nov 06, 2006 Posts: 101 Location: California

ive built one now and am finding myself here because i could not tune 1v/O whatsoever.
i now see that the ON semiconductor 4046 was a fail and that's what ive got in it now.
i also have the nxp 4046 and will be installing it tonight to see if my results improve.

other than the tracking problems (about a semitone per two octaves), im enjoying the sound of this oscillator.
the "pips" in the triangle wave make it buzzier than others in my system,
but the osc FMs wonderfully and has a very wide range, well down into lfo territory.

edit:
problem #1: 100k in R2...changed that to 390R
i then swapped out the ON PLL for the NXP PLL--wow, what a difference.
it was remarkable how much my waveform improved. i can barely see the pips in the triangle now
its calibrated very well now and it sounds fantastic. cant wait to build the next one
too much coffee

fonik · Posted: Fri Jul 15, 2011 12:51 pm Post subject:

sorry about the trouble due to the error in the BOM.

all the more i am happy that you are happy now! tried the hardsync? it blew me away...

loopcycle · Joined: Nov 06, 2006 Posts: 101 Location: California

tehskull · Posted: Fri Jul 15, 2011 6:10 pm Post subject:

After swapping my 4046 for an NXP and a few hours of messing about with the trim pots, it is working beautifully! Sounds fantastic with my MFOS 10 step sequencer. The only thing that I do not understand is how to use the hard sync. Everyone says it sounds great so I am dying to hear it myself. Do you need 2 VCO's connected with this? Or does the CV connect to it? Or am i completely wrong lol?

emdot_ambient · Joined: Nov 22, 2009 Posts: 667 Location: Frederick, MD

You have to run an audio input (usually a wave from another VCO) into the Sync In jack. Basically you're turning this VCO into a slave and the external VCO into a master (as far as pitch goes). The master VCO restarts the period of the slave VCO, forcing it to have the same base frequency of the master.

Detuning the slave will create different timbres while maintaining technical pitch unity.

fonik · Posted: Sat Jul 16, 2011 2:41 am Post subject:

kupfer_m · Joined: Oct 14, 2010 Posts: 48 Location: Belgium

Hi,

What's the reason for the DC/AC switch for the LinFM input?
When would one use AC and when DC?

Thanks,
Jim

fonik · Posted: Sat Jul 16, 2011 3:33 am Post subject:

emdot_ambient · Joined: Nov 22, 2009 Posts: 667 Location: Frederick, MD

tokyomatik · Posted: Thu Jul 21, 2011 7:28 am Post subject:

hi mattias
i have a question about the skew function
i don't understand if it's possible to make it cv controllable
on the pcbs i was checking the in and outs
so i have
triangle
rampoid with his skew control
saw
sine
and pulse

but i don't see in wich way i could modulate the skew
just adding a connection from the tip of a jack to the middle pin (pin2) of the potentiometer could work?

fonik · Posted: Thu Jul 21, 2011 7:35 am Post subject:

tokyomatik · Posted: Thu Jul 21, 2011 4:25 pm Post subject:

vactrols?...it sounds interesting....
but really i don't know where to start..... Sad

why 2 vactrols?
1 for the triangle input & the other for the saw input? i'm already lost... Confused

let me try....(i did something similar to my voice of saturn....)
so, if i connect the positve of the vactrol to the tip of the jack, and the negative to the ground
and then i go to the potentiometer?...mhhh Rolling Eyes

somebody can give some tips....
so sad that an interesting function like modulating the skew is not already on board like for example the xr2206 vco....

peace

rosch · Joined: Oct 03, 2009 Posts: 164 Location: germany

the vactrol is a vc resistor. so the ldr part would do the job of the pot, while it's controlled by a cv applied to the led side of the vactrol.
i've seen an example of a voltage divider somewhere around here in a thread not so long ago. that explained quite well how to use a vactrol.

hop.sing · Posted: Fri Jul 22, 2011 2:44 am Post subject:

Here is an example for a vactrol panner, should work for skew also.

vac-crossfader.jpg

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fonik · Posted: Fri Jul 22, 2011 2:50 am Post subject:

that's what i was thinking of (buchla/mark verbos?). i recently ordered some H11F3 optocouplers, which are much cheaper than vactrol. i hopefully will be able to adapt the above ciruit easily...

rosch · Joined: Oct 03, 2009 Posts: 164 Location: germany

hop.sing · Posted: Fri Jul 22, 2011 6:40 am Post subject:

tokyomatik · Posted: Sat Jul 23, 2011 5:11 pm Post subject:

tokyomatik · Posted: Mon Jul 25, 2011 9:34 pm Post subject:

ok forget about modulate the skew...for now
i have more basic problems with the modules
i almost finished the first one, all the pots connected and just 1v/oct + the triangle output.... for a first test should be enough....(??) usually when i have at least sound coming out then i feel more motivated to mount all the rest Wink

but i don't have a 2k tempco right now
so i did maybe something strange, replacing it with a 2 metallic resistors
1k each 1%
and connected the triangle output to hear a sound to see if it works but
nothing....not even a beep!

Rolling Eyes

for the ics i have a nxp HEF4046, i also tried a fairchild but nothing changed
q1 q2 is a LM394....
uffff
ok...where should i start to see what is wrong?

fonik · Posted: Mon Jul 25, 2011 11:24 pm Post subject:

check to see if you have any signal on pins 4, 6, and 7 of the 4046.

check power on all ICs
check wiring

tokyomatik · Posted: Tue Jul 26, 2011 6:55 am Post subject:

hhmmm
so i checked the power at pin 8 & 9 of the 4046
i have 9.47v..... i'm powering my system with +/-12v
if i remove the 2 metallic resistors that i used to replace the 2k tempco
the value change to 9.27v...