Joined: Nov 29, 2008 Posts: 652 Location: Berlin by n8
Audio files: 23
Posted: Sun Jan 29, 2017 4:11 am Post subject:
I guess it is a Ringmodulator
Hi Guys,
i need your knowlegde about Ringmodulators, cos i have developed something but i need confirmation if iam on the right track.
As far as i know RM´s are four quadrant multipliers, so they can handle on both inputs positive and negative signals,
which is the main difference to "normal" VCA which normaly can not handle negative signals on the CV input.
First i needed a visual reference, so i did a excel calculation with two sinewaves (F * 9F) multiplied by each other.
Then i simulated my idea (with 1khz and 9 khz )and the visual results are matching well.
So i guess it looks not bad, but i want u to tell me if the results can be interpreted as Ringmodulation.
thanks in advance!
Ringmod exel + simulation.png
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Last edited by gabbagabi on Sun Aug 13, 2017 9:50 am; edited 1 time in total
Joined: Nov 29, 2008 Posts: 652 Location: Berlin by n8
Audio files: 23
Posted: Mon Aug 28, 2017 7:47 am Post subject:
my posted schemo above is only looking nice and works fine in the simulation, may if u match the tranis u get better results in reality.
my new attemp sounds much nicer, i used the single Transistor VCA i posted here, i happent that there was a deafzone, i had to add an offset to get rid of her. but when i see offset-cancelation - i see atomaticly a modulation opportunity, so i added a deafzone modulation pot.
i did not included input attentuators in the schemo nor on breadboard
soundsample1: bell-like sound where i crank the deafzone-pot from min to max, no EFX used
soundsample2: small bellsound with just a tiny amount of reverb and delay
cheers, bb
Ringmod_test.mp3
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some small bell tones.mp3
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Gabbagabi_STVCA_Ringmodulator.png
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Joined: Nov 29, 2008 Posts: 652 Location: Berlin by n8
Audio files: 23
Posted: Mon Aug 28, 2017 9:18 am Post subject:
alanwilder has asked me what a vca has to do with a rinmod. I thought i will post an explanation of the circuit here, cos for me it was hard to find a good one when i was going to be interrested in ringmods.
Ringmodulation is also called 4quadrant multiplikation, so far so good.
A normal VCA does 2 Quadrant multipikation. Means if there is a CV and a signal present to output swings up and down, the cv paints the shape. BUT the cv is only positive. If apply a negative cv to the vca it will be mute to output. see pic1
If we put a second vca that can react on negative CV (eg by inverting the cv) AND mix those 2 signals together we have a maschine that makes , i guess, 2 Quadrant Multiplikation. that means the output will swing up and down, even there where before silence, like a copy of the active part pasted into the muted part. see pic2
now the only thing we have to do for have ringmodulation is to invert the phase of the second part we hav created, which can be easily done by an inverter. see pic 3. between the shape in pic2 and 3 is only a little difference when the cv is going thru zero and a important that in the "second" part the phase is shifted - like the wave is going backwards.
pic 4 shows the concept in blocks
any corrections and additions welcome.
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pic1.png
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pic2.png
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pic3.png
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Last edited by gabbagabi on Tue Oct 03, 2017 8:17 am; edited 1 time in total
I verified your ringmod with 2 vcas t and it is indeed a balanced modulator. I have never seen this configuration before. Congrats. Something new, to me at least.
Now if you can come up with a linear frequency shifter without a phase shift network you would be my hero.
A frequency shifter just gives the sum and difference frequencies separately, whereas the balanced modulator gives both together. Every analog circuit I have seen uses 90 degree phase shift networks, and digital implementations use a complicated Hilbert transform. (Don't try too hard because this may not be possible). _________________ --Howard
my music and other stuff
Joined: Nov 29, 2008 Posts: 652 Location: Berlin by n8
Audio files: 23
Posted: Tue Aug 29, 2017 5:30 am Post subject:
thank you.
A new thing to think about constantly comes in the very right moment.
I will deliver this frequenzy shifting mobile, or die wihle trying
You already explaint it , but i could not get it.
Do you have a prefered source where i can learn what it is, best works for me is a optical reference - input waveform - output waveform.
Or what is the most "simple" one u know?
Joined: Nov 29, 2008 Posts: 652 Location: Berlin by n8
Audio files: 23
Posted: Tue Oct 03, 2017 5:21 am Post subject:
hi guys,
i dont know what went wrong in my post below from Mon Aug 28, 2017
i have played around on the breadboard with the same circuit again, but gave it a little bit more time and found out that it works not bad.
while playing it came to my mind that the signal attentuator which i normally put in front of the signal-in is kind of useless because with the cv attentuator and the offset u can archieve the same results, so i left it out and have more space on the PCB later. Iam not entirely shure here - any thoughts?
the RM/VCA goes above unity gain and i added a distortion option
the spikes on the top end of the saw in the example scope are coming from the vco and not from the RM
gabbagabi Ringmodulator and VCA.png
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gabbagabi Ringmodulator and VCA-scope.png
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Joined: Nov 29, 2008 Posts: 652 Location: Berlin by n8
Audio files: 23
Posted: Sat Nov 18, 2017 5:06 am Post subject:
thx!
find attached a simplyfied-Version-Simulation.
cheers,
ps: the k in function is to show what is in my opinion misspelled in english
I am still thinking about that frequency-shifting-thing - but it is a hard nut - thx for the challenge.
gabbagabi simple Ringmodulator.png
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and a double-switch to swop the inputs
