KVR Audio

janostman · Post by **janostman** » Sat Sep 13, 2014 6:16 pm

aciddose wrote:What on earth do you mean "maybe not but that's what it is", do you have any idea how the electronic circuit works?

http://en.wikipedia.org/wiki/Chopper_%28electronics%29

What you've described regarding "wrapping" is completely unrelated to anything the JU- synthesizers do. The waveforms are chopped using a single transistor. This is all done from gnd to +v, there is no multiplication (AM/ring) and no wrapping involved. Do you have any idea of the complexity that would be involved in implementing a circuit to wrap an analog voltage?

Obviously not.

Please, think before you speak.
there are no transistors inside the alpha-juno besides those in the chips.

Before the filter chips it's all digital domain.
Not a trace of analog.

And there is no complexity involved in doing anything at the levels these circuits work.
negative voltages only exists on analog synths. there are no such thing in a digital synthesizer.
What you see as a negative voltage on the scope is still on the positive side in the digital domain.

And how on earth did you get your link about chopped circuits to apply on the alpha-juno?

You can't analyze the alpha-juno as some analog synth because it's not.
If you refuse to see this then as I said, keep hunting.

aciddose · Post by **aciddose** » Sat Sep 13, 2014 6:33 pm

The oscillator core is a custom chip and contains transistors. You are extremely uninformed.

The scope when correctly connected shows only positive outputs from these chips.

This article covers the JU-, but not aJU-:

http://www.electricdruid.net/?page=info.junodcos

Some of the descriptions are a little off but close enough.

The aJU- oscillator chips are the same thing only with two integrators in order to make up the +oct pwm waveform.

The output mixer stage includes choppers. You should see that the +1 oct pulse is used to chop the ramp, or optionally the +3 oct pulse. With both chopper circuits active you get the final ramp waveform.

The sub circuit can also be chopped yielding the various waveforms.

You can see the main square waveform is most likely generated via a d-flipflop, as it does not respond to the pulse width input when used to chop the sub.

In order for anything you have said about 'digital domain' to make sense, the circuit would include a digital encoding of the PCM fed to a DAC, which is not a part of any of the JU- synthesizer's audio path.

janostman · Post by **janostman** » Sat Sep 13, 2014 6:43 pm

I know how the Juno-6/60/106 DCO's work.

What makes you think that the alpha-juno is the same?

You can push 100% digital into analog filter chips.
No need to to do any ramping with pulse to ramp shape.

I'd say the the DCO's in the alpha-juno is 100% digital, without shaping.

No PCM

aciddose · Post by **aciddose** » Sat Sep 13, 2014 6:44 pm

If it is, where is the DAC and the PCM data? There isn't any.

...because I have an alpha juno PCB in front of my face right now.

janostman · Post by **janostman** » Sat Sep 13, 2014 6:53 pm

aciddose wrote:If it is, where is the DAC and the PCM data? There isn't any.

...because I have an alpha juno PCB in front of my face right now.

You don't need PCM.

If you feed 2 sqr waves, f and f/2 to the filter, you have a crude saw wave.

aciddose · Post by **aciddose** » Sat Sep 13, 2014 7:05 pm

I'm sorry, but that simply isn't how the circuit works.

The aJuno DCO chip is a custom chip designed by Roland.

The chip in the aJU-1 is IC16, RD87123.

In fact don't just take my word for it, here it is:

I don't have time to fool around and take HQ macro photos of PCBs right now, but if you want to continue to BS about how the circuit works I'll be more than happy - in time - to post more photos including pin-by-pin signal analysis and circuit description to demonstrate that you are entirely incorrect.

antto · Post by **antto** » Sat Sep 13, 2014 7:05 pm

janostman wrote:
aciddose wrote:That isn't how the circuit works in the JU-, not even close.
Maybe not but that's what it is.
It's even used in the JP-8000 and called offset.

But if you want it to be something else then go ahead.

how is the "pwm sawtooth" of this thread remotely similar to the JP-8000's "trianglemod" waveform?
do explain

aciddose · Post by **aciddose** » Sat Sep 13, 2014 7:14 pm

Don't ask someone like this to prove to us further how incompetent they are... Please for the love of...

janostman · Post by **janostman** » Sat Sep 13, 2014 7:31 pm

Never mind, I don't have time for your macro photos of Dip-28 chips.

Keep hunting

aciddose · Post by **aciddose** » Sat Sep 13, 2014 8:48 pm

You seriously have some some kind of problem. The waveform output from the DCO chip is fully analog in amplitude before input to the filter.

You lack even the most fundamental understanding of either electronics or signal processing in either the analog or digital domains. You also lack a fundamental understanding of what defines a signal as either analog or digital.

For some reason, armed with your ridiculous lack of knowledge and experience you decide to join this discussion and attempt to argue what I've said, when the things I have said are statements of fact easily understood as such by anyone with the capability to understand these circuits in the real world.

You won't be successful in achieving anything but your own humiliation.

aciddose · Post by **aciddose** » Sat Sep 13, 2014 8:53 pm

I understand that it is beyond your ability to comprehend, but given the circuit present in the aJU synthesizers, the only options we have are for integrated PWM or integrators to be the source of the analog voltage output on each of the six output pins of the DCO.

It is trivial to demonstrate that any TTL circuit designed to produce PWM, followed by an integrator, is more complex than an integrator.

It is also trivial to demonstrate that the ramp output is not made up of a series of integrated pulses but rather a continuous ramp by measuring the output of the chip directly.

janostman · Post by **janostman** » Sat Sep 13, 2014 9:10 pm

aciddose wrote:I understand that it is beyond your ability to comprehend, but given the circuit present in the aJU synthesizers, the only options we have are for integrated PWM or integrators to be the source of the analog voltage output on each of the six output pins of the DCO.

It is trivial to demonstrate that any TTL circuit designed to produce PWM, followed by an integrator, is more complex than an integrator.

It is also trivial to demonstrate that the ramp output is not made up of a series of integrated pulses but rather a continuous ramp by measuring the output of the chip directly.

What you actually showed here or tried to with a custom chip containing 6 VCFs and 6 VCAs makes no difference to what enters them?

They are just the filters and amps in the analog domain. got nothing to do with the sounds or waves of the DCOs.

You just showed that the DCOs are not part of those custom chips.

And please don't use that tone if you want some good response.

aciddose · Post by **aciddose** » Sat Sep 13, 2014 9:19 pm

The DCO is right there, the OUT0 to 5 output continuous analog voltages.

How do you explain that?

aciddose · Post by **aciddose** » Sat Sep 13, 2014 9:25 pm

janostman wrote: What you actually showed here or tried to with a custom chip containing 6 VCFs and 6 VCAs makes no difference to what enters them?

Wrong.

What this image shows is a single custom chip labeled "DCO", the 87123, which feeds a single analog output for each voice.

The blocks labeled "A" through "F" represent each voice. On the schematic, only voice "A" is displayed because the other circuits are identical.

The VCF+VCA chip IR3R05 does combine the inner circuitry for both elements, but one chip is required per voice, unlike the DCO chip which contains all six.

You can see this in the image I posted of the PCB. There is the single DCO chip, you can see the top-side traces leading from OUT0-5 to each of the electrolytic capacitors which provide CR highpass filters + dividers before input to the IR3R05.

You can clearly see there are six rows of identical circuits making up the VCF+VCA sections for each voice.

janostman · Post by **janostman** » Sat Sep 13, 2014 9:26 pm

aciddose wrote:The DCO is right there, the OUT0 to 5 output continuous analog voltages.

How do you explain that?

I have modeled the Juno oscillators both in software and hardware.

Here is the Juno DCO modeled in FPGA.
100% digital.

Juno FPGA OSC.jpg

Roland Alpha Juno-2 pwm sawtooth