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Moon 524a sync behavior?
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Author Moon 524a sync behavior?
ranix
I picked up a Moon 524a to go with my 524 LFO, and I can't make much sense out of the sync input.

On all 4 channels, the sync input doesn't seem to cause what I'd expect. When I send a trigger pulse to the sync input, I expect the LFO to reset to some initial state no matter what.

Instead, I see the LFO get weakly pulled towards 0v

Has anyone else had issues with these?
drob842
It sounds like something may be up. I have not had a chance to play with a 524A in awhile, but I believe a pulse delivered to the sync input results in a reset of the LFO. Not sure why your module isn't properly resetting to 0.
ranix
cool thanks for the help, I'll hit up the distributor
JohnLRice
I got the set a couple months ago but haven't really played with it much. I'll do a demo soon?

Edit: I looked it up and I actually got my 524A (serial #4401) used from a wiggler at the end of August 2016 and I got the 524 (serial #4767) new from Noisebug mid August 2016 but really hadn't played with them much at all until now.
Sugarfree
I have the same problem. A pulse signal needs to be at least 4x faster than the LFO.
JohnLRice
OK, besides wanting to help out, I'm curious tooz! hihi Please stand by for a demo . . . . well, maybe go about your business while you wait because it might take me several hours to a couple days to get it done! Mr. Green
ranix
Cool! I hit up noisebug for info too, no reply yet but NAMM just happened so I figure they could use some time and I'm not in a real rush
JohnLRice
Since I needed to reorg my modular first, I haven't gotten much done yet. But I did get some 0'scope shots, here's some thoughts . . . if I'm reading the o'scope correctly? hmmm..... I'm using the sine outputs from the 524A Assistant/Expander module:

All 4 channels in Sync mode and using the trigger output of the o'scope as the Sync input. (the center of the image where the "T" is at the top is when the trigger happens) It looks like the wave forms are reset to their peak/max level and then free run until the next trigger?


As above, all 4 channels in Sync mode but using another LFO (a MOTM-320) as the 524A Sync input. (the o'scope is still sampling off it's internal trigger)


For the next two images the 524A is set to Gated mode. In the first image I'm using the internal trigger output of the O'scope and when a gate/trigger is present the LFO channels run freely but appear to be held high when the gate is low?


Same as above but using an external LFO as the gate source.


Now I could be doing something wrong with the oscilloscope setup etc but what I expected to see was the wave forms getting reset to 0V in Sync mode on a positive trigger and held at 0V in Gated mode when the gate/trigger input is low. hmmm.....

I'll try to do a video with audio next and additional measurements so that it will be easier to understand how things are working. Also I'll just look at one channel instead of 4 and use another o'scope input to view the trigger/gate wave form so it's easier to tell what is happening when.
Sugarfree
can you please test with a sync signal coming from one of the LFO channels?
JohnLRice
Sugarfree wrote:
can you please test with a sync signal coming from one of the LFO channels?
Here the top three oscilloscope traces are the sine outputs of the first three 524+524A channels, each set to a different frequency and not adjusted during the tests. The bottom trace is the 524 channel 4 square wave output which is being used as the Sync input for channels 1, 2 and 3 (as well as the o'scope's trigger) and it's frequency was changed during the tests. All channels set to Sync mode with no Sync input on channel 4.

Notice that the rate of the sync signal in relation to the frequency of the signal being sync'd greatly affects the output. If the sync signal has a higher frequency then the sync'd wave form, the sync'd wave form doesn't have a chance to complete a full cycle and will lose volume/strength.



Sugarfree
it looks like my module doesn't sync properly.

what kind of PSU are you running? +15V or +12V
JohnLRice
Sugarfree wrote:
it looks like my module doesn't sync properly.

what kind of PSU are you running? +15V or +12V
I have mine running at +-15v from a Power-One linear supply. What would you consider to be the correct way for it to sync?
Sugarfree
JohnLRice wrote:
I have mine running at +-15v from a Power-One linear supply. What would you consider to be the correct way for it to sync?


I expect it to work exactly as on your screenshots.
My LFO's don't retrigger like this though. They don't synch unless the pulse signal is very fast.
JohnLRice
Sugarfree wrote:
JohnLRice wrote:
I have mine running at +-15v from a Power-One linear supply. What would you consider to be the correct way for it to sync?


I expect it to work exactly as on your screenshots.
My LFO's don't retrigger like this though. They don't synch unless the pulse signal is very fast.
d'oh! Reading comprehension fail on my part. I thought you were saying that the screen shots didn't look right, but you weren't! oops

What ranges are you using? I've been using the audio ranges (approximately 130 Hz) because it was quicker/easier to set up on the o'scope (switches set to Audio and the Frequency knob at about 5/12 o'clock position) Let me know if you've been working in the LFO ranges and I'll double check.
Sugarfree
yes, LFO ranges.
I don't have an oscilloscope at hand, so it's easier to hear and observe.
JohnLRice
OK, it looks like there are some inconsistencies with the way the different modes of the 524A respond! eek! hmmm..... seriously, i just don't get it

Below are screen shots of Sync and Gated modes in both Audio and LFO ranges with the frequency set the same in both ranges. I managed to set the frequency close enough in each range so the slight differences shouldn't be significant to the the way the outputs look. (you can see the frequency of the top wave form in the lower right corner of the image) The top wave form is the sine output of channel 1 and the bottom wave form is the square output of channel 2 that is patched to the channel Sync input.

This image is with channel 1 in Audio range and Sync mode. The wave form restarts from its highest peak on the rising edge of the Sync input wave and then runs free until the next rising edge of the sync wave.


This image is with channel 1 in LFO range and Sync mode. The rising edge of the Sync input wave only seems to cause a very slight glitch in the wave while it runs free.


This image is with channel 1 in Audio range again but in Gated mode this time. The wave form is held high as long as the Sync input is low and when the Sync input is high the wave form runs free until the Sync input drops low again.


This image is with channel 1 in LFO range and in Gated mode. The wave form initially goes high on the falling edge of the Sync signal then drops to zero volts for as long as the Sync input is low and when the Sync input is high the wave form runs free until the Sync input drops low again.


So to summarize:
    * Audio Range Sync Mode: works OK?
    * LFO Range Sync Mode: doesn't work?
    * Audio Range Gated Mode: works OK?
    * LFO Range Gated Mode: works great?


Of course I've only tested the one module set I have here but it sounds like other people are also running into this? I'll send Gert an email and see what he thinks.
ranix
What Sugarfree is describing sounds familiar to me. I took some scope pictures (sorry, cheap scope and phone camera)

Here's the setup, a q106 pulse output to a mult measured on oscilloscope channel 1 to sync input on the 524a, 524 output to oscilloscope channel 2.
524 in LFO mode


here's sending a short 10vpp pulse to the sync input



here's a long pulse


here's cranking the pulse width to 100% to hold at +5v


pulse width to 0% for hold at -5v


a faster pulse


cranking up the frequency on the q106 to 32'


cranking up the frequency on the q106 to 16'


I agree with JLR's conclusion that LFO sync doesn't work, but I'll be damned if I know what it's doing

nice find btw, I hadn't tested with the LFO set to audio range!
JohnLRice
ranix wrote:
I agree with JLR's conclusion that LFO sync doesn't work, but I'll be damned if I know what it's doing
Thanks for the additional testing! thumbs up Could you verify if Sync works for you or not when the 524 channel being sync'd is in Audio mode please?
ranix
Works like a charm in audio mode:



ranix
I've got a little something going on in my 524, on both the small PCB risers. Not sure it's related, but it's interesting. There was some rework here:


Sugarfree
I have three Moon 524+A modules and all three have this problem.
I hope Gert finds a solution.
ranix
Sugarfree wrote:
A pulse signal needs to be at least 4x faster than the LFO.


I decided to check this out because my 5-pulser doesn't get enough love, so I tried triggering the 524 with 4 rapid pulses from a triangle wave through the 5-pulser. There doesn't seem to be anything special about a certain number of pulses that I can discern, and this didn't help me make any more sense out of it seriously, i just don't get it

here's the same signal zoomed in and zoomed out, 4 triggers per pulse on channel 1 and 524 in LFO mode on channel 2:
Sugarfree
I meant a constant fast pulse, not just short bursts.
anyway, it's probably just a continuous glitch, not a real synch.
Sugarfree
I wonder how is it even possible to break the sync feature for low range frequencies in Moon524...
Assuming that it has a clocking IC, restarting a cycle is as simple as applying proper voltage to one of its legs. It works regardless of the speed.

There is an overlap between 524's lowest audio range and its highest LFO range, so that the very same frequency can restart properly in one mode, but not in the other. This tells me that there's no problem with the IC itself, just with how the LFO mode is wired.
ranix
yeah, I'm hoping it will be as easy to fix the LFO mode sync as doing a simple rework with a flying wire

of course, if Moon properly released detailed datasheets for their modules like Synthesizers.com does maybe we'd be able to answer this for ourselves...

it would be nice if all the manufacturers provided schematics
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