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SEQUENTIAL/DSI => Prophet => Prophet Rev2 => Topic started by: Elephant_Shuffle on June 10, 2021, 02:32:20 PM

Title: 2nd Hand Rev2 - Issues?
Post by: Elephant_Shuffle on June 10, 2021, 02:32:20 PM
Hello all,

I'm new here, and took receipt of a 2nd hand Rev2 this week. I'm having a bit of an awkward start with it and was hoping that people would be so kind to let me know whether the below is expected behaviour?

1. Init patch (no changes to knob settings, just the basic empty patch), unison mode (8 voices), detuning 0
When playing keys, alternating between the two same notes repeatedly, leads to what sounds like some kind of phase shift for each key pressed. One key press produces a tone with a lot of high frequency content, then the next suddenly doesn't, then the next one may have a different kind of character again, and so on. The differences between key presses are stark, it sounds like phase shifting, or filtering, or shape mod, something between all three.

2. Same init patch as above with unison
Sub Octave just isn't audible sometimes in Unison mode. It's strange. Then when I turn Unison off and back in, it may suddenly appear and be clearly audible. Or if I switch an oscillator shape, it can suddenly appear - or disappear. It's quite intermittent and often fine, but not always.

3. Same init with unison as earlier
Playing a single note on the keyboard, turning up Osc Slop, pressing the same key, then turning Osc Slop back down. Now the timbre of the tone has markedly changed. Each time I set Osc Slop to another value above zero, then turn it down to zero again, the timbre of the tone has changed.


----------------
General 'issues' not related to unison:

1. It needs an absolutely crazy amount of gain
I realise it needs to accommodate for 16 voices, but it still seems off just how much I need to boost my preamps to get a reasonable signal out of the line outs. I tried creating the loudest sound possible (16 voice unison, 2 oscillators and one sub) and yes, that gave me quite a hot signal... so maybe it's fine. But it does need a lot of gain for normal operation.

2. The headphone output is much louder than the line outputs
Related to the gain observation above, but not much else to say about it.

3. It sounds completely different dependent on sound card/preamps used
This one out of all issues irks me the most.
I thought my soundcard was broken as the Rev2 sounded so tinny, but when I checked it over its own headphone out it sounded fine. So I tried a different soundcard/preamp and this sounded identical to the Rev2 headphone out, leading me to think soundcard 1 was bust.

But then I tried other gear and there was no discernible differences between the two soundcards/preamps. So somehow, only the Rev2 sounds starkly different depending on what soundcard/line in preamp I run it through


I appreciate that perhaps none of the above are actual issues, as this is the first analog polysynth I have ever owned. That said I'm no beginner to audio and synths, and while I may simply be out of my depth here and the unit I have operates as expected, the above all has baffled me.

So hopefully I will be schooled and it turns out all the above is as it should be.
Sorry for this long post, thanks for any help or pointers!











Title: Re: 2nd Hand Rev2 - Issues?
Post by: RobustAmerican on June 11, 2021, 01:59:47 PM
Whoa, that's a serious list of issues. You didn't mention how or if the Rev2 is connected to anything. 5 pin midi cables or usb? If it is connected to something, disconnect it. Start with just the power cable and headphones.
Do the issues persist?
Title: Re: 2nd Hand Rev2 - Issues?
Post by: Pl@ton on June 11, 2021, 03:07:40 PM
About 1 and 2, try to set the Osc Reset to ON for both oscillators in the misc parameters and see if the problem of change of sound persists.
 
Title: Re: 2nd Hand Rev2 - Issues?
Post by: Elephant_Shuffle on June 12, 2021, 04:15:22 AM
Thanks both! I appreciate it.

As for unplugging USB, I have the desktop version so I am using USB to play notes. I haven't had the chance to figure out the built-in sequencer yet.

Either way, I changed my jack cables from balanced to unbalanced, and now it sounds fine even through the interface that previously sounded tinny. I can't explain this but it's made a big difference.


The Unison issues persist, that is, if they truly are issues. I have attached two mp3's, both are of an init patch with 8 voice unison enabled. No other changes to the init patch.

I play two notes in quick succession, sorry for the lack of musicality, it's just to demonstrate the issue.

rev2-unison.mp3 is without osc reset, and this sounds really strange to me, especially from about 15 seconds in, the timbre starts jumping quite extremely

rev2-unison_oscreset.mp3 is the same but now with Osc Reset enabled. It is true that the issue is now basically gone, though there's still regular notes that lose quite a bit of top-end.


Maybe this is expected behaviour? I'd be happy if it is, as I rather deal with 'accepted' quirks (if they're even quirks) than feeling like I have a unit that's broken. It's just confused me so far.


Thanks again.
Title: Re: 2nd Hand Rev2 - Issues?
Post by: Pl@ton on June 12, 2021, 05:12:28 AM
You should try to do a calibration or two. It might help.
Title: Re: 2nd Hand Rev2 - Issues?
Post by: Elephant_Shuffle on June 12, 2021, 06:29:05 AM
I had run a calibration after updating the OS, but just tried it again two more times (in fact three times, but it got stuck once...). Unfortunately hasn't made a difference.

So I take it the observed behaviour in Unison mode is not as expected then?
Title: Re: 2nd Hand Rev2 - Issues?
Post by: Pl@ton on June 12, 2021, 09:31:58 AM
I can't tell you because the tempo on your example is really extreme (very very fast).
If "reset on" has helped, then it's because you were hearing phase cancellations, which is normal behaviour when reset is off.
The voices/oscillators run independently so sometimes several voices/oscillators are in opposition of phase, it's cancelling some sounds.
It's not a bug but a feature of this synth. It gives life to sounds.
To avoid that, for example to play bass lines where phase cancellations might be annoying, you can set "reset on", but it's still possible to have some phase cancellations, especially when using slot/detune and playing fast.
So, I'm not sure if there is a problem with your synth.

You should experiment while playing at "normal" (or slow) tempo.
Title: Re: 2nd Hand Rev2 - Issues?
Post by: maxter on June 12, 2021, 06:46:54 PM
Well, the Rev2 hasn't got balanced outputs, so by running balanced cables from it into an interface that has balanced inputs, the amplitude/volume would immediately be cut in half, at least... that's probably why the headphones output was louder, as I assume you used it in an unbalanced fashion.

Different impedances between outputs and inputs of devices and interfaces could also affect volume and timbre, but probably isn't the issue in this case.
Title: Re: 2nd Hand Rev2 - Issues?
Post by: Elephant_Shuffle on June 13, 2021, 01:30:41 PM
I can't tell you because the tempo on your example is really extreme (very very fast).
If "reset on" has helped, then it's because you were hearing phase cancellations, which is normal behaviour when reset is off.
The voices/oscillators run independently so sometimes several voices/oscillators are in opposition of phase, it's cancelling some sounds.
It's not a bug but a feature of this synth. It gives life to sounds.
To avoid that, for example to play bass lines where phase cancellations might be annoying, you can set "reset on", but it's still possible to have some phase cancellations, especially when using slot/detune and playing fast.
So, I'm not sure if there is a problem with your synth.

You should experiment while playing at "normal" (or slow) tempo.

Thank you for all the suggestions. I recorded that sequence quite fast to make the big timbre jumps happen more quickly, as it doesn't happen with every key press. But the same occurs when playing slowly. I can rationalise phase cancellations but the quite radical timbre jumps at about 15 seconds and 18-20 seconds in the rev2-unison.mp3 example are still a bit strange to me.

Well, the Rev2 hasn't got balanced outputs, so by running balanced cables from it into an interface that has balanced inputs, the amplitude/volume would immediately be cut in half, at least... that's probably why the headphones output was louder, as I assume you used it in an unbalanced fashion.

Different impedances between outputs and inputs of devices and interfaces could also affect volume and timbre, but probably isn't the issue in this case.

Absolutely explains the drop in volume I had and why it felt so silly quiet. I still don't understand why also the overall signal was pretty 'weak' as in no bass and a distorted top end, but anyway, using unbalanced cables sorted that all out.


Despite all the above, I've been programming this synth for the past few days and just tinkering around with it, and I do really like it. In normal operation, the unison 'jumpy behaviour' doesn't really stand out to me, either.
Title: Re: 2nd Hand Rev2 - Issues?
Post by: maxter on June 13, 2021, 04:27:24 PM

Absolutely explains the drop in volume I had and why it felt so silly quiet. I still don't understand why also the overall signal was pretty 'weak' as in no bass and a distorted top end, but anyway, using unbalanced cables sorted that all out.


I can't really explain how as I don't really "understand" how it happens, but in some sense "why" it happens is because the balanced input is expecting a signal on the tip, and the exact inverted signal on the ring (where anything positive is inverted to negative, and vice versa), of the cable. Anything that is NOT exactly the same signal as it's inverted counterpart, is treated as an interference, and therefore is "canceled" through deduction by the receiving interface. Which is a (or the?) main reason for using balanced cables in general.

Since an inverted signal was not present on the ring of the cable in this case, the interface calculated and removed what it "perceived" to be "interference", so the sound would definitely change not only by the drop in amplitude, but it could also "add" artifacts (by "removing" the supposed interference). I think...

I'm sure there are others, and likely videos, explaining it a lot better than I can.

https://www.reddit.com/r/synthesizers/comments/e3j1wu/balanced_cable_on_unbalanced_output_works_fine/

I didn't find any direct explanation what happens in your case specifically right now, but here's a good one explaining how it works in general.

https://www.youtube.com/watch?v=91JQRAjZ_Qw
Title: Re: 2nd Hand Rev2 - Issues?
Post by: Pl@ton on June 14, 2021, 12:40:58 AM
Thank you for all the suggestions. I recorded that sequence quite fast to make the big timbre jumps happen more quickly, as it doesn't happen with every key press. But the same occurs when playing slowly. I can rationalise phase cancellations but the quite radical timbre jumps at about 15 seconds and 18-20 seconds in the rev2-unison.mp3 example are still a bit strange to me.

It might be a problem of calibration.
Press a key x the number of voices you have and check if all have the same sound/tuning.
If not, you can reset calibration (press octave up and down and press global they follow the guide) and do several calibrations.