Use external filter module with Prophet 6

[smithymicky1]

Hi all,
I picked up my Prophet 6 on Saturday, and it is beautiful. It is my first ever synth and I'm very glad in the choice I made! I have been lost for hours in just the first 50 patches and have had a small go at creating a couple from scratch.
The question I had was: Can I attach an external filter module to the Prophet 6, such as say a SEM filter or something similar? When I was making my decision between the Prophet and the OB-6 I read the following article: http://www.musictech.net/2016/05/ob-6-review-three/
Near the end it said an alternative to the OB-6 would be to buy a Prophet 6 and (spend the £300 on a modular Oberheim filter!)

If I was to do something like this, which particular filter could I connect to the Prophet and how do I do it with just MIDI in/out?

Cheers guys!

[Paul Dither]

Congrats on your brand new Prophet-6!

As for simply attaching an Oberheim-ish filter:
A module might only make sense, if you're planning on getting into Eurorack anyway. Other than that, there are of course desktop modules by Oberheim himself, or Boomstar, which cost far more than 300 quid though.

There are also a couple of things to consider:
You can't simply add an external filter to a synth like the Prophet-6 and expect it to behave like the internal filters. Each voice consists not only its own oscillator, envelopes, but also filter, which is what true polyphonic articulation is about. If you add an external filter after the Prophet's signal path, it will modify the sound globally, just like an effect pedal would. You wouldn't get individual filter articulation per voice, but rather a monophonic one.
And since the Prophet-6 doesn't come with CV outputs, there's not really any way to make the Prophet and an external filter interact with each other in a deeper way, e.g. by controlling the external filter's behaviour by means of control voltages send from the Prophet-6.
Plus (and this is slightly related): Most filter modules only provide a mono input. So if you'd decide to send the Prophet's audio through a different filter, you can only do that in mono. Parameters like panning would lose any impact then.

Also: Adding an external filter has nothing to do with MIDI settings. Think of it as audio processing only.

[chysn]

"And considering it currently weighs in at £300 less than the OB-6, I’d say it is an alternative (spend the £300 on a modular Oberheim filter!)"

I read this as a rhetorical line, for the purposes of emphasizing the price difference, rather than a specific recommendation. Oberheim doesn't make modular components, and Oberheim-style filters won't work the way you'd want, as Paul Dither explained above; a synth with six-voice polyphony actually has six identical sets of filters, the function of which you simply can't re-create externally with the Prophet 6.

[smithymicky1]

Congrats on your brand new Prophet-6!

As for simply attaching an Oberheim-ish filter:
A module might only make sense, if you're planning on getting into Eurorack anyway. Other than that, there are of course desktop modules by Oberheim himself, or Boomstar, which cost far more than 300 quid though.

There are also a couple of things to consider:
You can't simply add an external filter to a synth like the Prophet-6 and expect it to behave like the internal filters. Each voice consists not only its own oscillator, envelopes, but also filter, which is what true polyphonic articulation is about. If you add an external filter after the Prophet's signal path, it will modify the sound globally, just like an effect pedal would. You wouldn't get individual filter articulation per voice, but rather a monophonic one.
And since the Prophet-6 doesn't come with CV outputs, there's not really any way to make the Prophet and an external filter interact with each other in a deeper way, e.g. by controlling the external filter's behaviour by means of control voltages send from the Prophet-6.
Plus (and this is slightly related): Most filter modules only provide a mono input. So if you'd decide to send the Prophet's audio through a different filter, you can only do that in mono. Parameters like panning would lose any impact then.

Also: Adding an external filter has nothing to do with MIDI settings. Think of it as audio processing only.

Thanks for your reply! That now makes sense after doing some more reading about each of the individual voice cards in the prophet, and the functions of each. So I found the following Boomstar SEM Filter Module: https://www.purelocal.com.au/products/studio-electronics-boomstar-modular-sem-eurorack-filter-australia
I understand that if compatible this filter would only effect the overall audio, would it do it in Mono?
Also would the place to plug this filter into the Prophet be the pedal input?

I see you have got a Pro 2, have you been happy with that synth? When researching the Prophet/OB-6 I found plenty of people were recommending it as an alternative with its 4 voice paraphonic mode.

[Paul Dither]

Thanks for your reply! That now makes sense after doing some more reading about each of the individual voice cards in the prophet, and the functions of each. So I found the following Boomstar SEM Filter Module: https://www.purelocal.com.au/products/studio-electronics-boomstar-modular-sem-eurorack-filter-australia
I understand that if compatible this filter would only effect the overall audio, would it do it in Mono?
Also would the place to plug this filter into the Prophet be the pedal input?

This module only allows for mono input and mono output, yes - most do. And no, you don't plug the filter into any pedal input. You have to plug the Prophet output into the filter input and connect the latter's output to your mixer or audio interface. In other words: There's no way around mono in this case.

And yes, the outboard filter would only affect the overall audio signal that comes out of the Prophet. There's not really any alternative.
You should also consider that the Prophet-6 is not really made for modular integration. It lacks CV in and out connectivity, so you can't make it interact with a modular system. You can only use modules as audio processing tools. For what you would like to do six of those SEM filters had to be part of the individual voice boards.

I see you have got a Pro 2, have you been happy with that synth? When researching the Prophet/OB-6 I found plenty of people were recommending it as an alternative with its 4 voice paraphonic mode.

Oh yeah, I'm very happy with the Pro 2. However, I wouldn't say that it could be a supplement for the Prophet-6. Those two are totally different synths.

First of all, the Pro 2 is for tweakers and those who want do dig really deep into sound design with its excessive modulation options. The Pro 2 is not really a modular synth, as there are of course still a couple of hard-wired connections in there, but it gets you as close to a modular system as a self-contained unit can. Compared to what it actually offers, the Prophet-6 is sonically a very flexible synth, but nowhere as deep as the Pro 2.

Then you might consider that the Pro 2 is a hybrid synth, i.e. it has digital oscillators, a digital character section, and digital delays.

Thirdly, there's a huge difference between polyphony and paraphony: In a polyphonic synth, each voice is articulated individually, from the oscillators via the filters to the VCA. In a paraphonic synth, the settings in the signal path that lie beyond the oscillators are shared amongst all oscillators. (Here it shows why it's important to differentiate between an oscillator and a voice. While an oscillator is part of a voice, a voice is made of everything that's implemented in the full signal path. In that sense, you can of course play different oscillators on a paraphonic synth, but only with a single-voice or monophonic articulation.)

However, in the paraphonic mode of the Pro 2, the four oscillators can be triggered independently, each with its own envelope. But the two filters are still shared by the all oscillators, which means - in case you're making use of the filter envelope - that the filter envelope won't be retriggered once a key is already held. There are a couple of ways to work around that a bit with the DC offset parameter, but strictly speaking a fully articulated filter behaviour per voice can't be achieved because the Pro 2 is a monophonic synth in the first place.

If pads are important to you, this is something you should consider amongst the question about whether 4 paraphonic voices would be enough.

If you don't care too much about full polyphonic articulation, you can of course also misuse the paraphonic mode of the Pro 2 by selecting 4 totally different oscillators, which is what Marc Doty describes as "articulated polyphony." I would rather use the term "quartet mode," since it enables you to play a chord with up to 4 different waveforms, which one could almost compare to 4 different instruments within an ensemble.

Sorry for the long post, but I hope it helps you in some way.

[smithymicky1]

Thanks for your reply! That now makes sense after doing some more reading about each of the individual voice cards in the prophet, and the functions of each. So I found the following Boomstar SEM Filter Module: https://www.purelocal.com.au/products/studio-electronics-boomstar-modular-sem-eurorack-filter-australia
I understand that if compatible this filter would only effect the overall audio, would it do it in Mono?
Also would the place to plug this filter into the Prophet be the pedal input?

This module only allows for mono input and mono output, yes - most do. And no, you don't plug the filter into any pedal input. You have to plug the Prophet output into the filter input and connect the latter's output to your mixer or audio interface. In other words: There's no way around mono in this case.

And yes, the outboard filter would only affect the overall audio signal that comes out of the Prophet. There's not really any alternative.
You should also consider that the Prophet-6 is not really made for modular integration. It lacks CV in and out connectivity, so you can't make it interact with a modular system. You can only use modules as audio processing tools. For what you would like to do six of those SEM filters had to be part of the individual voice boards.

I see you have got a Pro 2, have you been happy with that synth? When researching the Prophet/OB-6 I found plenty of people were recommending it as an alternative with its 4 voice paraphonic mode.

Oh yeah, I'm very happy with the Pro 2. However, I wouldn't say that it could be a supplement for the Prophet-6. Those two are totally different synths.

First of all, the Pro 2 is for tweakers and those who want do dig really deep into sound design with its excessive modulation options. The Pro 2 is not really a modular synth, as there are of course still a couple of hard-wired connections in there, but it gets you as close to a modular system as a self-contained unit can. Compared to what it actually offers, the Prophet-6 is sonically a very flexible synth, but nowhere as deep as the Pro 2.

Then you might consider that the Pro 2 is a hybrid synth, i.e. it has digital oscillators, a digital character section, and digital delays.

Thirdly, there's a huge difference between polyphony and paraphony: In a polyphonic synth, each voice is articulated individually, from the oscillators via the filters to the VCA. In a paraphonic synth, the settings in the signal path that lie beyond the oscillators are shared amongst all oscillators. (Here it shows why it's important to differentiate between an oscillator and a voice. While an oscillator is part of a voice, a voice is made of everything that's implemented in the full signal path. In that sense, you can of course play different oscillators on a paraphonic synth, but only with a single-voice or monophonic articulation.)

However, in the paraphonic mode of the Pro 2, the four oscillators can be triggered independently, each with its own envelope. But the two filters are still shared by the all oscillators, which means - in case you're making use of the filter envelope - that the filter envelope won't be retriggered once a key is already held. There are a couple of ways to work around that a bit with the DC offset parameter, but strictly speaking a fully articulated filter behaviour per voice can't be achieved because the Pro 2 is a monophonic synth in the first place.

If pads are important to you, this is something you should consider amongst the question about whether 4 paraphonic voices would be enough.

If you don't care too much about full polyphonic articulation, you can of course also misuse the paraphonic mode of the Pro 2 by selecting 4 totally different oscillators, which is what Marc Doty describes as "articulated polyphony." I would rather use the term "quartet mode," since it enables you to play a chord with up to 4 different waveforms, which one could almost compare to 4 different instruments within an ensemble.

Sorry for the long post, but I hope it helps you in some way.

Sorry for the really late reply! Have been away for the week.

Thanks a lot for the informative post, it's great to learn about the inner workings and possible limitations in some senses of the Pro 2. I was especially interested to hear that the filter doesn't articulate each time a voice is triggered!
A lot of people had suggested that the Prophet 6 and OB-6 were very similar - but after spending 2 hours on an OB-6 and about a couple of dozen on my Prophet 6 the sound difference is like night and day to my ears! They are such different synths! I loved the crazy filter sounds the OB-6 could produce and it seemed to have such a dark character to it. The Prophet 6 seems to be easier to program lighter happier sounds to it as well as some darker ones too.

But filter tweaking on that OB-6 seemed like endless fun, and such a good tool for making dance music! I really want to get access to that filter one day, but may look at either the OB-6 or the Pro 2. Is the Pro 2 12db filter nearly the same as the OB-6?

[Paul Dither]

Thanks a lot for the informative post, it's great to learn about the inner workings and possible limitations in some senses of the Pro 2. I was especially interested to hear that the filter doesn't articulate each time a voice is triggered!
A lot of people had suggested that the Prophet 6 and OB-6 were very similar - but after spending 2 hours on an OB-6 and about a couple of dozen on my Prophet 6 the sound difference is like night and day to my ears! They are such different synths! I loved the crazy filter sounds the OB-6 could produce and it seemed to have such a dark character to it. The Prophet 6 seems to be easier to program lighter happier sounds to it as well as some darker ones too.

But filter tweaking on that OB-6 seemed like endless fun, and such a good tool for making dance music! I really want to get access to that filter one day, but may look at either the OB-6 or the Pro 2. Is the Pro 2 12db filter nearly the same as the OB-6?

The Prophet-6 and the OB-6 are indeed very different sounding synths. They're complementary, but each one can't replace the other one.

The 2nd filter of the Pro 2 is not identical to the one of the OB-6, but it certainly gives you a similar flavor. Keep in mind though, that the Pro 2 sounds different from the OB-6 anyway due to the different oscillators etc. So given that you seem to like the OB-6 and you'd prefer individual filter articulation per voice, there's not really an alternative to the OB-6. The only reason to go for a Pro 2 instead would be if you want more modulation options and don't care too much about vintage-sounding stuff exclusively.

[PaulSchilling]

I would also recommend getting the OB-6 (module). But since you mentioned mono, and loving the sound of the OB filter... you know that you could buy an Oberheim SEM, and play it via MIDI from your Prophet-6 right? SEMs are about $800 or so.

[smithymicky1]

I would also recommend getting the OB-6 (module). But since you mentioned mono, and loving the sound of the OB filter... you know that you could buy an Oberheim SEM, and play it via MIDI from your Prophet-6 right? SEMs are about $800 or so.

I would love to get an Oberheim SEM.. Where do I look at one for around the price of $800?