KVR Audio

Urs · Post by **Urs** » Mon May 01, 2017 5:00 pm

nevernamed wrote:Not sure what would account for that since they use similar parts.

Well, the SEM has a handful of plain potentiometers in the signal path. Any presetable or otherwise digitally controlled synth like the OB-X needs to put ad/da conversion between its pots and the signal path. That is, any former passive section needs to become CV controllable. Hence there are sample & holds and OTAs involved. We've seen with the Pro-One and Prophet-5 that this can have a huge impact on levels and parameter ranges, which can result in major sound differences.

I can't go into detail as to what I have in mind, but I very much also like the idea of viewing the SEM as what it was meant to be: A Synthesizer Expander Module, meant to extend the sonic palette of, say, a Minimoog or an Oddyssey. I think there's a reason that the SEM was the first of that vintage breed to be revived alongside the Eurorack boom. It lends itself to be paired with its own kind as well as with others.

Richard_Synapse · Post by **Richard_Synapse** » Tue May 02, 2017 8:44 am

machinesworking wrote:IMO anyway a huge portion of the Oberheim sound is the filters. There's a cream to them that I don't hear in Moog or Sequential etc. synths. Playing pads on the Oberheim Xpander just sounds to me better than Sequential etc.

Interesting, I would expect a certain similarity in sound here as they both used Curtis filter chips. Perhaps the way the chips are used makes a difference in sound though.

machinesworking wrote: I'll never get whey there hasn't been a solid cross platform Memorymoog emulation though. That's a truly unique sounding synth that's hard to upkeep or get ahold of a working version of.

That's the reason, the scarcity coupled with the high price. Emulations of rare synths keep popping up all the time, but only if the vintage originals are somewhat affordable.

Richard

spunkmuffin · Post by **spunkmuffin** » Tue May 02, 2017 10:30 am

Urs wrote:I can't go into detail as to what I have in mind, but I very much also like the idea of viewing the SEM as what it was meant to be: A Synthesizer Expander Module, meant to extend the sonic palette of, say, a Minimoog or an Oddyssey. I think there's a reason that the SEM was the first of that vintage breed to be revived alongside the Eurorack boom. It lends itself to be paired with its own kind as well as with others.

A SEM clone plugin that can be used exclusively with other u-He monosynths.

EvilDragon · Post by **EvilDragon** » Tue May 02, 2017 11:03 am

Richard_Synapse wrote:Interesting, I would expect a certain similarity in sound here as they both used Curtis filter chips. Perhaps the way the chips are used makes a difference in sound though.

It's not just the chip, it's the electronics surrounding the chip as well... Depending on that, the chip itself can function to a greater or lesser extent differently.

egbert101 · Post by **egbert101** » Tue May 02, 2017 11:14 am

AnX · Post by **AnX** » Tue May 02, 2017 11:55 am

A poly Yamaha CS5/15 would be nice.

Urs · Post by **Urs** » Tue May 02, 2017 6:59 pm

egbert101 wrote:The 'SEM tone' might be more to do with the oscillator waveforms or oscillator circuit than the filters. I analysed both the square/pulse and sawtooth (in the SEM) and they seem to be classic waveforms with some kind of prefiltering (low pass?) going on before the filter stage, so they have a more rounded kind of shape than your typical sawtooth or square/pulse.

Interestingly, the OP-X PRO II emulation of the OB-X has four init sawtooth presets, including Brilliant, Clear, Damped, Normal.

Hmmm... I might do a little surgery with my oscilloscope probes one day... I've spent several days analysing the filter and IMHO the SEM sound is all about the filters, not entirely sure.

nevernamed · Post by **nevernamed** » Tue May 02, 2017 8:37 pm

Richard_Synapse wrote:
machinesworking wrote:IMO anyway a huge portion of the Oberheim sound is the filters. There's a cream to them that I don't hear in Moog or Sequential etc. synths. Playing pads on the Oberheim Xpander just sounds to me better than Sequential etc.
Interesting, I would expect a certain similarity in sound here as they both used Curtis filter chips. Perhaps the way the chips are used makes a difference in sound though.

machinesworking wrote: I'll never get whey there hasn't been a solid cross platform Memorymoog emulation though. That's a truly unique sounding synth that's hard to upkeep or get ahold of a working version of.
That's the reason, the scarcity coupled with the high price. Emulations of rare synths keep popping up all the time, but only if the vintage originals are somewhat affordable.

Richard

There is a lot of overlap between them yes. I think this guy is just stating a preference for Oberheim sound over the Sequential stuff. I have a prophet 5 rev 2 at the minute and there is a lot of overlap with that and the rest of the IC based Oberheims. You could get by impersonating one with the other for certain sounds/situations if you had to. There is a lot of emphasis on differences but there are similarities too.

egbert101 · Post by **egbert101** » Tue May 02, 2017 8:55 pm

egbert101 · Post by **egbert101** » Tue May 02, 2017 9:07 pm

Ingonator · Post by **Ingonator** » Tue May 02, 2017 11:03 pm

egbert101 wrote: This wiki page (hopefully it is correct) does a great job of listing all the relevant Synthesizers and the chips they use:

https://en.wikipedia.org/wiki/CEM_and_S ... nthesizers

Exactly the page that i and i guess also some others at KVR often use when listing which synths used which chips. That page is indeed a great reference for that.

Synths like e.g. the SEM and Minimoog are not listed there as they are based on discrete circuits instead of pre-built chips, same is true for the OB-X except the envelope generator chips.

About certain filter and Osc circuits also this page is interesting, including the CEM3320 filter and CEM3340 VCOs.

The Alesis Andromeda A6 used chips too but it seemed to use "ASIC" chips built by Alesis. someone posted about some of the chips here:
http://electro-music.com/forum/topic-37001.html
Details about the circuits and/or chips are also found in the Service manual:
https://medias.audiofanzine.com/files/a ... 471585.pdf

spunkmuffin · Post by **spunkmuffin** » Wed May 03, 2017 12:11 am

Ingo I think you're great but teh

Ingonator · Post by **Ingonator** » Wed May 03, 2017 6:14 am

spunkmuffin wrote:Ingo I think you're great but teh

A typo that does not happen in all cases and for sure i am not just too stupid to do it right or do it on purpose. Sometimes i also correct posts if i notice typos myself.

With all due respect some people here at KVR are really smartasses concerning such typos.

egbert101 · Post by **egbert101** » Wed May 03, 2017 8:08 am

Urs · Post by **Urs** » Wed May 03, 2017 8:22 am

egbert101 wrote:
Urs wrote: Hmmm... I might do a little surgery with my oscilloscope probes one day... I've spent several days analysing the filter and IMHO the SEM sound is all about the filters, not entirely sure.
Well, nothing particularly special about the waveforms other than there appears to be some prefiltering going on before the filter (and that the Sawtooth is by default a reverse Sawtooth or sloping downward). I can reproduce around 99% the same waveforms by adding 2 pole 12dB Low Pass at around 5300 Hz, which is considerably lower than the default starting cut off point in the Arturia version (at 15kHz). That's about as far as I got trying to recreate the SEM in TAL-Sampler.

So, which hardware do you compare with? Do you have a vintage SEM or any of the re-releases?

A lowpass at 5.3k? I'll need to check that out...

Minimoog Softsynth Shootout: Diva MiniV3 Monark Legend Minimonsta vs Model D