Oakley ASV: New 5U module being designed

[Leverkusen]

I am not sure if I fully understand the signal path. I guess one of the envelopes goes to the VCA. But the LFO does not and it's not possible to open the VCA by hand/externally or tap the filter output, right?

Signal path is the traditional VCO1 & VCO2 -> VCF -> VCA. There is an additional triangle wave output on VCO1 that can go direct to the VCA bypassing the VCF. Envelope 1 can control VCO2 pitch and VCO2 pulse width (via normalised connections on the socket field) and VCF frequency. Envelope 2 controls VCA only although, like Envelope 1, has its own output socket.

The level of Envelope 1 being sent to the VCF's control input is also controlled by a positive CV at the ENV1 ACCENT socket. This is useful for velocity controlled filter sweeps. The socket is normalised to +5V when there is no plug inserted.

With no jack inserted into the gate socket the gate is high so both envelopes are in sustain mode. You can then allow the VCA to open (drone mode) with the sustain control on Envelope 2. Although without any CV in the Key CV socket both VCO's will both be oscillating at quite a low frequency.

Tony

Ah, I missed the ACCENT input, respectively I thought it would expect a trigger rather than CV.

So the idea is that velocity response and tremolo would be achieved via the filter - they both would not affect the triangle wave then, right?

I wonder if additional VCA offset and CV inputs could be an option for a possible MU version?

I like the unconnected gate high/drone mode. That's a nifty idea.

Looking forward to sound examples!

[Synthbuilder]

So the idea is that velocity response and tremolo would be achieved via the filter - they both would not affect the triangle wave then, right?

Yes. The level of triangle wave is only affected only by the VCA envelope.

I wonder if additional VCA offset and CV inputs could be an option for a possible MU version?

Both MOTM and MU layouts are identical. One of the quirks of the two formats is that a 5U wide and four wide MU are almost the same width. Actually, the available panel space for the MU is slightly smaller, because of the panel folds, which is why there is some additional space to the left and right sides of the prototype MOTM build.

Ultimately, one has to make compromises when designing an 'all in one' module and some favourites will be missed out. Generally I design things for my own needs and I almost never use tremolo (pure VCA modulation) so it wasn't included. That said, this is a modular unit so the output of the ASV could simply be connected to a separate VCA module for more comprehensive amplitude control.

Tony

[Leverkusen]

So the idea is that velocity response and tremolo would be achieved via the filter - they both would not affect the triangle wave then, right?

Yes. The level of triangle wave is only affected only by the VCA envelope.

I wonder if additional VCA offset and CV inputs could be an option for a possible MU version?

Both MOTM and MU layouts are identical. One of the quirks of the two formats is that a 5U wide and four wide MU are almost the same width. Actually, the available panel space for the MU is slightly smaller, because of the panel folds, which is why there is some additional space to the left and right sides of the prototype MOTM build.

Ultimately, one has to make compromises when designing an 'all in one' module and some favourites will be missed out. Generally I design things for my own needs and I almost never use tremolo (pure VCA modulation) so it wasn't included. That said, this is a modular unit so the output of the ASV could simply be connected to a separate VCA module for more comprehensive amplitude control.

Tony

Ah, okay. Then I misunderstood something - I did not calculate the panels but thought you mentioned using surplus space on a MU panel somewhere in this thread and just had in mind that MU is a little wider. But yes, at some point it is nearly the same width again.

I totally understand your approach of designing something coming from your own point of view/need. Actually I appreciate this very much. Would you mind explicating your idea of not feeding the triangle into the mixer but to the VCA w/o going through the filter?

[Synthbuilder]

I did not calculate the panels but thought you mentioned using surplus space on a MU panel somewhere in this thread and just had in mind that MU is a little wider.

At some point I hope to make a dedicated MU VCO. The additional panel width afforded by a double width MU panel compared with the 2U wide MOTM one should allow for some extra features.

Would you mind explicating your idea of not feeding the triangle into the mixer but to the VCA w/o going through the filter?

Triangles are pretty boring harmonically, and a similar sound can be obtained by a lightly filtered squarewave. The filter in the ASV is a state variable filter, ie. with -12dB/octave slopes in LP and HP modes and -6dB/octave in bandpass mode. In high pass and band pass modes the filter can be used to accentuate the higher harmonics of the VCO outputs. This is great sound but will lack the power because there is little fundamental left. This is where the triangle wave comes in. This can be added to the thin filtered signal giving back a simple fundamental tone. It's a very powerful feature.

I first came across the idea in the Yamaha CS-30 although they used a sinewave straight into the VCA. I then used the triangle version in the many Oakley modded SH-101s I did for folk over the years. It's easy to do on any modular with mixer prior to the final VCA and indeed one of the reasons I developed the Discrete VCA module for the Oakley Modular which has two inputs available. The technique is not hugely useful on low pass filters - the fundamental is always present even at high resonances - but with HP and BP filters it's great.

It's worth noting that the sub-osc is a triangle. So if you want to filter a triangle wave then click VCO1 up an octave and use the sub level on the mixer.

Tony

[Synthbuilder]

Some sound samples have been loaded to the project webpage:

http://www.oakleysound.com/asv.htm

Forgive the self indulgent nonsense of the last track. I couldn't help myself.

Tony

[Dr Gris]

Sounds great!!

//M

[Leverkusen]

Yes, the examples do sound great. I am also impressed by the additional triangle trick! I tried it with Doepfer SEM Filter and a mixer but it always sounded like a triangle wave and filtered saw. This one is much better.

When do you think will it available?

[Synthbuilder]

When do you think will it available?

Now.

I've just got internet back after two days without it. There was a major system fault at the local exchange.

I'll be uploading the project webpage for this in the next few minutes.

Tony

[Synthbuilder]

OK - I have just uploaded some basic information to the project webpage. Photographs of the new issue boards should be up there on Monday. The Builder's Guide is just a preliminary although the parts list in there has been validated. I will add some more information to the Builder's Guide about the specifics of constructing the module in the next few days.

Calibration is straightforward. You need only a voltmeter and your favourite method of tuning oscillators. No 'scope is required.

I am now taking orders for boards. I have a few issue 1 socket boards left going at half price. Remember these are only suitable if you use lead free solder and don't have a weak soldering iron.

http://www.oakleysound.com/asv.htm

Tony

[oozitron]

Two things I would like to be able to do:
1) send LFO > VCO2 (only) while sync is on
2) send LFO > VCO2 (only) (with sync off) for slight pitch detuning & swirlyness

I'd like to be able to do this without patching.

Would it be fairly easy to hand-wire in an additional ON-OFF switch into the path that goes from the VCO 1/2 FM pot output to the VCO 1 FM?

If the switch was ON then you would get "normal" behavior, but if the switch was OFF then the LFO modulation would only go to VCO 2.

thanks!
Drew

[Synthbuilder]

Would it be fairly easy to hand-wire in an additional ON-OFF switch into the path that goes from the VCO 1/2 FM pot output to the VCO 1 FM?

Probably not easy. But it may be possible. Somehow you'd have to get your new switch in between the panel and the PCB - the existing switches have their pins protruding through the PCB. Perhaps you could cut down the extra switch's pins to stumps and wire them in from there. There's not a lot of space to put any extra switches though:



Tony

[oozitron]

Oh yeah, I realize it would be crazy to try to put it on the PCB. I was thinking it would mount on the left edge of the panel with a couple flying wires to the PCB. Might have to make the panel a bit wider for it to fit.

Also, I upgraded my machine to the newest FPExpress software (from the US site) and it won't open your panel file. Says it was created with a newer version of the software (?)

This is a beautiful looking & sounding project. Thanks for all your work!
Drew

[Synthbuilder]

Also, I upgraded my machine to the newest FPExpress software (from the US site) and it won't open your panel file. Says it was created with a newer version of the software (?)

I'm using 6.11. Probably worth getting it from Schaeffer direct.

http://www.schaeffer-ag.de/en/downloads ... no_cache=1

Tony

[emi2345]

I would like to a do a full voltage controlled voice card at some point which would be especially designed for polyphonic use. This wouldn't be a module as such but part of a polysynth project.

That would be the ultimate dream, a semi-modular polyphonic system with 5 or 6 voice cards combining the best bits of the Oakley modular system. Maybe in a 10U wide box. Each card could have a ‘one of 3’ style VCO switch for sine/tri/saw/pulse and a ‘svco’ style switch for saw/pulse, waveshape cv and sync cv would be nice. Envelope and a second vrg-style with one-shot, ad and cv for up and down which is such a simple but amazing Oakley module. A discrete ladder lp filter with resonance and a basic chip filter for hp-bp would be awesome. Something quirky on the card to give the synth a signature too. I got to play with a Korg PS-3300 today and the voltage controlled resonators give it such an incredible rich swirly phasery sound.

I’m sure this would be phenomally complicated and require a bazillion vcas and smt (not to mention midi) but if it could integrate nicely with the Oakley system it would make the ultimate synthesiser.

[Synthbuilder]

That would be the ultimate dream, a semi-modular polyphonic system with 5 or 6 voice cards combining the best bits of the Oakley modular system.

It might be somewhat simpler than that.

In the meantime...



Because two is better than one.

Tony

[emi2345]

It might be somewhat simpler than that.
Tony

What kind of design did you have in mind? Is this ASV going to be the basis for it?

[Synthbuilder]

What kind of design did you have in mind? Is this ASV going to be the basis for it?

Quite possibly but I'll need to add another filter - probably a transistor ladder but definitely a four pole of some sort. And all the modulation paths have to be voltage controlled since you need one set of global controls to affect all voice cards simultaneously.

Ultimately, it needs to be simple enough to make it affordable and not too physically large. And yet be interesting enough to make it stand out against the likes of the OB-6, DM12 etc.

Tony

[emi2345]

+1 to the transistor ladder filter. This last week I’ve been in a studio with a ridiculous selection of vintage synths (minimoog, prophet 10, memorymoog, cs80, ps3300, gleeman pentaphonic, obx, 2600, jp8) and the oakley system with discrete ladder filter I brought was often used for mono and effects work. It sounds just as juicy but is much more reliable with precise tracking and being modular has more sonic possibilities. A polyphonic addition would be superb and I’d love to build one. Keep us updated on any progress or design ideas you have for it!

[Leverkusen]

Oh yes, me too would love to build an Oakley Poly...

[oozitron]

There's not a day that goes by that I'm not thinking about building a Four Voice ASV. The Obie 4VS has been a "dreamsynth" of mine since buying this album in high school:


I realize that the ASV is not a direct SEM clone, but everything of Tony's has really impressed me so I have confidence that it will fill the bill.

I will, however, go with white panels and a more SEM-like font to help fool my brain :-)

1) What is the depth of the complete ASV?

2) Would the FourMix be a good mixer for four ASVs? (I built one for my modular and it's my favorite mixer)

Drew

[Synthbuilder]

What is the depth of the complete ASV?

You should allow approximately 60mm.

Would the FourMix be a good mixer for four ASVs?

Yes, but if it were solely for mixing the ASVs then I'd be tempted to reduce the gain by a factor of four. As it stands the Fourmix will clip if all four ASVs are going full pelt and the Fourmix's levels are at maximum. So on the Fourmix make R25 8K2.

Tony

[Baldanders]

Hi, I just ordered the PBCs for the ASV a couple of days ago. i am thinking about mounting it not in my (to be constructed) main 5U rack, but in its own, slightly slanting case that should sit in front of said case (and next to my Future Retro XS synthesizer that also has some semi-modular capability). For this, it would be ideal if the socket board was mounted ABOVE the pot/switch board. Construction-wise it's obviously simple to do that, but I wanted to ask if lengthening the ribbon cables would lead to noise problems? Power would be coming in on the rear of the case from the main rack's PSU via a "Tiny-XLR" plug.
Thanks for any insights!

[Synthbuilder]

I wanted to ask if lengthening the ribbon cables would lead to noise problems?

Possibly. Any increase in the length of an unshielded connector will increase the chance of crosstalk and interference. However, I don't think it will make a significant difference in this case. I spent quite some time trying to work out how signals are allocated in those ribbon cables so as to reduce any chance of detrimental cross talk. That said keep them as short as possible and make sure they don't get too close to the boards.

It's always best to build any project into a grounded metal case if possible.

Tony

[oozitron]

Seems that TL072CN chips are not available around here.

Can TL072ACP chips be used instead? (ie, use ACP for all 072?)

Drew

[Synthbuilder]

Can TL072ACP chips be used instead?

Yes. The ACP is an improved specification (lower voltage offset) TL072 so can always be used in place of the CN variant.

Tony