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Oakley ASV: New 5U module being designed
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Author Oakley ASV: New 5U module being designed
Synthbuilder
The Oakley ASV (analogue synthesiser voice) module. A complete traditional analogue synth voice as a four MU space or 5U MOTM module. 2 saw core VCOs, SVF, 2 EGs, and a simple sinewave LFO.

Socket board and pot/switch board done. I have just placed the main board and will start to track on Monday. A dual VCO module will plug into the main board, the schematic is captured but still need to place and track. The boards are all mounted parallel to the front panel. The pots are vertical mounted 16mm Alpha/ALPS.

The main board - no tracks yet and the components IDs will need to ordered, sized and placed. This one is a four layer board.



The pot board - copper flood on lower side not shown.


The socket board - copper flood on lower side not shown:


Tony
eljay
This looks really interesting, tell us more. It seems ideal to create a multi-voice analogue system, are there any plans to produce a multi-channel midiDac to go with it? Looking forward to hearing what it sounds like.

What happened to the 'strange audio something' project, is this a spin off from it?
Synthbuilder
eljay wrote:
This looks really interesting, tell us more. It seems ideal to create a multi-voice analogue system, are there any plans to produce a multi-channel midiDac to go with it?

It could be used to simplify a 5U polyphonic system. Although given the size of it I think it would be limited to four voices at the most.

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.

As for a polyphonic midiDAC - I did one with Paula Maddox called the polyDAC. When I got out of selling PCBs in 2007 Paula made the design open source and Elby now sell parts for this. There are no plans to make this product again but I will have to look at a complex polyphonic controller if the polyphonic voice card system does come to fruition.

Quote:
What happened to the 'strange audio something' project, is this a spin off from it?

The Mysterious Audio Plaything is still ongoing. It's a big project and I have the intention of making it ready made. The SVF design used in the AVM is the same one as on the MAP.

Tony
Synthbuilder
Main board and dual VCO board laid out and ready to be manufactured. I'll be ordering all four AVM boards early next week.

The main board:



The front panel design. The big holes are knobs, the medium size holes are sockets (all along the bottom) and the small holes are toggle switches. This design is the 5U wide MOTM style panel but it will also fit in a four wide MU panel. The items shown in brackets on the various modulation input pots are the normalised sources. eg. ENV1 is routed to VCO2 pitch when no plug is inserted into the VCO2 FM socket.



Tony
Synthbuilder
I had some time today to finalise the gerbers for the PCB designs. All four boards that make up the AVM have now been ordered from the factory. Hopefully, the PCBs will be for sale sometime in early November. That is, if I haven't made a cock up somewhere... which is possible, it's a very big project.

I am also hoping to have some MU panels made for this one. I'll be contacting Ben about this as soon as I know the design works.

Tony
Synthbuilder
The boards have arrived. Building of the prototype will commence shortly.

Tony
JohnLRice
Looks great Tony! thumbs up

I was just thinking, it would be sweet to have little self powered low profile desktop cases that would hold just one of these? Make it into something like the Oberheim SEM or Studio Electronics boxes?
Synthbuilder
JohnLRice wrote:
I was just thinking, it would be sweet to have little self powered low profile desktop cases that would hold just one of these? Make it into something like the Oberheim SEM or Studio Electronics boxes?

I didn't design it come out like the SEM but it has certainly ended up with a SEM vibe about it. It'll probably not sound that dissimilar either with the use of a state variable filter. But the VCOs, VCA, EGs and LFO are all very different so hopefully it will sound unique enough to have its own place in one's studio.

I'm probably going to have two side by side in an 'All Metal Parts' 20cm deep 5U high 19" rack with the PSU panel on the rear. I guess you could call that set up a 'two voice'. Oh hell, that sounds familiar. Dead Banana

Tony
Synthbuilder
This issue 1 board set:



Tony
jkjelec
Wow Tony that is quite impressive! It's peanut butter jelly time! It looks like it would be easy to banana-ize it thanks to your separate PCB for the jacks.
Dr Gris
I'm curious if this is inspired by anything existing?
You say it's not a SEM, so...what is it?
A SH-2 with a SVF would be awesome...nudge...nudge hihi
Anyway, it looks perfect thumbs up

//M
Synthbuilder
Dr Gris wrote:
I'm curious if this is inspired by anything existing?
You say it's not a SEM, so...what is it?

Envelopes are based on the AS3310 chip (modern CEM3310 clone) which puts it in Pro One territory. The filter I originally designed for the MAP which is my version of the one in the SEM. The VCOs are based around my 'one of three' VCO which was originally based on the third series Minimoog VCO but over various PCB issues morphed into something else. There's only saw or pulse, but VCO1 also has a triangle output that can be fed directly to the VCA input. The Sub-osc is based around the one I designed for the TB3031 and has a triangle wave output. The VCA is pretty standard LM13700 fare.

To be honest I've no idea what it'll exactly sound like until it's been built - which should be sometime next week.

Tony
Dr Gris
Well, on paper that sounds fabulous and I'm sure it will in real life too !! nanners

//M
Flareless
I'm very excited to check out this module Tony! I'm totally digging the SEM vibel
josaka
On The oscillator tunings.. smile ..the hordijk osc system is a godsend..
the man/norm/lower switch on each osc is so useful.. ('normal' puts the osc tune(disengages the course tune) and you use the fine tune for detune on each osc..) it really works well instantly musical all osc instantly in tune just flick it into manual for standard use this way you can kind of have preset using the different modes..I am surprised no one has taken this up...
..bit late in the day for a suggestion smile smile smile

..your Voice does look epic.. we're not worthy (scouring the studio for a space to fill.. )
Synthbuilder
josaka wrote:
On The oscillator tunings.. smile ..the hordijk osc system is a godsend...

thumbs up

At some point I will be looking into doing an MU (ie. not MOTM) double width VCO. That'll give me chance to revisit tuning options. The double width MU is significantly wider than the double width MOTM modules so I should be able to do something useful with the extra space.

Tony
Synthbuilder
Dr Gris wrote:
A SH-2 with a SVF would be awesome...nudge...nudge hihi

One of the interesting things about the SH-2 is that the second VCO is mounted directly above the mains transformer. This means the frequency is slightly modulated by 50Hz. This gives the SH-2's VCO2 a slight growl and a different sound to VCO1.

The Oakley SVCO's core is very similar to that in the SH-2 (and SH-1, System 100, etc). Indeed, the SVCO and COTA were a deliberate attempt to get at the sound of an SH-1 in a modular.

Tony
Dr Gris
NIce. Atm I have 3 SVCO's and a COTA. Now I just need a mains transformer in there... hihi

//M
Ricochet
Cwejman! Cwejman!

great project thumbs up we're not worthy

I'll integrate it in my new build system applause
Synthbuilder
Well it mostly works. The mechanics are perfect but I'm going to respin the main board because some things could be done better*. The VCO board is all good. The pot board and socket board are fine electronically but if you use lead free solder or have a weak soldering iron some of the grounded connections are quite hard to solder. They are fine with 60/40 solder and a Weller TCP soldering iron. I'll probably offer up the issue 1 pot and socket boards at half price as they will compatible with the new issue 1.1 main board.

The upshot is that I'll be ordering the production issue 1.1 boards today.

I'm very pleased with the sound of the unit. Photos and sound samples will be forthcoming shortly. I'll also make a start on the documentation.

Tony


* For those that are interested in such things and why making a complex project on your own is unlikely to come out right first time this is what was wrong with the main board.

The gate LED comes on when the gate is off. d'oh!

The sub-octave divider gives a not particularly clean output and therefore not suitable to generate a triangle wave. (Sounded fine though)

The sub-octave divider triggered on the falling edge of the VCO and so didn't line up properly to make the triangle waveform.

The 8' setting was prone to stray pick up from other parts of the board.

The offset trim for the final VCA was affected by the level of the triangle to VCA setting.

The sync off switch sent +12V to the FET controlling the sync instead of -12V. (Yikes, why am drawing 1A when the sync is off...)

The sawtooth and pulse outputs were swapped over on the interconnect between the main board and the VCO board.

All were fixable with a few track cuts, cludges with green wire and a few resistors mounted on the underside. I'll be keeping this one but the remaining four issue main boards will go in the bin.
Synthbuilder
This is the standard MOTM format with printed Scheaffer panel and I've used black knobs for this particular build. The small knobs are 1900H clones from Thonk, the big ones their MXR clones and the medium size ones are Davies small bold knobs.





The reverse side showing the triple deck sandwich of boards.

Leverkusen
It looks great, especially with the black knobs!

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?

I would place it side by side with my Haible Living VCOs...
Synthbuilder
Leverkusen wrote:
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
Synthbuilder
The project webpage is up on my site:

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

The page is still in its infancy and I will adding to it as the module nears availability. The Builder's Guide is a preliminary version but it does include the full parts lists for all the boards. Again, this will be embellished as I find time. A User Manual will also be available once the boards are ready.

I will be looking at getting some MU panels made for this project at some point. For standard Oakley/MOTM format the FPD file is available from the project page.

PCB pricing will be as follows:

Main board issue 1.1 - 30GBP
Pot/switch board issue 1.1 - 20GBP
Dual VCO Board issue 1 - 15GBP
Socket board issue 1.1 - 10GBP

You could, if you really love wiring, forgo the socket board but I wouldn't recommend it as there are a lot of connections there and they all go back to the box headers on the main board. The other three boards are pretty much required for any build of the ASV. The pot and socket board holds several key parts of the ASV circuit, namely the audio mixer, the VCF control mixer and precision voltage sources for the pots and switches.

I will have a very limited number of issue 1 Pot/switch boards and Socket boards. As stated in a previous post these will be half price but I only would recommend these if you have a decent soldering iron. My 50W Weller was fine so long as I used 60/40 solder. It struggled with lead free solder. My gas powered iron had no problem with either.

Current consumption appears to around 180mA but I will measure this more carefully next week.

Tony
Synthbuilder
I should add that I'm not taking orders for boards just yet. I need to make sure everything works properly before taking people's money.

Tony
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