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Oakley SRE330 News
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Author Oakley SRE330 News
Synthbuilder


This is a picture of the first prototype which has been sold already. Basically, it is an SE330 but with several key differences:

1. Stereo in and stereo out
2. Full 19" rack width
3. Triple 'Solina' style ensemble mode as well as the SE330's quad and dual ensemble/chorus modes.
4. LED metering.
5. Classic NE570 companding noise reduction.

This first prototype uses an issue 1 board which I thought could be improved a little - wrong sized component legends and some of the trimmers were a little too sensitive - so I've made an issue 2. They arrived last week and testing was completed yesterday.

Now I need to order some new power supply boards for it - although it could work with any decent +/-15V supply capable of supplying 250mA.

I am planning to make these available as ready made units although I will look into selling PCBs too. Price is yet to be confirmed. It would be nice to have them ready before the end of the year.

This is what the prototype sounds like.

[s]https://soundcloud.com/takla-makan/sre330-noodling[/s]

The above is my playing around with the controls. In this sound sample set you hear the raw sawtooth first from a Roland Alpha Juno 2, and then the rest of the set I'm processing the Juno's mono output with the SRE330 to produce a rich string synth sound. At extreme modulation depths the induced vibrato effect can be very pronounced.

[s]https://soundcloud.com/takla-makan/lowrey-vs-sre330[/s]

This above sample set uses a Roland Alpha Juno to create a raw sawtooth pad which is then sent to both an Oakley Sound SRE330 and a Lowrey Symphonic Ensemble unit from 1975. The Lowrey ensemble is basically their version of the triple ensemble circuitry from the Solina string machine complete with TCA350Y BBDs.

In this set you hear the same sound firstly played through the Lowrey and then the SRE330 in Triple Ensemble Mode. I crossfade between the two effects after each sound to show how similar they sound. However, they are not identical. The Lowrey is noisier with considerable modulation oscillator breakthrough and there is some of sort of peak in the frequency response which isn't there in the more mellow SRE330. The latter could be added with EQ should one wish to replicate that part of the sound.

It should be noted that the SRE330's and Lowrey's outputs have been put into mono for this sample set to recreate the sound of most analogue string machines.

Tony
Paradigm X
wow looks great! applause
terjewinther
This is really cool. I donĀ“t need one, but I want one and will buy one and build it, just because I like building, and and love chorus sounds on strings and noise and those things.

I do hope you will provide files for the front panel, and hints about where one can get an empty rack that fits, othervise this will be a challenge to build.

I notice that you need el.caps on the power needs to be low enough to go into a single space 19" rack cabinet. Could you please provide info in the builders manual regarding the maximum hight of these for the builders?
Synthbuilder
terjewinther wrote:
I do hope you will provide files for the front panel, and hints about where one can get an empty rack that fits, othervise this will be a challenge to build.


I'm looking to get rack cases for this project. These would be pre-drilled and labelled. Might be a bit expensive to ship outside the UK though.

The Scheaffer file for just the front panel would also be available as normal.

Quote:
I notice that you need el.caps on the power needs to be low enough to go into a single space 19" rack cabinet. Could you please provide info in the builders manual regarding the maximum hight of these for the builders?


That's a RPSU in the SRE330 prototype so the ones I have used there are the ones given in the Oakley Parts Guide. They're 1000uF 50V electrolytics, Rapid part: 11-3938.

Once I'm happy with the SRE330 build I'll write a Builder's Guide for it and update the generic Parts Guide to include any manufacturers part numbers. I don't think you'll find any problems getting 1000uF caps to fit though.

Tony
Leverkusen
Wow - the examples sound gorgeous! applause

Since I already have an ensemble effect in the rack I'll wait for the 5U delay though, hoping it will go down to chorus speed too, and put it besides the flanger module for some occasional extra strings...
Eric the Red
Hey Tony - is this the "secret synth project" you have been dropping hints at in the 5U forum a few weeks/months ago?
Synthbuilder
Eric the Red wrote:
is this the "secret synth project" you have been dropping hints at in the 5U forum a few weeks/months ago?


No, that's the Mysterious Audio Plaything. Work is ongoing. The prototype has been built and the first set of boards designed. This is a standalone multivoice synth with some unusual features as well as being able to interface with any modular. Again the plan is to make it ready made but there is potential for PCBs and cases to be made available too.

Tony
Blake Smith
Those samples sound lovely. Still working on a se330 though.

That pcb is going to be huge.
Synthbuilder
Blake Smith wrote:
That pcb is going to be huge.


It's a lot less deep compared to the SE330 but it is about 75% wider. It also has four layers of copper - the usual two outer layers plus two sandwiched inside. The four layers mean I can make the component density higher without impacting on performance. Indeed having one mostly solid plane of copper solely for 0V improves performance. Those extra layers do mean it is a more expensive board to make though.

The additional length of the board will make it more problematic sending it through the post. The thinner Filtrex boards can be sent in tubes but for these I will have to find some sort of box.

Tony
Eric the Red
Thanks Tony
Dr Gris
I really want this!
Any idea of how deep this will be?
I'm thinking of mounting it in a flightcase (30cm deep) with modular (5U) stuff.
And route the ins & outs to a front panel somehow.

I guess ins & outs in the front isn't an option because of panelspace...??

Cheers
//Magnus
Synthbuilder
Dr Gris wrote:
Any idea of how deep this will be?


The prototype case is 250mm deep but that has to include space for the +'/-15V power supply and I/O board. I think I can make any bespoke casing I have made a bit smaller - perhaps 220mm.

Quote:
I guess ins & outs in the front isn't an option because of panelspace...??


It won't fit on the standard panel - although you may be able to get four 3.5mm TRS sockets on there.

Tony
Dr Gris
Thanks Tony for your reply.
250mm is cool.
Trying to stay away from 3.5mm as much as I can.. hihi
I'll find a solution.

Looking forward to when it's available.

//M
Synthbuilder


A limited number of SRE330 PCBs are now available. Also available are the optional RPSU issue 2 power supply module for it and the SRE330 I/O PCB designed to make the socket wiring easy and a useful anti-thump unit.

I'm in the middle of writing the documentation for all three new boards and these should be ready before the end of this week.

More details and photos at the usual place:

http://www.oakleysound.com/sre330.htm

At some point I am hoping to offer these as ready made units.

Yes, I am aware of just how expensive the main board is. But it is large and four layer. That's not cheap to produce although it is a thing of beauty to be sure.

Tony
Dr Gris
Awesome!!
But unfotunately I don't think I have the time for DIY these days... cry
I'm hoping for a ready made unit one day.

Great work Tony, I love it's sound!! love

//M
babysealclub
Absolutely beautiful!
Synthbuilder
The first version of the Builder's Guide has been uploaded to the site. The direct link is here:

http://www.oakleysound.com/SRE330-BG2.pdf

There may be a few typos but the parts lists should be correct. Let me know if you find anything obviously wrong.

The User Guide, which also contains all the calibration details, will hopefully be online sometime early next week.

Tony
Eric the Red
Out of curiousity, what would shipping cost to send a set of boards across the pond to the States?
Synthbuilder
Eric the Red wrote:
Out of curiousity, what would shipping cost to send a set of boards across the pond to the States?


My standard rate is 9GBP for any order over 35GBP.

Tony
bujbot1
Hi Tony,

Do you know if there's a mouser project link anywhere for this build? I'm very interested in it but am trying to get a feel for the total component cost.

Thanks.
Synthbuilder
bujbot1 wrote:
Do you know if there's a mouser project link anywhere for this build?

None that I know of. I don't think you'll be able to get everything from Mouser though.

Tony
Synthbuilder
Boards now back in stock.

These are issue 2.1 boards and are basically the same as issue 2 but have a smaller hole diameter for the trimmers to suit the recommended Bourns and Vishay devices.

http://www.oakleysound.com/sre330.htm

Tony
BTG
any idea of a ready made source of these?
Synthbuilder
BTG wrote:
any idea of a ready made source of these?


I'm planning to do some but I've not had a chance to get back to the metal shop with the detailed design they need to make the case.

Right now any official ready made Oakley Sound SRE330 modules are just vapourware. I'll probably get there but I'm slow and easily distracted by other things.

Tony
Rex Coil 7
Synthbuilder wrote:
BTG wrote:
any idea of a ready made source of these?


I'm planning to do some but I've not had a chance to get back to the metal shop with the detailed design they need to make the case.

Right now any official ready made Oakley Sound SRE330 modules are just vapourware. I'll probably get there but I'm slow and easily distracted by other things.

Tony
Just populated and calibrated PCBs would be an enormous help. Between having basic metal working skills and possession of/knowledge of how to use an o-scope, I think most people have the former over the latter.

So just offering populated/calibrated boards would get most folks far ahead of the game ... the enclosure is mostly handled with FPE cover panels, as well as a bit of time with a hand held drill motor. That level of offering would take less of your own time as well, Tony.

seriously, i just don't get it I'm not tellin' ... I'm just sayin'.

(I am VERY interested in the SRE330 ... the audio demos sound just excellent.)

nanners screaming goo yo SlayerBadger! applause
Firechild
I would like to Emulate the ELKA SYNTHEX Chorus 3 setting which mode should I use?
Synthbuilder
Firechild wrote:
I would like to Emulate the ELKA SYNTHEX Chorus 3 setting which mode should I use?

Sadly I haven't played with a Synthex for many years so I'm unsure now of the details. However, from the schematic each voice channel has two separate delay lines with the delay time of each controlled by its own low frequency modulation oscillator, one running faster than the other. There are two identical channels, one for the upper voice and one for the lower voice. The differences between the various chorus modes are changes in the wet/dry mix, the relative mixes between the two delay lines and the modulation frequency for one of the delays.

The SRE330, and the SE330, cannot replicate the Synthex as the second delay line in each of its channels in QUAD mode is controlled by both the triangle wave and sine wave LFOs. You can't just control that second delay line with its own distinct LFO. In the Synthex you have a separate LFO per delay line. The Synthex is a much simpler system but one that cannot be replicated by the more complex SRE330.

This also means that the SRE330 is not able to replicate the ARP Omni as that has three separate delay lines each modulated by its own LFO.

That said, it may be possible to get close to the topology of the Synthex by using the stereo mode of the SE330 (or dual mode of the SRE330). Sum the L & R outputs of the ensemble into mono in your mixing desk and the resulting sound will give you two delay lines controlled by two separate LFOs. You can't change the relative frequency difference between the LFOs - it's fixed at 1.2:1 - but they are free running and different enough to give you a reasonable amount of movement.

Tony
Rex Coil 7
Synthbuilder wrote:
... This also means that the SRE330 is not able to replicate the ARP Omni as that has three separate delay lines each modulated by its own LFO.

Tony
Ho--kay. That bit of news is something I was not aware of. Thanks for the information, Tony. Straight shooter, you.

cool
Synthbuilder
Rex Coil 7 wrote:
Ho--kay. That bit of news is something I was not aware of. Thanks for the information, Tony. Straight shooter, you.

The Omni is pretty unique in many respects. It's not as rich as the other string ensembles although it does sound nice enough. It's actually probably one of the simplest ensemble units - basically its simply three BBD delay lines each modulated by their own free phase LFO with no dry signal added.

It is interesting that ARP decided to use this topology rather than the one used on the Solina (ie. the 3-phase mode on the SRE330).

Tony
Dr Gris
I've contacted LED-man about building one for me. I'm excited w00t

//Magnus
Dr Gris
And it's finally here!!!
Crazy many variants of chorus in this box, love it!!

Thanks Tony!
//Magnus
tioJim
Hello Tony

Think I'm about to embark upon an SRE330 build but I do like a pro solution for an enclosure so ...

Synthbuilder wrote:
I'm looking to get rack cases for this project. These would be pre-drilled and labelled. Might be a bit expensive to ship outside the UK though.


... any developments on this?

Thanks
Jim
Synthbuilder
tioJim wrote:
... any developments on this?

Sadly not. Paul at Krisp1 looked into doing this for me some while ago and couldn't find enough people interested to make it economically viable. I think the SRE330 is perhaps too big and expensive a project for many people.

Tony
tioJim
Synthbuilder wrote:
tioJim wrote:
... any developments on this?

Sadly not. Paul at Krisp1 looked into doing this for me some while ago and couldn't find enough people interested to make it economically viable. I think the SRE330 is perhaps too big and expensive a project for many people.

Tony


No worries, thanks Tony. It is a bit of behemoth! I'll probably need to set aside a few afternoons for this one wink
Pav
Hi , I'm needing to free up a pa20 lump used with my sre330 and I was thinking of changing to a 1 Amp rated a/c wall wart. Before I drill hole for power socket , worth the question.
I'm thinking the current draw stated is close to the ballpark 250ma recommended for such a supply.
Psu docs suggest retrofitting this should not require removing any diodes, but not whether I need to remove a fuse. There is the question of current limiting resistors I expect..?

I wondered if you could have had a header and jumper system on Psu pcb or retrofit a switch so that it was easier to choose either pa20,pa30 etc.
Synthbuilder
Pav wrote:
Psu docs suggest retrofitting this should not require removing any diodes, but not whether I need to remove a fuse. There is the question of current limiting resistors I expect..?

No need to change anything. A single phase power pack should work if the RPSU has been built for centre tapped line lump. The RPSU documentation suggests not to fit the additional diodes and fuses needed for centre tapped operation to save a bit of money. If you've already built it for a PA20 then you can either add the new socket on the back - or, my preference, buy a new plug for your new 1A AC power pack and fit that to the lead. The benefit of the latter is that if the new PSU doesn't work then you can go back to the PA20.

The new 1A power pack should work - but since the RPSU now has to work on a single phase (two wire) input the rectification will only be half wave. That is, the smoothing caps are charged up 50 times a second and not 100. This means that the voltage across the smoothing caps will have a lower average voltage than before. This may cause problems but this will depend on the voltage output of the power pack. Most power packs are a little, er, inaccurately specified. So give it go, but if your SRE330 output hums, or the power pack itself gets too warm and buzzes, then go back to the PA20.

Tony
quarterturn
I just finished my build of the SRE330. I wasn't feeling the linear power supply route, so I tried a TPS5430-based dual-supply module off eBay. For my purposes it works great - I don't hear any intolerable noise in the audio. I bought a +/-12V model, so I had to do the following mods: R1 and R4 replace with 3322 0805 resistors, and R2 and R5 stack a 1003 0805 resistor. This changes the voltage divider so that the TPS5430's put out +/-15.1V, which is great as it gives me a tiny extra for voltage drop over cables and traces. Anyhow I can power the thing off a 19 or 20V laptop adapter, which are all over the place in my home.

I'm having a problem with the level meter which I am troubleshooting. Possibly there is no issue and my iPhone signal gen just does not put out enough voltage to light up "LO" (don't see how 400 mV is going to get past the reverse polarity diodes after the buffers). However I see 22R between the U11 comparator 15V pin 3 and other nearby chips Vcc, and that seems like a lot.
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