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alanwilder81
Joined: Sep 03, 2016 Posts: 310 Location: italy
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alanwilder81
Joined: Sep 03, 2016 Posts: 310 Location: italy
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Posted: Mon Nov 21, 2016 10:46 am Post subject:
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do you own one of those filters? or ever ventured on building DIY Mutable Instruments filters? |
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L´Andratté
Joined: Sep 23, 2012 Posts: 150 Location: Hamburg, Germany
Audio files: 5
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alanwilder81
Joined: Sep 03, 2016 Posts: 310 Location: italy
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Posted: Mon Nov 21, 2016 12:30 pm Post subject:
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thanks !
nowadays the OTA 3080 seems as rare as the purple unicorn.Over priced as well. I wonder if it can be replaced happily with the lm13700.
There's a lot of debate on the net whether or not the latter can be up to the specs of the original 3080. Someone swears it is
The first link you got me had lots of 3080's. Which synth does it belong to ? |
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L´Andratté
Joined: Sep 23, 2012 Posts: 150 Location: Hamburg, Germany
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Posted: Mon Nov 21, 2016 1:55 pm Post subject:
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Polyfusion Modular, a legendary Moog offspring (I think) with some remarkable circuits.
3080/13700 are interchangable, the latter including diode bias and darlington buffer, which I both never use, there will be no problem that´s not esoteric
Edit: 13700 probably less noisy
Sorry Phobos, we´re hijacking your thread? |
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alanwilder81
Joined: Sep 03, 2016 Posts: 310 Location: italy
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Posted: Mon Nov 21, 2016 2:45 pm Post subject:
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l andratte
its my fault. I screwed up Phobos thread, i always go off topic with my questions.If you dont mind,we can keep this conversation as PM.
As for lm13700. They are readily available in italy, 1.50 euros-dollars each.
Not a big deal. Apparently the mutable instrument LPF alone calls for three of them. i cant quite figure out though, where the output and input are located. |
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Cynosure
Site Admin
Joined: Dec 11, 2010 Posts: 966 Location: Toronto, Ontario - Canada
Audio files: 82
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Posted: Mon Nov 21, 2016 7:02 pm Post subject:
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Great stuff Phobos!! (***Calls Roland's lawyers****)
Alan - I am actually working on a Roland filter clone right now, but I am tweaking it a bit to make it sound more to my taste. The classic Roland filter is actually very simple. It follows the same topology for most of the popular Roland synths (SYSTEM-100, JUPITER-8, SH-101, JUNO series). It is just four OTA integrators in a row. Start with the single low-pass filter example in the LM13700 datasheet and add four of them together. Then add expo control to the CV control and a feedback loop for resonance. I will share mine when I get time to finish it, but I am working slow and doing a lot of tweaks. _________________ JacobWatters.com |
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alanwilder81
Joined: Sep 03, 2016 Posts: 310 Location: italy
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Posted: Tue Nov 22, 2016 2:29 am Post subject:
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thanks Cynosure !
you shed some light on the topology ! I've always wondered what all the big classic Roland synths shared in common, sound wise. And now it's starting to become obvious.
Their original schematics are far too confusing to an untrained man like me,so that's why i turned to this thread to get some knowledgeable chap to advice me
Is there any way to get the schematics you re working on?
i'm not looking for bells and whistles, bit just for a basic solid roland tone for my DIY synth
im really curious to hear you filter then, when your done tweaking it.roland forever !
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alanwilder81
Joined: Sep 03, 2016 Posts: 310 Location: italy
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alanwilder81
Joined: Sep 03, 2016 Posts: 310 Location: italy
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PHOBoS
Joined: Jan 14, 2010 Posts: 5591 Location: Moon Base
Audio files: 705
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Posted: Tue Nov 22, 2016 8:57 am Post subject:
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Skrog Productions wrote: | Looks great , love the logo | Thanks for comming up with it in the chat.
alanwilder81 wrote: | phobos,
i truly like that ADSR module ! Roland FTW !
i've been a Roland sound fan forever, in particular of the Jupiter 4 and Promars raw filter.
Do you have any Roland filter schematics,be it clone or modification of the original? i've been on the hunt for long, but internet offers 70's schematics which are confusing at best and use obsolete components
I'd be happy with modern schematics of some sort ! | Thanks! And no, I don't have any other Roland schematics. I actually have no idea how the filters sound, I am not really familiar with any commercially
availlable synths. Well I have heard a moog and probably some other stuff, but never played with any myself and would probably not recognize
anything by sound alone.
I was going to mention to wait untill it is 8:08pm, stand in front of a mirror and say 3'O three times to summon the Roland guy but I see he has
already arrived in this thread
L´Andratté wrote: | Sorry Phobos, we´re hijacking your thread? |
how about I use my superpowers to split this thread and make a new dedicated Roland circuits thread ? It might attracked some more people as well.
Cynosure wrote: | Great stuff Phobos!! (***Calls Roland's lawyers****) | _________________ "My perf, it's full of holes!"
http://phobos.000space.com/
SoundCloud BandCamp MixCloud Stickney Synthyards Captain Collider Twitch YouTube |
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alanwilder81
Joined: Sep 03, 2016 Posts: 310 Location: italy
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Posted: Tue Nov 22, 2016 9:25 am Post subject:
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Phobos
the Roland sound is not easy to describe as with any other synth,but it sounds very different to the classic American synths, to put it mildly.
To my ears, much sweeter, more mellow, melancholic,at times.
Fantastic Juno and Jupiter 8 pads but also the Jupiter 4 industrial -like sound.
Check out the early Human League stuff 1979 1980.
That s the sound that made me fell in love with analog synthesizers and my ultimate dream is to reproduce that eerie dark ambient atmosphere with the character of an old-school Roland filter. |
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alanwilder81
Joined: Sep 03, 2016 Posts: 310 Location: italy
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Posted: Tue Nov 22, 2016 9:43 am Post subject:
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Phobos,
i opened a new thread about Roland stuff.Sorry for taking your discussion off-topic lol |
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PHOBoS
Joined: Jan 14, 2010 Posts: 5591 Location: Moon Base
Audio files: 705
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Posted: Mon Jan 23, 2017 2:42 pm Post subject:
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Finished an ARP 4072 VCF (Yusynth design) with the PCB's I got for christmas from AlanP, Thanks Alan!
I did add an extra PCB for pots and jacks to change the spacing and to have the controls on the left and connectors on the right, which
gives me a bit more finger room when placing it besides other modules that also have the knobs and connectors in the same position.
I did a quick test, mostly to calibrate it, and it sounds nice. I might replace the knobs later whenever I order some.
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_________________ "My perf, it's full of holes!"
http://phobos.000space.com/
SoundCloud BandCamp MixCloud Stickney Synthyards Captain Collider Twitch YouTube |
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alanwilder81
Joined: Sep 03, 2016 Posts: 310 Location: italy
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Posted: Mon Jan 23, 2017 4:33 pm Post subject:
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excellent as usual, phobos
i've built one too, and it sounds freaking amazing.I am currently running the Thomas Henry 555 VCO through the ARP filter.
The PWM on that VCO in particular amazes me. Dark, metallic, brassy if you like, very early 80's tone.
I wonder what's the major contribute to the tone i got.
The VCO itself or the ARP filter?
a winning combination, anyway |
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alanwilder81
Joined: Sep 03, 2016 Posts: 310 Location: italy
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Posted: Mon Jan 23, 2017 4:37 pm Post subject:
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i am going to add the dual ganged pot soon, as a cure for the signal bleed through that many people seem to get. in my case is hardly noticeable though. It's a hell of a filter. hats off to Yves Usson who delivered us such gem |
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AlanP
Joined: Mar 11, 2014 Posts: 746 Location: New Zealand
Audio files: 41
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Posted: Mon Jan 23, 2017 9:17 pm Post subject:
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Heh, it always makes me laugh when I see this. I go to all this effort to avoid doing wiring, and what do people do?
Very nice job, Phobos! |
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PHOBoS
Joined: Jan 14, 2010 Posts: 5591 Location: Moon Base
Audio files: 705
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Posted: Thu Oct 05, 2017 10:29 am Post subject:
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it is nice to not have to any wiring but the spacing just didn't really work for me. Thanks again for the PCB for it, It's a really nice filter.
I haven't really tested the moog filter yet other than a quick test and some calibration as I need some knobs for it and a bigger case.
Besides the ARP VCF I have built some more modules and most recently finished a Mutable Instruments Braids:
more info about that here
I also have PCBs and parts for a MI Clouds, Rings and a PCB for Elements (thanks again Alan) and with all that I definitely need a bigger
case. A bigger problem is actually space for a case or casespace™. I managed to reorganise my scraprack a bit and made a new one that
can fit in it with 2 84HP rows:
It also needs a new power supply which I am currently designing so more about that next. _________________ "My perf, it's full of holes!"
http://phobos.000space.com/
SoundCloud BandCamp MixCloud Stickney Synthyards Captain Collider Twitch YouTube |
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PHOBoS
Joined: Jan 14, 2010 Posts: 5591 Location: Moon Base
Audio files: 705
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Posted: Fri Oct 06, 2017 2:03 am Post subject:
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For the powersupply I have been looking at some cheap switched mode power supplies on ebay. Because they would need
some extra regulation the output voltage has to be at least 15V which is too bad as the 12V is much more common and also
cheaper. I did find a 15V 3.5A version but I was curious how much a toroidal transformer would set me back. I couldn't
find many at first besides Conrad and it wasn't even that expensive. After doing some more searching I finally located a 50VA
for a lower price than the switched mode supplies, the current is lower too of course. Eventually I settled on a 120VA, not that
I need that much current at the moment but I'd rather get something with a bit more juice now than having to built yet another
supply at a later stage.
Of course I'd need some regulators that can handle the power for which a standard LM317/LM337 isn't sufficient. After looking around
a bit I found the LT1083 which can handle 7.5A. However the negative counterpart (LT1033 with only 3A) is obsolete. But as I know
now you can make a bipolar supply with 2 positive regulators for which I started a thread here.
So ideally with 120VA I could get 2x5A which is way more than I need but let's design the PSU for it anyway to be on the safe side.
Usually I just add some caps that I think should be sufficient but this time I am calculating the minimum values. I found some equations
and used the example from here.
Quote: | The key point is that C1 must be big enough so that its voltage doesn't sag below the sum of the supply's output voltage plus the regulator's dropout voltage. C1 gets a pulse of current from the rectifier twice per 50Hz cycle, i.e. every 10msec. It charges to a peak determined by the transformer secondary voltage minus some IR drop and the forward drop of either one or two rectifier diodes. For the next 9msec or so, it is discharged by the load current on the supply. Charge is Q=C×ΔV= i×Δt. Rearranging gives C=i×Δt/ΔV.
You know I (supply load current) and Δt (about 9msec at 50Hz), so if you know ΔV (how much C1 can sag) you can solve for C.
Guessing that the dropout voltage of your reg is about 2V, and you want 7.5V out, that means that the minimum input voltage to the reg is 9.5V. If you start with a 12Vrms tranny, the capacitor will charge to 1.4*12-2V (peak is 1.414×rms, 2V drop in two diodes)= 15V. ΔV=15-9.5=5.5
Finally, C=2×0.009/5.5 = 0.0033 FARADs!!! = 3300uF |
The supply voltage is already the same although the voltage drop over the diodes (SB560) is lower but let's use the 2V anyway.
To calculate ΔV I need the dropout voltage and according to the datasheet for the LT1083 it is about 1.4V @5A. The mimimum
input voltage to the regulator is 12V + 1.4V = 13.4V, so ΔV is 15V - 13.4V = 1.6V.
C = 5×0.009/1.6 = 28125uF. So for <5A 6 capacitors of 4700uF (28200uF) should be sufficient.
At the moment I am looking into snubber networks. _________________ "My perf, it's full of holes!"
http://phobos.000space.com/
SoundCloud BandCamp MixCloud Stickney Synthyards Captain Collider Twitch YouTube |
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PHOBoS
Joined: Jan 14, 2010 Posts: 5591 Location: Moon Base
Audio files: 705
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wmonk
Joined: Sep 15, 2008 Posts: 528 Location: Enschede, the Netherlands
Audio files: 15
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Posted: Sat Oct 07, 2017 8:03 am Post subject:
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Where did you get the transformer? Mine wasnt cheap
For the bipolar supply I used a LM723 based design, opamp for the negative part and a bunch of power transistors to handle the current. For the capacitors I used Panasonic 105 degC, 35V. Not sure where I got them from, maybe eoo-bv.nl? Otherwise probably Farnell or TME. _________________ Weblog! |
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PHOBoS
Joined: Jan 14, 2010 Posts: 5591 Location: Moon Base
Audio files: 705
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Posted: Sat Oct 07, 2017 8:24 am Post subject:
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Toroidal transformer from here.
Personally delivered as the guy from the store happened to be in the neighbourhood They also send me a photo of it beforehand when I
asked about any mounting hardware.
regulator + power tors is indeed an option but the LT1083 seems like an easier and smaller option. I am also not sure how well transistors
would be protected against possible shorts they usually don't like it. I guess you could add some protection though.
I'll be getting the Samxon caps from eoo-bv.nl. Haven't checked Farnell or TME. I did find some nice rubycons at mouser but they use Fedex
for which I have to stay at home which is not an option. _________________ "My perf, it's full of holes!"
http://phobos.000space.com/
SoundCloud BandCamp MixCloud Stickney Synthyards Captain Collider Twitch YouTube |
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piedwagtail
Joined: Apr 15, 2006 Posts: 297 Location: shoreditch
Audio files: 3
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Posted: Sat Oct 07, 2017 1:51 pm Post subject:
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Big toroidals have a nasty in rush current; that could be an issue.
Quote: | When a transformer is first energized, a transient current up to 10 to 15 times larger than the rated transformer current can flow for several cycles. Toroidal transformers, using less copper for the same power handling, can have up to 60 times inrush to running current. Worst case inrush happens when the primary winding is connected at an instant around the zero-crossing of the primary voltage, (which for a pure inductance would be the current maximum in the AC cycle) and if the polarity of the voltage half cycle has the same polarity as the remanence in the iron core has. |
R |
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PHOBoS
Joined: Jan 14, 2010 Posts: 5591 Location: Moon Base
Audio files: 705
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Posted: Sun Oct 08, 2017 4:04 am Post subject:
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Yes, you are correct about the inrush current although I expect it won't be too bad with this supply but I could add a softstart circuit.
I am thinking a simple transformerless supply which powers a 555 timer that turns on a relay after a short time. The relay will
short out a low value (high power) resistor in series with the mains input of the transformer. Maybe powering it from the secondary
of the transformer would work too as it is pretty low current. But the advantage of a seperate (transformerless) supply would be that
it could be built on a small board which can simply be put in series with the transformer.
A simple thermistor might be enough too though. _________________ "My perf, it's full of holes!"
http://phobos.000space.com/
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PHOBoS
Joined: Jan 14, 2010 Posts: 5591 Location: Moon Base
Audio files: 705
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Posted: Thu Oct 12, 2017 1:36 pm Post subject:
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After reading up a bit more about it I am pretty sure I wouldn't need to limit the inrush current. It wouldn't hurt though and
I do switch it on together with some other gear so it might not be a bad idea to do it anyway. While searching on how to
calculate the correct capacitor I came across this design which happened to be designed for the voltage and current I need.
I also really like how the zenerdiodes are incorporated into the bridge rectifier, something I would have never thought of.
The way the 555 is setup is something I came across when looking for some softstart example ciruits, I might have done it
different otherwise.
I drew up 2 versions:
The first one uses a relay with an SPST switch which is what I currently have in my possesion.
The second version uses a relay with an DPDT switch whch would be better since it indicates
if the relay itself is actually working, instead of just showing the output state of the 555.
I did test the circuit and it works fine.
----
I found some nice Nichicon caps at TME that I will probably order. They're a bit more expensive than the Samxon KM
caps but the specs are much better. I also might have underestimated the current through the diodes/bridge rectifier a bit.
Using this circuit simulation it seems that the peak current for a 5A output with 22800uF in caps can go up to about 45A.
If I understand the datasheets correct this isn't really a problem though as the peak current rating is much higher than
the average current rating. I did a bit of a mock-up to test how I am going to actually built and position everything and
from that decided that I will go for some big square bridge rectifiers. Since there is hardly any difference in price
between different ratings (and I couldn't find any other major differences between them) I will probably get some
that are suitable for 35A/100V.
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_________________ "My perf, it's full of holes!"
http://phobos.000space.com/
SoundCloud BandCamp MixCloud Stickney Synthyards Captain Collider Twitch YouTube |
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