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Roland filters clones with LM 13700
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alanwilder81



Joined: Sep 03, 2016
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PostPosted: Thu Dec 15, 2016 5:02 am    Post subject: Reply with quote  Mark this post and the followings unread

to cynosure
as soon as you re done with that filter,id really love to hear a demo of it !
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alanwilder81



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PostPosted: Thu Dec 15, 2016 5:10 am    Post subject: Reply with quote  Mark this post and the followings unread

thanks cynosure !
for the sake of clarity and completeness, could you also show me the complete schematic for your filter?
i am not quite good at extrapolating single parts from schematics and then putting them together Embarassed Embarassed
i kinda guess what you mean regarding the Juno 60 section res and the Thomas Henry diagram, but dont want to risk to f**k it up after i purchase a costly LM 13700 lot Smile
so, any help will be much appreciated !
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ringroad



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PostPosted: Fri Dec 16, 2016 12:44 am    Post subject: Reply with quote  Mark this post and the followings unread

My filter is basically the 703e from here : http://fa.utfs.org/diy/roland700/703e_a3.jpg

My redrawing (with some notes) - you'd have to sub in the LM13700s, should be easy enough from looking at the pin mapping in the datasheets:


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alanwilder81



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PostPosted: Fri Dec 16, 2016 1:47 pm    Post subject: Reply with quote  Mark this post and the followings unread

excellent ringroad.

i really dig the sound of your filter! i will attempt to build it ! thanks Smile
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Cynosure
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PostPosted: Fri Dec 16, 2016 7:14 pm    Post subject: Reply with quote  Mark this post and the followings unread

alanwilder81 wrote:
thanks cynosure !
for the sake of clarity and completeness, could you also show me the complete schematic for your filter?

I will share the schematic eventually, but it will take a while. I want to look into making PCB's and maybe sell them. I will release the schematic once that happens.

With regards to the 703 and ringroad's design - those opamp buffers aren't required if you use an LM13700. They have a builtin transistor buffer that you can use. That is why I recommended starting from the single pole LPF in the LM13700 datasheet.

Also, LM13700 aren't that pricey. They are a bit more than opamps and CMOS chips, but less than a lot of other stuff.

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Ayab



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PostPosted: Sat Dec 17, 2016 10:55 am    Post subject: Reply with quote  Mark this post and the followings unread

I certainly remember looking at some detail about cloning Roland System 700 and 100 filters on

www.ua726.co.uk

And pcb and stripboard versions - but has been taken down now. Maybe post a comment on the blog and ask for details.
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ringroad



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PostPosted: Sat Dec 17, 2016 12:26 pm    Post subject: Reply with quote  Mark this post and the followings unread

For the masochists out there all the stripboard layouts should still be up there - I did a load of the System 100 bits (including the diode VCF), and there's a layout for the 702a/b/c state variable filter, the fizzy 12db one.

I've done (for personal use) PCBs of some of the System 700 stuff and mentioned any corrections to the schematics in the posts too, if that helps at all.
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wackelpeter



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PostPosted: Sat Dec 17, 2016 12:40 pm    Post subject: Reply with quote  Mark this post and the followings unread

Cynosure wrote:


Also, LM13700 aren't that pricey. They are a bit more than opamps and CMOS chips, but less than a lot of other stuff.


I'm not really sure but i've seen them going up in price a bit since i started doing DIY stuff here time ago.
I don't know if this could be an indicator that they, at least the DIP version, also will be coming obsolete soon or if these are just normal or temporal price changes...

No matter i use them in all builds with CA3080 as an substitute even if i only need just on section of them... Only some CA3080 like in the TZVCO, the one which uses the W.Jung trick, can't be substituted with an LM13700.

@ringroad ...so i must be a very obsessive masochistic person... Smile
I've never made or build a proper PCB... all my cases are stuffed with stripboards and some of them i can tell, where literally a real torture to debug and fix all my errors...

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ringroad



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PostPosted: Sat Dec 17, 2016 12:44 pm    Post subject: masochism Reply with quote  Mark this post and the followings unread

wackelpeter wrote:

@ringroad ...so i must be a very obsessive masochistic person... Smile
I've never made or build a proper PCB... all my cases are stuffed with stripboards and some of them i can tell, where literally a real torture to debug and fix all my errors...


Hats off, there is definitely a buzz to be had in doing your own layout and getting the thing working. It definitely improved my debugging skills, and I wasn't reliant on waiting for PCBs to wing their way across the seas.
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wackelpeter



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PostPosted: Sat Dec 17, 2016 1:00 pm    Post subject: Reply with quote  Mark this post and the followings unread

Better keep the hat on, it's very cold outside... Very Happy

I'm sure it's harder to make your own layout for a PCB and get that correctly as soon as it's etched there's mostly not much possibilities to fix any errors made before... That's the only good thing with stripboard, you can desolder things and move them around the board or cut/add traces afterwards easily and mostly have enough space left for possible mods, additional IC's and everything you need to get the circuit working for your desired needs...
...and i don't do any layouts before i solder for my stripboards, just look at the schematic how much space i could need for the surrounding parts on each IC how to connect them, maybe add a bit of space as reserve and then go on and solder my way through the schematics...

Cheers Bastian

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Ayab



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PostPosted: Sat Dec 17, 2016 5:24 pm    Post subject: Reply with quote  Mark this post and the followings unread

the ua76 blog certainly had some detail about the process the author went through cloning the pcb for the 700 filter that wilder81 might find interesting - it is not on the blog anymore.
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alanwilder81



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PostPosted: Sat Jan 21, 2017 12:49 pm    Post subject: Reply with quote  Mark this post and the followings unread

hello guys,

i am very confused about the below shruti VCF circuit. Reading through the analysis i seem to understand it both offers VCF and VCA.
here's the link to the original schematic,in case the image quality of what i pasted wasn't good enough.

http://mutable-instruments.net/static/schematics/Shruthi-Analog-SMR4-mkII-v01.pdf

clear, it's a 4 integrator cells in a row with a feedback loop.
However,it's not clear where the VCA is located. i'd rather leave it out , only to use the the filter part.
And, how are the I-RESO and I-GAIN points supposed to be connected? ( marked in red)
what about the JP1, JP2, JP3, JP4 ,J2 and the inputs row on the left do ? (all marked in green)

understanding this it's a bit over my head, so any help would be welcomed !
thanks Smile Smile


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gdavis



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PostPosted: Sat Jan 21, 2017 4:13 pm    Post subject: Reply with quote  Mark this post and the followings unread

alanwilder81 wrote:

However,it's not clear where the VCA is located. i'd rather leave it out , only to use the the filter part.

It's the circuit in the lower right. You may want to replace it with an output buffer of some sort.

Quote:
And, how are the I-RESO and I-GAIN points supposed to be connected? ( marked in red)

Nets with the same name should be connected together. They just use labels to avoid running lines across half the page which can be hard to read.

Quote:
what about the JP1, JP2, JP3, JP4 ,J2 and the inputs row on the left do ? (all marked in green)

JP1 looks like a second audio input to the VCA. The value for the resistor connected to it (R10) is "DNP" which I can only guess means "Do Not Place". I don't see it on the board so I suspect it's not used.

JP2 and JP4 also aren't used but look like they could optionally be used to tap high pass and band pass outputs from the filter.

JP3 is a jumper to select between 2-pole and 4-pole filter outputs.

J2 is the external audio input that allows the filter to process other signals.

The row of inputs on the left are your CV inputs for controlling the VCF and VCA as well as the oscillator input to the filter. In the Shruthi, this connected to the controller board (which has it's own schematic).

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wackelpeter



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PostPosted: Sat Jan 21, 2017 4:21 pm    Post subject: Reply with quote  Mark this post and the followings unread

I'm not sure if you really want to include this into your modular Setup, as to me it Looks as it's adapted for +/-5V operation.

The VCA is in the lower right Corner.

I-Reso connects to IC3OTA1 pin1 and I-Gain isn't needed if you wantto ommit the VCA...

Have a look at one of the original Roland VCF's System 100, SH101 etc. as they share mainly the same structure mainly with different OTA's and buffers behind them, but otherwise mostly identical...

edit: there was someone faster and more precise as can be seen Smile

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gdavis



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PostPosted: Sat Jan 21, 2017 4:46 pm    Post subject: Reply with quote  Mark this post and the followings unread

Good point about the power supply though. To replace the 5V supply with 12 or 15 it looks like you'd just need to adjust the CV input circuits to keep the bias currents in the right range and maybe the audio levels if they're not loud enough.

BTW, you're not going to save much by leaving the VCA out. The OTA and opamp are going to be there anyway, may as well use them.

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alanwilder81



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PostPosted: Sun Jan 22, 2017 3:50 am    Post subject: Reply with quote  Mark this post and the followings unread

thanks gdavis and wackelpeter Smile , you clarified a lot the whole matter.

i'd like to include this in my setup because it sounds Roland-ish.
Have you ever tried it or built it ?
Does it looks like it s designed to work with +-5 V ? do you see it as a drawback ?
as for the VCA, i wanted to leave it out mostly for the sake of simplifying the circuit rather than merely saving costs.
all in all, as wackelpeter suggested,i might have a look at the original Roland VCF's System 100 or SH101. Sure they share a similar topology.
And they do have the sound im after.However i am tempted to give this ambika clone a go because it uses modern components Cool

damn, i am really confused
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wackelpeter



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PostPosted: Sun Jan 22, 2017 4:18 am    Post subject: Reply with quote  Mark this post and the followings unread

Most of all the old Roland VCF's can be found here including mostly schematics and some simple notes:

http://fa.utfs.org/diy/roland_filters/

As for what the +/-5V Operation goes, you may have to adjust a few things to have them interact with the Signals in your modular Setup which usually handles higher outputs as gdavis already pointed out.

There's also an Adaption of the old System 100 VCF by frequency central around and also the Adaption from the System 700 VCF shown above seems as it's worth a tryout.

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alanwilder81



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PostPosted: Sun Jan 22, 2017 4:50 am    Post subject: Reply with quote  Mark this post and the followings unread

thans wackelpeter,
i've known that nice roland pace for long. trouble is,those old schems are confusing to me at best,they use obsolete components, so thats the reason why i turned to a modern roland filter clone. supposedly clearer schems and easy to come by components Smile
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alanwilder81



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PostPosted: Thu Jan 26, 2017 9:16 am    Post subject: Reply with quote  Mark this post and the followings unread

hey guys !

i came back to this project today, and i've been weighing the idea of building that. A doubt arose when you asked me if i was sure to include this in my modular. Are there drawbacks? were you referring to the filter working with a 5 V supply instead of a regular 12 or 15 V ?

so, once i get the voltage supply regulated, would i have to lower the input raw signal level? and same for the CV modulation? Smile Smile

if you think that it's all it takes for the filter to wor, then i might breadboard one and see how it sounds.

I a desperately trying to get an alternative sound to the beefie ARP, Moog and Oberheim filters i have built already.
And Roland OTA s -like topology may get to the ballpark

cheers all
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gdavis



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PostPosted: Thu Jan 26, 2017 12:56 pm    Post subject: Reply with quote  Mark this post and the followings unread

According to the manual, the Shruthi is designed to work with an unregulated supply (e.g. wall wart or battery) anywhere from 7.5V to 9.0V. The upper left of the VCF schematic shows the +/-5V supply generation from the unregulated input.

This may work up to 15V but it's inefficient and might overheat depending on how much power this thing actually consumes and the ratings of the converter and regulators (actually, the max input of the converter is rated at 15V so that would be pushing it).

You could certainly bread board it as-is with a 9V supply or battery (or leave out the upper left part if you already have a regulated +/-5V supply) and feed it some 0-5V CV's to see how it sounds. Making it suitable for a modular system with different voltages would take a little engineering but is doable.

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alanwilder81



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PostPosted: Thu Jan 26, 2017 2:13 pm    Post subject: Reply with quote  Mark this post and the followings unread

thanks gdavis, Smile
clear explanation.That design looks promising but it may be a bit if an hassle and difficult for me to modify it, in order for it to fit my modular, so more realistically i come up with a new idea.
Ringroad ,some time ago nicely provided me with his own re drawing of the Roland 703 filter.
if my attached picture is not clear enough, here's the link to the drawing

http://electro-music.com/forum/phpbb-files/703e_schematic_001_232.pdf

It's got a nice sound, very early Roland vibe.
it apparently doesn t take any modding , besides subbing in a LM13700 in place of the 3080.
My question is if i can also replace the obsolete CA 3140 with, say, TL071 or 081. Is the CA 3140 doing the buffer in that design, after the OTA ?
i hope any general op amp can do the job,if so.

i seem to recognize the classic OTA s row, 4 of them to form 4 poles, with a resonance feedback loop.
it would be amazing if cold get away with it Smile


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gdavis



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PostPosted: Thu Jan 26, 2017 2:54 pm    Post subject: Reply with quote  Mark this post and the followings unread

Ya, I think most general opamps should be fine. I would use a quad opamp to reduce part count.

The output of the OTA is a current. The opamp with cap in the feedback loop acts as an integrator, converting the current into a voltage.

If you think of each stage as an RC low pass filter, the OTA is the R and the opamp + cap is the C. The current going into the Ibias input of the OTA is essentially varying the R which is what changes the cuttoff frequency of the filter (f=1/2piRC).

If you wanted to tackle the Shruthi filter I could walk you through the changes. No guarantees since I don't have the actual circuit here to test it Wink, but it shouldn't be too difficult, would just take some patience.

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alanwilder81



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PostPosted: Thu Jan 26, 2017 3:17 pm    Post subject: Reply with quote  Mark this post and the followings unread

thanks gdavis for clear explanation, once again, and for your willingness to help me out with modifying the previous project. Smile
I think i am going to breadboard the 703 Roland now. It looks feasible.And it has that old school sound we all know and love. Cool Cool
as for the components,sure i better go for a quad op amp, like a TL074, to cut down costs and space.
i noticed a pc 1458 op-amp, in the lower section, and wonder why they used two different op amp, both pc 1458 and CA 3140, instead of just one type.
Yet neither of them are specialized op amps.
Also,PNP and NPN trannies are respectively 2SA733 Q and 2SC945 Q, obsolete, and i hope te be able to replace them with garden variety BC 557 and BC 547. Wink

what do you think?
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gdavis



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PostPosted: Thu Jan 26, 2017 3:41 pm    Post subject: Reply with quote  Mark this post and the followings unread

I can't see any reason for using the different opamps, I wouldn't worry about it.

From a quick glance, the tranny subs should be fine. I think the A variety would be the closest match.

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alanwilder81



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PostPosted: Thu Jan 26, 2017 4:05 pm    Post subject: Reply with quote  Mark this post and the followings unread

excellent gdavis Smile

i can add now a new weapon to my arsenal. As soon as its breadboarded i will tell you the results. however i want to completely leave out the upper LED section if it doesnt harm Very Happy Very Happy
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