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Roland filters clones with LM 13700
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gdavis



Joined: Feb 27, 2013
Posts: 359
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PostPosted: Thu Jan 26, 2017 5:04 pm    Post subject: Reply with quote  Mark this post and the followings unread

alanwilder81 wrote:
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


Ya, I'd probably leave that out at first too. Blinky lights in the modular can be fun though Smile

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alanwilder81



Joined: Sep 03, 2016
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Location: italy

PostPosted: Fri Jan 27, 2017 3:22 am    Post subject: Reply with quote  Mark this post and the followings unread

gdavis...lol Smile
i also love LED s blinking ,especially in my ADSR s.
there s something about them. trouble is i havent got the components handy to do the upper part.
need to do another order. Laughing Laughing
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ringroad



Joined: Feb 28, 2012
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PostPosted: Fri Jan 27, 2017 12:58 pm    Post subject: level indicator Reply with quote  Mark this post and the followings unread

Definitely miss out the LED level detector for now; I need to update that part, was originally confused by the crossings out in the original schematic.

Even so the version of that I've got on my 703b clone doesn't seem particularly reliable - it gets stuck on green even when there's no signal passing through.
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alanwilder81



Joined: Sep 03, 2016
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PostPosted: Thu Feb 02, 2017 4:07 am    Post subject: Reply with quote  Mark this post and the followings unread

yes ringroad,
i'll definitely leave the led s out. By the way,on doing further researches on the 703 filter, i stumbled across the Yusynth redrawn of the old circuit. his take looks fairly similar to yours, and whats more, he also showed a cool 12 db oct variation of that, present on the Roland 700 system.
Also,in case you didnt know and were interested in , in that Yusynth page you can find all the schematics of the above Roland semi modular synth.
But i am pretty positive you know that all already Cool .

That said, when i have spare time i am going to breadboard the VCF and we can discuss about the outcome
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ringroad



Joined: Feb 28, 2012
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PostPosted: Thu Feb 02, 2017 6:37 am    Post subject: Reply with quote  Mark this post and the followings unread

yeah

Had a look at Yves' site before, the photos were very handy - cheers Yves Smile

The original Roland schematics on Florian Anwander's site suggest there were a couple of versions of the 703a, one with mylar 1.5nF caps in the core and LM301s as buffers, the other with 470pF polystyrene and CA3140s.

I spent a fair amount of time peering at photos of track layouts to try and make sure I've got the schematic and layout right (the Roland schematics for the VCA and the 703b have errors) - although I did stuff the LED bit, whups. Apart from that, it should just be the same as the original.

I've built a stripboard and PCB versions of the 703a, both seem to work ok. As you might expect it's a lot fizzier than the later 24db VCF.

Here's my clone of the 703a in acrylic, sliders and all

(Don't make a panel this big out of acrylic. Also don't use slide potentiometers)


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alanwilder81



Joined: Sep 03, 2016
Posts: 325
Location: italy

PostPosted: Sat Feb 04, 2017 8:28 am    Post subject: Reply with quote  Mark this post and the followings unread

hey ringroad,
i am glad you found Yves s work useful, like i did.
now, you said
""I spent a fair amount of time peering at photos of track layouts to try and make sure I've got the schematic and layout right (the Roland schematics for the VCA and the 703b have errors)""

Where are errors ? it's not clear whether you refer to Florian Anwander s old schematics or Yves s redrawn. any case, good to know Smile
What op amps and transistors did you employ for the 703 reissue?
now i learn there's even another different op amp type,the LM301 in a filter variation you mention. I wonder why not just use one type,both for the integrators and for the summing stages.Have you got any ideas?
i have the TL0xx serier, they say they should be fine.
thanks Smile
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ringroad



Joined: Feb 28, 2012
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PostPosted: Sat Feb 04, 2017 12:36 pm    Post subject: system 700 schematic corrections Reply with quote  Mark this post and the followings unread

Actually just looked again briefly at Yves' schematics, think they're correct now. fwiw, on the 706 LFO, D12 and C5 go to -15V (can't imagine you'd want to build that one, but... just in case).

Though possibly futile I've been trying to make clones as close as possible without sending myself mad, so I've used the same transistors (mostly 2SC945 and 2SA733), same track layout, same opamps - albeit DIP versions rather than cans.

I laid the board out for 301s on the VCFs, but I ended up using the CA3140, just because I had some to hand. I've got another 703a board built up ready for testing with the 301s - I can't imagine there will be much difference. The bigger mylar caps on the 703a might make a slight difference, maybe try experimenting to see which you prefer.

I imagine TL0xx will work, dunno how it change the sound - if you're going for "roland-y sounding" I can't imagine it'd matter.
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alanwilder81



Joined: Sep 03, 2016
Posts: 325
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PostPosted: Sat Feb 04, 2017 1:26 pm    Post subject: Reply with quote  Mark this post and the followings unread

thanks ringroad !

I second you on the approach of wanting to accurately reproduce the old circuitry. Howewer, I had a look at my italian seller catalog, and yes, he sells LM 3140 for 1.50 eur-dollars each. Shocked
just a bit cheaper it goes the pc 1458, but in my humble opinion, it's not worth spending that extra money to exactly recreate the original circuit.
That would be absurdely expensive, not to mention the trannies i cant get hold of.
sure, i am after that Roland sound so madly Cool Cool ,i hope i can get away with normal op amps and transistors.Time will tell.
Have you got more audio bits of your filter?
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ringroad



Joined: Feb 28, 2012
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PostPosted: Sun Feb 05, 2017 4:51 am    Post subject: Reply with quote  Mark this post and the followings unread

I wouldn't fret too much about the parts. There are some demos of both the filters on https://soundcloud.com/ringroad
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StephenGiles



Joined: Apr 17, 2006
Posts: 502
Location: England

PostPosted: Sun Feb 05, 2017 8:00 am    Post subject: Reply with quote  Mark this post and the followings unread

The filter does what it should and well! It would be interesting to my tired ears to hear a sample of it working on long decaying chords which I prefer.
Many thanks
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alanwilder81



Joined: Sep 03, 2016
Posts: 325
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PostPosted: Thu Feb 09, 2017 9:21 am    Post subject: Reply with quote  Mark this post and the followings unread

thanks ringroad Smile
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alanwilder81



Joined: Sep 03, 2016
Posts: 325
Location: italy

PostPosted: Fri Jul 14, 2017 4:53 pm    Post subject: Reply with quote  Mark this post and the followings unread

hello folks,

i am back to my DIY projects after taking some time off.
Today i put together the Roland 703 VCF in a breadboard, and a doubt arouse.

In the third integrator cell, circled in red in the below picture, the offset trimmer wiper is connected to the 3080 negative input through the 470 k resistor.

My question is : in the other three cells (the first, the second, and the fourth) the offset trimmer, trough 470 k resistors goes to the positive 3080 input instead. Why would the third cell be different ? Is there a schematics mistake? ( both the original Roland and Ringroad redrawing schem appear to show the same configuration).

Surprisingly , the Yves Usson take on redrawing the 703 VCF shows otherwise.
The third cell is just identical to the other three .

Any hints please? many thanks


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alanwilder81



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PostPosted: Fri Jul 14, 2017 5:00 pm    Post subject: Reply with quote  Mark this post and the followings unread

i am going to post the whole Ringroad schematics


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ringroad



Joined: Feb 28, 2012
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PostPosted: Fri Jul 14, 2017 11:58 pm    Post subject: Reply with quote  Mark this post and the followings unread

I think you're right; comparing the overlay against the traces suggests that the leg of the 470K is going to pin 3 - good spot.

I'll update the schematic.

Annoying cos I thought I'd been meticulous about getting these right, but clearly not enough... thanks for reporting it anyway!
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alanwilder81



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PostPosted: Sat Jul 15, 2017 12:54 am    Post subject: Reply with quote  Mark this post and the followings unread

thanks ringroad !

did you make a 703 vcf off the schematics you provided me? Does it work ?
What puzzles me the most , is whether or not there's a mistake in the original Roland 703 VCF schematics. You simply limited yourself to faithfully copy the original 1:1 .
And no one apparently pointed out any error in the original Roland schems, as far as i know.

I'll attach the Yves Usson redrawing that shows the 4 integrator cells being completely identical, as i expected them to be.
R22 ( 470 k, from the trimmer wiper), is connected to the positive input of the 3080 just like it happens on the other 3 cells.

Thanks for any ideas !


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ringroad



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PostPosted: Sat Jul 15, 2017 6:11 am    Post subject: Reply with quote  Mark this post and the followings unread

hah, I take it all back, I was right!

I was looking at the wrong part of the layout. The attached picture shows a part of the original component layout overlaid across a photo of an (original) 703e board.

I made a PCB, there's probably a picture upthread. It works fine, although it still doesn't have a panel (I've diverted into looking at the 100m for now).


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alanwilder81



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PostPosted: Sat Jul 15, 2017 7:10 am    Post subject: Reply with quote  Mark this post and the followings unread

thanks ringroad,
so you confirm it works.

At this point i am very confused.
Take into consideration the third cell.
In the Yves Usson's redrawing, the R22 goes to the positive input of the 3080, but both in the original and your redrawing, R22 is connected to the negative input of the 3080.

Somebody must be wrong here, no question.

Why is it so?


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ringroad



Joined: Feb 28, 2012
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PostPosted: Sat Jul 15, 2017 7:53 am    Post subject: Reply with quote  Mark this post and the followings unread

As far as I understand it, the trimmers are for zeroing out any DC offsets.

Like I say, I've compared the Roland schematic to a photo of the original Roland 703e board, and it matches that photo. I don't know why the Roland engineers chose to vary the configuration for the third cell.

It's easily possible that there are different versions of the 703e (as there are for the VCA) which have the trimmers in a different configuration, in which case Yves and I would both be right.

Does it matter? I'm guessing not, but I don't really know. Try and it and see!
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Blue Hell
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PostPosted: Sat Jul 15, 2017 8:05 am    Post subject: Reply with quote  Mark this post and the followings unread

I think it would not matter where you add the offset, as long as it can go both positive and negative.

The only change would be the rotational direction of the trimpot .. unless you exchange pos and neg there as well .. so probably it was changed to make the pcb layout a little easier.

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alanwilder81



Joined: Sep 03, 2016
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Location: italy

PostPosted: Sat Jul 15, 2017 9:06 am    Post subject: Reply with quote  Mark this post and the followings unread

thanks both Ringroad and Blue hell Smile

well, i am quite a greenhorn , I know next to nothing about OTA's functioning so i feared i could blow them if not correctly employed.

it's better to ask twice before powering the module up and possibly seeing hours and hours of labor and money go smoke

Plus i am trying to get grasp with these wonderful OTA filters and their topology, so this apparent discrepance between different drawings led me to find out more
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Cynosure
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PostPosted: Tue Oct 03, 2017 6:50 am    Post subject: Reply with quote  Mark this post and the followings unread

Here is an audio demo of the filter that I made. I plan to make it available in the new year, so I won't be posting the schematics anytime soon. PM me if you have any questions though, or hit me up in chat.

https://youtu.be/bCuhE78LPdo


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PHOBoS



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PostPosted: Tue Oct 03, 2017 9:59 am    Post subject: Reply with quote  Mark this post and the followings unread

it sounds great jake Very Happy
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Cynosure
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PostPosted: Tue Oct 03, 2017 3:05 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thanks Phobos Smile
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halfshavedyaks



Joined: Jul 12, 2018
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PostPosted: Thu Jul 12, 2018 9:18 am    Post subject: Reply with quote  Mark this post and the followings unread

I have recently built the FC State 700 and System X filters.

The State 700 has the rather odd behavior of having very low level until the resonance is turned up. With the resonance down the gain is about -12dB though with it above 75% and the frequency set somewhere useful then gain can approach unity, or even exceed it.

So I'm wondering:

Does the original Roland 700 multi state 12dB filter have the same behaviour?

Can anything be done to even out the level?

Does anyone else here have the FC State 700 and if so what is your experience of it?

Unfortunately I don't have the FC schematics.
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ringroad



Joined: Feb 28, 2012
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PostPosted: Thu Jul 12, 2018 1:51 pm    Post subject: Reply with quote  Mark this post and the followings unread

I had a bit of a faff with the resonance pot on my stripboard version of the 703a/b, but my own clone PCB version seemed to behave as you'd expect.

Though this is from memory - my clone isn't hooked up at the moment, desk is chaos at the moment due to a new toy. I had a quick flick through my test recordings but it didn't really prove anything.

If I get a chance over the weekend I'll hook it up and do a test. (Though it'd probably be better if someone with a State 700 piped up)

I guess the schematic would be very similar to the original, just with an LM13700 instead of the CA3080s. One side of the dual resonance pot has an effect on the level going in, fwiw.
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