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Schematic advice
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Uncle Krunkus
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PostPosted: Sat Jul 08, 2006 10:15 am    Post subject: Schematic advice Reply with quote  Mark this post and the followings unread

To anyone out there who knows more about electronics theory than me, (that's alot of people! Laughing )
Here is a link to the schem of a DS8 clone which is basically a DS7 plus a noise generator and a basic filter. The DS7 schem is at the same site if you want to compare the two.

http://m.bareille.free.fr/ds7clone/ds8.pdf

The noise generator Q1&2 goes through a basic filter U4 before being mixed into the signal being sent to the OTA (U1)
My questions are,
1. Could any noise source be connected to C9? ie what peak to peak noise signal could the mix/OTA section handle?
2. What does R36 do? The DS7 simply has R27 connected to pin1 of U3A. R36 is only in the DS8 version. Is it something to do with biasing? Can it be gotten rid of?
3.What if the whole circuit was put across 12V instead of the 5V regulator? I think maybe the LM324s might have to be upgraded, anything else to watch?

Any ideas anyone has would be greatly appreciated. Smile

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PostPosted: Sun Jul 09, 2006 2:08 am    Post subject: Reply with quote  Mark this post and the followings unread

As you may know, since it´s usually you helping me, i can´t guarrante for anything. Little knowlage *2, is that better or worse?
Anyway, i can´t see why this should not like 12v. At least all parts should have no problem with that.
About the first question: Look at the other DS7 thread. in the first post dnny describes a mod to get additional inputs for the vca. There you can connect your noise and filter or the london synphony orchestra.

BTW.: What do you think of having a white noise signal in the bus of the modular, like gate and stuff? Many modules can use a noise source, some with an fixed filter, others with adjustable filter, but in any case the same noise base-material
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zipzap



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PostPosted: Sun Jul 09, 2006 2:18 am    Post subject: Reply with quote  Mark this post and the followings unread

are you sure the numbering in question 2 is correct? I don´t get what you mean.
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Uncle Krunkus
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PostPosted: Sun Jul 09, 2006 2:22 am    Post subject: Reply with quote  Mark this post and the followings unread

Yeah, it's right. Make sure you're looking at the DS8 schem.
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PostPosted: Sun Jul 09, 2006 2:45 am    Post subject: Reply with quote  Mark this post and the followings unread

Now I see - the question - not the answer unfortunately.
Are you trying to get the ds8 onto the ds7 pcb?
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Uncle Krunkus
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PostPosted: Sun Jul 09, 2006 2:48 am    Post subject: Reply with quote  Mark this post and the followings unread

No, I'm trying to design a better version of the DS8.
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PostPosted: Sun Jul 09, 2006 3:04 am    Post subject: Reply with quote  Mark this post and the followings unread

No that sounds cool! Having never built the ds7, i was thinking about the same thing. My idea was tho build a drumbox with a selection of different instruments, maybe have a few things pachable.
In general we are dealing with a little synth here, so we know what to do.
For some voices, like cymbals it would be cool to have a ringmod (exor-metal) source and attack on the envelope. other voices like woodblocks could be very simple, like the cgs drum simulator http://www.cgs.synth.net/
Some Lofi-Sampler would be way cool to add some special flavour.
Then there could be another Envelope, lfo, distortion to be used where needed.
I´m looking forward to hear of the improvements you will find.
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PostPosted: Sun Jul 09, 2006 4:24 am    Post subject: Reply with quote  Mark this post and the followings unread

heya, before i knew the DS8 existed, i built the DS7 adding a noise source and a simple BPVCF to 'pitch' the noise which works supergood. an 'attenuverter' or whatever would be cool for the VCF sweep here i think.

as for external noise or whatever, i definitely would keep it in 5v p-p range

yeah r36 there provides the 2.5v bias from U3:A.. the 324s are fine on 12v you would probably have to change som stuff..

josh
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Uncle Krunkus
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PostPosted: Sun Jul 09, 2006 4:39 am    Post subject: Reply with quote  Mark this post and the followings unread

I'm still finishing my SoundLab, and I don't want to take on too much at this stage, but I'm thinking about modular stuff.
The idea is to build a 2*5 modular unit which is basically 1 DS8 drum voice. For the noise source I want to incorporate Ray Wilson's multi-flavoured noise source so you can dial up a colour of noise. For extra modules you wont need to add the noise source, so it will be multipled from module to module. Great idea about the XOR noise. I could easily include that so there is a 5th option.
Then, on each module, apart from the normal DS8 controls there will also be a simple parametric EQ which can control just the colour of the noise even further. Possibly switched so it can also EQ the entire drum. The random trigger and/or gate on Rays noise source could randomly close a 4066 switch to vary the tone/sweep/mix on one or a number of drums.
I'm hearing from the modular dudes that they don't like soldering flying leads to the front panel, so all the pots will be mounted on the stripboard.
And I'm following a bit of advice from Mosc about designing the front panel first and building the rest based on that.
So the idea is, you build one module, and you have a kick arse drum voice. If you want you can add extra, easier to build, additional modules as well, but you don't have to.
I've found a kit for a Midi to 8 velocity controlled triggers. This would be perfect to run it from what ever midi signal you like.
More ENV control would be nice, but I think I've already bitten off more than I can chew!! Laughing

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PostPosted: Sun Jul 09, 2006 6:30 am    Post subject: Reply with quote  Mark this post and the followings unread

Man that sounds cool! I also have some stuff to finish first, we all know that problem i guess, but a nice drumbox is a must-have.

Making it velocity sensing is super, which midi kit do you want to go for?
Good idea about the randomizing function.
A sine-osc with slight distortion is also important for many sounds.
Something i would like to include, see if i can manage, is a direct connection to the bus system of my old 16 channal modular mitec mixing board. Should be easy, i just fear noise problems.
Bring in as many signals as i want, not using any mixing channals, having access to all the aux and subgroup routing of the desk. If i have a drumbox i´ll want delays and reverbs and stuff on different voices.
So, enough dreaming future talk, current project is waiting....
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PostPosted: Sun Jul 09, 2006 2:26 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
I'm hearing from the modular dudes that they don't like soldering flying leads to the front panel


That's the goddam truth!

As to your schematic,i'd say it's very much suck and see.
Using a noise transistor is a very variable process,i put an opamp in to amplify the 2N2222 i used.It was weedy.I think you'll have breadboard the thing modularly,to get it all working to your satisfaction.
Thomas Henry swears by the 2N2712,a punk transistor as he calls it.It's a crap component but it spits out fiery noise.

Robert
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PostPosted: Sun Jul 09, 2006 6:37 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
Thomas Henry swears by the 2N2712,a punk transistor as he calls it.It's a crap component but it spits out fiery noise.

Robert


I hand picked a noise transistor for a snares circuit I was working on and after trying 4 or 5 transistors, I finally picked the one I liked. It is a very variable process and even two 2N2712's sounded different. They also had different signal levels. One of the 2N2712's sounded very "gritty" and another smooth as silk! It's all in the quality of the semiconductor and it's fabrication process. In my experience, I have concluded that imperfections and impurities in the semiconductor material silicon yield different electrical results when back biasing their junctions.

Bottom line is, use a transistor socket or solderless breadboard and try a bunch of your transistors in your stock draw! You may find that your 2N3904 or '06 sound the best Very Happy
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PostPosted: Sun Jul 09, 2006 6:56 pm    Post subject: Reply with quote  Mark this post and the followings unread

I've got heps of transistors, (some really old ones from the 60s and 70s) and plan on having a noise festival as part of the R&D for this project. I'll have to plan it for a day when Felicity & the girls are out. (of town hopefully! Laughing)
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PostPosted: Sun Jul 09, 2006 7:05 pm    Post subject: Reply with quote  Mark this post and the followings unread

Here's the front panel so far.
Any ideas, criticisms or praises are welcome. Cool


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PostPosted: Mon Jul 10, 2006 1:20 am    Post subject: Reply with quote  Mark this post and the followings unread

Looks organized. This should be very very flexible! The super drum.
Would be way cool if you could get the sens. pot to add some overdrive at high settings. What´s that gain/cut? a dual pot with axis in the axis?
For building a drumbox i would definitely include some instruments that are simpler, more spezialized.
EG for a bassdrum you propably won´t need the lfo, a cymbal should have an attack, a woodblock type of sound needs almost nothing. But that is only an opinion.
The thing about design is very interesting to me. I had situations where i had already finished the panel for several modules (i use 16*25 cm panels), had it partly filled when i decided that i need another pot somewhere.
Flying Wires! Man i wish i had a camera. My stuff looks kind of organic from the inside... Somehow i can´t keep things tidy. Maybe it has to do with that multiple module panel thing. Say i have a vcf, lfo, vclfo, 2*vca, mixer, all an separate boards. Then i design a 16*25 panel to house everything, try to make it ergonomic, logic and look cool. Drill the holes and stuff everything in.
BTW, it´s about the same thing with my drawers at home.
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PostPosted: Mon Jul 10, 2006 2:39 am    Post subject: Reply with quote  Mark this post and the followings unread

Gain/Cut controls whether you boost or cut the frequency set in the parametric. The Parametric EQ is the Frequency/Gain-Cut/Q controls. I know what you mean about specialised modules, but I'm just doing this one which will cover (almost) anything. I don't want to steer users towards pre-conceived ideas of what percusion sounds should be included in their arsenal. The idea is to provide enough flexibility so that you can create new sounds which don't fall into the standard categories like kick, snare, hi-hat, cymbal, etc. etc. BTW What do you mean about attack for a cymbal? I can't imagine a percusion sound with less attack than a cymbal. It has basically no attack at all. Unless you mean a reverse cymbal? In that case we've already left reality behind anyway hey? (which kind of ties in with what I just said!?)
The reason I want to do the panel first is so I won't be tempted to add things later. The projects I take on now have to be fairly well defined first otherwise I know they will lay around for years waiting to be completed. If I don't tie it down first it will end up being bigger than Ben Hur!! Laughing Anyone would of course be welcome to modify the idea if they want to though.

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PostPosted: Mon Jul 10, 2006 3:11 am    Post subject: Reply with quote  Mark this post and the followings unread

I understand. In fact you´re right, i was kind of thinking of the traditional instruments. I don´t know if that is because of listening practice and fashion, or because those snares and kicks work so well.
But creativity first! New sounds is whats great, and those knobs will definitely encourage to create.
I ´would include an attack for some reasons:
Effect sounds like reversed cymbals. Cymbals played with soft mallets - very slow attack, even in nature. Background waving noise floor, like a jazzdrummer brushing the snaredrum. Choice of slightly laid back, soft feel or on the beat, kicking feel.
But of course this feature will not be necessary for every instrument.
There is so much that could be included... How about a (random) trigger delay? Human feel.... I´m getting carried away.

ps: Nothing electric, but it was quite an experiance to me and some of the best drum sounds (with attack), so if you haven´t already done so, listen to Jack De Johnette on Keith Jarret trio: Alway let me go. (or almost any other one of them)
- Sorry for the OT
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PostPosted: Mon Jul 10, 2006 9:55 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
I'm hearing from the modular dudes that they don't like soldering flying leads to the front panel


Not this modular dude. I prefer the method myself. In fact, I use the pots to hold on the bracket, which contains the board(s). I make the bracket out of flashing material. Because I drill my own panels, I don't have to worry so much if a hole may be slightly out of kilter. Which happens.

Cheerio,
Scott


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PostPosted: Tue Jul 11, 2006 1:17 am    Post subject: Reply with quote  Mark this post and the followings unread

Well, that looks nice. Would you show us what it looks like from the inside?
As i said i got no camera, a friend took some pics of my sequencer, hase´t mailed them yet. Think i´ll post them in the sculpture post...
I drill myself as well, so i know exactly what you mean. Btw, i use 0,8 or 1mm aluminium, glued to 4-5mm wood. Very stable, light, very easy to drill and cut, even with fully assembled modules (add another led, etc).
But to keep things organised, well, there must be just some simple rules to follow. Probably just the opposite from what i am doing: Lots of small PCBs, pots and switches flying around in different (random) distance, 2 types of wire (red and white), pcbs not mounted, lying ontop of each other due to front panel layout. Yesterday i had to change a broken switch in the middle bottom of the 25*16 panel. Miracle i didn´t destroy everything else around.
I build all these sweet sounding little things, and then i can´t wait to have them "in the box". That´s the problem i guess.

Hey Uncle, just read the title of the thread. I kind of forgot.
Can´t give real advice but what interests me about the schematic is how you do that parametric eq. Is it a state variable fadeable in the feedback of an amp? Or is there another (simpler) way to get en para eq? If it is the SV how about a switch for lp-bp-hp?
I said i would include some drive, but the traditional way just to overdrive the mixing board or hook some drive pedal inbetween works super.
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PostPosted: Tue Jul 11, 2006 1:52 am    Post subject: Reply with quote  Mark this post and the followings unread

found a picture. just a smaal bit of the inside, but you can propably imagine...


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Uncle Krunkus
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PostPosted: Tue Jul 11, 2006 4:29 am    Post subject: Reply with quote  Mark this post and the followings unread

The real reason for putting a parametric in was mainly just for the noise. Now I like noise as much as the next electro-music head, but a parametric EQ lets you pull a thin band of frequencies to the front, or alternatively you could set it to cut with the Q turned down and you get the same kind of effect as a HP or a LP or a Notch. This kind of control over the noise would be really cool for a drum voice IMHO. Remember I'm trying to make this thing different to what you might already have in a modular like an SV filter.

The thing that's keeping me awake at night is thinking about the voltage. Confused Having the DS8 part running on 5V with an ad-hoc 1/2V derived from an op-amp won't fit with trying to mix in Ray's noise generator. (which apparently puts out up to 10Vp-p Shocked )
On top of that, the parametric will need to be built with dual supply amps like the TL074.
So I'm thinking I may need to do a complete re-build of the DS8 part using new amps (TL074?) and run it on +/-12V.
Anyone got any hints, tips, warnings etc??

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PostPosted: Tue Jul 11, 2006 5:03 am    Post subject: Reply with quote  Mark this post and the followings unread

What should happen with +-12v? Ok, You´ll have to use real instead of virtual ground, eg like with R25/R26. Some twiggeling there. But if i look at the schematic i see a vco, a lfo, an envelope and a vca.
I´m truly no opamp expert, but looking at the datasheet of the lm 324 it´s special feature seems to be that it can run rail to rail from single supply. Perfect for an battery powered unit. I´m sure the whole thing will run just perfect with 074s.
Hope some of our more experianced friends will correct me if i´m wrong!
About the eq, of course i know what it is, and filtered noise is a good idea. I was just wondering how you build a simple parametric eq. The way i know, you need one or many state variable filters, use the BP and add or substract that from the original. Quite a lot to do imo. Is there a more simple way?
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PostPosted: Tue Jul 11, 2006 5:05 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
cut with the Q turned down and you get the same kind of effect as a HP or a LP

Are you sure?
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PostPosted: Tue Jul 11, 2006 6:37 am    Post subject: Reply with quote  Mark this post and the followings unread

Yeah, a HP can easily be created by using a notch with low Q set to a low frequency. A HP is the opposite. Sure you get a bit of a bounce up on the other side of the trough but not anything to worry about. Especially as it is just noise we're carving.
The parametric circuit I want to try uses 3 op-amps. An input buffer, a bandpass filter, and the third one forms a gyrator, or variable inductor. I just found the schem. It's basic, and probably rough at this stage, but the theory behind it works.


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