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 Forum index » DIY Hardware and Software » Ken Stone designs - CGS
Wavetable?
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zthee



Joined: Feb 20, 2008
Posts: 413
Location: Stockholm

PostPosted: Mon Jul 07, 2008 3:17 am    Post subject: Wavetable?
Subject description: A few questions...
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Posted Image, might have been reduced in size. Click Image to view fullscreen.

I've just finished a wavetable module after the schematics on the CGS site. As you can see I've breadboarded it.. It all works! ..sort of.. Confused

Posted Image, might have been reduced in size. Click Image to view fullscreen.

Above is the output of the module. I think this should be a sine-wave. Apparently it isn't.

The CGS page for reference.

My first thought was that it's a problem with the counters. But I've checked all the connections twice, and they all go to the correct place (except pin 10 on the 4024 - that's a N.C. and should be pin 9 instead..)

So the counters seems to work fine.

I had my friend burn me 2 eproms (One 2716 and one 2732) - and both gives the same result.

The output form the eprom to the DAC looks like this:

Posted Image, might have been reduced in size. Click Image to view fullscreen.
(It's pin 9 of the 2716, but generaly all the output pins look the same).
It's a pulse wave - I've only zoomed in on the bottom part, to show the small irregularities - thinking that they might generate a problem? It should be a normal squarewave?

To me - it feels like it's either the DAC or the eprom?

What kind of output should I be seeing from pin 4 and 2 of the DAC?

And is there anyone that has a working eprom to spare?

Thanks! Smile
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andrewF



Joined: Dec 29, 2006
Posts: 1174
Location: australia
Audio files: 4

PostPosted: Mon Jul 07, 2008 6:59 am    Post subject: Reply with quote  Mark this post and the followings unread

The wavetable needs a high freq wave on the input, I usually plug in a tri or saw from a vco, and crank it up - much much higher than you would normally set your vco.

Some VCOs can't go high enough (Paia for example).

Where did you get the ROM data?
Some of Ken's chips contain unusual waveforms, so don't expect to see sine or tri waves.
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zthee



Joined: Feb 20, 2008
Posts: 413
Location: Stockholm

PostPosted: Mon Jul 07, 2008 7:03 am    Post subject: Reply with quote  Mark this post and the followings unread

I've used a TH XR2206 as the controling VCO.

I got the .BIN from here -> http://home.freeuk.net/lowpass/VCDO.html

Here's some picture of the waveformes:

Posted Image, might have been reduced in size. Click Image to view fullscreen.
Posted Image, might have been reduced in size. Click Image to view fullscreen.
Posted Image, might have been reduced in size. Click Image to view fullscreen.
Posted Image, might have been reduced in size. Click Image to view fullscreen.
Posted Image, might have been reduced in size. Click Image to view fullscreen.

Edit: Did the CGS wavetable module have it's own .bin file? I just assumed it was the same as the VCDO..
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fluxmonkey



Joined: Jun 24, 2005
Posts: 696
Location: cleve

PostPosted: Mon Jul 07, 2008 6:43 pm    Post subject: Reply with quote  Mark this post and the followings unread

zthee wrote:
I've used a TH XR2206 as the controling VCO.

I got the .BIN from here -> http://home.freeuk.net/lowpass/VCDO.html

Here's some picture of the waveformes:

Posted Image, might have been reduced in size. Click Image to view fullscreen.


well, there's yr problem... thats not an audio waveform... it's a space invader graphic file...

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zthee



Joined: Feb 20, 2008
Posts: 413
Location: Stockholm

PostPosted: Tue Jul 08, 2008 12:00 am    Post subject: Reply with quote  Mark this post and the followings unread

Damn it! I knew I've seen those guys before! Haha Very Happy

So your advice is to burn a new eprom?
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Ilanode



Joined: Sep 14, 2007
Posts: 80
Location: Berlin/FRG

PostPosted: Tue Jul 08, 2008 1:12 am    Post subject: Reply with quote  Mark this post and the followings unread

zthee wrote:
So your advice is to burn a new eprom?

You might use your's as CV-source for unsual LFO-waveforms. A slew limiter could be usefull here.
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zthee



Joined: Feb 20, 2008
Posts: 413
Location: Stockholm

PostPosted: Tue Jul 08, 2008 3:41 am    Post subject: Reply with quote  Mark this post and the followings unread

Yeah, I thought about that.

And even though it's not the correct waveforms it still sounds kinda nice.. Smile

I built the display-driver aswell. But it's not working at all. Or; it displays 1 and refuse to change. I'm running it on +15V - but that shouldn't be a problem?

This circuit is driving me mad! And it's the last of the 23 modules I've built for my modular.. Almost complete and then this comes along. Sad
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Ilanode



Joined: Sep 14, 2007
Posts: 80
Location: Berlin/FRG

PostPosted: Tue Jul 08, 2008 4:51 am    Post subject: Reply with quote  Mark this post and the followings unread

The display probably runs on 5V!?
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andrewF



Joined: Dec 29, 2006
Posts: 1174
Location: australia
Audio files: 4

PostPosted: Tue Jul 08, 2008 8:43 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
Did the CGS wavetable module have it's own .bin file? I just assumed it was the same as the VCDO..


There were a few different versions - at least, putting out different waveforms and for different chips - 64, 128, etc.
I cannot comment whether they are compatible with the digisound version, best check with Ken.

yep - the display adapter needs 5V, also it is quite tricky wiring up the led display, many different varieties - some are common cathode, some common anode, some don't have common anything! The first two I built never worked properly until this was worked out.
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otherunicorn



Joined: May 11, 2008
Posts: 136
Location: Australia

PostPosted: Tue Jul 08, 2008 6:27 pm    Post subject: Reply with quote  Mark this post and the followings unread

The VCDO ROM is compatible with my circuit. What's going on with your circuit however, is anyone's guess!
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zthee



Joined: Feb 20, 2008
Posts: 413
Location: Stockholm

PostPosted: Wed Jul 09, 2008 1:46 am    Post subject: Reply with quote  Mark this post and the followings unread

Ah, that's to bad, I was hopping that the ROM would be the magic solution to it all Smile

I'll keep guessing and hopefully I'll solve it in the end.

Thanks!
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otherunicorn



Joined: May 11, 2008
Posts: 136
Location: Australia

PostPosted: Wed Jul 09, 2008 2:26 am    Post subject: Reply with quote  Mark this post and the followings unread

Check your address and data lines. more than likely, something is out of order.
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zthee



Joined: Feb 20, 2008
Posts: 413
Location: Stockholm

PostPosted: Fri Jul 18, 2008 2:46 pm    Post subject: Reply with quote  Mark this post and the followings unread

I got the displaydriver up and going by running it on 5V - so now it works!

Let's celebrate with some pictures!

Posted Image, might have been reduced in size. Click Image to view fullscreen.

Posted Image, might have been reduced in size. Click Image to view fullscreen.

Haven't figured out the problem with the ROM though.. Hope to solve it within the next month or so. I've checked, rechecked and double checked the adress & data lines and all is going to where it should be acording to the schematics. But I think that if I check it like 12 more times I'm gonna find the error! Smile

Thanks for helping out!
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CJ Miller



Joined: Jan 07, 2007
Posts: 371
Location: 127.0.0.1

PostPosted: Wed Jul 30, 2008 3:52 am    Post subject: Reply with quote  Mark this post and the followings unread

You must have gotten a few lines scrambled somewhere. Looking at your scope shots, I can see the waveforms, but they are not reading back in sequence somehow. Your circuit basically works, more or less.

Possibilities? The ROM could have been burned weird. Did you make the burner yourself? Or did you use an EPROM with a slightly different pinout? Are unused logic inputs grounded? Solder bridge or mismatched wire on one or more data or address lines?

Good idea using the XR2206 as a wavetable VCO, I have drawn up some plans a few months ago for something similar. My digital projects have kept getting sidetracked. Good luck!
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dar303



Joined: Jul 15, 2007
Posts: 97
Location: Sweden

PostPosted: Sun Aug 03, 2008 1:34 pm    Post subject: Reply with quote  Mark this post and the followings unread

I burned the eprom for zthee using a sunshine pro burner. I have made several other wavetable roms for myself before but not using this data. I'll try to put one of his roms in my oscillator, even though I have bigger waves I shoud see waveforms and be able to read the data.
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zthee



Joined: Feb 20, 2008
Posts: 413
Location: Stockholm

PostPosted: Sun Aug 03, 2008 1:55 pm    Post subject: Reply with quote  Mark this post and the followings unread

Would be great if we could arrange that sometime in the future!

I've used it even though the output is strange. The digital noise is kinda fun to filter and modulate with Smile
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Etaoin



Joined: Jun 30, 2005
Posts: 760
Location: Utrecht, NL

PostPosted: Fri Aug 08, 2008 2:49 pm    Post subject: Reply with quote  Mark this post and the followings unread

Didn't know you still wanted to see the scope pics...

I'll pull out my working CGS wavetable this weekend and make some pics. I had one of the last (or the last) set of boards from Ken.

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zthee



Joined: Feb 20, 2008
Posts: 413
Location: Stockholm

PostPosted: Fri Aug 08, 2008 3:09 pm    Post subject: Reply with quote  Mark this post and the followings unread

Etaoin wrote:
Didn't know you still wanted to see the scope pics...

I'll pull out my working CGS wavetable this weekend and make some pics. I had one of the last (or the last) set of boards from Ken.


Oh, we're going to check it out on wednesday! So if it's to much of a hassle don't bother.. Smile

But thanks anyway!

I'll report back as soon as I know what I did wrong!
I'm still asuming I've done a really simple error, but I still can't find it..
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