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Pehr
Joined: Aug 14, 2005 Posts: 1307 Location: Björkvik, Sweden
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sneakthief
Joined: Jul 24, 2006 Posts: 569 Location: Berlin
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Peake
Joined: Jun 29, 2007 Posts: 1113 Location: Loss Angeles
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Posted: Sun May 25, 2008 8:18 pm Post subject:
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Here 'tis. |
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Tim Servo
Joined: Jul 16, 2006 Posts: 924 Location: Silicon Valley
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Posted: Sun May 25, 2008 8:46 pm Post subject:
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Hey Peake,
Correct me if I'm wrong, but that sounds more like you're modulating the VC Noise Clock. The Noise Filter (R54) is a non VC passive filter and yields a more subtle change to the sound. Right? Wrong?
Tim (has been wrong once or twice...) Servo |
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Peake
Joined: Jun 29, 2007 Posts: 1113 Location: Loss Angeles
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Posted: Mon May 26, 2008 11:36 am Post subject:
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Oh- I'm wrong
I'd thought "filter" may have not been literal. Looks like I'll have to buy an SN-Voice board and see for myself... I was looking at ATARI POKEY specs yesterday and they use logic to mimic a high-pass filter effect- I made the ASSumption that something similar may occur in the TI chip as well, and posted away. |
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State Machine
Janitor
Joined: Apr 17, 2006 Posts: 2809 Location: New York
Audio files: 24
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Posted: Wed May 28, 2008 4:03 am Post subject:
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Quote: | Does anyoe have a sound example? is it a high apss filter or low pass? |
Hi,
Just a suggestion. Could you post a sound example of what yours is doing? Then we can compare the sounds of our units
Thanks,
Bill |
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Pehr
Joined: Aug 14, 2005 Posts: 1307 Location: Björkvik, Sweden
Audio files: 2
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State Machine
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Joined: Apr 17, 2006 Posts: 2809 Location: New York
Audio files: 24
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Posted: Thu May 29, 2008 9:07 am Post subject:
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Quote: | could, I'll record later today or tomorrow and post here. |
OK, I can make a comparison to my SN voice noise filter Thanks !
Bill |
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Pehr
Joined: Aug 14, 2005 Posts: 1307 Location: Björkvik, Sweden
Audio files: 2
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State Machine
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Joined: Apr 17, 2006 Posts: 2809 Location: New York
Audio files: 24
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Posted: Thu May 29, 2008 7:06 pm Post subject:
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This sounds like normal behavior to me. The noise filter acts as a Low Pass Filter (LPF). Turning the noise filter pot CW shifts the center frequency, or the filters 3 dB point, lower in frequency thus cutting off more and more energy of the noise spectrum.
The Noise INIT controls the VCO (CD4046) that provides the noise clock to the SN76477 chip. This clock is used by the chips internal digital PR Noise Gen. When you go MIN on the INIT causes the clock to drop significantly in frequency and thus the minimal effect that the filter pot has on the signal.
It's interesting to note the sound of the noise generator when the INIT is set to maximum. The generator is being clock at the highest frequency. In doing so, you will notice a distinct lower frequency pattern to the sound within the higher frequency noise. The reason this is present is because the PR generator has a specific "run length" and the pattern will repeat every so many counts using the following equation (2^n-1) where "n" is the bit width of the shift register used in the PR noise generator. So if the shift register were 10 bits, the run length would be 1023 counts of the noise clock. If the noise clock were about 1 KHz, you would hear a distinct pattern of sound at about 1 HZ .......... I hope I explained that OK ......
Bill
Hope this helps !
Bill Last edited by State Machine on Fri May 30, 2008 4:09 am; edited 1 time in total |
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fonik
Joined: Jun 07, 2006 Posts: 3950 Location: Germany
Audio files: 23
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Posted: Fri May 30, 2008 12:06 am Post subject:
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State Machine wrote: | I hope I explaned that OK ...... |
as always, bill.
BTW tom wiltshire recently released his PIC based noise gen which pattern will repeat in ...err... 142 million years n _________________
cheers,
matthias
____________
Big Boss at fonitronik
Tech Buddy at Random*Source |
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Pehr
Joined: Aug 14, 2005 Posts: 1307 Location: Björkvik, Sweden
Audio files: 2
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Posted: Fri May 30, 2008 1:24 am Post subject:
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State Machine wrote: | It's interesting to note the sound of the noise generator when the INIT is set to maximum. The generator is being clock at the highest frequency. In doing so, you will notice a distinct lower frequency pattern to the sound within the higher frequency noise. The reason this is present is because the PR generator has a specific "run length" and the pattern will repeat every so many counts using the following equation (2^n-1) where "n" is the bit width of the shift register used in the PR noise generator. So if the shift register were 10 bits, the run length would be 1023 counts of the noise clock. If the noise clock were about 1 KHz, you would hear a distinct pattern of osund at about 1 HZ .......... I hope I explaned that OK ...... |
Interesting However, I'm not sure that's what I hear. There seems to be a glitch, perhaps crosstalk, from the LFO to the noise init. When I change the LFO rate, the sound of the noise changes too... _________________ YouTube channel
flickr photostream
http://loxodrom.blogspot.com
http://www.garageband.com/artist/loxodrom
http://soundcloud.com/loxodrom |
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Pehr
Joined: Aug 14, 2005 Posts: 1307 Location: Björkvik, Sweden
Audio files: 2
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State Machine
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Joined: Apr 17, 2006 Posts: 2809 Location: New York
Audio files: 24
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Posted: Mon Jun 02, 2008 5:28 pm Post subject:
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Cool ending . it's like the floor dropping out from under the SN Voice. It really generates some very cool bass tones. Is that random Klee sequencing going on there?
Will have to get back to this LFO interference. It might be some bleed over into the CD4046 VCO.
Bill |
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Pehr
Joined: Aug 14, 2005 Posts: 1307 Location: Björkvik, Sweden
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State Machine
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Joined: Apr 17, 2006 Posts: 2809 Location: New York
Audio files: 24
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Posted: Tue Jun 03, 2008 3:09 pm Post subject:
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Quote: | So are anyone else experiencing the trouble with the LFO bleed to the noise? |
I will take some time this evening and pay close attention for this and let you know. I will get some noise going and vary the LFO and listen for any interference.
Quote: | Perhaps I could try and replace the PPL and see what happens. |
I suppose you meant the PLL Unlikely that it's the cause, if it's in a socket, you can try it. better yet, if you have one from a different manufacturer, that would be better. Mine is an RCA chip but I will report what I have in mine when I give you my results.
Bill |
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Pehr
Joined: Aug 14, 2005 Posts: 1307 Location: Björkvik, Sweden
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State Machine
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Joined: Apr 17, 2006 Posts: 2809 Location: New York
Audio files: 24
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Posted: Wed Jun 04, 2008 4:03 am Post subject:
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Quote: | Yes, PLL of course |
Sure .... I bogged down with computer repairs last evening but promise I will get a chance to check this for you within the next 1 to 2 days .... Boy, seems like we all have busy lives these days ....... Robin and I have been house hunting also ........ I really need a full finished basement to support all our inetrests
OK, you will hear from me
Bill |
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Photon
Joined: Mar 22, 2005 Posts: 363 Location: Boston
Audio files: 1
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Posted: Wed Jun 04, 2008 6:19 am Post subject:
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State Machine wrote: | Robin and I have been house hunting also ........ I really need a full finished basement to support all our inetrests |
We're in the middle of buying a house right now. The days of doing this stuff in my apartment dining room are coming to an end
Of course, now theres no money to put towards DIY!
Pehr, your noise filter sweep sample sounds very similar to my SN-Voice. I'll try to compare your sample to mine soon and let you know.
Peter |
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fonik
Joined: Jun 07, 2006 Posts: 3950 Location: Germany
Audio files: 23
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Posted: Wed Jun 04, 2008 7:06 am Post subject:
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State Machine wrote: | Robin and I have been house hunting also ........ I really need a full finished basement to support all our inetrests |
you will enjoy it, believe me. dot is a high school teacher doing a lot of work at home, paper used to be almost everywhere in our flat and i was soldering right upon the computers keyboard. the house we bought this year is a true relief for both of us... so good luck, bill. _________________
cheers,
matthias
____________
Big Boss at fonitronik
Tech Buddy at Random*Source |
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RF
Joined: Mar 23, 2007 Posts: 1502 Location: Northern Minnesota, USA
Audio files: 28
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Posted: Wed Jun 04, 2008 7:05 pm Post subject:
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Jeese - it's moving time in the synth diy community. Jennie and I just purchased a house with a full finished basement. We have a music room - and I got a dedicated room for building stuff.
Course, now I don't have time for any building....and the music eq. is still in boxes... |
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State Machine
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Joined: Apr 17, 2006 Posts: 2809 Location: New York
Audio files: 24
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Posted: Thu Jun 05, 2008 5:58 am Post subject:
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Fonik, RF, Photon ........... wow , I am not alone .. House hunting is sometimes nerve racking right? But fun at the same time. Its an adventure of seeing homes and bargaining with people.
Thanks for the good wishes and good luck to you guys with your new homes ! I am looking very much to having more living space and dedicating a finished basement area for our arts and crafts. Having the living space look more like a "living space" rather than a lab is a nice prospect.
OK, I will get back OT ....
Bill |
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