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Uncle Krunkus
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Joined: Jul 11, 2005 Posts: 4761 Location: Sydney, Australia
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Posted: Thu Apr 27, 2006 6:47 am Post subject:
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Okay,
First, the PSU I was running it off was humming. (I pulled the 4066 and there was hum irrespective of the main frequency control)
It disappeared when I went to a 9V battery for power. (I'll fix this soon)
I also noticed that there are plenty of sub sonic power fluctuations getting through to the output no matter what the speed of the clocks is. Jan, I reckon this might be causing those curves between samples on the trace. I'm gonna do a quick sketch of the clock circuit as well just in case you can see something amiss there. Maybe I need bypass caps. But how many? And where? And what value? .01uF seems to be popular for bypass caps. _________________ What makes a space ours, is what we put there, and what we do there. |
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blue hell
Site Admin
Joined: Apr 03, 2004 Posts: 24083 Location: The Netherlands, Enschede
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Posted: Thu Apr 27, 2006 11:20 am Post subject:
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Sounds like a mistake in the grounding ... told you I heard hum
But WTH do the subsonics come from ... could you post a sketch of the PSU maybe ?
Hmm, wish I could simply see and touch the thing ... that would help maybe ... this can be hard to say something sensible about.
Could also be that excessive current is drawn by the circuit for some reason. _________________ Jan
also .. could someone please turn down the thermostat a bit.
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blue hell
Site Admin
Joined: Apr 03, 2004 Posts: 24083 Location: The Netherlands, Enschede
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Posted: Thu Apr 27, 2006 11:23 am Post subject:
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Missing bypass caps should give glitches, not hum. You didn't connect an electrolitic capacitor reverse biased somewhere ? _________________ Jan
also .. could someone please turn down the thermostat a bit.
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Uncle Krunkus
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Joined: Jul 11, 2005 Posts: 4761 Location: Sydney, Australia
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Posted: Thu Apr 27, 2006 3:47 pm Post subject:
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No, the hum is separate. Caused by an unregulated crapola 9V adaptor. I'll knock up a little regulated PSU for it today. Forget the hum.
The sub sonics (or what look like large curves on my 300ms updating Winscope) are being made by the number of digital chips across the power, I'm almost sure of it.
Stop Press!!
I think I just spotted a reversed electro! Jan you're a genius!!
I'll get back to you. _________________ What makes a space ours, is what we put there, and what we do there. |
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Uncle Krunkus
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Joined: Jul 11, 2005 Posts: 4761 Location: Sydney, Australia
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Posted: Thu Apr 27, 2006 3:58 pm Post subject:
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Sorry, false alarm.
It was just a trick of the stripboard.
I've designed a little sub board that plugs in to where the 4520 chips are and works as an auto reversing dual 4 bit counter. Lucky I have the reality of a new baby to distract me, cos I think I could easily drive myself insane! _________________ What makes a space ours, is what we put there, and what we do there. |
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Uncle Krunkus
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Joined: Jul 11, 2005 Posts: 4761 Location: Sydney, Australia
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Posted: Sun Apr 30, 2006 5:09 am Post subject:
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New PSU and the hum is gone.
I'm still a bit sus about the output though. When I change from the DC coupled output to the cap (.01uF) the squared off wave turns into a series of spikes. Why can't I uncouple the DC and retain the shape of the wave?
Is it just because I'm "looking" at the waveshape through my mixer and into the soundcard?
Anyway, I'm working on the reverser mod now, as I know it will improve the sound by a long way. _________________ What makes a space ours, is what we put there, and what we do there. |
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blue hell
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Joined: Apr 03, 2004 Posts: 24083 Location: The Netherlands, Enschede
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Posted: Sun Apr 30, 2006 4:55 pm Post subject:
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Uncle Krunkus wrote: | (.01uF)
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That might be a bit smalish, it depends on impedances driving from and driving into, but yoy might even need an electrolitic one. Increasing it to .47 uF will improve things.
Quote: |
Why can't I uncouple the DC and retain the shape of the wave?
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Because your ;etting through high frequencies, for a first order high pass RC filter you'll have signal drop of 6 dB / Octave below the cutoff frequency (fcutoff=1/(2*pi*R*C) . This will distort the wave, noting you can do a bout that. But the good news that below a certain frequency you can't hear the signal anymore, so typically one would try to set the cutoff frequency around 20 Hz or so. What C is needed for that depends on the R you have, which is somewhat hard to estimate but the imput impedance of the input you put thes signal in might be in the manual of the device in question.
When you need a large capacitor, either from calculation or from experimentation, it might have to be an electrolytic type, in that case connect the plus side to your circuit using the minus side as the output.
Maybe read the section 'time domain considerarations' at http://en.wikipedia.org/wiki/RC_filter and have a look at the graphs there. _________________ Jan
also .. could someone please turn down the thermostat a bit.
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piedwagtail
Joined: Apr 15, 2006 Posts: 297 Location: shoreditch
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Posted: Sun Apr 30, 2006 6:17 pm Post subject:
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Congratulations,on your arrival,Uncle K.
Just skimming through here,(i can't see the sch. on this linux-stem)but noticing you're using a 4520 counter in the sketch.I've found them to be most pedantic about their clock pins!
I followed Ken Stone and put a filter in there,4k7 series,33n pin to earth.Cleaned it up no end.
Robert |
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Uncle Krunkus
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Joined: Jul 11, 2005 Posts: 4761 Location: Sydney, Australia
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Posted: Mon May 01, 2006 3:34 am Post subject:
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Well, looking back I've got the output of the TL071 as a voltage follower. Looking forward I've got a line in on a Behringer MX1602 mixer. I figure they should both be pretty high, yeah?
Hey Robert,
what do mean by "pedantic about their clock pins" ? I haven't had any hassles with the 4520. (Although I am about to replace them with a DIY auto reverse clock made of 4024s and 4030s) _________________ What makes a space ours, is what we put there, and what we do there. |
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piedwagtail
Joined: Apr 15, 2006 Posts: 297 Location: shoreditch
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Posted: Mon May 01, 2006 7:17 am Post subject:
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fussy!
Looking at cgs.synth,you'll see in his sequential switch he implements this...
Quote: | I had some trouble on the prototype unit with some brands of 4516 counters. It seems some of them are pedantic about the speed of the rising and falling edges of the clock pulse. The problems experienced were: the counter advancing on both rising and falling edges of the clock pulse, skipping steps, or stepping back and forwards between two steps. The offending devices were Mitsubishi and Fairchild. The National Semiconductor device worked perfectly. |
I made a mistake above,i breadboarded with 4520(a ST HCF4520BE) putting a 3n3 in series with a 4k7 to earth.It stopped playing up and divided the clock nicely as a 2/4/8 divider.
Robert |
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blue hell
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Joined: Apr 03, 2004 Posts: 24083 Location: The Netherlands, Enschede
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Posted: Mon May 01, 2006 11:21 am Post subject:
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Uncle Krunkus wrote: | I figure they should both be pretty high, yeah?
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Opamp output should be near zero omhs, that's good and it can be ignored. For mixer in lets assume 47 kE. And lets say you want 20 Hz for the cutoff frequency, so :
20 = 1 / (2*pi*47e3*C) or C = 1 / (40*pi*47e3) = 17 uF ... hmm bit higher than expected. _________________ Jan
also .. could someone please turn down the thermostat a bit.
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Uncle Krunkus
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Joined: Jul 11, 2005 Posts: 4761 Location: Sydney, Australia
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Posted: Mon May 01, 2006 1:51 pm Post subject:
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Thanks Jan,
I'll give it a go.
And let you know! _________________ What makes a space ours, is what we put there, and what we do there. |
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Uncle Krunkus
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Joined: Jul 11, 2005 Posts: 4761 Location: Sydney, Australia
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blue hell
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Joined: Apr 03, 2004 Posts: 24083 Location: The Netherlands, Enschede
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Posted: Tue May 02, 2006 10:19 am Post subject:
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Uncle Krunkus wrote: | Yes! |
Phew
& sample sounds waay better indeed. _________________ Jan
also .. could someone please turn down the thermostat a bit.
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Scott Stites
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Joined: Dec 23, 2005 Posts: 4127 Location: Mount Hope, KS USA
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Posted: Tue May 02, 2006 12:13 pm Post subject:
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Yep, sounding very good! |
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Uncle Krunkus
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Joined: Jul 11, 2005 Posts: 4761 Location: Sydney, Australia
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Posted: Thu May 11, 2006 3:05 am Post subject:
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I've almost finished two auto reverse Gamera chips. The first one sounds good already. Two should make it even smoother!!
As for the front end, I'm wondering how to make an input which will kick over the 4017 from any constantly recurring signal in, whether it be sine, saw, square etc. and anywhere from 160Hz -> 100Khz. I s'pose a schmitt trigger will be in there somewhere. Some kind of pre-gain/diode clamping kind of thing to square it off maybe?
Any ideas would be much appreciated.
I also realised that it could be simplified a lot to make it easier for a DIY project. You really only need 4 clocks; 2 ramps & 2 reversing, then a rotary switch for each sample ( and you could dial up which clock fed each time slot. That pulls the chip count down to just 15! _________________ What makes a space ours, is what we put there, and what we do there. |
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Uncle Krunkus
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Joined: Jul 11, 2005 Posts: 4761 Location: Sydney, Australia
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Posted: Fri May 12, 2006 7:25 am Post subject:
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Here's the latest sample.
I'm begining to think that this project's ends don't justify the means.
I think maybe I should do some work finishing my Soundlab and get back to it later.
I'm satisfied with it so far. I think I'd like to hear it backing up the rest of the synth to work out how much more time is worthwhile investing.
"A creative person makes a lot of stuff. An artist knows what to keep." _________________ What makes a space ours, is what we put there, and what we do there. |
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mosc
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Joined: Jan 31, 2003 Posts: 18198 Location: Durham, NC
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Posted: Fri May 12, 2006 9:10 am Post subject:
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I think you forgot to add the sample... _________________ --Howard
my music and other stuff |
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Scott Stites
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Joined: Dec 23, 2005 Posts: 4127 Location: Mount Hope, KS USA
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Posted: Fri May 12, 2006 2:06 pm Post subject:
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Yeah. Whachoo doin? Holdin' out on us? |
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Uncle Krunkus
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zipzap
Joined: Nov 22, 2005 Posts: 559 Location: germany
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Posted: Fri May 26, 2006 5:24 am Post subject:
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cool project! For kicking the 4017, i once dit this with an lm358 as a comperator and a diode to get ground and high. Worked well for playing my sequencer with the bassguitar.
I saw some shematic how to use a phased lock loop with an divider in it´s feedback to multiply an incoming wave. Might be useful to clock this with slower signals. |
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