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LektroiD
Joined: Aug 23, 2008
Posts: 822
Location: Scottish Borders
Audio files: 1
G2 patch files: 2
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 Posted: Thu Sep 23, 2010 7:13 am Post subject:
Clocking the sample & hold externally |
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Hi, I have finished the sample & hold, but can't seem to trigger it, I have been using a saw LFO to trigger other modules, but doesn't seem to trigger the sample & hold.
I would like to keep everything in time (although I have no sequencer as yet) I'm presuming I need to build a proper clock circuit; where would I find one, or should the saw LFO be OK, and maybe I've made a mistake on the S&H clock in?
Any help appreciated |
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kkissinger
Joined: Mar 28, 2006
Posts: 1095
Location: Kansas City, Mo USA
Audio files: 15
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| Posted: Thu Sep 23, 2010 10:33 am Post subject:
Re: Clocking the sample & hold externally |
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| LektroiD wrote: | Hi, I have finished the sample & hold, but can't seem to trigger it, I have been using a saw LFO to trigger other modules, but doesn't seem to trigger the sample & hold.
I would like to keep everything in time (although I have no sequencer as yet) I'm presuming I need to build a proper clock circuit; where would I find one, or should the saw LFO be OK, and maybe I've made a mistake on the S&H clock in?
Any help appreciated |
Does your circuit work when clocked from the internal oscillator?
Can you try a square wave for your external clock instead of a sawtooth wave?
Note that the LED should light up with an external clock. Does it light up for you?
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http://kevinkissinger.com |
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Sebo
Joined: Apr 27, 2007
Posts: 433
Location: Argentina
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LektroiD
Joined: Aug 23, 2008
Posts: 822
Location: Scottish Borders
Audio files: 1
G2 patch files: 2
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| Posted: Thu Sep 23, 2010 3:58 pm Post subject:
Re: Clocking the sample & hold externally |
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| kkissinger wrote: | | LektroiD wrote: | Hi, I have finished the sample & hold, but can't seem to trigger it, I have been using a saw LFO to trigger other modules, but doesn't seem to trigger the sample & hold.
I would like to keep everything in time (although I have no sequencer as yet) I'm presuming I need to build a proper clock circuit; where would I find one, or should the saw LFO be OK, and maybe I've made a mistake on the S&H clock in?
Any help appreciated |
Does your circuit work when clocked from the internal oscillator?
Can you try a square wave for your external clock instead of a sawtooth wave?
Note that the LED should light up with an external clock. Does it light up for you? |
Thanks for your reply, I get a faint glow on the LED (at best) when I use any sort of CV, but nothing seems strong enough to trigger it, doesn't matter where it's sourced from. I'm wondering if there's a way to increase the CV gain from the external input signals. Maybe a resistor is inhibiting this?
I'll investigate further, and report back with any findings. |
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kkissinger
Joined: Mar 28, 2006
Posts: 1095
Location: Kansas City, Mo USA
Audio files: 15
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| Posted: Thu Sep 23, 2010 4:46 pm Post subject:
Re: Clocking the sample & hold externally |
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| LektroiD wrote: | Thanks for your reply, I get a faint glow on the LED (at best) when I use any sort of CV, but nothing seems strong enough to trigger it, doesn't matter where it's sourced from. I'm wondering if there's a way to increase the CV gain from the external input signals. Maybe a resistor is inhibiting this?
I'll investigate further, and report back with any findings. |
Look for a solder bridge in the LED driver circuit. Perhaps a short is pulling down the clock signal.
Also, try to apply a positive DC voltage to the ext input and measure your source voltage both plugged in and unplugged. If your unplugged voltage is, say 10v and your plugged in voltage drops a lot, say down to 3v -- then suspect a solder bridge.
Keep us posted!
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http://kevinkissinger.com |
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yusynth
Joined: Nov 24, 2005
Posts: 1045
Location: France
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| Posted: Sun Sep 26, 2010 11:28 am Post subject:
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The Sample&Hold circuit expects a positive SQUARE or a PULSE as an input. The sampling is triggerred by the rising edge of the PULSE.
You said that you are using a SAW LFO, a SAW is not recommended for this circuit because there is no schmitt trigger at the input. Check your SAW : if the stiff edge is a falling edge it won't work. If the stiff edge is a rising edge it should work. Try to reverse your saw.
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LektroiD
Joined: Aug 23, 2008
Posts: 822
Location: Scottish Borders
Audio files: 1
G2 patch files: 2
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| Posted: Thu Sep 30, 2010 10:11 pm Post subject:
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I've tried a square wave, but still not strong enough to run, at least the saw made the light flicker, albeit faintly. The Square doesn't even manage that.
I also tried swapping the TL074 with another from stock, just in case the op amp was blown. It seems there's simply not enough voltage coming in to drive it. |
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yusynth
Joined: Nov 24, 2005
Posts: 1045
Location: France
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| Posted: Thu Sep 30, 2010 11:11 pm Post subject:
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Normally the clock input is expecting at least 5V (10V is better) to work properly. Normally the LED is shining mid-bright when externally clocked.
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LektroiD
Joined: Aug 23, 2008
Posts: 822
Location: Scottish Borders
Audio files: 1
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| Posted: Sat Oct 02, 2010 7:00 am Post subject:
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| yusynth wrote: | | Normally the clock input is expecting at least 5V (10V is better) to work properly. Normally the LED is shining mid-bright when externally clocked. |
This would be the problem, I'm using your VCLFO 1&2, which only push out +3.4V / -3.4V. I guess I need to build a specific clocking device to run this externally, either that or somehow increase the voltage between the input socket and the board. What does everyone else use for clocking? |
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yusynth
Joined: Nov 24, 2005
Posts: 1045
Location: France
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| Posted: Sat Oct 02, 2010 8:39 am Post subject:
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| LektroiD wrote: | | yusynth wrote: | | Normally the clock input is expecting at least 5V (10V is better) to work properly. Normally the LED is shining mid-bright when externally clocked. |
This would be the problem, I'm using your VCLFO 1&2, which only push out +3.4V / -3.4V. I guess I need to build a specific clocking device to run this externally, either that or somehow increase the voltage between the input socket and the board. What does everyone else use for clocking? |
The output range of the VC-LFO 1 & 2 should be more than +/-3.4V . Are you powering them in +/-15V ? You should have at least +4.2/-4.2V
I have just check with my module and I have no problem triggering the S&H with the VC-LFO.
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LektroiD
Joined: Aug 23, 2008
Posts: 822
Location: Scottish Borders
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| Posted: Sat Oct 02, 2010 9:23 am Post subject:
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| yusynth wrote: | | LektroiD wrote: | | yusynth wrote: | | Normally the clock input is expecting at least 5V (10V is better) to work properly. Normally the LED is shining mid-bright when externally clocked. |
This would be the problem, I'm using your VCLFO 1&2, which only push out +3.4V / -3.4V. I guess I need to build a specific clocking device to run this externally, either that or somehow increase the voltage between the input socket and the board. What does everyone else use for clocking? |
The output range of the VC-LFO 1 & 2 should be more than +/-3.4V . Are you powering them in +/-15V ? You should have at least +4.2/-4.2V
I have just check with my module and I have no problem triggering the S&H with the VC-LFO. |
I use the MFOS wall wart adaptor which is 12V. Maybe I need a different supply for these modules, what would you recommend? |
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yusynth
Joined: Nov 24, 2005
Posts: 1045
Location: France
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