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alanwilder81
Joined: Sep 03, 2016 Posts: 310 Location: italy
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Posted: Tue Aug 22, 2017 6:32 am Post subject:
555 VCO output volume varying with frequency |
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hello everyone.
self -explanatory title.
MY newly built 555 VCO exhibits a remarkable volume amplitude fluctuation depending on the frequency i set it to.
It gets louder as the frequency increases.
the effect is most pronounced with the triangle wave, as ,at low frequencies its is almost inaudible.
What might be wrong? i Suspect this is not a normal behavior !
thanksfor any suggestions |
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JovianPyx
Joined: Nov 20, 2007 Posts: 1988 Location: West Red Spot, Jupiter
Audio files: 224
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Posted: Tue Aug 22, 2017 9:44 am Post subject:
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Can you show us a full schematic?
What it reads like is something similar to a VCO passed through a low pass filter, but you don't mention a filter. Have you measured the voltage of the output with an oscope? _________________ FPGA, dsPIC and Fatman Synth Stuff
Time flies like a banana. Fruit flies when you're having fun. BTW, Do these genes make my ass look fat? corruptio optimi pessima
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wackelpeter
Joined: May 05, 2013 Posts: 461 Location: germany
Audio files: 10
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Posted: Tue Aug 22, 2017 10:46 am Post subject:
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Well at some extent it is normal behaviour or human ear response, what you experience.
The lower frequency of waveforms like triangle or sine are perceived at a "feeled" lower volume at the human ear... I guess it has something to do with the dynamics within the waves... for example in square or saw you have at least one flank of the wave a rapid change in Amplitude, which the human ear can detect much better. pls someone correct me if this is nonsense.
It's somewhat similar to a 5Hz Square vs. 5 Hz sine at the same amplitude... The first you hear the clicks the latter you can't hear as long as your not amplifieng it to some extend were perhaps the membranes of your Speakers begin to flutter...
Best is to check at it with an scope... if they have the same amplitude and the amplitude stays the same everything is normal... _________________ https://soundcloud.com/bastian-j |
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wackelpeter
Joined: May 05, 2013 Posts: 461 Location: germany
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blue hell
Site Admin
Joined: Apr 03, 2004 Posts: 24079 Location: The Netherlands, Enschede
Audio files: 278
G2 patch files: 320
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Posted: Tue Aug 22, 2017 2:28 pm Post subject:
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Interesting read that 2nd link :-) _________________ Jan
also .. could someone please turn down the thermostat a bit.
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alanwilder81
Joined: Sep 03, 2016 Posts: 310 Location: italy
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alanwilder81
Joined: Sep 03, 2016 Posts: 310 Location: italy
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Grumble
Joined: Nov 23, 2015 Posts: 1294 Location: Netherlands
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wackelpeter
Joined: May 05, 2013 Posts: 461 Location: germany
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Posted: Tue Aug 22, 2017 11:33 pm Post subject:
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I don't know exactly but i guess measuring the voltage with a DVM on a changing frequency output is not the best option, on the scope you can see level changes better.
What came into my mind is the HF-trimmer, might have something to do with it, as far as i understand it has something to do with compensating for lower Levels at high a constant output, might have to do with how it's generated: with an comparator as Long as the triangle output is over the treshold the comparator output Switches from rail to rail and giving a stable voltage out via the resistro divider at it's output...
But at least that would be the opposite from what your telling...
Also interesting, regarding the Square output, would be to know if the square frequency output also changes or at least the pulsewidth...
As with variable treshold via the triangle with changing Amplitude this could occour too, without changing the PWM manually or by CV...
...And at least, know my memories came back, there was an issue with the sine output being a bit low on some builds, which Fonik solved. There is a thread regarding this at the Forums here... Looking at my printed schematic the 100k R34 in the sine shaper is reduced to 56k, i guess that's how it ended up in my build, but i'm always a bit lazy with documenting my changes. _________________ https://soundcloud.com/bastian-j |
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wackelpeter
Joined: May 05, 2013 Posts: 461 Location: germany
Audio files: 10
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Posted: Tue Aug 22, 2017 11:40 pm Post subject:
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Grumble wrote: | human ears are more sensitive to higher frequencies |
Correct, but only to a certain degree... when it reachs the upper Hearing Limits of the human ear then the perceiving curve goes down again.
With my tinitus and slightly deafness, i'm having trouble Hearing frequencies above 12Khz if i can trust my ears and DVM...
A Hearing test i had to absolve now twice, showed that i lost a lot of sensitivtiy in the frequency range of human speech... Not the best circumstances trying to be "musically" productive. _________________ https://soundcloud.com/bastian-j |
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