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Gate or Trigger Levels
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fonik



Joined: Jun 07, 2006
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PostPosted: Fri Feb 08, 2013 4:20 am    Post subject: Gate or Trigger Levels
Subject description: Why limit these?
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every now and then i read here about gate and trigger levels and their standardization.

my point of view:
don't care to limit the level of the gate or trigger, but the threshold of the input! it is the input that has to be defined. for the output i would go for the highest voltage possible to be sure to be able to trigger anything.

i am currently working on the thomas henry CMOS ADSR and i will add stage gates and an end trigger. i see no reason to limit these, i will just let the opamps (comparators) swing to their limits (roughly 10V for a TL072 powered by 12V).

why would one limit the gate/trigger outputs to i.e. 5V?

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Paradigm X



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PostPosted: Fri Feb 08, 2013 7:16 am    Post subject: Reply with quote  Mark this post and the followings unread

Matthias

I cant offer any assistance, noob as you know, but I too find this really confusing. There are a number of projects where you have to decide early (klee/dave's midi2clock).

My best guess at this stage is to make as high as possible, so they can be more easily attenuated. So on that basis i think I agree with your assumption to leave high.

I obviously would also be interested to hear what others think.

Regards
Ben
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PHOBoS



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PostPosted: Fri Feb 08, 2013 8:04 am    Post subject: Reply with quote  Mark this post and the followings unread

well for analog levels I use -5V...+5V so for me it makes perfect sense to have triggers/gates at 0/+5V. This also has the advantage that
you can use it directly with digital circuits that use a PIC/arduino and run on 5V.

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corex



Joined: Mar 02, 2010
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PostPosted: Fri Feb 08, 2013 2:43 pm    Post subject: Reply with quote  Mark this post and the followings unread

I can't think of a good reason within a modular, but perhaps if interfacing with external devices then a 5V gate would be useful.
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Thomas_Henry



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PostPosted: Fri Feb 08, 2013 4:33 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hello Fonik,

If you decide to go that route, then I suggest you provide pads for the voltage divider on the outputs anyway. If a person wants standard synth levels, then he or she can pop in the two resistors (3k and 1.5k, which gives a +5V output and 1k impedance). If they don't want this, then the 1.5k is left out and the 3k is replaced either with a jumper (0 output Z) or a 1k resistor (1k output Z).

Also, I hope you will make the staging outputs completely optional, as per my original design. A person can just leave out the quad op-amp (assuming that's what you're using) and associated components if staging is not desired.

Thomas Henry
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JRock



Joined: Mar 05, 2010
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PostPosted: Thu Feb 14, 2013 11:59 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hey. Glad I was cruising through on a late night Cool

I have a cabinet filled with a bunch of CMOS logic that I didn't chop down the output on (Outputting ~11V to 13V). I felt the same way. Nothing's more frustrating than not being able to trigger your trigger input because the signal's too weak.

It's caused me some problems though. Current Draw on my system is one. LEDs, Gates, Triggers, you get a bunch of them all going at the same time and it get's taxing on the PSU.

It's caused me problems on envelopes too. They're expecting 5 or 7V. If you send 16th notes at 160 BPM or higher and the Gates and Triggers aren't knocked down a little bit from 13V the EG starts missing notes (it just stays on).

I agree that the threshold should be defined by the inputs. It might be easier if the standard was an 8 to 10V trigger because you wouldn't have to add a pair of transistors at the input to boost the gate level to work with CMOS powered by 12 or 15V.
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