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--- aout_lc_module [2016/08/04 23:43]
psykhaze
+++ aout_lc_module [2016/08/04 23:46] (current)
psykhaze [Introduction]
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 =====Introduction=====
-The idea behind the AOUT_LC module was to realize control outputs with parts that are easy to get in most countries. After a discussion with Karl Dalen about the difficulity to find DIY friendly DACs with a serial interface. He proposed these {{http://www.midibox.org/users/kd/KDdac.pdf|circuits}}, and the discrete solution was selected because of the simplicity.
+The idea behind the AOUT_LC module was to **realize control outputs with parts that are easy to get in most countries**. After a discussion with Karl Dalen about the difficulity to find DIY friendly DACs with a serial interface. He proposed these **{{http://www.midibox.org/users/kd/KDdac.pdf|circuits}}**, and the discrete solution was selected because of the simplicity.
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-In difference to the [[AOUT_Module]] or [[AOUT_NG module]], this project doesn't require a special (expensive and hard to get) DAC IC, instead resistors are formed to a discrete R-2R ladder network. Building such a circuit means a lot of soldering effort, but as the MBHP is indented as a Do-It-Yourself platform, and not as a commercial product, this argument is very weak. However, the resistor ladder could be replaced by a DAC with parallel interface (see Karl's schematics), this would still have the advantage, that the DACs are accessible via a serial chain (-> low number of uC pins are allocated), and that the software driver doesn't need to be adapted for a proprietary interface.
+In difference to the **[[AOUT_Module|AOUT]]** or **[[AOUT_NG]]**, **this project doesn't require a special (expensive and hard to get) DAC IC**, instead **resistors are formed to a discrete R-2R ladder network**. Building such a circuit means a lot of soldering effort, but as the MBHP is indented as a Do-It-Yourself platform, and not as a commercial product, this argument is very weak. However, **the resistor ladder could be replaced by a DAC with parallel interface** //(see Karl's schematics)//, this would still have the advantage, that the DACs are accessible via a serial chain (-> low number of uC pins are allocated), and that the software driver doesn't need to be adapted for a proprietary interface.
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-Regarding the quality of the "discrete DAC" outputs it should be mentioned, that it directly depends on the chosen resistors. The tolerance should be 1% or lower (Metalfilm) and stable over the typical temperature range. The results can be dramatically improved by selecting the best matching resistors: just buy a set of 100 pieces , measure the resistance and take the ones with the best matching values for the ladder circuit.
+Regarding the quality of the "discrete DAC" outputs it should be mentioned, that it **directly depends on the chosen resistors**. The tolerance should be **1% or lower (Metalfilm) and stable over the typical temperature range**. The results can be dramatically improved by selecting the best matching resistors: just buy a set of 100 pieces , measure the resistance and take the ones with the best matching values for the ladder circuit.
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 In order to increase the flexibility, the MBHP_AOUT_LC PCB provides two different resolution options. The first channel can either be controlled with 12bit or 8bit resolution, the second channel with 4bit or 8bit resolution:
-{{ ::neonking:mbhp_aout_lc_res_options.gif?300 |}}
+{{ ::neonking:mbhp_aout_lc_res_options.gif |}}
 The 12/4 bit option is used by MIDIbox SID (the filter is controlled with 12bit, the resonance with 4bit only).
 In the MIDIbox CV firmware the resolution option is selectable. 8/8bit is enough if the module should control V/Oct CV inputs via Note or CC events. 12/4bit should be selected if channel #1 is connected to a Hz/V input, or if high-resolution events (NRPNs, PitchWheel) are desired.

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