Main: Summing design flaw fixed; better headphone vol. range
- Multiple R and C value adaptions - Line Input: No relevant difference between INA134 and own circuit -> LM833 chosen - Signal busses/ summing module inputs fixed - TODO: On-Air Button - TODO: Update PCB layout
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README.md
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README.md
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@ -42,9 +42,9 @@ This results in a signal flow like this: ![](docs/signal-flow.jpg)
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### Tasks
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- [x] Requirements collection
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- [ ] Electrical design draft/ proof of concept (breadboard)
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- [ ] Proof of concept validation
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- [ ] First PCB layout
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- [x] Electrical design draft/ proof of concept (breadboard)
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- [x] Proof of concept validation
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- [x] First PCB layout
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- [ ] More testing/ validation
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Help is always appreciated!
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@ -55,7 +55,7 @@ Help is always appreciated!
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- [x] Microphone summing and line output driver
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- [x] Adjustable headphone mix and output volume
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- [ ] ESD protection and galvanic isolation of line inputs and outputs
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- [ ] VU meter
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- [x] VU meter (own PCB)
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- [ ] Mute and On-Air buttons
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@ -76,8 +76,6 @@ But in our case we just need on/ off and some gain range to adjust for different
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TODO: Integrate the On-Air button with it's LEDs
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For long-lasting endurance of the microphone level potentiometer, we're using one with conductive plastic as resistor element (Bourns model 91).
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#### Line Input/ Input Module
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The line input must not be amplified at all, because loudness control of the headphones is done by the headphone amplifier section.
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But the differential line-level signal must be converted to a single-ended signal by the input stage.
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@ -87,14 +85,18 @@ The second part of that circuit was taken from the [circuitlib audio mixer tutor
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TODO: How to achieve galvanic isolation?
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TODO: Use https://www.ti.com/product/INA134 for input conversion?
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#### Summing
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Summing is needed in two places: Creating the sum of all microphones (not adjustable, fixed output gain) and for the headphone mix (one input level adjustable).
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A simple summing circuit using one operational amplifier is enough for our application, like in [circuitlib audio mixer tutorial](https://www.circuitlib.com/index.php/tutorials/product/39-how-to-build-an-audio-mixer).
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The mixer design uses inverting op-amp circuits, because they require less components and signal routing.
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Normally an audio mixer should take care of adding signals in-phase, because otherwise two microphones might cancel each other out.
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In our case, there are just two types of summing: All microphones for the interpreter unit's line-out and the individual headphone mixes.
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Because the stage input is quite independent of the interpreter's microphones, no special phase/ inversion considerations are needed.
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And the microphones connected to our unit will experience the same inversions anyways.
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#### Line Output Driver
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TODO: Either use https://www.ti.com/product/DRV134 or http://www.thatcorp.com/1600-series_Balanced_Line_Driver_ICs.shtml.
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Line Output conversion is done by the [DRV134](https://www.ti.com/product/DRV134) IC.
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TODO: How to achieve galvanic isolation?
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@ -104,8 +106,17 @@ The headphone output needs a maximum output power of about 0.1 W and should put
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For the first draft, we're using one LM386 audio power amplifier even though it has a quite high minimal amplification of factor 20.
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#### VU Meter
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Because the LM3916 LED bar graph driver is obsolete, we either have to re-create it's function with some comperators or have to use a microcontroller.
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When searching for VU meter circuits, many use the LM3916 LED bar graph driver, which already has the right scaling built in.
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But this chip is obsolete and not produced any more, so we designed our own chain of comperators to drive a set of LEDs.
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#### User Interface Hardware
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For the potentiometers, we first wanted to use ones with a conductive plastic resistor element for maximum longevity from Bourns, but these are hard to find with logarithmic scaling.
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An affordable and easily obtainable (Reichelt) alternative was found in the Alps RK11K and RK14K series.
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They are available in linear and logarithmic scale, as well as single (mono) and dual (stereo) units and have a nice feeling.
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Another potentiometer from Omeg was tried, but it had a "jump" in the resistor value at some knob positions.
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TODO: On-Air button
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## Notes
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@ -122,18 +133,65 @@ Approximate prices in Euro.
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Connectors and Buttons (User Interface)
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| Count | Art. No. | Description | Price |
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|-------|--------------------|------------------|-------|
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| 1 | Neutrik NCJ 6 FAH | Line Input | 1,27 |
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| 1 | Neutrik NC3 FD-LX | Microphone Input | 3,44 |
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| 1 | Neutrik NJ3 FP-6-C | Headphone Output | 5,40 |
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| 1 | Neutrik NC3 MD-LX | Line Output | 3,22 |
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| 1 | Neutrik NAC3 MPA-1 | Main Power Input | 3,33 |
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| Count | Art. No. | Description | Price |
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|-------|---------------------|---------------------|-------|
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| 1 | Neutrik NAC3 MPA-1 | Main Power Input | 3,33 |
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| 1 | Neutrik NCJ 6 FAH | Line Input | 1,27 |
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| 1 | Neutrik NC3 MD-LX | Line Output | 3,22 |
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| 1 | | | TODO |
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| 3x1 | Neutrik NC3 FD-LX | Microphone Input | 3,44 |
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| 3x1 | Neutrik NJ3 FP-6-C | Headphone Output | 5,40 |
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| 3x1 | TODO | Mute Button | TODO |
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| 3x1 | TODO | On-Air Button | TODO |
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| 3x4 | Alps RK11K1120-A503 | 50K log. Gain/ Vol. | 1,32 |
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| 3x1 | Alps RK14K12B0A0R | 50K log. Vol. (st.) | 1,50 |
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| 1 | Vishay M64{Y,Z}104 | 100K Trim Pot. | 0,95 |
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Sub-Components
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| Count | Art. No. | Description | Price |
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|-------|--------------------|------------------|--------|
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| Count | Art. No. | Description | Price |
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|-------|---------------------|---------------------|-------|
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| 1 | Traco Power TXL 035-1515D or TOP 60533 | Power Supply | ~48,00 |
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PCB Components: TODO when schematic is finished
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| Count | Art. No. | Description | Price |
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|-------|---------------------|---------------------|-------|
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| 3 | NE5534 | Low-noise Op-Amp | 0,54 |
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| 8 | LM833 | Generic Op-Amp | 0,88 |
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| 3 | LM386N-4 | Audio Power Amp | 0,83 |
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| 1 | DRV143 | Line Driver | 4,50 |
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| TODO | TODO | El. Capacitor | TODO |
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| TODO | TODO | Cer. Capacitor | TODO |
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| TODO | TODO | Resistor | TODO |
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VU Meter Components
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| Count | Art. No. | Description | Price |
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|-------|---------------------|---------------------|-------|
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| 1 | Vishay M64{Y,Z}104 | 50K Trim Pot. | 0,95 |
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| 1 | LM833 | Generic Op-Amp | 0,88 |
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| 2 | 1N4148 | Signal Diode | 0,02 |
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| 1 | 1k Metal Film | Resistor | TODO |
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| 1 | 3.9k Metal Film | Resistor | TODO |
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| 1 | 47 uF | El. Capacitor | TODO |
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| 1 | 100k Metal Film | Resistor | TODO |
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| 3 | LM339 | Quad-Ch. Comperator | 0,29 |
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| 5 | 100 nF | Cer. Capacitor | TODO |
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| 1 | 1 uF | El. Capacitor | TODO |
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| 5 | Vishay TLHR 5404 | LED red | 0,18 |
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| 4 | Vishay TLHY 5404 | LED yellow | 0,14 |
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| 3 | Vishay TLHG 5404 | LED green | 0,17 |
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| 12 | 390R | Resistor | TODO |
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| 1 | 39R | Resistor | TODO |
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| 2 | 68R | Resistor | TODO |
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| 1 | 100R | Resistor | TODO |
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| 1 | 150R | Resistor | TODO |
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| 1 | 270R | Resistor | TODO |
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| 1 | 390R | Resistor | TODO |
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| 1 | 680R | Resistor | TODO |
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| 1 | 1K | Resistor | TODO |
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| 1 | 1.5K | Resistor | TODO |
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| 2 | 2.7K | Resistor | TODO |
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| 1 | 3.9K | Resistor | TODO |
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Binary file not shown.
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@ -360,53 +360,6 @@ X VO+ 8 1600 150 300 L 59 59 1 1 O
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ENDDRAW
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ENDDEF
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#
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# JBeyerstedt-Library_INA134PA
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#
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DEF JBeyerstedt-Library_INA134PA U 0 10 Y Y 1 F N
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F0 "U" 800 500 60 H V C CNN
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F1 "JBeyerstedt-Library_INA134PA" 800 400 60 H V C CNN
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F2 "Package_DIP:DIP-8_W7.62mm" 800 340 60 H I C CNN
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F3 "" 0 -200 60 H I C CNN
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$FPLIST
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P8
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$ENDFPLIST
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DRAW
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S 300 300 1300 -900 0 1 0 N
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X REF 1 0 -750 300 R 59 59 1 1 W
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X IN- 2 0 -200 300 R 59 59 1 1 I
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X IN+ 3 0 -450 300 R 59 59 1 1 I
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X V- 4 1600 -750 300 L 59 59 1 1 W
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X SENSE 5 1600 -200 300 L 59 59 1 1 I
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X OUTPUT 6 1600 -450 300 L 59 59 1 1 O
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X V+ 7 1600 150 300 L 59 59 1 1 W
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X NC 8 0 150 300 R 59 59 1 1 N
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ENDDRAW
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ENDDEF
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#
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# Jumper_Jumper_3_Bridged12
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#
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DEF Jumper_Jumper_3_Bridged12 JP 0 0 Y N 1 F N
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F0 "JP" -100 -100 50 H V C CNN
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F1 "Jumper_Jumper_3_Bridged12" 0 110 50 H V C CNN
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F2 "" 0 0 50 H I C CNN
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F3 "" 0 0 50 H I C CNN
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$FPLIST
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Jumper*
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TestPoint*3Pads*
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TestPoint*Bridge*
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$ENDFPLIST
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DRAW
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A -65 -50 89 1282 518 0 1 0 N -120 20 -10 20
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C -130 0 20 0 0 0 N
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C 0 0 20 0 0 0 N
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C 130 0 20 0 0 0 N
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P 2 0 1 0 0 -50 0 -20 N
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X A 1 -250 0 100 R 50 50 1 1 P
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X C 2 0 -150 100 U 50 50 1 1 I
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X B 3 250 0 100 L 50 50 1 1 P
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ENDDRAW
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ENDDEF
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#
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# Switch_SW_Push
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#
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DEF Switch_SW_Push SW 0 40 N N 1 F N
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Load diff
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update=Thursday, 12 November 2020 at 23:33:32
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update=Sunday, 13 December 2020 at 21:49:58
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last_client=kicad
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[general]
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version=1
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@ -242,7 +242,7 @@ dPairViaGap=0.25
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[schematic_editor]
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version=1
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PageLayoutDescrFile=
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PlotDirectoryName=
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PlotDirectoryName=../../
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SubpartIdSeparator=0
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SubpartFirstId=65
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NetFmtName=Pcbnew
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File diff suppressed because it is too large
Load diff
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