NGF ADSR: flat Version

NGF ADSR flat side view

NGF ADSR flat side view

This is a derivation off the ADSR for my NGF-E project. Because this one is a stand alone module I have removed all additional features from the Next Generation Formant project. Nonetheless it is still based on original Elektor Formant ADSR schematic. I made some error corrections and added my changes to the design. All parts are updated to today (2017/10) available parts. I have made a few changes to fix some shortcomings of the original. A triple range switch was added for finer adjustment of the ADSR CV-output signal. The attack rise time is shorter now as in the original. The gate input is buffered. The fixes a fault in the original when working with analog sequencers. A manual single shot is added. This comes in handy while testing patches and in live performance. The output voltage is slightly raised to reach really 5V. Due to the design of the original Elektor Formant ADSR the output of the original ADSR keeps a residual voltage of about 0,5V. I have put an (adjustable) compensation in my design to correct this and keep the original behavior if needed as well. The driver circuitry for the output indicator LED is changed for better linearity.
Most noticeable change is moving to a “flat” design. The depth of the module is reduced and most important no more potentiometer wiring is needed!

The documentation for download can be found in my website.

NGF ADSR flat back PCB populated

NGF ADSR flat schematic back PCB

NGF ADSR flat front PCB populated

NGF ADSR flat schematic front PCB

This is a close clone of the Elektor Formant ADSR. Here i only describe the changes i have made. The description of the other parts of the circuitry can be found in the original Elektor Formant documentation. The gate signal input resistance is raised from 33kOhm to 1megOhm with the input buffer IC1A. This protects against double triggering with the falling edge of the gate signal when using sequencers. R30 is used to fix the input to a defined potential when no signal is attached to the input. R34 and R35 in combination with a push button give you the single shot feature. C1 was lowered to 6n8 from 10nF. In combination with C2 and the raised charging voltage through IC1B/R9 this makes for faster attack time. The load capacitor of 10u was replaced with three selectable capacitors of 2,2uF 3,3uF and 6,8uF. This make for a finer adjustment of the response times of the ADSR. The voltage divider R19/R21 was adjusted to ensure that the output level of 5V is reached when the offset option with R32/R33 is used. If this feature is not used R25 should be lowered to 5k1. Construction conditioned the output at IC1D only reaches a minimal voltage of about 0,5V. To compensate for this i added IC2A. With R32/R33 you can trim the output down to zero volts. If the ADSR is not used the output voltage is now at -0,5V. If you don’t want to use this feature just leave R33 out and you will have the original behavior of the original Elektor Formant ADSR. The current consumption was lowered with using the TL064 and a low current led.

NGF ADSR flat front PCB populated

NGF ADSR flat front PCB populated

NGF ADSR flat back PCB populated

NGF ADSR flat back PCB populated

NGF ADSR flat module side view

NGF ADSR flat module side view

NGF ADSR module front view

NGF ADSR module front view

NGF-E Project: RFM

NGF-E Project: RFM stuffed PCB

NGF-E Project: RFM stuffed PCB

This is my replacement of the original Elektor Formant RFM module. It follows closely the original. Because this one is for my Next Generation Formant project i started with the original Elektor Formant RFM schematic and added my changes to the design. All parts are updated to today (2017/10) available parts. The connections are the same as in the original to keep the possibility for internal wiring. If you don’t need those features just leave them out. This PCB provides all functions as in the original Elektor Formant RFM. The only change I have made is adding a wet/dry potentiometer. So you can adjust the balance between the input signal and the filtered signal

The documentation for download can be found in my website.

NGF-E Project: RFM schematic

NGF-E Project: RFM schematic

The schematic follows closely the original Elektor Formant RFM. For details refer to the original documentation.

NGF-E Project: RFM faceplate

NGF-E Project: RFM faceplate

NGF-E Project: RFM back view

NGF-E Project: RFM back view

NGF-E Project: Mix Out (COM)

NGF-E Project: Mix Out (COM) stuffed PCB

NGF-E Project: Mix Out (COM) stuffed PCB

This is my replacement of the original Elektor Formant COM module used in my Next Generation Formant project. I discarded the original circuitry because of the TL085 used with his unusual pinout and the availability of dedicated audio operational amplifiers. I used a more effective filter implementation for tone control. A mixer front end with four external inputs is added to make patching easier. A optional level indicator makes it easier to find the right volume level for best SNR. The maximum output volume is adjustable to protect your PA

The documentation for download can be found in my website.

NGF-E Project: Mix Out (COM) schematic

NGF-E Project: Mix Out (COM) schematic

Nothing special in this schematic. The tone control is a Baxandall type.
Calibration procedure and more information on my website.

NGF-E Project: Mix Out (COM) front view

NGF-E Project: Mix Out (COM) front view

NGF-E Project: Mix Out (COM) back view

NGF-E Project: Mix Out (COM) back view

NGF-E Project: ADSR

NGF-E Project: ADSR stuffed PCB

NGF-E Project: ADSR stuffed PCB

This is my take on the ADSR. Because this one is for my Next Generation Formant project i started with the original Elektor Formant ADSR schematic and added my changes to the design. All parts are updated to today (2017/09) available parts. The connections are the same as in the original to keep the possibility for internal wiring. If you don’t need those features just leave them out. This PCB provides all functions as in the original Elektor Formant ADSR. I have made a few changes to fix some shortcomings of the original. A triple range switch was added for finer adjustment of the ADSR CV-output signal. The attack rise time is shorter now as in the original. The gate input is buffered. The fixes a fault in the original when working with analog sequencers. The output voltage is slightly raised to reach really 5V. Due to the design of the original Elektor Formant ADSR the output of the original ADSR keeps a residual voltage of about 0,5V. I have put an adjustable compensation in my design to correct this and keep the original behavior if needed as well.

The documentation for download can be found in my website.

NGF-E Project: ADSR schematic

NGF-E Project: ADSR schematic

This is a close clone of the Elektor Formant ADSR. Here i only describe the changes i have made. The description of the other parts of the circuitry can be found in the original Elektor Formant documentation. The gate signal input resistance is raised from 33kOhm to 1megOhm with the input buffer IC1A. This protects against double triggering with the falling edge of the gate signal when using sequencers. R12 is used to fix the input to a defined potential when no signal is attached to the input. R33 and R36 in combination with a push button give you the single shot feature. C1 was lowered to 6n8 from 10nF. In combination with C2 and the raised charging voltage through IC1B/R9 this makes for faster attack time. The load capacitor of 10u was replaced with three selectable capacitors of 2,2uF 4,7uF and 10uF. This make for a finer adjustment of the response times of the ADSR. The voltage divider R24/R25 was adjusted to ensure that the output level of 5V is reached when the offset option with TR2 is used. If this feature is not used R25 should be lowered to 5k1. Construction conditioned the output at IC1D only reaches a minimal voltage of about 0,5V. To compensate for this i added IC2C. With TR2 you can trim the output down to zero volts. If the ADSR is not used the output voltage is now at -0,5V. If you don’t want to use this feature just turn TR2 to ground and you will have the original behavior of the original Elektor Formant ADSR. The current consumption was lowered with using the TL064 and a low current led.
Calibration procedure and more information on my website.

NGF-E Project: ADSR faceplate

NGF-E Project: ADSR faceplate

NGF-E Project: ADSR back

NGF-E Project: ADSR back

NGF-E Project: VCA

NGF-E Project: VCA stuffed PCB

NGF-E Project: VCA stuffed PCB

This is my take on the VCA. Because this one is for my Next Generation Formant project i started with the original Elektor Formant VCA schematic and added my changes to the design. All parts are updated to today (2017/08) available parts. The connections are the same as in the original to keep the possibility for internal wiring. If you don’t need those features just leave them out. This PCB provides all functions as in the original Elektor Formant VCA. The CA3080 are replaced with LM13700. The signal level is raised to 10Vpp for a better signal to noise ratio. The added volume indicator us useful for finding the appropriate signal level. The volume indicator is optional. You can leave it out with no problems for the other functions.

The documentation for download can be found in my website.

NGF-E Project: VCA schematic

NGF-E Project: VCA schematic

This is a close clone of the Elektor Formant VCA. It consists off two OTA’s in serial configuration. The first OTA provides the log response and the second one the linear response. IC2A sums up the external and internal audio signal. The circuitry around IC1A provides the log converter, IC1B the linear current source for the second OTA.
Calibration procedure and more information on my website.

NGF-E Project: VCA front view

NGF-E Project: VCA front view

NGF-E Project: VCA back view

NGF-E Project: VCA back view

NGF-E Project: LFO

NGF-E Project: LFO PCB

NGF-E Project: LFO PCB

Here is the LFO module for my NGF-E project. It provides triangle, ramp up, ramp down and square wave output (-5V to +5V) This design follows closely the original from the Elektor Formant.

The documenatation for download can be found in my website.

NGF-E Project: LFO schematic

NGF-E Project: LFO schematic

The oscillator consists of an integrator IC1A and an OpAmp Schmitt-Trigger IC1B. The triangle wave of the oscillator arises through the feedback of the trigger output to the input of the integrator. At the integrator output IC1A arises a triangle with the amplitude of the hysteresis of the Schmitt-Trigger. The input voltage of the integrator sets the rise and fall time of the voltage output. The square wave output is buffered with IC1C. The circuitry around IC1D provides the saw output. IC3C inverts the saw.

NGF-E Project: LFO faceplate

NGF-E Project: LFO faceplate

NGF-E Project: White and coloured noise, random voltage

NGF-E Project: White and coloured noise, random voltage PCB

NGF-E Project: White and coloured noise, random voltage PCB

This is the noise module for my Next Generation Formant project. It is a combination of two original Elektor Formant modules. The Noise module from Elektor Formant book one and the Coloured Noise (CNC) module from book two. It provides a white noise output, a fixed coloured noise output, a variable coloured noise output “red” “blue” and a random voltage output. The noise is derived from the reverse biased BE diode of an NPN transistor.

The documentation for download can be found in my website.

NGF-E Project: White and coloured noise, random voltage schematic

NGF-E Project: White and coloured noise, random voltage schematic

Noise source is the reverse biased BE diode of NPN transistor Q1. The following operational amplifier IC1A and IC1B amplifies the noise to 10Vpp. IC1C is the buffer for the white noise output. The high pass filter C5/R23 and R13/R19 in the feedback loop of IC1D provides a bass boost for the fixed coloured noise output. IC2B is configured as a 12dB low pass. So you get a low frequency random voltage. The changing speed is set with P1A/P1B which sets the corner frequency of the low pass filter. IC2A / LED1 makes the fluctuation visible. Tr1 adjust the brightness of LED1. In the feedback loop of IC3B is an adjustable filter combination which gives you a wide range of adjustable coloured noise with P1 and P2. The output is buffered with IC3A.

NGF-E Project: White and coloured noise, random voltage faceplate

NGF-E Project: White and coloured noise, random voltage faceplate

NGF-E Project: White and coloured noise, random voltage

NGF-E Project: White and coloured noise, random voltage

NGF-E Project: 24dB LP / HP

NGF-E Project: 24dB LP / HP VCF

NGF-E Project: 24dB LP / HP VCF

This is my take on the 24dB LP / HP VCF. This filter type is widely used in many synthesizers. Because this one is for my Next Generation Formant project i started with the original Elektor Formant schematic and added my changes to the design. All parts are updated to today (2017/7) available parts. The connections are the same as in the original to keep the possibility for internal wiring. If you don’t need those features just leave them out. This PCB provides all basic functions as in the original Elektor Formant. The additional functionality is put on an add-on board. The CA3080 are replaced with LM13700. The LP/HP switch is replaced with DG419 to avoid wiring problems. The signal level is raised to 10Vpp for a better signal to noise ratio. The exponentiator for generating Iabc for the OTA’s is temperature compensated. The additional function on this PCB is the linear TM input and the sign changer for the ENV input for easier use when the filter is switched to high pass mode. All other additional functions are on the add-on board. The add-on board provides voltage control for Q and the volume indicator.

The documentation for download can be found in my website.

NGF-E Project: 24dB LP / HP VCF schematic

NGF-E Project: 24dB LP / HP VCF schematic

NGF-E Project: 24dB LP / HP VCF PCB

NGF-E Project: 24dB LP / HP VCF PCB

NGF-E Project: 24dB LP / HP VCF

NGF-E Project: 24dB LP / HP VCF rear view with AddO PCB

NGF Project: 12dB Multimode VCF

This is my take on the 12dB Multimode VCF. This filter type is widely used in many synthesizers. You can find it in Electronotes or in the SEM modules and in many others as well. Because this one is for my Nest Generation Formant project i started with the original Elektor Formant schematic and added my changes to the design. All parts are updated to today (2017/4) available parts. The connections are the same as in the original to keep the possibility for internal wiring. If you don’t need those features just leave them out. This PCB provides all basic functions as in the original Elektor Formant. The additional functionality is put on an add-on board. The The CA3080 are replaced with LM13700. The JFET transistors are replaced with OpAmps. The signal level is raised to 10Vpp for a better signal to noise ratio. The exponentiator for generating Iabc for the OTA’s is temperature compensated. The only additional function on this PCB is the linear TM input. All other additional functions are on the add-on board.

The add-on board provides voltage control for Q, a sign changer for the ENV input for easier use when the filter is switched to high pass mode and volume indicator. This will be covered in another post.

Specs and features

  • 12dB highpass filter, 12dB lowpass filter, 6dB bandpass filter, notch filter
  • Temperature compensated exponentiator
  • 10Vpp signal level
  • TM log input
  • TM lin input
  • Positive and negative ENV control (with AddOn PCB)
  • Volume display (with AddOn PCB)
  • Voltage controlled Q (with AddOn PCB)
  • Runs on +/-15V and +/-12V (with minor resistor value changes)
    NGF Project: NGF 12dB Multimode VCF stuffed PCB

    NGF Project: NGF 12dB Multimode VCF stuffed PCB

    NGF Project: 12dB Multimode VCF schematic

    NGF Project: 12dB Multimode VCF schematic

    NGF Project: 12dB Multimode VCF Front view