Piratelogic EVE User manual

EVE
servo evaluation pcb
VERSION 2020.0
SUBJECT TO PER ANENT DEVELOP ENT
Piratelogic EVE 2020.0 Manual 05/03/2022@07:37:22 Page 1

Contents
Before you start ....................................................................................................................................................................................................................... 3
Prerequisites..........................................................................................................................................................................................................................................................................................................3
Warranty / Disclaimer.......................................................................................................................................................................................................................................................................................3
A ailability ...............................................................................................................................................................................................................................................................................................................3
Copyright...................................................................................................................................................................................................................................................................................................................3
Design scope............................................................................................................................................................................................................................................................................................................3
Bill of materials......................................................................................................................................................................................................................................................................................................4
Schematic description......................................................................................................................................................................................................................................................................................5
Line buffer.......................................................................................................................................................................................................................................................................................................5
4th order high pass...................................................................................................................................................................................................................................................................................5
PXE input buffer...........................................................................................................................................................................................................................................................................................5
Loop Mixer.......................................................................................................................................................................................................................................................................................................6
Limiter...............................................................................................................................................................................................................................................................................................................6
Power..................................................................................................................................................................................................................................................................................................................6
Impro ements o er EVE ersion 2018:........................................................................................................................................................................................................................................6
Main design considerations................................................................................................................................................................................................ 7
Ser o loop gain.......................................................................................................................................................................................................................................................................................................7
Enclosure parameters......................................................................................................................................................................................................................................................................................8
Low Pass Filter.......................................................................................................................................................................................................................................................................................................8
Crosso er points..................................................................................................................................................................................................................................................................................................9
Rumble High Pass Filter....................................................................................................................................................................................................................................................................................9
Accelerometer settings................................................................................................................................................................................................................................................................................10
Bias....................................................................................................................................................................................................................................................................................................................10
Gain...................................................................................................................................................................................................................................................................................................................10
Highpass filter ..........................................................................................................................................................................................................................................................................................10
Lowpass filter............................................................................................................................................................................................................................................................................................10
Configuring the Ser o Feedback Loop......................................................................................................................................................................... 11
DIYaudio test case............................................................................................................................................................................................................................................................................................11
Basics........................................................................................................................................................................................................................................................................................................................11
Example ScanSpeak ..........................................................................................................................................................................................................................................................................................12
Free air response....................................................................................................................................................................................................................................................................................12
Closed box response..............................................................................................................................................................................................................................................................................12
Loop phase.............................................................................................................................................................................................................................................................................................................13
Loop bandwidth...................................................................................................................................................................................................................................................................................................13
Amplifier bandwidth.........................................................................................................................................................................................................................................................................................13
Building EVE ............................................................................................................................................................................................................................. 14
Power requirements........................................................................................................................................................................................................................................................................................14
Choosing Components....................................................................................................................................................................................................................................................................................14
Onboard Regulators.........................................................................................................................................................................................................................................................................................14
PCB Layout ............................................................................................................................................................................................................................... 15
Top layer names..................................................................................................................................................................................................................................................................................................15
Bottom layer - names.....................................................................................................................................................................................................................................................................................16
Bottom layer - alues.....................................................................................................................................................................................................................................................................................17
PCB circuit..............................................................................................................................................................................................................................................................................................................18
Dri er Selection..................................................................................................................................................................................................................... 19
O erall design considerations..................................................................................................................................................................................................................................................................19
Main selection criteria...................................................................................................................................................................................................................................................................................19
Accelerometer Selection.................................................................................................................................................................................................... 20
The original Philips MFB sensor...............................................................................................................................................................................................................................................................20
Measurement specialities ACH-01.........................................................................................................................................................................................................................................................20
Piratelogic Sensors.........................................................................................................................................................................................................................................................................................21
Starbass ClingOn................................................................................................................................................................................................................................................................................................21
Starbass Stripper..............................................................................................................................................................................................................................................................................................21
StarBass 26 ...........................................................................................................................................................................................................................................................................................................21
StarBass 54............................................................................................................................................................................................................................................................................................................21
ClingOn ariants C1, C2, C3..........................................................................................................................................................................................................................................................................22
Addendum.................................................................................................................................................................................................................................. 23
Errata.........................................................................................................................................................................................................................................................................................................................23
Document history..............................................................................................................................................................................................................................................................................................23
About the author................................................................................................................................................................................................................................................................................................24
Piratelogic EVE 2020.0 Manual 05/03/2022@07:37:22 Page 2

Before you start ....
Thank you for purchasing the EVE pcb, please note this manual is subject to permanent de elopment so
expect grammar & spell checks, corrections and impro ements, read the ERRATA section before building EVE !!
Prerequisites
In order to successfully assemble the pcb the following prerequisites are needed.
◦ESD safe working en ironment : EVE contains ESD sensiti e jFet de ices, please adhere to guidelines for
safe handling of ESD sensiti e components during assembly of the sensors.
◦SMD soldering station : the EVE design uses surface mount technology and requires handling and use of
an appropriate soldering station to a oid thermal damage to the used parts when soldered onto the PCB.
Warranty / Disclaimer
Although this pcb has been de eloped with lots of lo e, tenderness and de otion and has been tested with
numerous MFB enclosures it is subject to constant research and de elopment and as such no guarantees
and/or warranties can be gi en for the correct / optimal / failure free working of the module. No
responsibility is taken for any damage resulting from the use of this module.
Designing & building servo drive systems like described in this manual requires a
thorough understanding of and working experience with the underlying electronics. An
engineering degree and experience with component level board repair is strongly advised.
This is N starter project !!!!
A ailability
Bare EVE printed circuit boards without components are a ailable for 15 euro a piece by sending an email to
chris*nospam*piratelogic.nl – replace *nospam* with the standard @. At the time of writing pricing for a smd
prepopulated pcb are being negotiated and will appear here in future manual updates. Pricing excludes VAT
and shipment.
Copyright
The EVE circuit design is free for use both for hobby as well commercially.
Design scope
Back in 2017 EVE got originally de eloped as a quick and dirty solution to add ser o bass functionality to an
ADAM A7 monitor in conjunction with a StarBass IV accelerometer equipped woofer. EVE 2020.0 basically
follows an identical setup with the quick and dirty parts remo ed and has been optimized using user input to
impro e both its performance as well as its ease of implementation.
MAY THE MUSIC PASSING THROUGH THIS DEVICE
SOMEHOW HELP TO BRING JUST A LITTLE MORE PEACE
TO THIS TROUBLED WORLD
Piratelogic EVE 2020.0 Manual 05/03/2022@07:37:22 Page 3

Bill of materials
The parts listed below are surface mount de ices, the schematic parts listed Cx and Rx are through-hole
components which alues are setup dependend. The LCSC identifiers can be used with
https://jlcpcb.com/parts .
Piratelogic EVE 2020.0 Manual 05/03/2022@07:37:22 Page 4
Part Value Packa ge Des c ription LCSC MOUSER MPN
78XX 7812 SOT89-3 Voltage stabilizer C8615 CJ78L12
79XX 7912 SOT89-3 Voltage stabilizer C8626 CJ79L12
C17 100n C0805 SMD capacitor C49678 CC0805KRX7R9BB104
C18 100n C0805 SMD capacitor C49678 CC0805KRX7R9BB104
C19 100n C0805 SMD capacitor C49678 CC0805KRX7R9BB104
C2 10n C0805 SMD capacitor C1710 CL21B103KBANNNC
C20 100n C0805 SMD capacitor C49678 CC0805KRX7R9BB104
C21 100n C0805 SMD capacitor C49678 CC0805KRX7R9BB104
C22 100n C0805 SMD capacitor C49678 CC0805KRX7R9BB104
C3 10-16 SMC_A SMD capacitor C7171 TAJA106K016RNJ
C7 10n C0805 SMD capacitor C1710 CL21B103KBANNNC
C9 10-16 SMC_A SMD capacitor C7171 TAJA106K016RNJ
IC1 5532 SO08 AUDIO AMPLIFIER C7426 NE5532DR
IC2 5532 SO08 AUDIO AMPLIFIER C7426 NE5532DR
IC3 5532 SO08 AUDIO AMPLIFIER C7426 NE5532DR
IC4 5532 SO08 AUDIO AMPLIFIER C7426 NE5532DR
LED- CHIP-LED0805 LED FC-2012HRK-620D
LED+ CHIP-LED0805 LED FC-2012HRK-620D
LINE.GAIN 5K B25P POTENTIOMETER 652-3362P-1-502LF
PXE.BIAS 5K B25P POTENTIOMETER 652-3362P-1-502LF
PXE.GAIN 5K B25P POTENTIOMETER 652-3362P-1-502LF
R1 1501 R0805D SMD resistor C4310 0805W8F1501T5E
R11 1001 R0805D SMD resistor C17513 0805W8F1001T5E
R12 1002 R0805D SMD resistor C17414 0805W8F1002T5E
R13 1003 R0805D SMD resistor C17407 0805W8F1003T5E
R14 4702 R0805D SMD resistor C17713 0805W8F4702T5E
R15 1003 R0805D SMD resistor C17407 0805W8F1003T5E
R17 1001 R0805D SMD resistor C17513 0805W8F1001T5E
R19 1003 R0805D SMD resistor C17407 0805W8F1003T5E
R2 4702 R0805D SMD resistor C17713 0805W8F4702T5E
R20 1001 R0805D SMD resistor C17513 0805W8F1001T5E
R23 680R R0805D SMD resistor C17798 0805W8F6800T5E
R25 1002 R0805D SMD resistor C17414 0805W8F1002T5E
R26 1002 R0805D SMD resistor C17414 0805W8F1002T5E
R29 1002 R0805D SMD resistor C17414 0805W8F1002T5E
R3 1001 R0805D SMD resistor C17513 0805W8F1001T5E
R30 1002 R0805D SMD resistor C17414 0805W8F1002T5E
R31 680R R0805D SMD resistor C17798 0805W8F6800T5E
R32 680R R0805D SMD resistor C17798 0805W8F6800T5E
R4 4701 R0805D SMD resistor C17673 0805W8F4701T5E
R6 4701 R0805D SMD resistor C17673 0805W8F4701T5E
R8 1001 R0805D SMD resistor C17513 0805W8F1001T5E
R9 1001 R0805D SMD resistor C17513 0805W8F1001T5E
T1 BC849 SOT23 NPN TRANSISTOR 863-BC849CLT1G
T2 BCV62 SOT143B PNP current mirror 726-BCV62CE6327
C84256
C84256

Schematic description
Line buffer
The line buffer circuitry performs the following functions:
•The incoming audio signal arri es at LINE.IN where passes DC blocking capacitor C1 which together
with R2 and the input resistance of the 5532 - typically 300K – forms a 1st order high pass set at
3.9hz.
•To minimize EVE's rf input susceptibility the lowpass filter R1,C2 is used, with C2=10n the LPF is set
at 10Khz. To a oid microphonics make sure to use a NP0 for C2 !
•Depending on your setup and power amplifier gain setting the EVE gain can be set between 2.6 and
11x with LINE.GAIN to adapt for use with to low gain final stages.
4th order high pass
The bandwith for the incoming line buffer signal is set by the 4th order HPF build around IC1b and IC4b and
the 2nd order LPF around IC4a.
PXE input buffer
The pxe input buffer processes the incoming accelerometer current signal and performs the following
functions:
•The accelerometer current souce signal enters EVE at PXE.IN where it passes rf filter R9,C7 which
corner freqency is set to 7234 hz. To a oid microphonics make sure to use a NP0 for C7 !
•To adapt for jFet Vgs ariations EVE allows the accelerometer bias oltage set for optimal linear
operation by setting PXE.BIAS oltage for T1, the standard StarBass bias oltage is 6V.
• The output of the current mirror T2 arri es at IC2a which allows phase in ertion of the
accelerometer signal. Sensor signal gain and low pass is pro ided by IC3a, for measurement
purposes the accelerometer signal is made a ailable ia PXE.OUT. Use the OPENLOOP jumper to
perform open/closed loop measurements.
Piratelogic EVE 2020.0 Manual 05/03/2022@07:37:22 Page 5

Loop Mixer
The buffered, amplified and lowpassed StarBass signal arri es at IC3b where it is summed with the incoming
audio signal ia R26. C15, C16, R27 and R28 are used for setting loop gain and shaping.
Limiter
LED+ and – are used to limit the output of IC3b. Take care not to illuminate these externally to a oid the
introduction of DC components into the feedback loop - thanks esl63@diyaudio for bringing this to my
attention . The phase in erter IC2B is used to build the symmetric OUTPUT 3+ and 1-.
Power
7812 and 7912 are standard oltage regulators to allow EVE from being operated from the power amp rails,
E e's current draw is 40mA max, use R33 and R34 to bleed of excessi e rails (regulator inputs are max +/-
35V).
Impro ements o er EVE ersion 2018:
•Input buffer
•Low noise pxe buffer with adjustable accelerometer bias oltage
•Through-hole loop shaping / filter parts & rails bleeders
•Max rails +/- 60V
•Open/closed loop mode switch
•led loop limiter
•Symmetric line out
•ne5532 opamps
•50x50 mm pcb size.
•JST headers
Piratelogic EVE 2020.0 Manual 05/03/2022@07:37:22 Page 6

Main design considerations
Being designed as a generic mfb correction module EVE supports a wide ariety of dri er, enclosure and
loopgain choices. Because of this generic setup it is not possible to pro ide a common set of component
alues, to assist the user with making educated choices the following information is gi en. Ser o / Motional
feedback does not work with Helmholtz resonator based enclosures such as bass reflex boxes.
Ser o loop gain
EVE has been designed to offer a theoretical maximum ser o loopgain of 20dB, refer to below graph for the
relation between ser o loopgain and a Q0.7 enclosure frequency response. Ser o loopgain determines:
•The F3mfb, the higher the amount of gain the lower the resulting F3mfb will be.
•Maximum SPL, the 'extra' energy is rerouted to low extension.
•The amount of second and third harmonics supression a ailable .
Piratelogic EVE 2020.0 Manual 05/03/2022@07:37:22 Page 7

Enclosure parameters
The first step is to set the low frequency pole for your mfb box F3mfb equal to the dri er physical resonance
frequency F3dri er or higher, choosing alues below F3dri er will se erely limit dri er efficiency due to
usage outside it's physical limits.
The second step is to choose an enclosure olume using the standard closed box design formulas combined
with the dri er T&S parameters – to ease down on the in ol ed math use a program like WinISD. Start with an
enclosure Q of 0.7. As displayed abo e 12dB MFB loopgain allows you to split F3box in half so if the desired
lower frequency pole of your finished box F3mfb is 60hz the chosen F3box should be 120hz or lower.
Example WINISD response plot for a
dri er with a Fc of 60hz mounted in a
sealed Q=0.7 enclosure with a natural
Fbox of 120hz which is mo ed down to
Fmfb of 60hz.
Keep in mind that the higher
Qbox is chosen (= smaller box)
the harder the dri er will need
to work to reach the required
excursion, as such one is
discouraged from using Qbox
alues abo e 1 as it will limit
system efficiency and SPL.
Low Pass Filter
The 3rd step is to decide on a low pass filter frequency -
Flpf - using the dri ers datasheet as reference. EVE's
onboard lowpass filter follows a 2nd order Sallen Key
setup, as such it is ad ised to choose Flpf at least 1
octa e away from the first occurrence of cone breakup.
In the example on the right cone breakup occurs in the
red region onwards 2500hz making 1250hz or lower a
alid choice for Flpf
For mfb to work best the dri er cone mo ement
needs to be pistonic in the area your loop is
acti e in – oicecoil mo ement must mimic the
cone without any partial ibrations like shown for
the guitar speaker image (courtesy
https://www.premierguitar.com) on the right.
Without pistonic mo ement the correction signal
will contain distortions that will mess up your
control loop. None pistonic mo ement, also called
cone breakup, introduces partial distortions
which are not 'heard' by the accelerometer and
thus not co ered by the feedbackloop.
Piratelogic EVE 2020.0 Manual 05/03/2022@07:37:22 Page 8

Crosso er points
Using F3mfb and Flpf and F3box the component alues for the desired crosso er points can be calculated. The
blue cur e represents F3mfb and the green cur e Flpf. These alues were calculated using http://sim.okawa-
denshi.jp/en/OPstool.php for the lowpass and http://sim.okawa-denshi.jp/en/OPseikiHikeisan.htm for the
highpass filters.
Rumble High Pass Filter
When choosing alues for the rumble hpf be aware of the fact that the ser oloop will attempt to correct cone
motion right down to the lower pole of the EVE circuit. So if the system is offered a 5hz signal from a wobbly
recordplayer it will make the connected dri er follow this signal no matter it's amplitude. In the oldskool
days this was the reason why commercial amplifiers were often equipped with a so called “SubSonics” filter.
Be careful not to set the rumble frequency too low, -3dB @ 10hz may look nice on your spec list but will
se erly stress your dri er when connected to a 500 watt Class D amp. Perform a LF sweep before deciding on
how low you want things to go and keep in mind that a erage electronic music starts at 20hz.
In case EVE is to be used with existing acti e enclosures it's build-in rumble and lowpass filters may need
disabling:
•Disabling the rumble filter : omit R7, R10, R16, R18 and replace C5, C6, C10, C11 with wire bridges.
•Disabling the lowpass filter : omit C13, C14 and replace R22, R24 with 0 ohm resistors.
Piratelogic EVE 2020.0 Manual 05/03/2022@07:37:22 Page 9
R7,R10,R16,R18 (K) R22,R24 (K)
100 15 106 2.2 47 100 1055 1n5
100 18 88 3.3 47 100 703 2n2
220 10 72 3.9 47 100 595 2n7
220 12 60 4.7 47 100 493 3n3
220 15 48 2.7 100 220 397 3n9
220 18 40 3.3 100 220 325 4n7
220 22 32 3.9 100 220 275 5n6
220 27 27 4.7 100 220 228 6n8
220 33 21 5.6 100 220 191 8n2
4 t h o r der R um b l e f il ter I C1 B , I C4 B Q = 0.5
2n d o rd er Lo wp ass f ilter I C1 C Q= 0.7 4
C5,C6,C10,C11 (nF) Frequency (hz) C14 (nF) C13(nF) Frequency (hz) C16 (nF)

Accelerometer settings
Bias
All StarBass accelerometers use a jFet transistor as impedance transformer with the pxe sensor element
connected between it's gate and source. To obtain linear operation the jFet is biased into its ohmic region by
setting Vgs to 0Vdc and placing a resistor o er the pxe element which itself beha es like a capacitor :
image courtesy of https://www.industrial-electronics.com/electrnc-d cs-9e_8.html
To minimize StarBass distortion while maximizing it's output EVE2020 allows you to bias the pxe oltage
between 4 and 8V using the PXE.BIAS potentiometer to accommodate for different Vgs oltages. For further
information regarding jFet gate-source pinch off oltages see https://en.wikipedia.org/wiki/JFET
Gain
Acceleration sensor output is determined both by its sensiti ity in mV/G as well as the dri ers linear cone
excursion - to reproduce a certain SPL a small diameter dri er will need to perform larger excursions then a
large diameter dri er, as such the accelerometer output is depended on the dri er cone diameter. Longstroke
dri ers with a high Xmax will typically exhibit a relati e high signal output when compared to standard
dri ers. To accommodate for this ajust PXE.GAIN which sets the gain for the incoming accelerometer signal.
Highpass filter
To a oid problems caused by the difference between the mirror output and opamp input DC le els a capacitor
C8 was added to the circuit. The lower pole for the accelerometer signal Fpxe.low determines the low end
loop stability and should be chosen at least at one tenth of F3mfb, too high alues in respect to F3mfb will
cause phase shift induced LF oscillations. Starting alues for C8 and R19 are 680n and 120K setting Fpxe.low
at 2hz. See also the topic Amplifier bandwidth in the chapter Configuring the Ser o Feedback Loop .
Lowpass filter
The high pole for the accelerometer signal – Fpxe.high – a oids dri er breakup from entering the summation
signal at IC3b. As a starting alue half the low pass filter frequency Flpf should be used when calculating C12.
C12 Sensor cut-off frequency C12 Sensor cut-off frequency
2n2 7200 hz 8n2 1940 hz
3n3 4822 hz 10n 1591 hz
3n9 4080 hz 15n 1061 hz
4n7 3386 hz 22n 723 hz
5n6 2842 hz 33n 482 hz
6n8 2340 hz 47n 338 hz
Piratelogic EVE 2020.0 Manual 05/03/2022@07:37:27 Page 10