blackbeauty+symasym*anleitung.diy-audio-shop.de/symasym-bb.pdf ·...

BlackBeauty -‐ SYMASYM – Builder’s Manual

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BlackBeauty -‐ SYMASYM

Builder’s Manual

Author: Rudi_Ratlos

(The image above shows my SYMASYM prototype)


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Contents

• 1 Foreword ................................................................................................................... 3 • 2 Which tools do you need for the build? .................................................................... 4 • 2 Which tools do you need for the build ...................................................................... 4 • 3 Components of the NJW – SYMASYM Group-‐Buy Fehler! Textmarke nicht definiert. • 4 The Soft-‐PowerOn -‐ PCB ........................................................................................... 8 • 5 The NJW-‐SYMASYM Backend-‐PSU ........................................................................... 11 • 6 The NJW – SYMASYM – PCB .................................................................................... 15 • 7 Adjusting the Quiescent current ............................................................................. 25 • 8 The Speaker Protection section ............................................................................... 28 • 9 Appendix ................................................................................................................. 30


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1 Foreword

The SYMASYM – amplifier has been developed by the German Michael Bittner in 2005. This is the thread describing its birth:

http://www.diyaudio.com/forums/solid-‐state/60918-‐explendid-‐amplifier-‐designed-‐michael-‐bittner-‐our-‐mikeb.html

The SYMASYM has become famous in Germany, after Holger Barske, editor of the German audio-‐magazine “Klang+Ton“, organized a Group-‐Buy in the German Analog-‐Forum: http://www.analog-‐forum.de/wbboard/index.php?page=Thread&threadID=25151

All technical questions regarding SYMASYM can be found in this thread:

The layout of the SYMASYM at hand is based upon its version 5.3. Additionally I have included a CAP-‐multiplier, a PSU-‐ and a Speaker-‐Protection-‐Circuit on the PCB.

This manual is intended to support you in building your amplifier.

It also documents the build of the PSU-‐, Speaker-‐Protection-‐ and Soft-‐PowerOn section/PCB.

Please read these instructions before you start with your project.

Good luck in the building and enjoy the sound.

Rudi


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Which tools do you need for the build?

2 Which tools do you need for the build You need a soldering iron, a desoldering tool and solder.

My Weller Magnastat soldering iron is a 50 watt soldering iron with 2 tips: a fine tip to solder the small transistors, resistors, ... and a wide tip to solder large components or connectors, particularly if their pads lie within a large copper area. The solder that I use is 0.5mm thick.

What else do you need?

You will need a digital multimeter to measure AC and DC voltages and resistor values. It would be nice, if your multimeter provides a means of measuring the HFE of the small transistors (BC548B). You will then be sure about the correct pin assignment (EBC or CBE).


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Use the multimeter to measure the value of a resistor before you solder it onto the PCB. Maybe an employee of your provider of electronic components has packed an incorrect value into your basket, for example: a 10K ohm instead of 10 Ohm. Such an error may lead to unpredictable results with the finished board that are very difficult to debug. I even measure a resistor’s value, after I have soldered it, to be sure not to have broken it while bending its legs. The alcohol (Isopronanol, 75%) and the toothbrush are needed to clean grease stains and dirt from the PCB before you start to solder, and to remove the solder-‐flux when you have finished. Please do not clean the PCB with water after soldering. Water and solder flux enter into a greasy, unpredictable result.

On the left you see a PCB that was cleaned with water after soldering. The image on the right shows the same board cleaned with alcohol after soldering.

The magnifying glass is used (for example) to assure yourself of the state of a solder joint, to decipher the inscription on a small transistor, ... What about the carpet knife? It may be used to scrape a copper-‐trace … A drill rig would obviously not be bad and / or a small battery-‐powered drill.


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And -‐ last but not least: the bending tool of Reichelt. Please bend a component’s legs very gently! Do not break any component’s legs.

For mental support you may need one of these “tools”:

or or


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For the construction of the NJW -‐ SYMASYM you do not need a function generator, an oscilloscope or other “highly-‐sophisticated” electronic devices (as long as you work carefully). Please take care when you handle the 110V/230V mains voltage. Generally, when you start your build, you should solder the components with small heights (diodes, resistors, …) first and then proceed with the components with larger heights like transistors, capacitors, connectors,… . Work from the shorter to the taller.

3 Components of the NJW – SYMASYM Group-Buy Additionally to the SYMASYM – PCB I offer the following “hard-‐to-‐get” – components:

-‐ the C1 input-‐capacitor, Vishay MKT1822 / 4.7µF paralleled by a MKP1837 / 10nF -‐ the MPC74 0R22 / 5W emitter resistors -‐ matched pairs of NJW0281G / NJW0302 transistors

and, if you like to have it, a “Soft-‐Power-‐On” – PCB. As output-‐transistors you can use:

-‐ the ONSEMI MJL4xxx – transistors in TO264-‐case -‐ the ONSEMI NJW0xxx – transistors in TO3-‐P case -‐ the SANKEN 2SC3263 / 2SA1294 in TO3-‐P case

I do not recommend to use the TOSHIBA 2SC5200 / 2SA1943 transistors, since they have a tendency to oscillate.


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4 The Soft-PowerOn - PCB Let us start with the Soft-‐Power-‐On PCB. The task of the SPO-‐PCB is to limit, for a short period, the inrush current flowing into your transformers after mains power on -‐ until the transformer(s) are “saturated“. This limitation will prevent your fuses from melting if a very big inrush current flows. The SPO-‐PCB is required / recommended if you use transformers with a total power >500W. Find its schematic below:

Mains Hot is connected to pin 4 of connector X3; Mains Cold (Neutral) is connected to pin 4 of connector X1. Connect the primary winding(s) of your transformer(s) to poles 1-‐3 of connector X1 resp. X4. You can connect the leads of a PowerOn – Switch in your case’s front to contact 1 and 2 of the connector labelled X2. This switch needs to conduct less than 50mA of current. As long as relay K3 is open, mains current will not flow. Relay K3 will be activated, as soon as the 7805 voltage regulator has reached 5VDC on its output, and mains current will flow, but since relay K4 is still open, the current will be limited by 2 NTCs wired in series. I am using a value of 22 Ohm for the NTCs.


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If you do not have NTCs, you may use power-‐resistors instead (for example 2 pieces of 25W METALL 100 (this is the Reichelt component name) in parallel and screw them onto the bottom plate of your case. About 1 second later relay K4 will be activated by the output of the LM555 timer and transistor T1. The delay is determined by potentiometer R6 and capacitor C1 and can roughly be calculated as: 1.1 * R1 * C1. You can change these values at your needs. A value of 47K – 68K for R6 is sufficient in my eyes! Only a few cycles of 50/60Hz mains are needed to saturate the connected transformer/s. From now on the mains current will flow unhindered through K3 and K4, passing a subsequent Mains DC-‐filter, into the 4-‐pole output connectors. Connect your Shown below is the SPO-‐PCB as seen from above (“looked-‐through”).

Please take care of the orientation of the TAMURA-‐transformer, when you insert it into the PCB and solder it. Pins 1-‐4 of the TAMURA-‐transformer must point to the right side of the PCB!


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Users of 230VAC/50Hz MAINs need to solder a wire between Pin 2 and Pin3 of the TAMURA-‐transformer (to serialize the primary windings of the transformer). Users of 115VAC/60Hz MAINs need to solder a wire between Pin 1 and Pin 3 and a wire between Pin 2 and Pin 4 of the TAMURA-‐transformer (to parallel the primary windings). I have added 4 holes adjacent to the solder -‐ pins of the TAMURA that you can use for this purpose. Please test the functionality of the SPO-‐PCB, before you connect your amplifier to it. The Status-‐LED will shine (for example), when the MAINs current flows unhindered. This is the BoM for the Soft-‐PowerOn PCB:

This is the URL of the Reichelt –shopping -‐cart for the SPO – PCB: https://secure.reichelt.de/index.html?&ACTION=20&AWKID=945445&PROVID=2084 The shopping cart does not include the NTCs, since Reichelt does not offer them.


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5 The BlackBeauty-SYMASYM Backend-PSU

At the time when I did the layout for the SYMASYM, I had a “dual-‐Mono-‐build” in mind, giving each channel a transformer and PSU of its own. I therefore integrated the Backend-‐PSU on the SYMASYM’s PCB. Below is the schematic of the resulting PSU:

Shown below is the silkscreen of the Backend-‐PSU.


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The backend-‐PSU is connected to a transformer with 2 secondary windings, rated at 25 VAC, resulting in DC-‐voltages of about +/-‐ 35VDC. I recommend to use toroids from Talema, which can be bought from www.tme.eu, or – as I did – order a custom-‐built 4x25VAC transformer from BADEL.

Before you continue: Please be very careful when you handle the 230V/115 VAC mains voltage, the transformer and the power supply PCB. I therefore recommend you to use of a “current limiter”, while you are testing.

I built my current limiter 40 Watt / 230 Volt high-‐voltage halogen bulb-‐tester with socket (Price: 5 € on eBay) and wired it into the “hot lead” of the transformer’s primary winding. The purpose of the current delimiter is to ensure that a short on the power supply or output stage will not cause big harm. The output of the secondary windings is limited to 40 watts by the bulb-‐tester. At 40 watts the 2 secondary windings provide a current of about 500mA, which is high enough to adjust the SYMASYM and even to listen to music at low volumes.


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Be sure to correctly connect your transformer to the 4-‐pole PCB-‐connector located in the middle on the PCB’s left side. The transformers that I normally use, have 2 secondary windings labelled as follows: Winding 1: red – black Winding 2: yellow – orange The end of winding 1 (the black wire) together with the start of winding 2 (the yellow wire) constitute “GND” and need to be screwed into pole 2 and 3 of the 4-‐pole PCB connector as shown on the image below.

The alternating voltages of the transformer’s secondary windings are rectified by four diodes D7-‐D10. I recommend to use MUR8x0 rectifier diodes here. As a rule of thumb each ampere that flows into the output stage shall be buffered with about 5.000μF capacitance on its power-‐rail. The shown 10.000µF power cap has a grid of 10mm and a maximum diameter of 35mm.


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The suggested backend-‐PSU will give you a total capacitance of 2x1.000µF + 10.000µF + 2x1.000uF per Power-‐Rail, which is more than enough. Capacitors with a rating of 40V are sufficient, if you use transformers with 24-‐25 VAC secondary windings. Before connecting a PSU to a SYMASYM, remove the fuses and verify the PSU’s output voltages and check, if the 2 LEDs shine.

The following image shows an image of my prototype:

This is the BoM for the BlackBeauty-‐SYMASYM – Backend -‐ PSU:

… and this is the according Reichelt shopping cart: https://secure.reichelt.de/index.html?&ACTION=20&AWKID=939684&PROVID=2084


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6 The BlackBeauty – SYMASYM – PCB The BlackBeauty– SYMASYM PCBs contains 3 sections:

-‐ the SYMASYM, version 5.3, with cap-‐multiplier, on the left side -‐ the backend-‐PSU in the middle of the PCB -‐ the Speaker Protection circuit on the right side

It is really best practice to solder the components with small heights (diodes, resistors, …) of all sections first and then proceed with the components with larger heights like transistors, capacitors, connectors,… Do not solder the SpeakerProtection section, before you have successfully checked the build of the SYMASYM-‐ and the PSU-‐section.


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You need some time to do a successful build of the SYMASYM. Take care, before you solder a component. Measure the value of a component, before you solder it, verify that you are using the correct component (for example transistor) at its specific location, check that you did not solder a short, … I have attached the schematic of the SYMASYM, its silkscreen (with values) and its silkscreen (with names) at the end of this document. The kernel of the SYMASYM – circuit is identical to version 5.3 of Michael Bittner’s SYMASYM. I have expanded the circuit by a CAP-‐multiplier that smoothes the voltages supplied to the front-‐end and gave my SYMASYM-‐version pairs of NPN-‐ and PNP -‐ output-‐transistors (instead of only one of each). This SYMASYM will then support speakers with lower impedance (<4 Ohm). If you connect an active pre-‐amplifier to the SYMASYM, it is advised to lower its total gain. In this case choose a 1K resistor for R36 and use 22 Ohm resistors for R29 and R30. If you do not use an active pre-‐amplifier, then short R29 and R30 and use a 499 Ohm resistor as R36. The attached schematics / the PCB’S silkscreen show wrong values (a mix of the values). Either – or: see above. If you do not use a pre-‐amplifier at all, but use a dual potentiometer (for example an ALPS 20K dual log. potentiometer), this potentiometer shall be connected as follows:


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Further information about the use / the not-‐use of active-‐preamplifiers can be found on the web-‐site of Michael Bittner respectively in the German Analog-‐forum: http://www.analog-‐forum.de/wbboard/index.php?page=Thread&threadID=25151 Start your build by cleaning the component-‐ and the solder-‐side of the BlackBeauty – SYMASYM with Isopropanol and a piece of tissue. As I recommend in the foreword, begin with the wire-‐links, resistors and diodes. Go on with the MICA caps and the small capacitors.

I have selected (put into the BoM) a 10x3mm, grid: 10mm capacitor for the Zobel element (C15 – R14). All other WIMA capacitors have a grid of 5mm. Most of the resistors are standard 0.25W resistors; I myself use Metall resistors, 1% precision, produced by YAGEO /Vitrohm. They are rated at 0.6W. Resistors R22, R35, R24 and R80 – 1W types, these are the emitter base blockers – need to be mounted vertically. There are 4 resistors with a bigger “footprint”: the Zobel-‐resistor R14, the 4 power-‐rail resistors (R37, R45, R46 and RR47 – you can use MPC74 0R22 resistors in these positions) and resistor R14 on the output (EMI-‐filter resistor). Take 2W type resistors for these. As output-‐transistor emitter resistors I recommend to use MPC74 0R22 resistors. The output-‐resistor R58 is a 10 Ohm / 2 W resistor (AndrewT. recommends to use a 4 Ohm resistor on the output) with about 20 turns of 1mm enameled wire wound around it. Please take care of the orientation of the pins of a device, when you solder the small transistors, diodes and LEDs – and use the correct transistor at a specific location.


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You can choose 2SK170 (BL, GR), BC550C, MPSA18 and 2N5551 as the input differential transistors Q1 and Q2. My own tendency goes to the 2SK170 respectively the MPSA18. I will put Q1 and Q2 into small 3-‐pin IC – sockets to be able to change them quickly and to listen to the resulting differences in sound. But take care: the PCB silkscreen shows the 2SK170 – transistor pinout; if you use the MPSA18, you have to rotate it by 180 degrees (flip the MPSA18 for example). The input resistors Q1 and Q2 shall be very closely matched. I have enclosed the images of the used transistors below:


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I recommend to bend the pins of a transistor, before you solder it to avoid mechanical tension.

I have added the input-‐, DC-‐blocking capacitor C1 with a variable grid from 5mm to 27,5mm. Choose a value from 3.3µF to 10µF for it. I recommend to use the Vishay MKT1822 / 4.7µF capacitor, paralleled by a MKP1837 / 10nF. Please do not buy a “fancy” input-‐capacitor. The only purpose of C1 is to block DC. You can use 40V type electrolytic-‐capacitors with your 25VAC transformer. C3 can be a 16V type capacitor. The 4 1000µF rail-‐capacitors C47, C48, C49 and C50 have a grid of 7,62mm. Their diameters must not exceed 18mm. Solder these caps at the very end! The circuit uses 2 LEDs (diameter: 3mm) to show you the presence of the +/-‐ 35VDC rail voltages. The anode of a LED (the longer pin) is denoted with the letter “a” on the PCB’s silkscreen. Before you solder the trim-‐resistor R18, please adjust it to its maximal value of 500 Ohm (the resistance between the pin below the screw and the wiper). When you solder the Emitter resistors R82, R26, R20 and R25 (MPC74 0R22 / 5W resistors), please put a match (or something similar) underneath them, so that they stand up 1-‐2mm from the PCB and the air can circulate around them.


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The PCB uses two 3-‐pole jumpers (Jumper 1 and Jumper 2) to activate / deactivate the on-‐board CAP-‐multiplier.

If you put a jumper-‐cap on positions 1-‐2 of the jumper, the CAP-‐multiplier is activated. If you put a jumper-‐cap on positions 2-‐3 of the jumper, the SYMASYM’s frontend will be powered from the backend-‐PSU’s power-‐rails. An activated CAP-‐multiplier will smooth the voltages needed for the frontend of the SYMASYM. It will furthermore (by means of the 36V Zener-‐diode) restrict the frontend-‐voltages to values < 36V and protect the input transistors (for example: the maximum gate-‐drain breakdown voltage of the 2SK170 is 40V), in case that you are using a transformer with >25 VAC secondaries. You also have the possibility to power the SYMASYM’s frontend from an external PSU that is connected to the 3-‐pole connector on top of the input-‐cap (Pin1: -‐V, Pin2: GND, Pin3: +V). Do not install any jumper-‐cap on jumper 1 and jumper 2 in this case..


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The last thing to do is to screw the output -‐transistors, MJE-‐ drivers and the TEMPCO transistor Q11 (BD139) onto your heatsink. I have included a drill template to do this. It shows the holes for the stand-‐offs and the transistors listed above. Please print the template at 100%, cut it, stick it to the heatsink and mark the holes with a center punch.

Drill the indicated holes (use a 2.5 drill); then tap 3mm threads.


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All of the transistors that need to be screwed onto the heatsink, have a metallic back for better heat conduction.

The metallic back of any transistor may not be in electrical contact with the heatsink. Use suitable insulation material to insulate the transistors from the heatsink and do not forget to insulate the screws as well (needed for the MJE – drivers).

I have included 3 stripes of Silicone insulating film in the Reichelt cart. The stripes are self-‐adhesive on one side. You need 2 stripes for the 8 output-‐transistors in TO3-‐P or TO264 case; the last stripe will be used for the 4 MJE – drivers (TO220 case) and the 2 BD139 TEMPCO transistors (I used a TO220 case template for them as well). The following image shows the size in mm and the position of the hole of the needed insulation pads:


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Stick the Silicone pads onto the heastsink. Take the PCB as a template for the position of the angle and bend the legs of the transistors upwards. It shall finally look this (this is a different PCB though):

Do not (never!) use Polyamid or Polyacryl screws! Plastic screws do not provide a tight contact to the heatsink and will be the reason for thermal runaway problems.


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Turn the PCB with its solder side up and insert the 7 transistors and screws (do not forget the washers for the MJE-‐screws) into the PCB. I then taped the transistors with pieces of adhesive tape to the PCB. Turn the PCB, try to fix the screws 1 or 2 mm and install the 8mm stand-‐offs. Then fix the screws tightly and take a look at your work! The transistors shall seat solidly on the heatsink. Then measure the resistance of each transistor’s legs opposite the heatsink. None of the legs shall be in contact with the heatsink! Do some small solder points on each transistor on the PCB’s component side, remove the stand-‐offs and screws, remove the adhesive tape and solder the transistors on the PCBs solder side! Then solder the four 1.000µF on top of the output-‐transistors. DIYing is not an easy job; it sometimes takes a lot of patience, but: it is fun nevertheless! The last thing to do is to solder a wire to connect SignalGND to PowerGND on the PCB’s solder side. I have indicated this wire by the big white line on the following image:

I will attach this image to the Email. After all of the soldering and drilling has been done, clean the solder-‐side of the PCB with Isopropanol and take a close look at all the solder-‐points. No shorts present? Are you content with your work? Take your time checking your build! Do it carefully!


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7 Adjusting the Quiescent current Connect the SYMASYM-‐PCB to your power supply. Please do not yet insert fuses into the fuseholders on the PCB, but bypass (bridge) the fuse / fuseholder by a 10 Ohm / 0.6W resistor.

I have done this using 2 croco-‐clips. The pink arrow points to the 10 Ohm resistor. Why is the 10 Ohm resistor needed? If you have done a good job and soldered the PCB without doing any error, the quiescent current will be about 150 mA (2 x 55mA flowing through the output-‐transistors and add some mA for the frontend and drivers) per power-‐rail. The voltage drop across the 10 Ohm resistor will then be 1,5V and its power consumption will be 150mW, no problem for a 0.6 W type resistor. (Remember: the Reichelt METAL resistors are rated at 0.6W)


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If you have done an error, causing much more current to flow during the adjustment phase, the 10 Ohm resistor will smell and thus will prevent further damage from your build. Please short the input (Input + = Input -‐) and do not connect a load (speaker etc.) on the output. Please use the bulb-‐tester! Power On. Do the PCB’s LEDs glow (meaning voltage is present)? I hope so. Please touch the 10 Ohm resistors then. They should get warm but not hot, and they should not give smoke-‐signals at all. In case the LEDs do not shine or the 10 Ohm gets too hot: Power Off. You have done an error then and have to inspect your build once more. If you have not done an error: wait some minutes and check the temperature with your fingers then. They shall be warm, but not hot. Power Off. Remove the 10 Ohm resistors and insert the 2 fuses (I use 2.5A, fast fuses). Adjust your DMM to DC, 200mV scale, and connect it to the two measuring points MP1 and MP2, which are located in the middle of the PCB near the Emitter resistors. Power On. Your DMM should show 0 mV. Now turn the trim-‐potentiometer counter-‐clockwise, decreasing its resistance. You won’t see any change on your DMM’s display during the first 10-‐15 turns, but then the DMM should show values like: 5mV, 10 mV, 15 mV, …


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You are measuring the voltage drop across the two emitter resistors R82 and R25. The recommended value for the quiescent current, flowing through an output-‐resistor of the SYMASYM during the adjustment-‐phase, is 50-‐55mA. Since you are measuring the voltage across 2 emitter-‐resistors, please go on turning the screw of the trim-‐potentiometer, until the display of your DMM shows about 24 mV – 25mV.

Are you able to do this adjustment?

Congratulations !


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Please leave the build as is for about 15-‐30 minutes, check the value of the voltage drop again and re-‐correct it, if necessary. I ask you to measure the DC-‐offset on the output (the DC-‐voltage between the speaker connector X1 and GND) as well. The DC-‐offset should be lower than 10mV. This is the end of the adjustment phase. Power Off the PSU. Connect a music source to the input, connect a speaker to the SYMASYM (connect the red plug to the connector X1 and the black plug to a GND connector of the PSU), switch on music, listen to it and enjoy.

8 The Speaker Protection section The schematic of the speaker protection is given in the appendix. The purpose of the speaker -‐ protection board is two-‐fold: 1 -‐ to suppress power-‐on -‐ and turn-‐off noise) (my old SYMASYM had a power-‐off hiss) 2 -‐ to protect a loudspeaker in case a DC voltage > 1V is being applied due to an error in your work For these purposes the speaker is connected (via a relay) to the amplifier only about 4-‐5 seconds after Power-‐On and separated immediately after switching off the mains or in the event of a DC detection. The Speaker Protect circuit is powered by the AC (!) voltage of the transformer’s secondary winding. I have used AC to power the Speaker protection circuit to make sure that the protection relay is powered off immediately, when you switch off the mains power.


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The alternating voltage is rectified by a diode 1N4001, then decreased by a 5V1 Zener diode, smoothed and fed to a 78L24 voltage regulator. Once the switching voltage at the base of transistor Q13 is reached (delayed by R38/C26 – you may want to choose other values – it is up to you), the relay K2 (24 volt type) closes and connects the amplifier’s speaker signal to the speaker. R31 and C24/C1* in conjunction with B1 form a low pass filter that switches off the relay when it detects a “DC-‐like voltage” at the AMP’s speaker output.

Please take care of the polarity of the capacitors (C24 and C1 * in particular), when you solder the PCB, the positioning of the bridge rectifier, the LED (the longer pin – the Anode – is connected to the transistor on top of it) and the grid of the relay used. To use the onboard-‐speaker protection, please run a wire from X1 (the SYMASYM PCB’s speaker connection, labeled “Speaker” on the SYMASYM PCB) to the 6.3mm Faston connector labeled “AMP” in the Speaker-‐Protection-‐Section of the PCB and connect your speaker (the red plug) to the 6.3mm Faston Connector labelled “Speaker” in the Speaker-‐Protection-‐Section. I wish you all a successful build and: ENJOY THE SOUND. Best regards – Rudi


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9 Appendix


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Schematics of the SYMASYM:


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Schematics of the Backend-‐PSU:

Schematics of the Speaker-‐Protection:


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SYMASYM Silkscreen with values:


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SYMASYM Silkscreen with names:


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BoM I have set up a BoM for the NJW – SYMASYM that you can access from here: NJW-‐SYMASYM incl. SpeakerProtection for 2 PCBs: https://secure.reichelt.de/index.html?&ACTION=20&AWKID=940926&PROVID=2084 The BoM does not include the parts that I have offered in the components’ group-‐buy. NJW-‐SYMASYM Backend PSU for 1 PCB: https://secure.reichelt.de/index.html?&ACTION=20&AWKID=939684&PROVID=2084

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