Michael is having big problems in his business, the software Synetic Company.
I think he will delay a little to be tracking this thread again.... so, be patient with his delay.
He is in the middle of a terrible hush.... confusion, problems with machines and dead lines.
I will be tracking, but i cannot answer too much complicated questions, as i have not his know how.
regards,
Carlos
I think he will delay a little to be tracking this thread again.... so, be patient with his delay.
He is in the middle of a terrible hush.... confusion, problems with machines and dead lines.
I will be tracking, but i cannot answer too much complicated questions, as i have not his know how.
regards,
Carlos
I will be tracking this thread daily,as there are some guys constructing
Till them finished, this thread will be pushed alive.
regards,
Carlos
Till them finished, this thread will be pushed alive.
regards,
Carlos
Hi All,
Putting the first amp together. I'm waiting on a few parts, but wanted to vet the general plan. I'm splitting the circuit much like Graham recommended for the Gem. I plan to put the output (paralleled 3281's) and driver transistors on the heat sink. I also plan to put the BD135 on the heat sink with the 100nf cap between the collector and base. The other components on the power end will be connected directly to the transistor legs. The rest of the circuit will be on a pp wired board, with a short connection to the base of the BD135. Also a short connector for the feedback. The 1000u/100n for each rail will be on the board too, but the connector to the power transistors should be only a couple of cm.
The 100u/100nf for each rail are located about 5cm from the imput transistor connections. Is this ok or should I add a small cap to ground for each rail, next to the input transistor connections?
Reasonable? See any problems?
Sheldon
Putting the first amp together. I'm waiting on a few parts, but wanted to vet the general plan. I'm splitting the circuit much like Graham recommended for the Gem. I plan to put the output (paralleled 3281's) and driver transistors on the heat sink. I also plan to put the BD135 on the heat sink with the 100nf cap between the collector and base. The other components on the power end will be connected directly to the transistor legs. The rest of the circuit will be on a pp wired board, with a short connection to the base of the BD135. Also a short connector for the feedback. The 1000u/100n for each rail will be on the board too, but the connector to the power transistors should be only a couple of cm.
The 100u/100nf for each rail are located about 5cm from the imput transistor connections. Is this ok or should I add a small cap to ground for each rail, next to the input transistor connections?
Reasonable? See any problems?
Sheldon
Hi sheldon !
The 5cm from the 100uf/100nf to the inputtransistors should not be
a problem, of course shorter is better, but the currents are not
big and not varying too much. The bd135 must be mounted on the
heatsink as it tracks temperature and adjusts bias.
I think it's better to keep the 100nf for the bd135 between collector
and emitter as close as possible to vas, and not directly to the
transistor itself. Your "between the collector and base" was a typo ?
It should not be necessary to use 2 outputpairs with +/- 36v,
but will of course increase powerhandling for 4ohm speakers.
Mike
The 5cm from the 100uf/100nf to the inputtransistors should not be
a problem, of course shorter is better, but the currents are not
big and not varying too much. The bd135 must be mounted on the
heatsink as it tracks temperature and adjusts bias.
I think it's better to keep the 100nf for the bd135 between collector
and emitter as close as possible to vas, and not directly to the
transistor itself. Your "between the collector and base" was a typo ?
It should not be necessary to use 2 outputpairs with +/- 36v,
but will of course increase powerhandling for 4ohm speakers.
Mike
Hi Mike,
Thanks. Yes, I meant collector/emitter. I'm new to the whole electronics terminology, so by VAS you mean the driver transistors (mje15030/15031). VAS I assume means voltage amplification?
If that's the case, connect the cap right next to the base resistors?
Sheldon
Hmm, thinking about that, and looking at the circuit, the diffferential amp with current mirror would be the VAS, and the BD 135 sets the bias for the output stage. So the cap should go next to the 330p divider?
Thanks. Yes, I meant collector/emitter. I'm new to the whole electronics terminology, so by VAS you mean the driver transistors (mje15030/15031). VAS I assume means voltage amplification?
If that's the case, connect the cap right next to the base resistors?
Sheldon
Hmm, thinking about that, and looking at the circuit, the diffferential amp with current mirror would be the VAS, and the BD 135 sets the bias for the output stage. So the cap should go next to the 330p divider?
Hi sheldon,
Yes, the 2nd diffamp with the currentmirror is the vas, and the drivers
are directly connected to it. So, connecting the 100nf before the basestoppers
to the drivers would be ok.
Mike
Yes, the 2nd diffamp with the currentmirror is the vas, and the drivers
are directly connected to it. So, connecting the 100nf before the basestoppers
to the drivers would be ok.
Mike
Thanks,
Oh, and yes, the paralleled transistors are to give me a little more room for driving 4ohm speakers. By the way, the overall bias current will double, I assume?
Sheldon
Oh, and yes, the paralleled transistors are to give me a little more room for driving 4ohm speakers. By the way, the overall bias current will double, I assume?
Sheldon
Yes, the overall bias current will double !
I also have 4ohm speakers and no problems with driving them per single pair,
the mjl3281/1302 is still quite good at ~8 amperes, the double
pair would only be necessary if you permanently drive the 4ohms
at full/very high power.
You might consider increasing the fuses to 3amperes if you plan to
drive the 4ohm speakers at high levels.
For full outputpower (not clipped) you get peaks of ~8amperes,
this gives 5.7A sinus, and for half waves you get 2.83A average.
Mike
I also have 4ohm speakers and no problems with driving them per single pair,
the mjl3281/1302 is still quite good at ~8 amperes, the double
pair would only be necessary if you permanently drive the 4ohms
at full/very high power.
You might consider increasing the fuses to 3amperes if you plan to
drive the 4ohm speakers at high levels.
For full outputpower (not clipped) you get peaks of ~8amperes,
this gives 5.7A sinus, and for half waves you get 2.83A average.
Mike
Hi Mike,
I don't plan to drive them hard for long periods, but I do want some head room. But thinking about that, more transistors won't
help, because that's voltage limited, so I wouldn't need to increase transistor count unless I wanted to drive 4ohm speakers at higher voltages? So for peak power output just one pair should give the same output. And, if my reasoning is correct, paralleled transistors would just reduce the heat generated by each device. So for my needs, I think you're right. One pair should do.
Sheldon
I don't plan to drive them hard for long periods, but I do want some head room. But thinking about that, more transistors won't
help, because that's voltage limited, so I wouldn't need to increase transistor count unless I wanted to drive 4ohm speakers at higher voltages? So for peak power output just one pair should give the same output. And, if my reasoning is correct, paralleled transistors would just reduce the heat generated by each device. So for my needs, I think you're right. One pair should do.
Sheldon
Have a prepared photo machine, to have a picture of your expression when first time
Listening your amplifier.
You will feel good.... prepare the machine Sheldon...and send me the image, please.
I had informs that people jumped and dance hearing this amplifier the first time, so happy they felt with it.
regards,
Carlos
Listening your amplifier.
You will feel good.... prepare the machine Sheldon...and send me the image, please.
I had informs that people jumped and dance hearing this amplifier the first time, so happy they felt with it.
regards,
Carlos
Sheldon said:
Yes, with 2 pairs you might get 5 watts more and less distortions
at full power, but you might degrade peformance at lower levels,
which, at least for me, is much more important.
I measured outputvoltage while listening music, and 5 watts were
already quite heavy...
I was not able yet to really push the amp over it's limits with the
4ohm speakers, but i don't know how big your rooms are...
For higher voltages i would recommend 2 pairs, but not for 36v supply.
Mike
Thanks Mike,
One more question(for now anyway), as my experience with transistor amp design is nil. The fuses, I assume from your pictures, and guessing from the text, are for the rails. It looks like no current flows when a fuse goes, but I'm not comfortable guessing from the schematic, and I don't want to miss something. Is a safety resistor around the fuse required to keep the output from going hard to one or the other rail when a fuse gives up?
Carlos,
When I get a camera around here, I'll post some pics. Still have a way to go waiting for some parts.
Cheers,
sheldon
Sheldon
One more question(for now anyway), as my experience with transistor amp design is nil. The fuses, I assume from your pictures, and guessing from the text, are for the rails. It looks like no current flows when a fuse goes, but I'm not comfortable guessing from the schematic, and I don't want to miss something. Is a safety resistor around the fuse required to keep the output from going hard to one or the other rail when a fuse gives up?
Carlos,
When I get a camera around here, I'll post some pics. Still have a way to go waiting for some parts.
Cheers,
sheldon
Sheldon
Hi Sheldon,
yes, the fuses are directly in the rails-supply, immediately following
after the input of the supplyvoltage.
I used no safetyresistors, but in this case i am not absolutely sure
if necessary or good.
I once had a blown fuse in the negative rail, this resulted in the amp
going completely dead, i will check what happens if the fuse in the
positive rail blows.
Edit: I checked blown fuses in sims, if the negative blows, the amp
goes dead (off), if the positive blows it keeps "working", but gives
~1v dc at output. If you bypass the fuses with ~100ohm, this DC
goes down to 1mv. These safetyresistors might be a good idea,
but they eventually burn up... (In case of blown fuse)
But, it won't flip over to complete railvoltage in such a case without
these resistors.
Mike
yes, the fuses are directly in the rails-supply, immediately following
after the input of the supplyvoltage.
I used no safetyresistors, but in this case i am not absolutely sure
if necessary or good.
I once had a blown fuse in the negative rail, this resulted in the amp
going completely dead, i will check what happens if the fuse in the
positive rail blows.
Edit: I checked blown fuses in sims, if the negative blows, the amp
goes dead (off), if the positive blows it keeps "working", but gives
~1v dc at output. If you bypass the fuses with ~100ohm, this DC
goes down to 1mv. These safetyresistors might be a good idea,
but they eventually burn up... (In case of blown fuse)
But, it won't flip over to complete railvoltage in such a case without
these resistors.
Mike
I have tried 4 ohms and volume all way up.
The amplifiers really produces enormous sound pressure.... the speakers are clearly hitting their limits inside the magnet core.
The speakers used were 50 watts rms each one, and those normally do not hit the end with this power.....power was around 130 over 4 ohms...... two units... three way speakers were used, 7 ohms measured with 1 Kilohertz and 8 ohms as nominal impedance.
6,8 ohms in series with the speaker, 1 kilohertz 10 volts of sinusoidal audio entering, and voltage was divided by two, half over the 6.8 ohms and half over the speaker.... showing me that real impedance was around 6.8 ohms.
regards,
Carlos
The amplifiers really produces enormous sound pressure.... the speakers are clearly hitting their limits inside the magnet core.
The speakers used were 50 watts rms each one, and those normally do not hit the end with this power.....power was around 130 over 4 ohms...... two units... three way speakers were used, 7 ohms measured with 1 Kilohertz and 8 ohms as nominal impedance.
6,8 ohms in series with the speaker, 1 kilohertz 10 volts of sinusoidal audio entering, and voltage was divided by two, half over the 6.8 ohms and half over the speaker.... showing me that real impedance was around 6.8 ohms.
regards,
Carlos
Ok guys,
Only when I start putting this thing together do I really look carefully at the schematic. Or, more accurately, it take me many times to begin to see things. So, the next question: that 220uf cap after the feedback divider, is that meant to be bipolar? If so, any recommendations as to type?
Mike, you may yet curse Carlos for encouraging the ignorant to build your amp.
Sheldon
Only when I start putting this thing together do I really look carefully at the schematic. Or, more accurately, it take me many times to begin to see things. So, the next question: that 220uf cap after the feedback divider, is that meant to be bipolar? If so, any recommendations as to type?
Mike, you may yet curse Carlos for encouraging the ignorant to build your amp.
Sheldon
Hi Sheldon,
sorry that i missed so many details...
The 220uf-cap after the feedbackdivider is a normal electrolytic,
(i used 470uf,16v here) can be a low voltage type, with plus to gnd.
It gets charged with ~12mv (depending on the hfe of the input-bjts)
And, you are really no ignorant... 😀 Carlos is really good in encouraging people !
Mike
sorry that i missed so many details...
The 220uf-cap after the feedbackdivider is a normal electrolytic,
(i used 470uf,16v here) can be a low voltage type, with plus to gnd.
It gets charged with ~12mv (depending on the hfe of the input-bjts)
And, you are really no ignorant... 😀 Carlos is really good in encouraging people !
Mike
Those amplifiers i could find, after search for 45 years, i really run to defend.
As i told before, more than 3700 units constructed, and only AKSA,GEM and SYMASYM 4 were accepted by my hard to satisfied listening tests, i use to defend them, in special against those that did not construct nothing and go all life long discussing the "sex of the angels"...when everybody knows that Angels do not have sex.
I could develop listening tests, A to B comparison methods and i do not believe in my own evaluation....i call friends to evaluate, a blind testing...no one can protect one brand related other brand, as the guys evaluating do not know what is playing as A or as B.
AKSA is magnificent, incredible, astounding, optimum equipment, the more pretty, as have wonderfull silk screen boards, special components selection and was very studied to produce the best possible BJT sound with the thopologie used...and also, the thopologie was hardly used, and now a days can kick many modern units...sounds incredible, have unsurpassed sound stage and clear trebles that i never heard before.
Well, Symassym have wonderfull trebles, impressive bass punch and his trademark could be Dynamics...his best characteristic.
GEM is the precious stone, rare as the Diamond, can reproduce 1 hertz...you can see speaker slowly going on and out.... trebles are perfect, not emphasized and natural...voices are wonderfull too...have good dinamics....it is natural, a natural sound amplifier.
I cannot leave without those amplifiers, each one with their characteristics, and i think they are very complementary, i cannot stay without any of them.
here some instructions to the happy guys that are constructing Symassym, Aksa and GEM.... this one is special to Symassym, as this thread is about FOCKER amplifier.... Focker Wulf was an aircraft airplane.... and the name sounds interesting in many languages.... this was the name i gave it, but Michael did not accepted as he is a very educated man, and this brand, in some languages can sound different, but i cannot be responsable of misunderstoodings of the therm.... sound is ligthweigth and at same time powerfull as the Focker airplane...if this means another thing in other language...what can i do related your interpretations..i cannot be responsable because of those things.
Poluted minds are not something i can control.... i cannot control mine!
Here is the text!.... God bless the King of Australia! Mr. Hugh Dean!
God bless the king of Ireland and UK, Mr. GM!
God bless the king of Germany, Mr. Michael Bittner.
Those guys made me happy, i am hearing, everyday their wonderfull designs, in my rest room, connected into my computer, and beeing my home theater.... in my point of view, those are the best (not forgeting the teacher of all of us...Mr. John Lindsey Hood).
Advises, of how to construct Symassym will be the next thread.
regards,
Carlos
As i told before, more than 3700 units constructed, and only AKSA,GEM and SYMASYM 4 were accepted by my hard to satisfied listening tests, i use to defend them, in special against those that did not construct nothing and go all life long discussing the "sex of the angels"...when everybody knows that Angels do not have sex.
I could develop listening tests, A to B comparison methods and i do not believe in my own evaluation....i call friends to evaluate, a blind testing...no one can protect one brand related other brand, as the guys evaluating do not know what is playing as A or as B.
AKSA is magnificent, incredible, astounding, optimum equipment, the more pretty, as have wonderfull silk screen boards, special components selection and was very studied to produce the best possible BJT sound with the thopologie used...and also, the thopologie was hardly used, and now a days can kick many modern units...sounds incredible, have unsurpassed sound stage and clear trebles that i never heard before.
Well, Symassym have wonderfull trebles, impressive bass punch and his trademark could be Dynamics...his best characteristic.
GEM is the precious stone, rare as the Diamond, can reproduce 1 hertz...you can see speaker slowly going on and out.... trebles are perfect, not emphasized and natural...voices are wonderfull too...have good dinamics....it is natural, a natural sound amplifier.
I cannot leave without those amplifiers, each one with their characteristics, and i think they are very complementary, i cannot stay without any of them.
here some instructions to the happy guys that are constructing Symassym, Aksa and GEM.... this one is special to Symassym, as this thread is about FOCKER amplifier.... Focker Wulf was an aircraft airplane.... and the name sounds interesting in many languages.... this was the name i gave it, but Michael did not accepted as he is a very educated man, and this brand, in some languages can sound different, but i cannot be responsable of misunderstoodings of the therm.... sound is ligthweigth and at same time powerfull as the Focker airplane...if this means another thing in other language...what can i do related your interpretations..i cannot be responsable because of those things.
Poluted minds are not something i can control.... i cannot control mine!
Here is the text!.... God bless the King of Australia! Mr. Hugh Dean!
God bless the king of Ireland and UK, Mr. GM!
God bless the king of Germany, Mr. Michael Bittner.
Those guys made me happy, i am hearing, everyday their wonderfull designs, in my rest room, connected into my computer, and beeing my home theater.... in my point of view, those are the best (not forgeting the teacher of all of us...Mr. John Lindsey Hood).
Advises, of how to construct Symassym will be the next thread.
regards,
Carlos
Advises, for the ones are constructing Symassym 4.
Those advises may be adapted to Symassym 5, Michael will tell us the differences...
Please Michael...go ahead.
......................................................................................................
Some advises to the ones that are constructing Symasym amplifier:
- When finished assemble, check for error, and do it many times, use for that a good ligth source or the prefered dayligth... and use lenses, observe if transistors are not in wrong places, or if they are not installed wrong position, this is a very common mistake.
- Now check electrolitic condensers polarity, and resistor values, marking in your schematic each one already checked.
- If you are not experienced, use the ohmeter and measure each resistor, yes, you can make it already assembled in the circuit, taking into your account that they have to measure the real resistance or a lower resistance related it’s value... if too much lower than the real value, invert the tester polarity, to obtain a more reasonable reading..... it is very common to make mistakes related the brown to the red strips in resistors, when tired or even bad ligth conditions.
- Now use a strong brush, with alcohol and clean under the board, to remove all solder flux, better than that is to use Kerozene, that is a jet plane fuel, a petrol solvent.... after cleaned, observe for shorts or solders that have no brigth.... those strange solders use to produce noise alike pops when you solder again... remenber to touch the solder iron in both parts, component leads and copper lines, wait for a second and touch the solder wire direct into the copper or direct into the component leads....do not touch the soldering iron tip with solder to force it melt.... do not breath into solder (never) as it can dry too fast and metal structure will be bad..will have crack, air entering,future oxide and resistance will appear in your soldering point.
- Even you are sure that your transistors are well mounted.... check them again.
- Now use your multimeter in a high resistance scale..... around 200K ohms or even bigger...and go measuring resistance from positive to ground and negative to ground....do not forget to invert the leads.....measuring ground to positive and ground to negative... the last measurement is from positive to negative...and invert it also....in none of those measurements, Symassym 4 will show you resistance lower than 22000 ohms...if you read something below that... check your circuit, something is wrong, i am sure.... if you did not find mistakes...do it again till you find.
- Now install diodes from positive to ground and from ground to negative.... the diode arrow will be pointing positive to the upper rail protection and the lower diode will be pointing the ground too. Those diodes are protection that you can remove after testing, their purpose is to avoid a very common human mistake, the polarity invertion... they must be soldered after the fuse, or after the protection resistor used to adjustments.... if polarity is inverted, it will drain all current to ground, fuse will burn or the protective resistor will be very hot.... it is more common than you can believe.... the more experienced guys also do that, and if they have some “standards” alike the use of red wire to positive, blue wire to negative and black wire to ground, for instance, more easy they can do that mistake.... because some repair made in the supply, some supply cable extension or something alike, can make you solder wires in wrong position...blue can be in the place of red.... and believing you have that “standard” to protect you, may lost enormous time burning circuits, till discover that you may invert your supply wires related your own standards.
- Install 100 ohms – 5 watts resistors in series with the supply, remember to fix them in small boards, but something stable not to move and touch amplifier, heatsinks or other metal parts, to avoid problems... use some wire length to have distance from your board....20 centimeter from your board is the minimum safe distance to avoid problems.... voltage will be measured over those resistors, and that voltage will be the evidence that current is flowing throught those resistors (one to each rail.)... the Multimeter must be in the DC voltage, the scale must be bigger than the supply rail voltage, so, will be bigger than 37 Volts. First check the supply voltage and polarity, measure it, observe if your 37 volts reduced.... and if this reduction is simetrical, or, the same reduction resulted of consumption, both rails (ground will have no resistor..this is a direct connection) may have same readings...if not, you will have bad supply or bad circuit, consumption beeing different each rail it is a sine of mistakes in the circuit or defective power supply..... well, measure there, directly over the resistor, for instance, try the positive one.... each resistor extreme will have the touch of its multimeter tip.... remember to clean the tips, with steel brush or even sandpaper, as pretty chromium is ot a guaranty of perfect contact, this chromium finishment can have some solder flux insulating it...clean it and be ready to read some voltage there.... the same voltage must appear measuring the negative rail resistor....now move your bias trimpot, this voltage must change.... adjust it to 10 volts.... and wait to see if both rails will maintain that voltage for long time....if voltage meaured is 37 Volts.... this is showing that your circuit board has a short circuit, and this normally appear when you read resistance...if not, your bias transistor was mounted wrong position or some mistake will be found around.... well, 10 volts over 100 ohms represents 100 miliamps of current, and that value is obtained dividing the Voltage by the resistance, and this is the result of Ohms law calculation.... the second sittuation, the wrong one, with 37 Volts over the 100 ohms resistor, will show us 370 miliamperes.... and this is the maximum rail current, limited by this resistor, so, it will be protecting the circuit against over current...if some transistor is assembled in a wrong position, the current there will not exceed 370 miliamperes, and that current is not so big to melt transistors...this way, without exploding transistors you can power on your amplifiers using this simple protective device.
- Current appearing normal, or voltage measured could be adjusted to normal value, use your Voltimeter again, DC scale, around 100 volts DC scale, and check the voltage over the output line... voltage must be small, under 1 volt when open and if appear normal, install a resistor, a 8R2 resistor or a 3R9 resistor to check voltage when the amplifier is loaded.... voltage have to reduce till reach something from 3 to 14 milivolts, normally you will find 3 milivolts.
- Now you can install your speaker, but do not forget to install a 6 amperes fuse to 4 ohms speakers or a 3 amperes fuse if you will use 8 ohms speakers. This fuse is installed in series with the positive output, the amplifier middle line, where the emitter resistors are going to.... the output of the coil you have in parallell with 10 ohms resistor...there is the positive output...the other output wire goes to ground. You will hear some audio.... will distort because of the supply voltage droping over the protective resistors...reduce the volume and observe the quality...beeing excelent (it is!)... switch all of and remove the rail protective resistors, and install in their place 6 ampere fuse if you intend to use 4 ohms speakers.....or install 3 ampere fuse if you intend to use 8 ohms speaker....yeah!..you can left there the worst condition fuse.... the 6 ampere to be able to use 8 ohms and replace to 4 ohms...but..... having some damage.... bigger fuse will represent more damaged in the board if some component goes shorted by accident..some metalic object that can fall inside the board, or some bad luck accident.....Alike my beloved AKSA, this circuit is a hell safe, it will not produce surprises
- You can remove or not the diodes used to avoid mistakes with supply polarity...your decision...they will be sleeping there till some invertion happen... or some inverted spike return from some different speaker (an electrostatic unit is a good example).
- Let your amplifier working for 1 hour, and go monitoring temperature with your Finger-O-Meter .... touch it and evaluate if normal temperature or hot fever.
- Check again the current....measure the voltage over the 0.1 ohms emitter resistors.... the voltage you will read there will be around 10 milivolts, remember to adjust your Voltimeter scale to a very low DC value...and no input audio for this measurement. Check th other emitter resistor...value must be the same....if bigger or lower, readjust to 10 milivolts
Conclusion in the next thread
Carlos
Those advises may be adapted to Symassym 5, Michael will tell us the differences...
Please Michael...go ahead.
......................................................................................................
Some advises to the ones that are constructing Symasym amplifier:
- When finished assemble, check for error, and do it many times, use for that a good ligth source or the prefered dayligth... and use lenses, observe if transistors are not in wrong places, or if they are not installed wrong position, this is a very common mistake.
- Now check electrolitic condensers polarity, and resistor values, marking in your schematic each one already checked.
- If you are not experienced, use the ohmeter and measure each resistor, yes, you can make it already assembled in the circuit, taking into your account that they have to measure the real resistance or a lower resistance related it’s value... if too much lower than the real value, invert the tester polarity, to obtain a more reasonable reading..... it is very common to make mistakes related the brown to the red strips in resistors, when tired or even bad ligth conditions.
- Now use a strong brush, with alcohol and clean under the board, to remove all solder flux, better than that is to use Kerozene, that is a jet plane fuel, a petrol solvent.... after cleaned, observe for shorts or solders that have no brigth.... those strange solders use to produce noise alike pops when you solder again... remenber to touch the solder iron in both parts, component leads and copper lines, wait for a second and touch the solder wire direct into the copper or direct into the component leads....do not touch the soldering iron tip with solder to force it melt.... do not breath into solder (never) as it can dry too fast and metal structure will be bad..will have crack, air entering,future oxide and resistance will appear in your soldering point.
- Even you are sure that your transistors are well mounted.... check them again.
- Now use your multimeter in a high resistance scale..... around 200K ohms or even bigger...and go measuring resistance from positive to ground and negative to ground....do not forget to invert the leads.....measuring ground to positive and ground to negative... the last measurement is from positive to negative...and invert it also....in none of those measurements, Symassym 4 will show you resistance lower than 22000 ohms...if you read something below that... check your circuit, something is wrong, i am sure.... if you did not find mistakes...do it again till you find.
- Now install diodes from positive to ground and from ground to negative.... the diode arrow will be pointing positive to the upper rail protection and the lower diode will be pointing the ground too. Those diodes are protection that you can remove after testing, their purpose is to avoid a very common human mistake, the polarity invertion... they must be soldered after the fuse, or after the protection resistor used to adjustments.... if polarity is inverted, it will drain all current to ground, fuse will burn or the protective resistor will be very hot.... it is more common than you can believe.... the more experienced guys also do that, and if they have some “standards” alike the use of red wire to positive, blue wire to negative and black wire to ground, for instance, more easy they can do that mistake.... because some repair made in the supply, some supply cable extension or something alike, can make you solder wires in wrong position...blue can be in the place of red.... and believing you have that “standard” to protect you, may lost enormous time burning circuits, till discover that you may invert your supply wires related your own standards.
- Install 100 ohms – 5 watts resistors in series with the supply, remember to fix them in small boards, but something stable not to move and touch amplifier, heatsinks or other metal parts, to avoid problems... use some wire length to have distance from your board....20 centimeter from your board is the minimum safe distance to avoid problems.... voltage will be measured over those resistors, and that voltage will be the evidence that current is flowing throught those resistors (one to each rail.)... the Multimeter must be in the DC voltage, the scale must be bigger than the supply rail voltage, so, will be bigger than 37 Volts. First check the supply voltage and polarity, measure it, observe if your 37 volts reduced.... and if this reduction is simetrical, or, the same reduction resulted of consumption, both rails (ground will have no resistor..this is a direct connection) may have same readings...if not, you will have bad supply or bad circuit, consumption beeing different each rail it is a sine of mistakes in the circuit or defective power supply..... well, measure there, directly over the resistor, for instance, try the positive one.... each resistor extreme will have the touch of its multimeter tip.... remember to clean the tips, with steel brush or even sandpaper, as pretty chromium is ot a guaranty of perfect contact, this chromium finishment can have some solder flux insulating it...clean it and be ready to read some voltage there.... the same voltage must appear measuring the negative rail resistor....now move your bias trimpot, this voltage must change.... adjust it to 10 volts.... and wait to see if both rails will maintain that voltage for long time....if voltage meaured is 37 Volts.... this is showing that your circuit board has a short circuit, and this normally appear when you read resistance...if not, your bias transistor was mounted wrong position or some mistake will be found around.... well, 10 volts over 100 ohms represents 100 miliamps of current, and that value is obtained dividing the Voltage by the resistance, and this is the result of Ohms law calculation.... the second sittuation, the wrong one, with 37 Volts over the 100 ohms resistor, will show us 370 miliamperes.... and this is the maximum rail current, limited by this resistor, so, it will be protecting the circuit against over current...if some transistor is assembled in a wrong position, the current there will not exceed 370 miliamperes, and that current is not so big to melt transistors...this way, without exploding transistors you can power on your amplifiers using this simple protective device.
- Current appearing normal, or voltage measured could be adjusted to normal value, use your Voltimeter again, DC scale, around 100 volts DC scale, and check the voltage over the output line... voltage must be small, under 1 volt when open and if appear normal, install a resistor, a 8R2 resistor or a 3R9 resistor to check voltage when the amplifier is loaded.... voltage have to reduce till reach something from 3 to 14 milivolts, normally you will find 3 milivolts.
- Now you can install your speaker, but do not forget to install a 6 amperes fuse to 4 ohms speakers or a 3 amperes fuse if you will use 8 ohms speakers. This fuse is installed in series with the positive output, the amplifier middle line, where the emitter resistors are going to.... the output of the coil you have in parallell with 10 ohms resistor...there is the positive output...the other output wire goes to ground. You will hear some audio.... will distort because of the supply voltage droping over the protective resistors...reduce the volume and observe the quality...beeing excelent (it is!)... switch all of and remove the rail protective resistors, and install in their place 6 ampere fuse if you intend to use 4 ohms speakers.....or install 3 ampere fuse if you intend to use 8 ohms speaker....yeah!..you can left there the worst condition fuse.... the 6 ampere to be able to use 8 ohms and replace to 4 ohms...but..... having some damage.... bigger fuse will represent more damaged in the board if some component goes shorted by accident..some metalic object that can fall inside the board, or some bad luck accident.....Alike my beloved AKSA, this circuit is a hell safe, it will not produce surprises
- You can remove or not the diodes used to avoid mistakes with supply polarity...your decision...they will be sleeping there till some invertion happen... or some inverted spike return from some different speaker (an electrostatic unit is a good example).
- Let your amplifier working for 1 hour, and go monitoring temperature with your Finger-O-Meter .... touch it and evaluate if normal temperature or hot fever.
- Check again the current....measure the voltage over the 0.1 ohms emitter resistors.... the voltage you will read there will be around 10 milivolts, remember to adjust your Voltimeter scale to a very low DC value...and no input audio for this measurement. Check th other emitter resistor...value must be the same....if bigger or lower, readjust to 10 milivolts
Conclusion in the next thread
Carlos
Advises to construct Symassym 4... conclusion.
- Here, is good to know that Michael, the designer, use 70 miliamperes to the output devices...so, this measurement, made over the emitter resistor will show you the current flowing into the output transistors only..... he will suggest to adjust to 7 milivolts in the place of 10 milivolts. The other measurement, over the 100 ohms protective resistor must be around 10 volts or a little bit more, because this is the total current measurement...all rail current measurement, not only the output as the one you make over the power output emitter resistors.
- The amplifier is excelent, sonics are great, his better characteristic is enormous dynamics and good punch of bass, also the treble is very good...but dynamics is the best word to describe it.
- You can put your fingers directly in the input.... the noise from mains, the 60 hertz mains frequency you body captured will be transmitted to input.... and will be amplified, 5 volts maximum will appear in the output, a little bit more than 3 watts RMS...but injecting real audio, you will have around 23 volts over your speaker...and this represents 132 Watts RMS.....depending if your supply can hold the voltage......if not loose too much voltage, if it is strong enougth..... 65 watts with no heard distortion (unclipped signal) is easy to have with 8 ohms and around 82 watts will be your dinamic peaks with a very small distortion....that distortion many guys can hear saying that “nothing is distorting”..... some of those guys use a lot of instruments, as their hearing evaluation may be faulty.
Reserve a good box, a good enclosure, think to use meters or peak meters...make it pretty, as i am sure, this amplifier will stay with you, beeing respected and apreciated for a long...long time.
Regards,
Carlos
- Here, is good to know that Michael, the designer, use 70 miliamperes to the output devices...so, this measurement, made over the emitter resistor will show you the current flowing into the output transistors only..... he will suggest to adjust to 7 milivolts in the place of 10 milivolts. The other measurement, over the 100 ohms protective resistor must be around 10 volts or a little bit more, because this is the total current measurement...all rail current measurement, not only the output as the one you make over the power output emitter resistors.
- The amplifier is excelent, sonics are great, his better characteristic is enormous dynamics and good punch of bass, also the treble is very good...but dynamics is the best word to describe it.
- You can put your fingers directly in the input.... the noise from mains, the 60 hertz mains frequency you body captured will be transmitted to input.... and will be amplified, 5 volts maximum will appear in the output, a little bit more than 3 watts RMS...but injecting real audio, you will have around 23 volts over your speaker...and this represents 132 Watts RMS.....depending if your supply can hold the voltage......if not loose too much voltage, if it is strong enougth..... 65 watts with no heard distortion (unclipped signal) is easy to have with 8 ohms and around 82 watts will be your dinamic peaks with a very small distortion....that distortion many guys can hear saying that “nothing is distorting”..... some of those guys use a lot of instruments, as their hearing evaluation may be faulty.
Reserve a good box, a good enclosure, think to use meters or peak meters...make it pretty, as i am sure, this amplifier will stay with you, beeing respected and apreciated for a long...long time.
Regards,
Carlos
Carlos,
thanks for doing my job !
You gave a perfect manual for constructing, just one detail, the "new"
symasym has 0.22ohms emitterresistors, and i use ~55ma idlebias,
this gives 12mv across a single 0.22ohm or 24mv across both.
For the very first listeningtest (with safetyresistors installed) i use
some old speakers, speakers that do not hurt if damaged...
Mike
thanks for doing my job !
You gave a perfect manual for constructing, just one detail, the "new"
symasym has 0.22ohms emitterresistors, and i use ~55ma idlebias,
this gives 12mv across a single 0.22ohm or 24mv across both.
For the very first listeningtest (with safetyresistors installed) i use
some old speakers, speakers that do not hurt if damaged...
Mike