Q73 will never see more than 5volts dc, therefore, Vceo rating is not an issue here.....rather you can select to-126 or to77 plastic encasulated transistor for this, be carefull not to use long leads here.....
Q72 and Q63 can run a bit cooler even with a small heatsink if you add 15k 5watt resistors in series with their collectors, this will ensure longer life for these CCS....
they can be small diodes with reverse voltage of at least 200volts, and 1amp, they are there to protect the collector emitter junctions of output transistors from inductive kicks coming from the speakers...😀
Hey!
Thanks for the replies!
I actually had base stopper resistors for the outputs, but I remove them, because R. Slone wrote in his book, that there is no nessecity. I'll put them back. 5R6 1W.
Have you actually seen a nonpolarized 470uf 16v cap. They are not available here.
BD135 is in TO-126, so it should be ok.
Why 5W? TRhere should be no more than 100V on this res, so max dissipation is 0.66W. I'll use a 10k 2W resistor, in case I need to increase CCS-s current.
I'll use 1n4004. Current MBR40250 with 40A is a slight overkill🙂
Regards,
Aq
Thanks for the replies!
I actually had base stopper resistors for the outputs, but I remove them, because R. Slone wrote in his book, that there is no nessecity. I'll put them back. 5R6 1W.
Have you actually seen a nonpolarized 470uf 16v cap. They are not available here.
BD135 is in TO-126, so it should be ok.
Why 5W? TRhere should be no more than 100V on this res, so max dissipation is 0.66W. I'll use a 10k 2W resistor, in case I need to increase CCS-s current.
I'll use 1n4004. Current MBR40250 with 40A is a slight overkill🙂
Regards,
Aq
raitraak said:
To not confused someone, we say the same package. Simply the ONsemi code for the TO-126 package it is TO225(AA).
I think you may stay in your choice of using the superb MBR40250. For the record, in my projects i use in these places MR502 but i think i'll change them with MBR40250 as you! Anyway, don't trust the 1N4004 with the Io of only 1A.
Fotios
Make a comparison
First of all i ask the forgiveness of all members, because i have posted this schematic before 1,5 year in an older thread but in pdf.
The reason it is not to advertise myself, but to give you the opportunity to make comparisons with your project and to take some ideas if you want especially in the VI limiter part and the feedback.
I builded this project about 2000 for making a series of amplifiers for P.A. use. Finally, i builded 40 units only (this was my budget) and sold them directly in clubs and sound contractors. Then the input in the market of the light class G or H P.A. amplifiers made my project useless due to its weight.
With each hamility, i can refer that all my 40 amplifiers used until today (mainly to drive subwoofers) and only 4 units have come back to my lab for repair (only for substituting burned output transistors; one to three as much per case).
This project it is based on my experience for 20 years with commercial power amplifiers (mainly USA origin) some of D. Self propositions and many experiments by myself for enough years. IT IS NOT A CLONE!
Take a look in the simple input stage up to VAS. Also the tripple darlington arangement in output as your project. And some significant variation in the usual arrangement of the shared emiter resistor between main drivers and output transistors (R23-R24). Also the Vbe multiplier MJE340 (Q10) had replaced before the production in BD137 as i said previous. And the supply level appears in schematic as +/-82 Volts increased finally in +/-88 Volts.
A lot of protection circuits included also in these projects.
Unfortunatelly i have in my hands only one prototype channel (quoted in the photo).
It is a real world construction, not in big words, but checked in the practice for 8 years under worst conditions such as continuous operation at full power for 4 to 8 hours daily.
First of all i ask the forgiveness of all members, because i have posted this schematic before 1,5 year in an older thread but in pdf.
The reason it is not to advertise myself, but to give you the opportunity to make comparisons with your project and to take some ideas if you want especially in the VI limiter part and the feedback.
I builded this project about 2000 for making a series of amplifiers for P.A. use. Finally, i builded 40 units only (this was my budget) and sold them directly in clubs and sound contractors. Then the input in the market of the light class G or H P.A. amplifiers made my project useless due to its weight.
With each hamility, i can refer that all my 40 amplifiers used until today (mainly to drive subwoofers) and only 4 units have come back to my lab for repair (only for substituting burned output transistors; one to three as much per case).
This project it is based on my experience for 20 years with commercial power amplifiers (mainly USA origin) some of D. Self propositions and many experiments by myself for enough years. IT IS NOT A CLONE!
Take a look in the simple input stage up to VAS. Also the tripple darlington arangement in output as your project. And some significant variation in the usual arrangement of the shared emiter resistor between main drivers and output transistors (R23-R24). Also the Vbe multiplier MJE340 (Q10) had replaced before the production in BD137 as i said previous. And the supply level appears in schematic as +/-82 Volts increased finally in +/-88 Volts.
A lot of protection circuits included also in these projects.
Unfortunatelly i have in my hands only one prototype channel (quoted in the photo).
It is a real world construction, not in big words, but checked in the practice for 8 years under worst conditions such as continuous operation at full power for 4 to 8 hours daily.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Re: Make a comparison
Sorry for a mistake. Instead R23-R24 i mean R33-R34.
You can find also in my web page some oscillographs taken from my DSO in the output of amplifier under different conditions of loading.
Fotios
fotios said:
Sorry for a mistake. Instead R23-R24 i mean R33-R34.
You can find also in my web page some oscillographs taken from my DSO in the output of amplifier under different conditions of loading.
Fotios
Thanks for the schematics fotios!
I looked at your design and decided to stick with my current design, mirrored input and VI-limit tracking of only one output transistor. Is there a need to monitor all of them?
Aq
I looked at your design and decided to stick with my current design, mirrored input and VI-limit tracking of only one output transistor. Is there a need to monitor all of them?
Aq
Nice design Fotios! 😉
Have you done any meausurements? I'd happy to see high-freq. (10-20kHz) square-wave response's o'scope pics.
How high is your slew rate?
THD?
IMD?
Thanks!
Have you done any meausurements? I'd happy to see high-freq. (10-20kHz) square-wave response's o'scope pics.
How high is your slew rate?
THD?
IMD?
Thanks!
raitraak said:
If the destination of your project it is for domestic use - which means not extreme stress for many hours - then i think that the VI tracking from only one pair of output transistors it is enough but under the presumption that all transistors are matched as for their beta (+/-10% toleration it is acceptable). In mine design, it is mandatory the tracking of VI from all output transistors because as i said these projects operate everyday under extreme conditions for many hours. For this reason i use the summing network from all emiters; to get each time the mid value of whole the VI component presented in output.
I repeat that for domestic use there is no need for so many countermeasures. Also you can see that i use a LM35DT (TO220 package) temp sensor for continuous tracking of the thermal state of transistors. This IC it is joined with the protection circuit of amplifier which continuously vary the drive current at the base of VAS to keep the junction temp of output devices in a safe margin. It operates in conjuction with a in/out comparator (which detects large phase shifts) which also can reduce the drive current of VAS. It is a kind of limiter. I don't use compressor because it distort the signal below 150Hz. For extreme heavy loading - such as a heavy short of output - due to delay of VI limiter to react in a such catastrophic condition for output devices, i prefer the use of two optocouplers tracking the output current which with the aid of two comparators deactivate abraptly the output relay. We speak here for war conditions!
Although P.A. loudspeakers have more stable behaviour than Hi-Fi loudspeakers, the problem of damage caused from the users of whole the P.A. system (drunk D.J.s or junkie performers) which lost under their situation the feel of sound pressure level and drives the system in continuous clipping mainly in the mid-low frequencies (in these all P.A. speakers are more sensitive) thus causing an assymetrical moving of the suspension system of speakers; then, the voice coils are scratched on the narrow gap of magnet assembly and shorted quickly. I have seen with my eyes a cone burned with a big flame!
We used fire extinguisher to save the cabinet of loudspeaker and probably the club!Sorry if you tired from the history.
Fotios
Andy L. Francis said:
Hi Andy and thanks for your kind words
Unfortunatelly due to my limitted budget i haven't a real spectrum analyser, except than a PC sound card based. Thus i don't use it for accurate measurements such as TIM or THD.
Instead, i have a good DSO Hameg and i have taken some measurements with square waves as you ask very correctly. Moreover also me i am based on these measurements and due to my expertise i can estimate the reproduction quality of my projects. Again, these measurements taken by using a medium quality signal generator (its rise time it is 100nsec!) to feed the input with square waves. Thus, i can't estimate with accuracy the slew rate of amplifier.
Before 4 months - at least - i had the posibility to buy a better generator (be it so Hameg again of 10MHz with rise time of 8nsec!)
I hope you can take some idea from the rise time reffered in each graph. Moreover an expertised person can examine the TIM and a little the THD from the shape of squares in output. I quote bellow 9 different measurements:
Fig.1 Full output swing without load in 10KHz square wave. Rise Time is 2,6 ìsec
An externally hosted image should be here but it was not working when we last tested it.
Fig.2 Full output swing with 8Ù load connected in 10KHz square wave. Slight deviation of Rise Time at 2,7 ìsec
An externally hosted image should be here but it was not working when we last tested it.
Fig3. Typical output swing without load in 10KHz square wave. Rise time it is only 1,25 ìsec
An externally hosted image should be here but it was not working when we last tested it.
Fig.4 Typical output swing without load in 20KHz square wave. Rise Time it is 1,8 ìsec
An externally hosted image should be here but it was not working when we last tested it.
Fig.5 Typical output swing with 8Ù load connected in 20KHz square wave. Rise Time deviation it is 1,95 ìsec
An externally hosted image should be here but it was not working when we last tested it.
Fig.6 Full output swing without load in 100Hz square wave. Tilt from rising to falling edge it is 1,6 Volts
An externally hosted image should be here but it was not working when we last tested it.
Fig.7 Full output swing with 8Ù load connected in 100Hz square wave. The tilt increased only to 2,4 Volts
An externally hosted image should be here but it was not working when we last tested it.
Fig.8 Full output swing without load in 20Hz square wave. Tilt from rising to falling edge it is 7,2 Volts
An externally hosted image should be here but it was not working when we last tested it.
Fig.9 Ringing of output after the output inductor reaction. The load connected it is 8Ù clear resistive in parallel with a 2 ìF MKT capacitor
An externally hosted image should be here but it was not working when we last tested it.
I hope my graphs can cover a little your questions
Regards
Fotios
With 7 pairs of those metal can OnSemi transistors that amp should be able to drive anything in existence 😀 Nice!
(QSC only uses 4 pairs of wimpy 2SC5200/2SA1943 devices in their RMX1450 amp with +-78V rails and seems to get away with it, but better safe than sorry...)
(QSC only uses 4 pairs of wimpy 2SC5200/2SA1943 devices in their RMX1450 amp with +-78V rails and seems to get away with it, but better safe than sorry...)
megajocke said:
I only use 3 pairs of MOSFETS on my amp but the rails are only +/-60 volts. IRFP240/9240. The transformer puts out 1000VA.
I do use a good heatsink and a mains powered fan to make sure it stays cool.
If I were to build another I would go for higher voltage rails to cope with transients.
I have seen 2 pairs of 2SC3281/2SA1302 used on +-60V so I guess your three pairs of similarly sized devices will be just fine! I've also seen one pair of 2SC5200/2SA1943 used on +-60V but that IMO is pushing it a bit. That amp was low-quality, cheap OEM made in China though. There is room for two pairs on the board but just one installed...
megajocke said:
I have been silly enough to buy cheap foreign amps off ebay rated at many hundreds of watts.
I test them to find they are somewhat less than 100 watts !
If you remove the cover on them you can see the minimal design with tiny heatsink, small transformer and tiny power transistors.
These amps are actually quite nice when it comes to the transformer - it's pretty big. The output stages are way underdesigned though for PA/disco duty...
For the record
In these amplifiers I used individual EI transformers per channel (instead cheap toroids) ordered from a great lab in Thessalonika in north Greece. Each one ordered at 650VA but in practice the core it is of 800VA (it is standard because it follows the size of winding frames standard 600VA-800VA and so on).
Special transformers, due to my stupid honesty i paid 80 Euros of today per piece.
Another one stupidity was the use of double 90X90X38mm PAPST fans (TYP 3656) per unit (26 today Euros per fan).
Only in the P.S. capacitors i made economy. Only 30000mF per channel.
But the profit was clearly ethical.
Yet today, some of my customers (mainly sound contractors) they stay to use these amplifiers to drive P.A. bandpass subwoofers bellow 150Hz because the class H or G amplifiers are inadequate to give the same results such these AB class amplifiers.
Moreover from fig.6-7-8 it is obvious the performance in frequencies bellow 100Hz.
Yet today, from time to time is presented a sound contractor for asking me to build a such amplifier for he. Of course my answeer it is NO THANKS.
If you wonder about Iq, it is 20mA per output device.
You are right, this project it is not an amplifier, it is a warmachine.
Fotios
In these amplifiers I used individual EI transformers per channel (instead cheap toroids) ordered from a great lab in Thessalonika in north Greece. Each one ordered at 650VA but in practice the core it is of 800VA (it is standard because it follows the size of winding frames standard 600VA-800VA and so on).
Special transformers, due to my stupid honesty i paid 80 Euros of today per piece.
Another one stupidity was the use of double 90X90X38mm PAPST fans (TYP 3656) per unit (26 today Euros per fan).
Only in the P.S. capacitors i made economy. Only 30000mF per channel.
But the profit was clearly ethical.
Yet today, some of my customers (mainly sound contractors) they stay to use these amplifiers to drive P.A. bandpass subwoofers bellow 150Hz because the class H or G amplifiers are inadequate to give the same results such these AB class amplifiers.Moreover from fig.6-7-8 it is obvious the performance in frequencies bellow 100Hz.
Yet today, from time to time is presented a sound contractor for asking me to build a such amplifier for he. Of course my answeer it is NO THANKS.
If you wonder about Iq, it is 20mA per output device.
You are right, this project it is not an amplifier, it is a warmachine.
Fotios
raitraak said:
Aq
In either case of your final choice about the implementation of your project may i point out some things.
These supply voltage levels from+/-80V and above are generally dangerous for you and the test procedure.
For this reason you can see in this forum only few persons occupied with such big projects. For this reason exactly i gave you my compliments because you must be very daring to try this project.
It is mandatory that any accidental short for example with the probe of your multimeter or your scope, will cause a big bang! with destructive results.
I suggest you (if you don't have one) to get a variac of 5A at least. When you try to make a check, allways shut down the power and wait to discharged the reservoir caps (you can solder a 3,9K / 5W resistor accross the leads of each cap to speed up the discharge). After this you can place the test leads, and by observing continuously the output, crank up slowly the variac. Usually when reached a Vcc of +/- 20 to +/-25Vdc at supply rails, any error revealed in the screen of scope. And this voltage it is not dangerous to destroy any component inside the circuit.
Fotios
Hey!
I already have 5k6 bleeder resistors in the supply. I plan to use dual lab supply with max 2x30 and 1.5 amp for testing. It also has current limiting.
I am learning PADS now, to create the layout, but it takes time. Hope to be back soon with board layouts.
Aq
I already have 5k6 bleeder resistors in the supply. I plan to use dual lab supply with max 2x30 and 1.5 amp for testing. It also has current limiting.
I am learning PADS now, to create the layout, but it takes time. Hope to be back soon with board layouts.
Aq
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