pcb,s
Hello mr destroyer x, I really wanted you to know that i,ve really enjoyed reading your posts in this thread.I aslo wanted to ask you if you know of anyone making pcb,s of this design.A few years ago i would have made my own pcb.But i,ve had 2 strokes,and my hands can,t really do this type of work anymore.So if you know of someone who has these pcb,s please let me know.I would really be gratefull.
Thanking you in advance for you time,I remain,
Evette😀
Hello mr destroyer x, I really wanted you to know that i,ve really enjoyed reading your posts in this thread.I aslo wanted to ask you if you know of anyone making pcb,s of this design.A few years ago i would have made my own pcb.But i,ve had 2 strokes,and my hands can,t really do this type of work anymore.So if you know of someone who has these pcb,s please let me know.I would really be gratefull.
Thanking you in advance for you time,I remain,
Evette😀
I am building symasym version 5_3 and i have some questions.
1) can i replace the 3.3pf feedback cap with a R-C network of 100k - 15pf?
2) can i replace the base resistors of the drivers with 100 ohm each one?
3) can i replace the base resistors of the output transistors with 4.7 ohm each one?
1) can i replace the 3.3pf feedback cap with a R-C network of 100k - 15pf?
2) can i replace the base resistors of the drivers with 100 ohm each one?
3) can i replace the base resistors of the output transistors with 4.7 ohm each one?
probably not for all 3 alterations.
If you are prepared to check the stability thoroughly for all combinations of inputs and outputs and loads then try some of your mods.
Have you read Roender's changing of the output devices?
If you are prepared to check the stability thoroughly for all combinations of inputs and outputs and loads then try some of your mods.
Have you read Roender's changing of the output devices?
no i havent read this.what is it about?where can i find it?
i thought that these replacement ,especially the RC network ,would improve stability, .
i thought that these replacement ,especially the RC network ,would improve stability, .
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MJE1503* series devices are not exactly driver transistors, Coda used them as output stage devices.
Transition frequency level of the Motorolas starts to get decent at 36mA quiescent current, sorta means they're faster when you bias them.
Transition frequency level of the Motorolas starts to get decent at 36mA quiescent current, sorta means they're faster when you bias them.
the 2sb/d can pass 20W @ 40Vce.
The MJE can pass between 20W and 50W @ 40Vce, depending on the Model chosen.
The MJE can pass between 20W and 50W @ 40Vce, depending on the Model chosen.
i have a 24-0-24 volt, +-32 volt dc transformer and i was thinking of replacing the mjes drivers of symasym with 2sb649 /2sd669. will it be ok?
what output transistors would be better for this amp? mjl21193-94 or 2sc5200-2sa1943?
what output transistors would be better for this amp? mjl21193-94 or 2sc5200-2sa1943?
changing to another transistor used as a driver will require you to work out the temperature de-rated SOAR of the substitute and compare that to the load line of the various loads you may attach.
We cannot do that for you.
Presumably the designer has already done this for his design.
Either copy the working design or learn how to re-design it.
We cannot do that for you.
Presumably the designer has already done this for his design.
Either copy the working design or learn how to re-design it.
you mean the curve of collector to emmiter voltage vs collector current at the safe operation area diagram?
Hi,
yes, the temperature de-rated safe operating area graphs where Vce vs Ic is plotted for single shot transients. DC is a single shot transient that has a time period of infinity.
David Eather shows how to do the calculations.
I disagree with his method of reducing voltage with increasing temperature in the second breakdown region.
I think one should maintain the same Vce and reduce the current. Power wise these are the same, but when one plots the values on the graphs one can see that the reduced current version maintains the same Vce and thus agrees with the manufacturer's data, whereas the reduced voltage version has moved to a new region that is less susceptible to second breakdown and the result is too low a de-rated power compared to what the device can pass.
yes, the temperature de-rated safe operating area graphs where Vce vs Ic is plotted for single shot transients. DC is a single shot transient that has a time period of infinity.
David Eather shows how to do the calculations.
I disagree with his method of reducing voltage with increasing temperature in the second breakdown region.
I think one should maintain the same Vce and reduce the current. Power wise these are the same, but when one plots the values on the graphs one can see that the reduced current version maintains the same Vce and thus agrees with the manufacturer's data, whereas the reduced voltage version has moved to a new region that is less susceptible to second breakdown and the result is too low a de-rated power compared to what the device can pass.
for a 4 ohm load at full power , will the 2sd669 be ok? my power supply is +-33volt dc.
loooking at the SOA of 2sd669 at 33 volt Vce the maximum coresponding Ic dc current is 0.6 A.
loooking at the SOA of 2sd669 at 33 volt Vce the maximum coresponding Ic dc current is 0.6 A.
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Hi,
and if Tc=45degC?
What is the gain when passing 600mA?
What load is that on the pre-driver and/or VAS?
If driver output is 600mA then what gain can the output device have?
What load current will that allow? What temperature will the output device be at just as this high current transient is about to start?
How long is it since the last high current passed through?
Has the device junction cooled sufficiently to let this transient to pass?
You have to design the whole output stage to suit the loads and operating conditions.
It is not enough to specify +-33Vdc and 4ohm load impedance.
and if Tc=45degC?
What is the gain when passing 600mA?
What load is that on the pre-driver and/or VAS?
If driver output is 600mA then what gain can the output device have?
What load current will that allow? What temperature will the output device be at just as this high current transient is about to start?
How long is it since the last high current passed through?
Has the device junction cooled sufficiently to let this transient to pass?
You have to design the whole output stage to suit the loads and operating conditions.
It is not enough to specify +-33Vdc and 4ohm load impedance.
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What changes have to be made in the schematic if symasym is to be driven directly by preamp?😕