Hi there,
My name name is Padelis and I am from Greece.I electronics here in Greece and I decided to build and amplifier for my home project studio.I bought a kit from a company here in Greece which is an 2x60watt amp.On the schematic the output transistors are bdw83 and the provided transistors are 2sd817(upgrade???).So what i want to ask you is what to do in order to make this amp better.I would like less distortion, more watts and be a little faster.I know that if i want to change the output transistors i will have to change the drivers too.So here i am to the more experts diyers asking for help and opinions!!!!
Thanx in advance
Padelis.
My name name is Padelis and I am from Greece.I electronics here in Greece and I decided to build and amplifier for my home project studio.I bought a kit from a company here in Greece which is an 2x60watt amp.On the schematic the output transistors are bdw83 and the provided transistors are 2sd817(upgrade???).So what i want to ask you is what to do in order to make this amp better.I would like less distortion, more watts and be a little faster.I know that if i want to change the output transistors i will have to change the drivers too.So here i am to the more experts diyers asking for help and opinions!!!!
Thanx in advance
Padelis.
Attachments
Maybe you could use a complementary design instead of quasi. Not that quasi is bad, it's just that there exists in these modern times some pretty good complementary output transistors.(no offense quasi
) You may not have to change the drivers, just use them in emitter follower darlington arrangment. Also wouldn't hurt to add small base resistors to those outputs. In doing this, you may also want to include a Vbe multiplier for bias and thermal stability instead of diodes as class AB emitter followers can be sensitive to temp. and bias changes. Loading the VAS with a current source might work also, however there are designs that don't use a CCS.
) You may not have to change the drivers, just use them in emitter follower darlington arrangment. Also wouldn't hurt to add small base resistors to those outputs. In doing this, you may also want to include a Vbe multiplier for bias and thermal stability instead of diodes as class AB emitter followers can be sensitive to temp. and bias changes. Loading the VAS with a current source might work also, however there are designs that don't use a CCS.
It seems as though you have already bought the amp kit.
The BDW83 is specified as a darlington and I cannot find information about the 2SD817. A more modern transistor would be a TIP142.
The number of changes required would not work well with the existing kit PCB so I would build as is and see what you think.
Use any upgrade money you have to build an excellent power supply using a 500va transformer with a seperate bridge and capacitor bank for each amp module. Use at least 10,000uf per rail (20,000uf total) per amp module.
Cheers
The BDW83 is specified as a darlington and I cannot find information about the 2SD817. A more modern transistor would be a TIP142.
The number of changes required would not work well with the existing kit PCB so I would build as is and see what you think.
Use any upgrade money you have to build an excellent power supply using a 500va transformer with a seperate bridge and capacitor bank for each amp module. Use at least 10,000uf per rail (20,000uf total) per amp module.
Cheers
psyche:
That circuit is really terrible (not due to the quasi output stage but due to the lousy rest) and probably from early seventies as it has ben already pointed out. Also, ECA book tells that 2SD817 is a Toshiba 1500V 1.5A TV horizontal deflection transistor, thus not suitable at all for an audio amplifier. Furthermore, Toshiba electronic components website does not contain any reference to that device (meaning that it was discontinued a long ago) and I couldn't find any other alternative manufacturer in google, so what you have are FAKE transistors, forgeries (very common in Southern European countries).
In my opinion you have been scamed, so it would be a good idea to return everything to the supplier and ask for your money back.
Also, remember that this forum is full of great projects to build, you just have to be patient and search. You should also search for threads on fake components and read them because I feel that local stores on your country are flooded of fake transistors and ICs (as it happens in Spain and Italy).
That circuit is really terrible (not due to the quasi output stage but due to the lousy rest) and probably from early seventies as it has ben already pointed out. Also, ECA book tells that 2SD817 is a Toshiba 1500V 1.5A TV horizontal deflection transistor, thus not suitable at all for an audio amplifier. Furthermore, Toshiba electronic components website does not contain any reference to that device (meaning that it was discontinued a long ago) and I couldn't find any other alternative manufacturer in google, so what you have are FAKE transistors, forgeries (very common in Southern European countries).
In my opinion you have been scamed, so it would be a good idea to return everything to the supplier and ask for your money back.
Also, remember that this forum is full of great projects to build, you just have to be patient and search. You should also search for threads on fake components and read them because I feel that local stores on your country are flooded of fake transistors and ICs (as it happens in Spain and Italy).
Hi there,
soryy for been away for soooooooooo long but i had completely forgot that thread.a few corrections:
the output transistors are 2sd718
I have built this amp a few months ago and it sounds simply good.I was just wondering if i could improve its performance, thats all! Now i am ready to build a new amp from the schematics that are posted here in the forum but i can't decide which one to build.These are all great.BTW what would you recommend me to build?Have in mind that i will use it in my studio.
Thank you guys you are great
Padelis
soryy for been away for soooooooooo long but i had completely forgot that thread.a few corrections:
the output transistors are 2sd718
I have built this amp a few months ago and it sounds simply good.I was just wondering if i could improve its performance, thats all! Now i am ready to build a new amp from the schematics that are posted here in the forum but i can't decide which one to build.These are all great.BTW what would you recommend me to build?Have in mind that i will use it in my studio.
Thank you guys you are great
Padelis
Advice...
Hello there,
If you want to build an excellent sounding amplifier do not hesitate to visit Michael Bittner’s web site - SymAsym5 amplifier
Here he’s known as MikeB and there is a whole thread about this amplifier. Do a little survey. Many of today’s Hi-Fi amplifiers have the same topology as this one (Harman Kardon HK-680 with slightly modified feedback, Mission Cyrus 2, except it has quasi complementary output stage and many others).
Hope this helps.
Regards,
Nick
Hello there,
If you want to build an excellent sounding amplifier do not hesitate to visit Michael Bittner’s web site - SymAsym5 amplifier
Here he’s known as MikeB and there is a whole thread about this amplifier. Do a little survey. Many of today’s Hi-Fi amplifiers have the same topology as this one (Harman Kardon HK-680 with slightly modified feedback, Mission Cyrus 2, except it has quasi complementary output stage and many others).
Hope this helps.
Regards,
Nick
Calispera Padelis,
the Texas Instrument made BDW83 were 150 watt devices capable of 15 amps curent.
Your replacements are only 80 watt specimen, and current capability is also much lower than that of the BDW83.
Unless they gave you a total of 8 of these devices your kit is no good. They are also likely to be copies, made in China, because the original Toshiba 2SD718 devices are ancient history too.
If you want to spend: build Aleph amplifiers.
If very little : go SKA
If you want it even more easy: do a GC.
the Texas Instrument made BDW83 were 150 watt devices capable of 15 amps curent.
Your replacements are only 80 watt specimen, and current capability is also much lower than that of the BDW83.
Unless they gave you a total of 8 of these devices your kit is no good. They are also likely to be copies, made in China, because the original Toshiba 2SD718 devices are ancient history too.
If you want to spend: build Aleph amplifiers.
If very little : go SKA
If you want it even more easy: do a GC.
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