Hi.I am clonning Marantz MA9s2 non compramise amplifier.I am about to finish but i could not find much information about choke (L002 please check pictures attached.)
Is it ferrite core or air coil? We only know the inductance (2x180mH ) but do not know the wire gauge and toroidal core.Any ideas? Thanks in advance.Best regards
Is it ferrite core or air coil? We only know the inductance (2x180mH ) but do not know the wire gauge and toroidal core.Any ideas? Thanks in advance.Best regards
looked to me that is a common mode mode choke for filtering out RFI from the dc psu...
a ferrite most likely, you can find them sold on line....pc crt monitors and crt color tv's have those but i doubt the ampacity is big enough for an audio ampflifier...
https://docs.rs-online.com/f8dd/0900766b816de17a.pdf
a ferrite most likely, you can find them sold on line....pc crt monitors and crt color tv's have those but i doubt the ampacity is big enough for an audio ampflifier...
https://docs.rs-online.com/f8dd/0900766b816de17a.pdf
Hmmm... you ain't gonna like my calculation... but... I did an x-check using two different approaches... and I arrived at... a 12A DC common mode choke, 180mili H. Big motha... it comes to an individual interpretation of what the DC rating of this choke should be... I used a pretty severe case, but everything was as per the specifications. This would be enormous if done with a typical E-Core laminate. They may have used a special toroidal core material as well - a highly inductive one.
But, that amp in general... OMG... the design, grounding, connection of zero PS point to chassis, PCB layouts, creation (design) AND execution of 0V reference potential for main PCB... superb in every way. Unbelievable. Also, only 4 gain stages, highly optimised input & VAS ... and only 3 resistors in a signal chain.... a true differential approach.... get outa here.
I'd ditch the HDAMs... e.g. the pre-amp section, altogether.
A man can learn so much from that design.
But, that amp in general... OMG... the design, grounding, connection of zero PS point to chassis, PCB layouts, creation (design) AND execution of 0V reference potential for main PCB... superb in every way. Unbelievable. Also, only 4 gain stages, highly optimised input & VAS ... and only 3 resistors in a signal chain.... a true differential approach.... get outa here.
I'd ditch the HDAMs... e.g. the pre-amp section, altogether.
A man can learn so much from that design.
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i suspect that the front end of the amp this psu supplied is class A so that loading is pretty much constant...
Fellas,
Have a better look... the choke supplies current to the main amplifier section. This is why my calculations pointed to a 12A rating... the worst-case power consumption/output, 4-ohm load.
The inductance could be calculated only if the amp is examined under load on a test bench.
I think I've provided enough info here, for something that should not really be encouraged... ripoff of the original design.
Have a better look... the choke supplies current to the main amplifier section. This is why my calculations pointed to a 12A rating... the worst-case power consumption/output, 4-ohm load.
The inductance could be calculated only if the amp is examined under load on a test bench.
I think I've provided enough info here, for something that should not really be encouraged... ripoff of the original design.
yes, that part where there is a common mode choke supplied -+65vdc to the amplifier front end, the input transimpedance and the VAS...notice that that psu just used 4700/80v, such small filters are just okay there....
there is another psu that supplied rails to the output stage, these one used 33000ufd/63volt caps ad probably +-50vdc rails, this is the higher current psu for the output supply......such designs are typical practice of Japanese, the reason being, that the output stage clips first, and the front end never clipped....such design principle was also advocated in the 70's by William Marshal Leach of Georgia Tech....
there is another psu that supplied rails to the output stage, these one used 33000ufd/63volt caps ad probably +-50vdc rails, this is the higher current psu for the output supply......such designs are typical practice of Japanese, the reason being, that the output stage clips first, and the front end never clipped....such design principle was also advocated in the 70's by William Marshal Leach of Georgia Tech....