Relative newcomer to working on amps etc , this represents the next stage on the learning curve from fiddling . I have a Sansui 9090 and I'm replacing the fuse resistors , protection relay etc , and will hopefully get it going. The derogatory comment I keep coming across re the 9090 is that it has ICs in the preamp , so I was thinking I could go the extra yard and replace the ICs with equivalent circuits. They are BA312 , and the datasheet gives the equivalent circuit as three transistors and a small number of resistors . The resistor values are given , but no info about the transistors. I could do a simple pcb and replace one or two or all the BA312 and feel like I had a really special 9090 at the end of it -if it's viable . Am I being over-enthusiastic? Would it be worth it , and if so what transistors would suit?
Hi,
You can't improve on what you already have without an extensive
analysis of the way the BA312 parts array chip is being used.
Comments like :
" SANSUI 9090 the early one from 1976, not 9090DB. It looks interesting,
120w, but oh dear, sodding ICs. It stinks & will never be Superfi! Flat Amp-
pre Tone board F2543 has 1x BA312; another Tone board F2544 has 2x
BA312; Equaliser (Phono) has 2x BA312 as well as 5 more in the Tuner
circuit as is not so bad. BA312 is a 7 pin thing, 3 transistors & 4 resistors,
but still a general IC with general values. Cop out. Not interested.
How hard could it be for a supposedly premium product
to use 3 lovely transistors instead of a sodding IC? "
Just shows completely prejudiced ignorance about the nature of such chips.
Its pointless setting up the line to make the chip if you can do better with
3 "lovely"(whatever than means) transistors and 4 resistors, you can't.
You won't get anywhere replicating the equivalent circuit with discrete
devices I would assume, the datasheet is far too sparse and unreadable.
rgds, sreten.
http://www.littlediode.com/datasheets/pdf/Datasheets-BA3/BA312.PDF
You can't improve on what you already have without an extensive
analysis of the way the BA312 parts array chip is being used.
Comments like :
" SANSUI 9090 the early one from 1976, not 9090DB. It looks interesting,
120w, but oh dear, sodding ICs. It stinks & will never be Superfi! Flat Amp-
pre Tone board F2543 has 1x BA312; another Tone board F2544 has 2x
BA312; Equaliser (Phono) has 2x BA312 as well as 5 more in the Tuner
circuit as is not so bad. BA312 is a 7 pin thing, 3 transistors & 4 resistors,
but still a general IC with general values. Cop out. Not interested.
How hard could it be for a supposedly premium product
to use 3 lovely transistors instead of a sodding IC? "
Just shows completely prejudiced ignorance about the nature of such chips.
Its pointless setting up the line to make the chip if you can do better with
3 "lovely"(whatever than means) transistors and 4 resistors, you can't.
You won't get anywhere replicating the equivalent circuit with discrete
devices I would assume, the datasheet is far too sparse and unreadable.
rgds, sreten.
http://www.littlediode.com/datasheets/pdf/Datasheets-BA3/BA312.PDF
Discrete construction is just one article of faith in "audio as religion" that has been endlessly misrepresented in non-tech audio circles for the past 30 years. The religion points to the old ways and parts suited to hand assembly as somehow embodying the acme of audio design.
Surely, they are just what is now old, cheap and simply fiddled with. That lunatic in the above quotation, parroting the articles of faith where facts might be useful, should be convincing enough in his waffling nonsense regarding the merits of ICs and indeed, the value of the post itself.
It's amazing how the BS sticks with the help of ignorance. The same guys are playing music through DACs infested with standard IC opamps but assume only the one they can see (and thus fiddle with) is likely the one holding back the sonic thrills. 'A bit like suspecting cables to be at fault since from outside the box, there are few other things to see. 🙄
Surely, they are just what is now old, cheap and simply fiddled with. That lunatic in the above quotation, parroting the articles of faith where facts might be useful, should be convincing enough in his waffling nonsense regarding the merits of ICs and indeed, the value of the post itself.
It's amazing how the BS sticks with the help of ignorance. The same guys are playing music through DACs infested with standard IC opamps but assume only the one they can see (and thus fiddle with) is likely the one holding back the sonic thrills. 'A bit like suspecting cables to be at fault since from outside the box, there are few other things to see. 🙄
Thanks for the replies , that's certainly cleared that one up , and saved me a lot of time !
It shows how invaluable this and other forums can be in sorting out the useful from the BS in the mass of information the internet supplies . Without the www I wouldn't even have started on soldering bits of circuits ( I just finished my first valve amp) , but it can be so easy to follow the wrong trail.
It shows how invaluable this and other forums can be in sorting out the useful from the BS in the mass of information the internet supplies . Without the www I wouldn't even have started on soldering bits of circuits ( I just finished my first valve amp) , but it can be so easy to follow the wrong trail.
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