881 teardown and rebuild
- Thread starter Meteli
- Start date
I am hunting "white noise" or constant hum that is in most 881's
So what I did was all the normal "tighten the screws" and ground wig things there are mention to fix it, nothing worked.
So I changed all the parts on driver board. including subtitute for 2SC984.
BD137 does not work, got smoke from resistors, equal amount of smoke so don't try it. but KSC2383 does work.
I drill a hole side of the heatsink and screw it on.
After the picture, I changed rest of the parts.
By changing resistors to metal film got huge affect on amps that use carbon resistors. Metal film gets rid of all that haze or fog that is in the sound. Yes you you could say resistors does not matter, but I have done now few of these resistor swaps and every time result is even more spectacular then changing electrolytics.
So did it remove that "881 hum" ? No...
So on with preamp section.
BA312 out, new diy in.
Did it help? No... maybe...
So I took and changed all the resistors out of the preamp tone board,
Took out second ground wire from board, did it help? no.
Next I got fedup and went overboard and changed everyting:
Deleted tape monitor switches from use, simply soldered jumper under them. My aim is to remove unessesary contacts from signal path.
Changed all small value capacitors to polypropylene
Even took out Sansui 9090 manual and change 881 tone board to 9090
C610 100uF -> 220uF
C25 1uF -> 2.2uF
Did it remove the 881 hum? YES! dead silent
It is tone/preamp board that causes that hum on 881, BA312 is one part, but I think it is resistors that cause it.
BUT...
Sound after every single resistor is metal film, not a single old transistor left, is amazing!
Now 881 sounds like live consert, sharp, clear everyting, but most amazing thing is bass. Now it is like there is dual subwoofers in the room, bass is so heavy you feel it in your chest and it mooves thing is a room.
It is when you listen one of the small Sansui's like 331 and you are amazed how something with 12 wats can make so huge base. Then you listen regular 881 and you got that "hifi" sound where that amazing base is gone. after those modifications you do not get 12w bass, you got 60w bass. It is like you got in your home cinema system with dual subwoofers.
881 from 1970's does not have as deep soundstage as very high power amps from 1990's got but it got that nice echo type of live consert feeling where stage is kind of limit of that depth. Very nice sound though and all that monster base will cover all your needs. Classical music sounds very nice with it, as base is usually difficult to get out from recordings, but current 881 I have even violins got presence. Metal or electronic music you need to take bass out selector, but that is why it is there.
So what I did was all the normal "tighten the screws" and ground wig things there are mention to fix it, nothing worked.
So I changed all the parts on driver board. including subtitute for 2SC984.
BD137 does not work, got smoke from resistors, equal amount of smoke so don't try it. but KSC2383 does work.
I drill a hole side of the heatsink and screw it on.
After the picture, I changed rest of the parts.
By changing resistors to metal film got huge affect on amps that use carbon resistors. Metal film gets rid of all that haze or fog that is in the sound. Yes you you could say resistors does not matter, but I have done now few of these resistor swaps and every time result is even more spectacular then changing electrolytics.
So did it remove that "881 hum" ? No...
So on with preamp section.
BA312 out, new diy in.
Did it help? No... maybe...
So I took and changed all the resistors out of the preamp tone board,
Took out second ground wire from board, did it help? no.
Next I got fedup and went overboard and changed everyting:
Deleted tape monitor switches from use, simply soldered jumper under them. My aim is to remove unessesary contacts from signal path.
Changed all small value capacitors to polypropylene
Even took out Sansui 9090 manual and change 881 tone board to 9090
C610 100uF -> 220uF
C25 1uF -> 2.2uF
Did it remove the 881 hum? YES! dead silent
It is tone/preamp board that causes that hum on 881, BA312 is one part, but I think it is resistors that cause it.
BUT...
Sound after every single resistor is metal film, not a single old transistor left, is amazing!
Now 881 sounds like live consert, sharp, clear everyting, but most amazing thing is bass. Now it is like there is dual subwoofers in the room, bass is so heavy you feel it in your chest and it mooves thing is a room.
It is when you listen one of the small Sansui's like 331 and you are amazed how something with 12 wats can make so huge base. Then you listen regular 881 and you got that "hifi" sound where that amazing base is gone. after those modifications you do not get 12w bass, you got 60w bass. It is like you got in your home cinema system with dual subwoofers.
881 from 1970's does not have as deep soundstage as very high power amps from 1990's got but it got that nice echo type of live consert feeling where stage is kind of limit of that depth. Very nice sound though and all that monster base will cover all your needs. Classical music sounds very nice with it, as base is usually difficult to get out from recordings, but current 881 I have even violins got presence. Metal or electronic music you need to take bass out selector, but that is why it is there.