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SX-1010 Tracking Hiss - Always Present - Especially When Treble Increased

paultlaw said:
OK pretty dumb question, what would happen if the transistors were Changed to slightly lower gain versions? Or is that just stupid talk?
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Actually they use super gain transistors for low noise amplifiers, because they have lower noise current contribution. Voltage noise involves r'bb and Vce sat parameters.
resistors make noise, some more than others
but I do not think this applies here.
This is one design where they did not use the jfet/bjt design in the flat amp, I suspect a different designer's choice.

Your problem is frustrating to you and entertaining to others :) You have enough help here with out my involvement but I will follow along to see if you find the solution.
Good Luck
 
The first step is to do the short of the one channel's input and then repeat all the front panel knob fiddling again - looking for differences.
 
OK so no diy probe yet?

Short pins 4 & 5 together and then listen for any difference in hiss by playing with tone control
Then do same on pin 8 & 9 and do the same.

I haven't done anything yet, I want to make sure I have the procedure down first.
 
Correct. No probing yet - no directions as to WHERE to probe (yet)

DIDN'T say to short 8 to 9.This is left as a clean reference, so unknown can be compared to known.

ALL inputs tested, MAY have different noise contributions - or some damn strange effects.

Depending upon results, the probe point lists will be chosen.

Assume nothing when directions aren't clear. GOOD to ASK.
 
Its hard to tell what the result is to be honest - bottom cover is off pins 4 and 5 shorted together. Tried all inputs and even played some music through the AUX
Its a bit more noisy with the bottom cover off anyway, but fiddling the treble tone controls still makes the overall hiss jump high.


Not sure what this testing has shown to be honest. Do i now short out the other side 8 & 9 and see if one side is contributing more hiss/noise than the other?
 
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Thanks Larry, it seems both sides are pretty much the same. I changed out some of the 4.7uf caps for wima film caps hoping for a difference. Results were what I expected, no difference. I had some 4.7uf film caps so used them
 
I have made my peace with the level of hiss present folks. It might improve with the new power supply board that Zebulon1 has made up for me,even if it does not it will bring peace of mind. A genuine and heartfelt thank you to Zebulon1!

Have been changing all bulbs for LED's, found it to be not that enjoyable actually - the bulbs in most cases were essentially fused with the rubber housing so most snapped off no matter which way i tried to get at them. They would not go toward front of receiver to remove, nor from the back.
On the bright side, i personally love the look of the new LED's, i hope they last a long time, used 1K resistor on each bulb, green LED's for the green indicators, and white for everything else.
 
PTL-Pioneer said:
I have made my peace with the level of hiss present folks. It might improve with the new power supply board that Zebulon1 has made up for me,even if it does not it will bring peace of mind. A genuine and heartfelt thank you to Zebulon1!

Have been changing all bulbs for LED's, found it to be not that enjoyable actually - the bulbs in most cases were essentially fused with the rubber housing so most snapped off no matter which way i tried to get at them. They would not go toward front of receiver to remove, nor from the back.
On the bright side, i personally love the look of the new LED's, i hope they last a long time, used 1K resistor on each bulb, green LED's for the green indicators, and white for everything else.
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I know this thread is 2 1/2 years old, but did you guys ever figure out the hissing? I have a 1010 which I rebuilt everything and it’s amazing, but it has the exact same hissing. I’m leaning toward it being a trait of the 1010 tone / preamp section because it goes almost fully away when the click that switch off.
 
Dan2021 said:
I know this thread is 2 1/2 years old, but did you guys ever figure out the hissing? I have a 1010 which I rebuilt everything and it’s amazing, but it has the exact same hissing. I’m leaning toward it being a trait of the 1010 tone / preamp section because it goes almost fully away when the click that switch off.
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Did you replace ALL the transistors? I rebuilt a 1010, no hiss on mine.
 
EastPoint said:
Did you replace ALL the transistors? I rebuilt a 1010, no hiss on mine.
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Yes, with the exact ones on the lists here on audiokarma. The hiss is very low but noticeable with my klipsch chorus 2 speakers (probably because of the horns). I did have a good friend of mine listen to his sx-1050 a couple days and he said it also has a hiss. Weird but I do have very good hearing though.
 
Dan2021 said:
I know this thread is 2 1/2 years old, but did you guys ever figure out the hissing? I have a 1010 which I rebuilt everything and it’s amazing, but it has the exact same hissing. I’m leaning toward it being a trait of the 1010 tone / preamp section because it goes almost fully away when the click that switch off.
Click to expand...
I rebuilt mine about a year and a half ago. No hiss at all.
 
Quite possible it's your speakers. Depends on their sensitivity. IIRC mine had a hiss with my Klipsch KG-4 or Sansui speakers @ 4ft. Sansui's are rated to between 96 and 98 db/1W/1M. But put the NLA's or KLH 17's no hiss. 89 to 91db/1w/1m.
 
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