I have a problem with my Sony cmt-nez3 micro system. It has pretty good sound and recently i changed speakers with ones that have better tweeters. Now hiss is constantly present when there is no sound playing. Problem is that i sit very close to the speakers as i used them as monitors (30cm).
Amp inside micro system is LM1876 and voltage is 43,8V (Vcc-Vee). Output inductors are present. There is no motorboating just higher frequency hiss. Hiss is present when i select audio in and disconnect input cable from pc. What modifications do you suggest to get rid of it?
Amp inside micro system is LM1876 and voltage is 43,8V (Vcc-Vee). Output inductors are present. There is no motorboating just higher frequency hiss. Hiss is present when i select audio in and disconnect input cable from pc. What modifications do you suggest to get rid of it?
Thanks for answer
Considering the price (around 110$) the unit is built extreemly well. It's all in SMD and supply filtering is 2200uF bypassed with lower values of smd capacitors. Main board is very well organised, but offcourse it's not in ground star configuration. Do supply capacitors need to be bigger (again i must say that there is no motorboating effect)?
Or should i build separate LM3886 amp?
Considering the price (around 110$) the unit is built extreemly well. It's all in SMD and supply filtering is 2200uF bypassed with lower values of smd capacitors. Main board is very well organised, but offcourse it's not in ground star configuration. Do supply capacitors need to be bigger (again i must say that there is no motorboating effect)?
Or should i build separate LM3886 amp?
Well, speakers that came with the system were awfull 10cm fullrange units. Their frequency response was bad enough so hiss can't be heard on them. These speakers that i use now are much bigger 3 way speakers, that i had left from other sony mini system which is dead. Speakers are very good comparing to the more expensive hi-fi speakers. Tweeter efficiency is not that important because frequency response of the whole speaker is (lets say)near flat, and the whole speaker efficiency is maybe just a little better than small fullrange units. Hiss is now noticable because speakers have extended freq. range.
Well i should have bought bigger system in the start. Sony has great 2 way with 4 digital amplifiers system at around 230$, and philips even have ribbon tweeter at that price. I don't know any model with 3886 in it except some Aiwa 5.1 receiver which had very low price (around 300$).
So is there a way to make this little amp not to hiss, or should i build 3886 amp and listen on it (or insert 3886 in the sony
) ?
Well i should have bought bigger system in the start. Sony has great 2 way with 4 digital amplifiers system at around 230$, and philips even have ribbon tweeter at that price. I don't know any model with 3886 in it except some Aiwa 5.1 receiver which had very low price (around 300$).
So is there a way to make this little amp not to hiss, or should i build 3886 amp and listen on it (or insert 3886 in the sony
) ?Since pictures tell you more than thousand words, here they are:
First is just view from the back, and behind the radiator on the right side is transformer (not torroidial).
Second is view from the back of the board which is on left on the first picture. Left on the board is backside of lm1876 and smd components around it.
And the last picture is just close view of the lm1876, power condensers and output inductors.
Any suggestions, now that you can see system inside?
First is just view from the back, and behind the radiator on the right side is transformer (not torroidial).
Second is view from the back of the board which is on left on the first picture. Left on the board is backside of lm1876 and smd components around it.
And the last picture is just close view of the lm1876, power condensers and output inductors.
Any suggestions, now that you can see system inside?
Attachments
Thank you for helping me !
Heatsink isn't that hot, it's most of the time around 35C.
I could change capacitors but there is only high frequency hiss, not 50hz. That's why i think that is probably some kind of oscillations. I have changed cables, with thicker ones, so i doubt that would be a problem (they are also short). Also there is output oscillation protection with conductors.
The hiss is present before amplifier as i also hear it on headphone connector, so maybe problem is in the preamplifier section and digital volume control. If that's the case, i can't do nothing.
Maybe i can bypass all of the electronics before amp and drive amp directly from the pc out with volume control as passive attenuator. Or just build 3886 amp separate of this sony, and leave it as it is.
Heatsink isn't that hot, it's most of the time around 35C.
I could change capacitors but there is only high frequency hiss, not 50hz. That's why i think that is probably some kind of oscillations. I have changed cables, with thicker ones, so i doubt that would be a problem (they are also short). Also there is output oscillation protection with conductors.
The hiss is present before amplifier as i also hear it on headphone connector, so maybe problem is in the preamplifier section and digital volume control. If that's the case, i can't do nothing.
Maybe i can bypass all of the electronics before amp and drive amp directly from the pc out with volume control as passive attenuator. Or just build 3886 amp separate of this sony, and leave it as it is.
Looks like a layout/wiring problem.I do encounter this kind of hiss sound when building my first and second amps and I do work hard to improve my layout/wiring skill.
Now after building my DDGC
,no more significant hiss sound.
Consider your Sony is a mass produced product,hissing is quite normal.
Now after building my DDGC
,no more significant hiss sound.
Consider your Sony is a mass produced product,hissing is quite normal.
Mx said:
I wonder if these new cables have higher capacitance and is making the amp' oscillate.
http://cache.national.com/ds/LM/LM1876.pdf
Page 6. Are the inductors paralleled with 10R (high wattage) resistors ?
Do both channels have the hiss ? (It could be input capacitor)
Just to be sure I tried thinner wires and the result is same. There are resistor in parallel with conductor at the output and there are input capacitors. And both channels have same hiss.
Maybe i am expecting to much of this amplifier, but in the age of t amp for 30$, maybe not .
@Leolabs - Man i was suprised when i saw your project.
I had that idea for the past few days for similar boxes (from old pc power supply). It's exactly the same as i have imagined it. It looks very good and i hope it sounds even better.
Maybe i am expecting to much of this amplifier, but in the age of t amp for 30$, maybe not
.@Leolabs - Man i was suprised when i saw your project.
I had that idea for the past few days for similar boxes (from old pc power supply). It's exactly the same as i have imagined it. It looks very good and i hope it sounds even better.- Status
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