Err Steeno,
how can they be the same if one is oscilation or excessive gain and the other is bad grounding.
Though they are both unwanted noise so could be condsidered the same that way.
But as indicated earlier its best to keep things uncomplicated.
And also if you dont know what your looking for its very hard to find it.
how can they be the same if one is oscilation or excessive gain and the other is bad grounding.
Though they are both unwanted noise so could be condsidered the same that way.
But as indicated earlier its best to keep things uncomplicated.
And also if you dont know what your looking for its very hard to find it.
Professor smith said:
Testing with wires is an easy thing.
Meanwhile, I think that the shortest trouble shooting would be possible only when we could see the schematics showing how each equipment has its grounding system and how connected each other. Otherwise, all things we are doing for the trouble shooting would be the same as trying to find out a good luck . . .
ok Babo
Here are the details of the grounding for amplifier and DAC.
but this is as far as I know:
The amp has a star earth. This is connected via back to back diodes and resistor in parallel to the chassis. Chassis is connected to IEC earth.
The dac only has the back to back diodes and resistor to IEC from chassis. I do not know whether the circuitry is connected to the chassis or not, although i was told it uses a floating earth, whatever that means.
That is all I know.
Here are the details of the grounding for amplifier and DAC.
but this is as far as I know:
The amp has a star earth. This is connected via back to back diodes and resistor in parallel to the chassis. Chassis is connected to IEC earth.
The dac only has the back to back diodes and resistor to IEC from chassis. I do not know whether the circuitry is connected to the chassis or not, although i was told it uses a floating earth, whatever that means.
That is all I know.
You didn't state if all your sources were disconnected from the dac unit. In other words, can you be sure that the problem is with the dac-amp connections.
And what kind of equipment are we discussing here, commercial stuff or DIY stuff. Brand names would even be helpful.
Is the hum you hear the same as the hum of the amp, only louder.
This is all total guesswork unless there is more info.
And what kind of equipment are we discussing here, commercial stuff or DIY stuff. Brand names would even be helpful.
Is the hum you hear the same as the hum of the amp, only louder.
This is all total guesswork unless there is more info.
Re: **interesting topic**
i found your post interesting, especially the montecarlo analisys.
Can you explain it a little further?
I am currently trying to ground my phonostage.
The gain is 67dB.
After experimenting with grounds a bit, the best result i could get was something like 7-8mV pk-pk 50Hz at the output.
It's not a huge noise, but still it can be heard at maximum volume at a couple of sztepfs away from the speaker.
Thr prototype is layed on a breadboard but i have implemented a star ground strategy.
I don't know if my grounding is correct or not and IF there is any way to get completely rid of this 7mV 50Hz, or not.
I still think my ground scheme is not optimal.
i will try to get the book you linked on your post.
one thing: i put a metal plate under the board to simulate a chassie and connect the GND of the power supply, where the star ground of the circuit to as well, to it (no diode nor resistor or thermistor from the ground to the chassie althoug i tried the CL-60 or a 10ohm resistor but it makes no difference to the hum at the output); if i disconnect input and output and measure the voltage with the meter in AC from from the plate to the GND input BNC of the oscilloscope, for example, i read 105V AC.
Is it an indication of a ground's issue?
Tarasque said:
i found your post interesting, especially the montecarlo analisys.
Can you explain it a little further?
I am currently trying to ground my phonostage.
The gain is 67dB.
After experimenting with grounds a bit, the best result i could get was something like 7-8mV pk-pk 50Hz at the output.
It's not a huge noise, but still it can be heard at maximum volume at a couple of sztepfs away from the speaker.
Thr prototype is layed on a breadboard but i have implemented a star ground strategy.
I don't know if my grounding is correct or not and IF there is any way to get completely rid of this 7mV 50Hz, or not.
I still think my ground scheme is not optimal.
i will try to get the book you linked on your post.
one thing: i put a metal plate under the board to simulate a chassie and connect the GND of the power supply, where the star ground of the circuit to as well, to it (no diode nor resistor or thermistor from the ground to the chassie althoug i tried the CL-60 or a 10ohm resistor but it makes no difference to the hum at the output); if i disconnect input and output and measure the voltage with the meter in AC from from the plate to the GND input BNC of the oscilloscope, for example, i read 105V AC.
Is it an indication of a ground's issue?
AndrewT said:
so what does that mean?
Babowana said:Professor,
Why not trying another DAC . . . ? Or, if no hum when your DVD player is connected instead of DAC, it must be that you have the problem from the DAC. Throw it away . . . it must be a poor product . . . Ring the bell . . . Close the curtain . . .
i tried shorting the amp input to ground and this gives minimal noise. Its not a poor product it is a very popular product which was bought on the basis of its good reviews.
Bill Fuss said:
The problem must be with the dac to amp because the only input i have going into the dac is an optical input which isolates it.
I am using the AKSA 55 amplifier as it goes.
The hum I hear is a little different from the amp alone because the amp hum is not sharp its like its been lowpass filtered whereas the dac hum is sharper and sounds like its been highpass filtered this time.
Same pitch i think.
Professor smith said:
I see . . .
I have a similar problem with hum from my Italian tube FM/AM tuner. Since I bought it about two years ago, I could have not used it for my personal reason. But, even these days I can't use it either. . . mmmdirtywordsmmm . . . this time due to another reason--the hum!!! So, I have recently e-mailed my question to the maker and got reply from its technical deaprtment. He has not indicated the ground loop problem, but something else. So, now I am going to open the cover to check inside today. I will come back if I find problem of mine . . . for your info . . .
Sorry if this is an off-topic . . .
Refer to my post #97 . . .
Actually, last time the technical department informed me that the problem (hum) must have been from the instable 7812 or 7912 installed inside and instructed me what to do. So, I opened the cover today, and found two 7812s and one 7912. And, I measured two of them working ok, but I could not believe my eyes with one 7812. I measured input voltage of 3.34V and output of 3.25V . . . Gee . . . and the figures were very instable . . .
So, today I re-sent an e-mail to the maker asking what the problem is and what I should do. And waiting his response . . .
Professor,
I highly recommend you to contact the maker of your DAC, too . . .
Actually, last time the technical department informed me that the problem (hum) must have been from the instable 7812 or 7912 installed inside and instructed me what to do. So, I opened the cover today, and found two 7812s and one 7912. And, I measured two of them working ok, but I could not believe my eyes with one 7812. I measured input voltage of 3.34V and output of 3.25V . . . Gee . . . and the figures were very instable . . .
So, today I re-sent an e-mail to the maker asking what the problem is and what I should do. And waiting his response . . .
Professor,
I highly recommend you to contact the maker of your DAC, too . . .
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