In my built a simple led is connected to J3.2 (SDA ready) and J2.2 (GND). That works well.
I also tried J3.4 (+5V) instead of J3.2 but then the Purifi module started shutting down repeatedly after ten seconds. The red leds on the Eval1 board flikkering irregularly. I checked the connections tried again with the same result. The led is fine at 5V so the behaviour of the Purifi surprised me.
I also tried J3.4 (+5V) instead of J3.2 but then the Purifi module started shutting down repeatedly after ten seconds. The red leds on the Eval1 board flikkering irregularly. I checked the connections tried again with the same result. The led is fine at 5V so the behaviour of the Purifi surprised me.
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Hi all, how quiet should a set up with Purifi amp be?
At first I did not notice a hum at all. But after finishing the amp I suddenly heard a hum. Rearranging the power cables helped but now I have gotten allergic and keep hearing a little hum when the music has stopped.
Just connected to the speakers the amp is dead silent.
With xlr cables connected it starts humming 50Hz. This I hear a 10 feet distance from the speakers.
With xlr also connected to a dac the humming is only just audible.
What ever I do else doesn't change the humming.
In my room at a quiet moment the background noise is 12 to 13 dB.
Three inches in front of a speaker I measure the hum at 16 to 17 dB.
Is this acceptable or should I check the wiring inside the amp?
Thanks for your input!
At first I did not notice a hum at all. But after finishing the amp I suddenly heard a hum. Rearranging the power cables helped but now I have gotten allergic and keep hearing a little hum when the music has stopped.
Just connected to the speakers the amp is dead silent.
With xlr cables connected it starts humming 50Hz. This I hear a 10 feet distance from the speakers.
With xlr also connected to a dac the humming is only just audible.
What ever I do else doesn't change the humming.
In my room at a quiet moment the background noise is 12 to 13 dB.
Three inches in front of a speaker I measure the hum at 16 to 17 dB.
Is this acceptable or should I check the wiring inside the amp?
Thanks for your input!
Checkout, really helpfull :
How To Find and Fix Hum Extended | PS Audio
"Sometimes hums and buzzes are quite obvious, sometimes not. The ‘hum noise’ usually comes in two flavors, a low non-irritating drone (50 or 60 Hz) or a slightly higher pitched buzz or raspy/irritating ‘angry insect’ sound (100 or 120 Hz). Video hum is usually seen as diagonal bars across the TV or screen of a projector.
The low non-irritating drone hum is usually internal to the equipment and is mechanical in nature. The higher pitched and more irritating ‘buzz’ is typically found emanating from the loudspeakers and is usually caused by a ground loop. The most common cause of hum is the ground loop – fortunately it is also the easiest to solve.
First, you should determine the type of hum you are dealing with. There are two basic types: 120Hz buzz, typically caused by ground loops, and 60Hz hum, typically a result of poor shielding, cable problems, or close proximity to strong magnetic fields.
To determine which of these you have, listen to the two examples.
60Hz hum caused by close proximity to other equipment or cables problems:
The specified audio id does not exist.
120Hz hum/buzz typical of ground loop problems...................."
How To Find and Fix Hum Extended | PS Audio
"Sometimes hums and buzzes are quite obvious, sometimes not. The ‘hum noise’ usually comes in two flavors, a low non-irritating drone (50 or 60 Hz) or a slightly higher pitched buzz or raspy/irritating ‘angry insect’ sound (100 or 120 Hz). Video hum is usually seen as diagonal bars across the TV or screen of a projector.
The low non-irritating drone hum is usually internal to the equipment and is mechanical in nature. The higher pitched and more irritating ‘buzz’ is typically found emanating from the loudspeakers and is usually caused by a ground loop. The most common cause of hum is the ground loop – fortunately it is also the easiest to solve.
First, you should determine the type of hum you are dealing with. There are two basic types: 120Hz buzz, typically caused by ground loops, and 60Hz hum, typically a result of poor shielding, cable problems, or close proximity to strong magnetic fields.
To determine which of these you have, listen to the two examples.
60Hz hum caused by close proximity to other equipment or cables problems:
The specified audio id does not exist.
120Hz hum/buzz typical of ground loop problems...................."
No...
This is definitely not acceptable. You have some kind of grounding problem in your system. Start with just the amp and speakers connected, then add components one at a time until the hum appears. Then investigate how these components are grounded and fix the problem. Why does it look like there are two ground wires from your AC inlet to the chassis ground terminal?
This is definitely not acceptable. You have some kind of grounding problem in your system. Start with just the amp and speakers connected, then add components one at a time until the hum appears. Then investigate how these components are grounded and fix the problem. Why does it look like there are two ground wires from your AC inlet to the chassis ground terminal?
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Thank you for the firm answer. I'll go looking for the grounding problem. First I will test the mains cables to the amp and the dac with everything else disconnected.
The extra wire to ground is the shielding of the mains cable from the inlet to the switch on the front. The shielding is not connected to anything else.
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I would...
I would suggest that you install a stick on wire organizer and use it to pull that internal AC cable as far away from the power supply wiring to the modules as possible: get that AC cable all the way to the side of the chassis as it appears to be really close to the wiring into the modules. Remember the shielding on thta cable does nothing at low frequencies, it is only effective at RF. Of course if you do not hear the hum with only the amp connected, then that cable is not the problem, but it is still a better layout to get it as far away from those other wires as possible, especially considering they are parallel.
I would suggest that you install a stick on wire organizer and use it to pull that internal AC cable as far away from the power supply wiring to the modules as possible: get that AC cable all the way to the side of the chassis as it appears to be really close to the wiring into the modules. Remember the shielding on thta cable does nothing at low frequencies, it is only effective at RF. Of course if you do not hear the hum with only the amp connected, then that cable is not the problem, but it is still a better layout to get it as far away from those other wires as possible, especially considering they are parallel.
Interesting with the four missing pins. Those are the sense pins for the output along with one of the output pins (there are five pins for each side of the output). I wonder why. The 36-pin connector is available from Samtec.
Tom
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Hello Barrows, thanks for your help so far. I fixed the internal mains cable to the side.
On my bench the hum is only audible with my ear to the speaker. But it's there.
I started testing with a ground wire. I've an iFi AC purifier with ground input. When I make a connection with case ground, xlr housing or any outside ground point on the dac it changes nothing.
I have connected the led in front to SDA ready and J2.2 GND. When I disconnect the led and I touch the bare J2.2 GND wire the hum is gone! But only with the ground wire in my fingers. When I touch the wire else where in the case the hum is there. What could cause this effect?
Even more strange. I took the iFi ipurifier to my workbench. Before connecting the ground wire to anything of the amp I touched it with my fingers. When I hold the ground wire in my hand I hear no hum. So it seems it has more to do with the mains grounding than with the amp. What could I do next?
Hi,
I finally opened this :
[PURIFI ORDERS] 2x Purifi 1ET400A + 1x PSU SMPS1200A400 Group buy : Free DHL shipping
I finally opened this :
[PURIFI ORDERS] 2x Purifi 1ET400A + 1x PSU SMPS1200A400 Group buy : Free DHL shipping
