Hi
I have some experience with electronics but I consider myself a newbie, so please be forgiving with my ignorance.
I bought a UcD180HG module and SMPS400A180 PSU and connected them mostly according to the Hypex recommended wiring for unbalanced input:
1) the "safety earth" from the mains is connected to the chassis
2) the PSU has a contact to the chassis through a metallic spacer
3) the "signal +" and "signal -" from the UcD module go with a twisted pair to a potentiometer ("signal +" to POT output, "signal -" to POT common pin)
4) the "signal GND" from the UcD module goes to the POT common
5) the POT input is connected to a CHINCH (positive pin)
6) the POT common pin is connected to the negative pin of the CHINCH
When running the amplifier with the input shorted (by the POT) - it is completely quiet. However, if I turn the POT to hear the sound - it is distorted. The kind of distortion is difficult to explain - sounds like the input audio modulates some high frequency carrier; it sounds metallic.
I am surprised by this and could not explain it to myself. I do not know how to troubleshoot the situation. The most trivial idea is to build a classic transformer PSU instead of the SMPS.
As most of you are more experienced than me, what would you advice me?
I will make some pictures of the assembly tomorrow morning.
Thank you, guys!
I have some experience with electronics but I consider myself a newbie, so please be forgiving with my ignorance.
I bought a UcD180HG module and SMPS400A180 PSU and connected them mostly according to the Hypex recommended wiring for unbalanced input:
1) the "safety earth" from the mains is connected to the chassis
2) the PSU has a contact to the chassis through a metallic spacer
3) the "signal +" and "signal -" from the UcD module go with a twisted pair to a potentiometer ("signal +" to POT output, "signal -" to POT common pin)
4) the "signal GND" from the UcD module goes to the POT common
5) the POT input is connected to a CHINCH (positive pin)
6) the POT common pin is connected to the negative pin of the CHINCH
When running the amplifier with the input shorted (by the POT) - it is completely quiet. However, if I turn the POT to hear the sound - it is distorted. The kind of distortion is difficult to explain - sounds like the input audio modulates some high frequency carrier; it sounds metallic.
I am surprised by this and could not explain it to myself. I do not know how to troubleshoot the situation. The most trivial idea is to build a classic transformer PSU instead of the SMPS.
As most of you are more experienced than me, what would you advice me?
I will make some pictures of the assembly tomorrow morning.
Thank you, guys!
I have built a few Hypex amps and would doubt if your problem is due to the SMPS.
The amp is designed to take a balanced input.
Are you using an unbalanced input ?
Its difficult to follow your wiring description without a diagram but Hypex do have a technical information sheet on how to wire their amps for unbalanced operation showing in detail the cable wiring from a phono to XLR
The amp is designed to take a balanced input.
Are you using an unbalanced input ?
Its difficult to follow your wiring description without a diagram but Hypex do have a technical information sheet on how to wire their amps for unbalanced operation showing in detail the cable wiring from a phono to XLR
Hi, guys
The PDF which has been mentioned multiple times (on this forum, and other places) Hypex Electronics B.V. is no longer available (404 error) so I used the https://www.diyclassd.com/img/upload/doc/an_wp/AN_Amplifier_signal_wiring.pdf
(1) "Right, the audio is modulating the 400kHz carrier."
I am aware of that but it is difficult to explain the distortion that I hear. It is similar to a sharp hiss which combines with the real sound. I may try to record the sound on my phone but I doubt how much this will help ...
(2) "is signal gnd connected to the chassis?"
No, it is not.
Here is my ugly attempt to draw a schematic of my setup, plus some pictures of my build. I know you will be laughing as it is very primitive, I am okay with that.
The PDF which has been mentioned multiple times (on this forum, and other places) Hypex Electronics B.V. is no longer available (404 error) so I used the https://www.diyclassd.com/img/upload/doc/an_wp/AN_Amplifier_signal_wiring.pdf
(1) "Right, the audio is modulating the 400kHz carrier."
I am aware of that but it is difficult to explain the distortion that I hear. It is similar to a sharp hiss which combines with the real sound. I may try to record the sound on my phone but I doubt how much this will help ...
(2) "is signal gnd connected to the chassis?"
No, it is not.
Here is my ugly attempt to draw a schematic of my setup, plus some pictures of my build. I know you will be laughing as it is very primitive, I am okay with that.
Attachments
(3) "Signal ground should be referenced to the chassis"
I assume this means "connect 'safety earth' from the mains to 'signal GND'", right ?
Because I already have connected "signal GND" from UcD to the "negative pin" from the CHINCH (and to the common pin of potentiometer).
What if the chassis was all plastic instead of metal - would the above still hold true?
I assume this means "connect 'safety earth' from the mains to 'signal GND'", right ?
Because I already have connected "signal GND" from UcD to the "negative pin" from the CHINCH (and to the common pin of potentiometer).
What if the chassis was all plastic instead of metal - would the above still hold true?
https://www.diyclassd.com/img/upload/doc/an_wp/AN_Amplifier_signal_wiring.pdf
This is the data sheet on the Hypex website that shows how one should connect unbalanced inputs.
Note the mention of how one should Not connect safety earth to chassis and that when this is not connected the amp should be built to double insulation standards
Remember you fitted a conductive stand off to the SMPS. This is decoupling any unwanted signals from the SMPS to chassis. I would make this an insulated stand off and connect the SMPS board tab via a short wire link directly to input power earth keeping any decoupled "rubish" away from chassis.
This is the data sheet on the Hypex website that shows how one should connect unbalanced inputs.
Note the mention of how one should Not connect safety earth to chassis and that when this is not connected the amp should be built to double insulation standards
Remember you fitted a conductive stand off to the SMPS. This is decoupling any unwanted signals from the SMPS to chassis. I would make this an insulated stand off and connect the SMPS board tab via a short wire link directly to input power earth keeping any decoupled "rubish" away from chassis.
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My previous amplifier was nx201ps by Anthony Holton and it had a dedicated pin for connecting to chassis - however it had the same effect, i.e. when connected the amp was producing hum/buzz and when disconnected the sound was crystal clear.
However, one evening while I was listening music it suddenly became quiet - in exactly the same way as if it was turned off from the mains (i.e. the sound volume gradually decreased to zero with the exaustage of the capacitors - about 8-10 seconds). After some investigation I found out that all 4 Schottky diodes in the left arm were gone. I could not find a reason for that, as the output FETs were supposedly survived - otherwise my speaker would have blown because of some large DC.
I replaced the diodes 2 or 3 times and each time they got blown. The only non-SMD transistors there are the 2 output FETs and a termo-sensing one between them. Desoldered and measured them - looked okay.
Now the module collects dust on the shelf as I do not know how to troubleshoot the issue ....
Anyway, the UcD with "safety earth" disconnected sounds okay. When I find some time to solder a DAC I will move to an entirely plastic enclosure - I suppose this will ensure Class 2 insulation (10mm plastic)
However, one evening while I was listening music it suddenly became quiet - in exactly the same way as if it was turned off from the mains (i.e. the sound volume gradually decreased to zero with the exaustage of the capacitors - about 8-10 seconds). After some investigation I found out that all 4 Schottky diodes in the left arm were gone. I could not find a reason for that, as the output FETs were supposedly survived - otherwise my speaker would have blown because of some large DC.
I replaced the diodes 2 or 3 times and each time they got blown. The only non-SMD transistors there are the 2 output FETs and a termo-sensing one between them. Desoldered and measured them - looked okay.
Now the module collects dust on the shelf as I do not know how to troubleshoot the issue ....
Anyway, the UcD with "safety earth" disconnected sounds okay. When I find some time to solder a DAC I will move to an entirely plastic enclosure - I suppose this will ensure Class 2 insulation (10mm plastic)
Connecting signal gnd, which is PSU 0V to safety earth would mean the mains fuse would be more likely to blow if the circuit developed a fault.
I'm interested to hear how this pans out.
I wouldn't attempt a Class 2 double insulated enclosure.
The OP complains of hiss, not hum - can this be caused through ground loops?
Or perhaps the open frame enclosure is allowing entry to some other source of interference.
We do not know the signal source - if it is battery powered or double insulated then it will not contribute to a ground loop.
Why are a Left & Right input both connected to same channel? Mix down to mono for a sub perhaps?
I wouldn't attempt a Class 2 double insulated enclosure.
The OP complains of hiss, not hum - can this be caused through ground loops?
Or perhaps the open frame enclosure is allowing entry to some other source of interference.
We do not know the signal source - if it is battery powered or double insulated then it will not contribute to a ground loop.
Why are a Left & Right input both connected to same channel? Mix down to mono for a sub perhaps?
"That pdf confirms signal ground should be connected to the chassis"
Actually the first PDF which I looked at was https://www.diyclassd.com/img/upload/doc/ucd/ucd180hg/Documentation/UcD180 + SMPS400.pdf
The link from my first message (https://www.diyclassd.com/img/upload/doc/an_wp/AN_Amplifier_signal_wiring.pdf) I actually opened and read about 20 hours later - the moment when I realized my mistake with the "safety earth".
So, if my enclosure was (as it will be after a while) entirely plastic - where should I connect the signal GND ?
Actually the first PDF which I looked at was https://www.diyclassd.com/img/upload/doc/ucd/ucd180hg/Documentation/UcD180 + SMPS400.pdf
The link from my first message (https://www.diyclassd.com/img/upload/doc/an_wp/AN_Amplifier_signal_wiring.pdf) I actually opened and read about 20 hours later - the moment when I realized my mistake with the "safety earth".
So, if my enclosure was (as it will be after a while) entirely plastic - where should I connect the signal GND ?
"The OP complains of hiss, not hum"
In the beginning, "signal GND" from the UcD was left floating - then there was a hum, really loud. But it disappears when "signal GND" is connected to "signal -" (and both - to the negative pin of the audio source)
After I disconnected the mains "safety eartch" from the enclosure - there is no hiss, so it appears the openness does not contribute to additional interference (even though it is next to the computer on my desk).
The signal source at first was my portable battery-powered MP3 player, but now I am listening from my PC.
The LEFT and RIGHT are mixed down to mono as I only have 1 speaker box in the room.
In the beginning, "signal GND" from the UcD was left floating - then there was a hum, really loud. But it disappears when "signal GND" is connected to "signal -" (and both - to the negative pin of the audio source)
After I disconnected the mains "safety eartch" from the enclosure - there is no hiss, so it appears the openness does not contribute to additional interference (even though it is next to the computer on my desk).
The signal source at first was my portable battery-powered MP3 player, but now I am listening from my PC.
The LEFT and RIGHT are mixed down to mono as I only have 1 speaker box in the room.
Your PC is most probably already connected to "safety earth" so when you introduced a "safety earth" connection to the UCD module you've got a hum caused by a ground loop.
Stick strictly to the Hypex instructions and you will be rewarded for that.
Unbalanced connection - no connection to the safety earth.
Ballanced connection - it depends on the rest of the system. Can be tested either way IMHO.
@Baka
It seems like you have not read my sentence from the start:
After that, when I disconnected the "safety earth" from the SMPS - I heard no "hiss" and "metal" distortion of the music from my portable player and only then I started listening music from my PC. The distortion is gone, even though the PC is probably connected to "safety earth".
It seems like you have not read my sentence from the start:
So, when I had a connection between "safety earth" and SMPS - I was listening from my battery powered player which obviously is not connected to any "earth" itself, but only as a consequence of being attached to the UcD and SMPS.
After that, when I disconnected the "safety earth" from the SMPS - I heard no "hiss" and "metal" distortion of the music from my portable player and only then I started listening music from my PC. The distortion is gone, even though the PC is probably connected to "safety earth".
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