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Old 5th November 2007, 12:49 PM   #1651
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Join Date: Jun 2003
Location: Singapore
Default Grounding clarifications - UCD400hg

Just finished up my UCD400hg today. Slight hiss on my speakers - audible only when i put my ears about 3 inches from the woofer. Any idea what's the problem?

Currently, I am not using the hypex grounding scheme as I am not very clear on the overall schema - I am basically using a star ground to the chassis, and using a ground uplift (2 ohm) connected to the mains earth. This it with RCA inputs

Now, I am thinking of redoing it according to the hypex scheme, and would like some confirmation on my understanding. According to the documentation, and my interpretation of the circuit diagrams, I need to:

1. Connect the chassis to the RCA ground (if I am using insulated RCA) and this will go to the signal ground on the board. If my interpretation is correct, that means that the chassis is connected at two points (on a stereo amp), one to each board. THis means that the signal ground is left floating?
2. I am not clear on the power supply ground. Do I connect the power supply ground (from the transformer secondaries) to the main's earth, or do I leave it floating? The diagram on the data sheet seems to show that it is connected to the main's earth. Can someone help clarify on this?

THanks!!!
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Old 11th November 2007, 01:36 PM   #1652
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Join Date: Jun 2003
Location: Singapore
Default Re: Grounding clarifications - UCD400hg

Quote:
Originally posted by alvinlim
Just finished up my UCD400hg today. Slight hiss on my speakers - audible only when i put my ears about 3 inches from the woofer. Any idea what's the problem?

Currently, I am not using the hypex grounding scheme as I am not very clear on the overall schema - I am basically using a star ground to the chassis, and using a ground uplift (2 ohm) connected to the mains earth. This it with RCA inputs

Now, I am thinking of redoing it according to the hypex scheme, and would like some confirmation on my understanding. According to the documentation, and my interpretation of the circuit diagrams, I need to:

1. Connect the chassis to the RCA ground (if I am using insulated RCA) and this will go to the signal ground on the board. If my interpretation is correct, that means that the chassis is connected at two points (on a stereo amp), one to each board. THis means that the signal ground is left floating?
2. I am not clear on the power supply ground. Do I connect the power supply ground (from the transformer secondaries) to the main's earth, or do I leave it floating? The diagram on the data sheet seems to show that it is connected to the main's earth. Can someone help clarify on this?

THanks!!!
Fixed the problem. Left both power and supply ground floating. Dead silence. I am very happy with my setup now. Still running it in, but I am getting great detail, very very good treble and my bass is coming back.... Extremely happy with it. Only problem is that it gets a bit hot in the enclosed space where I put my amp - I need to figure that out. the heat sinking is pretty minimal at the moment, just a sheet of aluminium added to the inside of the chassis. Here are the pics:

Specs:

UCD400hg at 53V rails.
Dual mono 330VA Nuvoterm tranformers
40000 microfards per channel, using Technics TakeII Bamboo Capacitors...
Hypex softstart.
Attached Images
File Type: jpg img_3076_1_3_1.jpg (95.1 KB, 2096 views)
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Old 11th November 2007, 03:01 PM   #1653
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Location: osorno , Chile
Does your box have ventilation holes up and down?

In my monoblocks I placed the modules vertically and made holes on the box to increase convective heat remotion. I noticed that the module that has the output coil downwards gets hotter than the one that has it upwards. I had to install an external heatsink to it (61VDC power rails)

Good luck,
M
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Old 11th November 2007, 03:13 PM   #1654
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Location: Singapore
Default heat...

Quote:
Originally posted by maxlorenz
Does your box have ventilation holes up and down?

In my monoblocks I placed the modules vertically and made holes on the box to increase convective heat remotion. I noticed that the module that has the output coil downwards gets hotter than the one that has it upwards. I had to install an external heatsink to it (61VDC power rails)

Good luck,
M
Hi it doesn't really heat up when i put in in open space. It just get warmish. I think the issue is that I am putting the amp in a cabinet. May need to get some forced ventilation for the cabinet.
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Old 17th November 2007, 01:47 PM   #1655
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Default Other pics...

Some other pics of my amp....


Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.
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Old 29th November 2007, 10:18 PM   #1656
lne937s is offline lne937s  United States
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Join Date: Dec 2004
Location: New York City
Default One module burned up...

After comming back from a trip to see friends, I tried to turn on my amp and one of the modules wouldn't turn on... Replaced both fuses, turned it back on and they immediately blew. On closer inspection, the area around the coil was burned up a little, so I'm guessing it's fried. I had a friend staying at my place, who may have done something, but I really don't know what happend. I'm betting on either our horrible ConEd electricity or user error...

Does anyone know what might have caused this?

Anyway, I was planning on eventually adding 2 more channels and actively biamping (my PSU and 1450VA transformer should easily handle 4 units)- this just gives me motivation to place an order with Hypex sooner...

So, will the current ST UcD 400's match my remaining channel?

I was thinking about using the HG for the high end (From ~800Hz up) and the ST for the bottom. Would it be better to stay with the ST all around to keep the sound the same?

Since I am planning on using a DCX, I will need some sort of volume control after the crossover... would it be better to use pots to passively attenuate the signal after the DCX or would it be better to connect a pot with ajumper to RG on the modules and adjust the gain there?

http://www.hypex.nl/docs/gainappnote.pdf

Reading through this again, I think it would probably be best not to adjust the gain... because the input would no longer be differential, at 0db gain at the buffer stage, Right?

And what happened to the US Dollar? ...these exchange rates are killing me.
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Old 29th November 2007, 11:37 PM   #1657
glt is offline glt  United States
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From the paper it seems that increasing the gain further improves the CMRR of the UCD stage. So it would be better to manipulate the gain at the input stage opamp but increase the gain for the speaker with the lower gain.
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Old 19th December 2007, 10:11 AM   #1658
igy137 is offline igy137  Hungary
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Join Date: Mar 2005
Location: Hungary
Default transformer noise

Hello All,

I recently built an amp with TR501/SupplyHG/UCD400HG.HxR. Soundwise, I'm very satisfied.
However, when finishing the chassis, I noticed, that the transformers are making some generating hum. This was not really disturbing when the chassis cover is removed, but I guess this is amplified if the cover is in place.
Although I do not feel vibration if touching the transformers, it definitely seems that they're making the noise.
I checked for DC on power the line, but the multimeter did not show anything.
Any hints solving this problem?

Thanks,
igy
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Old 19th December 2007, 07:23 PM   #1659
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Join Date: Aug 2003
Location: Santa Cruz, California
Default Re: transformer noise

Quote:
Originally posted by igy137
Hello All,

I recently built an amp with TR501/SupplyHG/UCD400HG.HxR. Soundwise, I'm very satisfied.
However, when finishing the chassis, I noticed, that the transformers are making some generating hum. This was not really disturbing when the chassis cover is removed, but I guess this is amplified if the cover is in place.
Although I do not feel vibration if touching the transformers, it definitely seems that they're making the noise.
I checked for DC on power the line, but the multimeter did not show anything.
Any hints solving this problem?

Thanks,
igy
This will sound odd, but put a cloth on the chassis cover then a couple of heavy items such as bricks. If the noise is reduced, it's likely the chassis, especially if it's magnetic material like steel, could be reacting to the field around the transformer.

Something like this might help:
http://www.partsexpress.com/pe/showd...number=268-010

You don't have to get this all the way from the States, as car audio places in Europe are very likely to carry something of the sort.
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Old 19th December 2007, 08:40 PM   #1660
igy137 is offline igy137  Hungary
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Join Date: Mar 2005
Location: Hungary
Default Re: Re: transformer noise

Quote:
Originally posted by DSP_Geek


This will sound odd, but put a cloth on the chassis cover then a couple of heavy items such as bricks. If the noise is reduced, it's likely the chassis, especially if it's magnetic material like steel, could be reacting to the field around the transformer.

Something like this might help:
http://www.partsexpress.com/pe/showd...number=268-010

You don't have to get this all the way from the States, as car audio places in Europe are very likely to carry something of the sort.

Thanks for the help! It's a standard 19" rack chassis, front and back plate is alu, the rest is steel.
I experimented a bit trying to push each side with my hands, it makes a small improvement, but still far from the open top version.
It's quite interesting, because otherwise the chassis is much more rigid with the cover on.
I'll play with it, but probably it's time to build a chassis using those 4mm thick alu sheets I have in the workshop (I wanted to avoid that, that's why I bough the rack).
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