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Class D Switching Power Amplifiers and Power D/A conversion

UcD400 Q & A
UcD400 Q & A
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Old 7th September 2017, 10:03 AM   #1801
Baka is offline Baka  Montenegro
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I don't know how beneficial could be the upgrade of that capacitor. I haven't done that replacement yet.

From the picture which I see the first what I would advise you to do is to replace the filter capacitor if that is Wima MKS (polyester) type. You can replace it with two 0,33uF MKP2 (polypropylene) caps, one above and the other below the pcb at the same pins.

This is the single biggest improvement IMHO.

Than you can concentrate to Hypex decoupling capacitors as well as those 4 naked BC capacitors.

Do you ultimately need those two coupling caps at the left bottom?

These are not perfect for that tusk since they are polyester caps as well. You can replace them with some better ones but since they will be bigger you should find some other position for them.
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Old 27th September 2017, 08:16 PM   #1802
meex is offline meex  Serbia
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Hi there..
Are there too much differences in sound quality between UCD with HxR voltage regulators and those without?
And how big that differences are? Which areas are most noticable?

Sorry if you already write about it but there are 180 pages
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Old 27th September 2017, 08:30 PM   #1803
Malefoda is offline Malefoda  France
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Yes they are worth the extra cost.
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Old 27th September 2017, 10:10 PM   #1804
maxlorenz is offline maxlorenz  Chile
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As in every amp, if you improve PS and/or power different stages from special/exclusive good quality PS, the improvement will be evident.

Check also "Balanced Power".

Regards,
M.
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Old 14th May 2018, 07:01 PM   #1805
Malefoda is offline Malefoda  France
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Yep another question:
Hypex's SMPSs feature mains filter. Some pretend, out of the blue, that if your chassis has mains filter it can degrade the sound. My chassis does use a filtered socket, then some wird to the 2 SMPS. It sound terrific, but is this a problem in any way?
BTW, thread started in 2004, I'm a happy user of UCD400 here Hope I'm not the last...
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Old 18th May 2018, 08:03 AM   #1806
Baka is offline Baka  Montenegro
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Quote:
Originally Posted by Malefoda View Post
Yep another question:
Hypex's SMPSs feature mains filter. Some pretend, out of the blue, that if your chassis has mains filter it can degrade the sound. My chassis does use a filtered socket, then some wird to the 2 SMPS. It sound terrific, but is this a problem in any way?
BTW, thread started in 2004, I'm a happy user of UCD400 here Hope I'm not the last...
Those filtered sockets usually use X and Y rated capacitors and some coils as well.

The coils are particulary problematic since they are put in series and can affect the performance of UCD modules.

Since Hypex SMPS is already filtered with AC rated capacitors I would try unfiltered IEC socket.

You should get the better result this way but YMMV.

I am also using unfiltered IEC socket for my SMPS and UCD modules.
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Old 18th May 2018, 10:40 AM   #1807
Malefoda is offline Malefoda  France
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Ok so I'll get in mind that one day, after all my other projects are done I'll try to remove the Schurter KMF1.1291.11 filtered socket for an unfiltered socket. Can it sound better than glorious?
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Old 27th June 2018, 10:26 AM   #1808
poleepkwa is offline poleepkwa
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I am looking for assistance on how to track down the buzz on the UCD400's/SMPS400 build in Ghent Cases.
I tested the monoblocks with another preamp and there they are working flawlessly.

The rest of the system consist of an Anthem MRX510 (2 prong plug, double isolated and these monoblock.
Nothing else connected to the Anthem, Nothing else plugged into the powerstrip.

When I plug in RCA-XLR cable there is a buzz. I tried various cable (DIY and bought) and it remains the same.
As soon as the amp is connect to the receiver it buzzes.
The RCA cables are as recommend by Hypex (pin1+3 to chassis on RCA, Pin 2 hot.)
I also tried with pin1 chassis and pin2 hot, floating shield on RCA, but that made the noise even louder.
I disconnected the shield on the UCD side, but that also had no effect.
I plug in a XLR terminated Cable it is there is no noise.


Connecting/disconnecting earth ground has not effect on the noise.

Any idea how I can get rid of this noise?

https://i.imgur.com/Nx1qjPY.jpg

Last edited by poleepkwa; 27th June 2018 at 10:48 AM.
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Old 2nd July 2018, 09:21 AM   #1809
Baka is offline Baka  Montenegro
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Hi,

Although the picture is quite big I can not see the connection from RCA neutral to the chasis.

If RCA is isolated from the chasis with plastic washers then you should provide a connection from RCA neutral to the chasis.

I am using these modules for years now and have never used J6 for DC Error and also never used J5 Pin1 for the SMPS standby. You could try to disconnect them as well.

I am using a simple standard connection described in SMPS400 manual at page 1 from the very beginning and without any operational issues so far.

With this approach my setup is dead quiet with the ear almost touching the tweeter.
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Old 3rd July 2018, 11:48 AM   #1810
poleepkwa is offline poleepkwa
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Hi Baka.

I did connect the Pin1 on the XLR directly to chasis ground. That did not have any affect, the slight noise remains. I have now tried it with 3 others different pre-amps, and there the UCD's are totally quiet. I think the problem is not with the amps, but more with the connection between my receiver and the Hypex.
I have to build one more and will leave the J5 and J6 disconnected to to see if that has any effect.
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