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Old 28th January 2009, 09:38 AM   #1
simingx is offline simingx  Singapore
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Default My humble UcD400 + SMPS6060 project

Just finished this over the weekend...

Click the image to open in full size.

2x UcD400HG
SMPS6060PFC from Red Rocks Audio, factory modified for +/- 60V output
2x 4700uF 100V Sikorel 105 for additional buffering (these things are expensive!)

Homebrew PGA2310 volume control / source selection.
Casing from an old NAD 216 amp, had to remote control everything as I don't want to put holes in the front panel

So far so good, the relay is needed to prevent the horrible POP when switching off the UcD400's while the modules are enabled. Is anyone else getting this?

There's only a very very slight hint of hiss audible (if you put your ears 1 inch from the tweeters) so I think it's OK.

The PSU is completely floating from the case. Later modifications will include an IEC socket to earth the PSU only.
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Old 28th January 2009, 04:14 PM   #2
DcibeL is offline DcibeL  Canada
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Quote:
So far so good, the relay is needed to prevent the horrible POP when switching off the UcD400's while the modules are enabled. Is anyone else getting this?
I assume that this is because the "turn-on" voltage for the UcD modules is staying high after the power is removed. If this 12V is removed from the UcD, they will turn off silently, then you can remove the power supply voltage pop-free.
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Old 29th January 2009, 03:19 AM   #3
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assume The "turn on 12V" is active low, if there's 12V on it it's already off.

The HG series also has UVL as well and will produce a silent turn off even when enabled with the rails removed, let alone that without the UVL there is still nothing one could consider a horrible pop.

The only way to produce a horrible pop is to feed one through the inputs. You might consider your supply sequencing for your digital volume controller, as per any other pre amp.
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Old 29th January 2009, 11:42 AM   #4
luka is offline luka  Slovenia
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Very nice!!

For what do you use uC?
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Old 29th January 2009, 01:08 PM   #5
simingx is offline simingx  Singapore
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Hi,
Thanks for the comments.
I didn't think it would be the preamp, but the relay now disables the amps upon power off, so there's no more artifacts when switching off.

The EI transformer has to go though... no place for such things here

Luka,
It's an ATMEGA8535... ancient
I have provision for a VFD to be attached, but as stated above, didn't want to put a hole in the front panel...
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Old 30th January 2009, 02:56 AM   #6
col is offline col  Australia
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Nice effort. I was going to get one of those SMPS for my own UcD400s. In the end though it was much cheaper for me to go the linear PSU route as I already had caps etc...

http://minirig.org.au/2008/12/22/minirig-hypex-ucd400/

Why have you got 2x 4700uF 100V Sikorel caps before the amp modules? Iv'e heard this is very bad for the SMPS and unnecessary.

col.
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Old 30th January 2009, 08:09 AM   #7
simingx is offline simingx  Singapore
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For the caps, more reserve wouldn't hurt now would it?

If it's about stability, I emailed Red Rocks about the issue and they say that they've tested the supply up to 4700uF external capacitance without issues... (I even put 2x 12000uF just for kicks, without any negative effects). The capacity of the SMPS is nice if the amp is ever going to be upgraded to 5 channels etc. Meanwhile I didnt' have any other transformers etc. so the SMPS looks like a nice alternative.
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Old 30th January 2009, 11:38 PM   #8
col is offline col  Australia
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OK, that is good to know that you can add a little external capacitor storage to the SMPS6060 without doing any harm.

Also, why are you using the small 18-0-18 transformer? I heard that the Redrock SMPS6060 can provide 3 different voltages and on request the Redrocks technicians will set these to what you desire before shipping. Could you not use a direct 18-0-18 from the SMPS and discard the small trafo?

col.
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Old 31st January 2009, 01:53 AM   #9
simingx is offline simingx  Singapore
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Yes the next modification will be to ditch the EI transformer... it was/is there to provide the analog/digital supply for the volume control. I got them to provide +/- 15V on the Aux outputs.

I think I'll still need a small transformer there though... don't want to share the analog and digital supplies from the same output.
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Old 4th February 2009, 08:26 PM   #10
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Wow this is awesome! How does it sounds? Which speakers are you torturing?
BTW, can you say approx. how much did it all cost?

Regards,
Igor
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