Snubberized PSU for Hypex UcD amp - god or bad idea?

[NicMac]

Hi All,
I'm building an amp based on the Hypex UcD 180HR (w. HxR) modules and I was thinking to use these bipolar supplies PSUs from chipamp.com. In addition to the 10.000uF (Panasonic TS) already present on each PSU rail I was thinking to add 1.000uF electrolytic (Panasonic FM) as well as 100uF, 10uF and 1uF Obbligato film caps.

The PSU is "snubberized" and my question is if I should leave it as it is or remove the snubber circuit. I have the impression that snubber circuits are not necessarily beneficial. Also I would like to know if the additional decoupling I'm planning makes any sense or if it might actually be detrimental.....

Any advise would be welcome!
Thanks,
Nic

[NicMac]

I obviously do not mean decoupling but bypass. Sorry.

[peranders]

The design you are referring to isn't designed in any scientific manner.
Discussion here:
Simulations by Thorsten:
http://www.diyaudio.com/forums/showt...197#post546197

Real world measurements made by a network analyzer, excellent Joseph_K starting here:
http://www.diyaudio.com/forums/showt...002#post548002

My "enhanced" snubberization.
http://www.diyaudio.com/forums/attac...amp=1109343379

http://www.diyaudio.com/forums/showt...094#post584094

http://www.hoffmann-hochfrequenz.de/...capacitors.pdf

If you want to reduce resonances you must make some measurements as you can see.

[NicMac]

Hi P-A,
I do not have the means to do serious measurements so I would rather go for a simple and proven configuration.
Comparing your "enhanced" version with that of Carlos it seem to me that the only difference (before the wires) is the absence of 100n/63MKS bypass caps. The snubber looks the same. If correct, this in practice means that I can use the chipamp psu boards and simply omit these caps.
After the wires (in my case on the power pins of the amp) you have a 100u/50YXF bypass and, differently from Carlos, a 1R/100n "snubber".
Did I miss something or would this be a good place to start?
Thanks,
Nic

P.S. I'm a very happy user of several of your JSR modules!

[peranders]

The basic mistake Carlos has done is to have one plastic cap without resistor + electrolytic cap. By this you won't reduce the resonances. If you just want to grab a resistor value, take 1 ohms. The effect of the snubber is very little if any but you may feel better

[glt]

I did exactly that, but didn't worry about taking out the snubber

http://farm4.static.flickr.com/3429/...e1ef570c7e.jpg

[NicMac]

I think I saw this rig before, maybe on the TPA forum, and I bet you are feeding it directly from a balanced DAC. The layout is very neat but a little bit to compact for my taste.
I got interested in the UcD modules because they take balanced signal natively and having build the Buffalo32S DAC (well - connected.... not much DIY in this) and the balanced RelaiXed pre-amp I was looking for a balanced power-amp.
I ordered the UcD180HR modules and later up-graded them with the HxR regulators from the same company. The latter has the feel of something made in a collaboration between P-A and Paul Hynes and I cannot believe that they are anything but extraordinary.......
Having other amps the UcD project was not priority until I recently realized that highly regarded >5k$ commercial amps like the Genesis GR180 got great reviews on TNT-audio and 6moons. This kind of spurred my interest in finishing this amp.
There seems to be nothing very particular about the implementation of the UcD in the Genesis amps. Some bypass caps on the supply pins (there are photos of these in the TNT-review - anybody recognize these caps?) and the power supplies.
I figure that if I can make a good supply I can make an amp sounding as well as the Genesis for a fraction of the price...
Thanks,
Nic

P.S. glt: I know you are interested in programming/making controllers for audio equipment (arduino based). You should have a look at the RelaiXed. The user interface made by Jos is brilliantly simple.

[glt]

nicmac,

Yes, feeding balanced from OPUS DAC. I like that preamp but right now I'm using Arduino to control the volume inside the WM8741 DAC, so I'm not even using a preamp. The only thing between the DAC and the UCD is the input CAP in the UCD :-).

I did take a look at the supply to the input opamp and the on-board regulator is actually better than any off-board 317-based regulator, so you do indeed need the HxR regulator to improve upon the local one. But then again, the PSRR or the opamp is over 100dB and the 15V regulator is pretty good and the PSRR of the amp section is 60 dB and the supply is not even regulated, so I figure may not worth the investment... (just my own priority on things).

I did built a "heavy duty" PS following a snubberized PS application note from national semi with two gigantic 15000 uF RIFA caps and large transformer from diycable, but have not transferred the modules yet...

[NicMac]

glt,
are there input coupling caps on the UcD? I heard that these amps were very sensitive to DC-offset so I kind of believed that they had no such caps. I also used the Buffalo32S (volumite volume control) directly with the UcD's but as I have a few SE sources I needed a preamp.
Are you suggesting that the op-amp and the high-current PSU is where most improvement can be done to the UcD?
Thanks,
Nic

[glt]

Yes, there is an input cap in the UCDs to block DC-offset.

I guess I wasn't too clear. I meant to say that I did not think improvement to the power supply feeding the input opamps would benefit much because the built in regulators is a pretty good one and the PSRR of those opamps are at 100dB. Whatever additional improvements here could be swamped by the lower PSRR of the amplifying section (60 db) and the fact that the PS is unregulated.