UCD180 questions

[phase_accurate]

Stereophile did a review of the HCA-2. It got quite good critics from the sonic point of view (which is always subjective of course). But the measurements were not that impressive at all.

http://www.stereophile.com/amplificationreviews/729/

I also doubt that it has a double feedback loop when looking at its specs. Furthermore, most topologies taking feedback from the output filter show less load dependancy than this one (wasn't one of their claims that it is less load dependant than all the other class-d amps ?).
It shows exactly the same load dependancy (in terms of frequency response) like a circuit that I call "the simple tweak". I use this expression for the most simple kind of feedback-takeoff from the output filter, that can be implemented with carrier-based class-d amps.

I have seen pictures of its inside and it is hard to tell much more than that it actually has a nice build-quality.

Another new class-d amp has been presented by Onkyo. It seems that it takes feedback before the output filter. It also got quite good reviews even though its mesurements werent overwhelming.
I wonder how anyone can still build class-d amps without overall feedback. It isn't that complicated after all. You don't even have to rely on existing patents. Simply use known feedback control techniques.
As I already said, class-d amps have the potential to sound good even when they don't look that exceptional on paper.

regards

Charles

[JohnW]

When I read the magazine reviews etc. I remember why I despise the Hi-FI industry so much.

Sure the front panel of the HCA-2 is very nice - it is after all an $1695 unit – but have a quick read of the operators manual: -

“A very low fuzz/crackling noise audible within 1-2 feet from the speakers is the HCA-2 own “self” noise and is normal”

Answers whey there’s no S/N specifications – 0.2% THD, self noise, Gentlemen are we really trying here?

Apparently, the designer developed the Harris Class D Eval. boards – I guess it explains all.

John

Hey – I’m in a real foul mood today – wonder why?

[classd4sure]

Hi,

Actually while I did email them for a laugh, it seems they already have a spy in our midst, paulmc CEO of bsaudio, has posted about their hummbuster before, perhaps he'd be so kind as to jump in, it would be interesting.

Hopefully he's been reading this already and taking notes for what not to do in the future (we like alot more cold hard facts and alot less bs and hype). Maybe you'd be interested in retro fitting it with a UCD module from Hypex C'mon Paul I know you're out there

Regards,
Chris

[FuriousD]

When I read the magazine reviews etc. I remember why I despise the Hi-FI industry so much.
Sure the front panel of the HCA-2 is very nice - it is after all an $1695 unit – but have a quick read of the operators manual: -

“A very low fuzz/crackling noise audible within 1-2 feet from the speakers is the HCA-2 own “self” noise and is normal”

Answers whey there’s no S/N specifications – 0.2% THD, self noise, Gentlemen are we really trying here?

Apparently, the designer developed the Harris Class D Eval. boards – I guess it explains all.

John

Hey – I’m in a real foul mood today – wonder why?

Hey John,

Why the long Face?

F.

[phase_accurate]

The HCA could very well be an old-fashioned implementation of a carrier based class-d amp. The only thing special about it is probably a "hand-sewn" summing integrator.

Although the specs are not that good it would only be fair to judge it after having heard it.



Regards

Charles

[matjans]

marketing talk doesn't make a product bad, it creates an aura around it. And that aura you have to like. Or not.

Take Linn. On their site they talk about their products in an ikea-kind-of style. simple, not too much information a customer wouldn't understand anyways. No nonsense (except for the K in all their products, of course )

Now take psaudio. A completely different approach. Beta tester reviews, (semi) technical articles about different technologies, features, benefits, you name it.

Although i personally like the linn-approach better, there are probably more people that like the psaudio approach. Who am i to judge their marketing techniques? Add to that the fact that S/N ratios, damping factors, power ratings, thd+n graphs and whatnot don't say anything about how the amp really sounds!

So, lets quit bugging psaudio (or open another thread for that) and get back to the ucd180.

How big are your transformers, va-rating, voltage etc. How does this influence sound?
What's the psrr of the ucd module? couldn't find that anywhere...
Do I need a state-of-the-art extremely low output impedance psu with a LOT of capacitance etc?
Has anyone tried building a nicely regulated supply for these babies? Or maybe even a (ie OPA549) 'buffered' supply?
Has anyone tried replacing the opamps used?

I have about zip experience with class d amps...

[Jan-Peter]

UsrV,

Very nice picture, that's what I love to see!!!!!

Indeed I would check the temperature, because in 4 ohm load and at higher soundlevels the T alone as heatsink will not be sufficient.
What is your powersupply voltage?

Did you already listen to the amps?

To the rest of the guys,

Perhaps we can start a new thread about 'what is currently available in the market on Class-D amplifiers?'


Best regards,

Jan-Peter

www.hypex.nl

[UrSv]

Originally posted by Jan-Peter
UsrV,

Very nice picture, that's what I love to see!!!!!

Indeed I would check the temperature, because in 4 ohm load and at higher soundlevels the T alone as heatsink will not be sufficient.
What is your powersupply voltage?

Did you already listen to the amps?

To the rest of the guys,

Perhaps we can start a new thread about 'what is currently available in the market on Class-D amplifiers?'


Best regards,

Jan-Peter

www.hypex.nl

Thanks JP,

See my response to Bruno a bit further down after the picture. Should be fine.

As for supply voltage the limit was 50 V for the module so naturally I chose 49.99.

I'm sad to say that I will be going out of town for a weeks and will not have the time to finish it before then so listening to it will have to wait for 10 days...

[Jan-Peter]

UrsV,

Yes indeed I just read you construction, looks indeed ok!

Have a nice trip!

Regards,

Jan-Peter

www.hypex.nl

[IVX]

Let's look inside caraudio class D amps, and PSaudio creation will not seems so poor anymore. They have, at the moment, typical specs: THD 1-2% (note that's for subwoofer app.!!!), damping factor 100. Noone of these called "simply"("stupid" is more exactly) class D, but only "adapted class D", "advanced" etc! To achieve THD 1%@100W someone use 1Mhz carrier even:
<The Xtant1.1i adds local and global multiple nested feedback loops with premium MOSFETs and
OPAmps for switching stability and audio signal accuracy within the full range spectrum. This
results in an extremely high switching speed—over 1MHz
This enhances the musical reproduction by ensuring the higher frequencies (cymbals and
the like) compliment the entire frequency range to bring new realism to the Class D amplifier
sound experience.
The Audiophile Full Spectrum Class D Technology with Xtant’s attention to detail results in a
Class D amplifier that sounds better than many audiophile Class A/B amplifiers. It exhibits an
extremely low noise floor (-100db) eliminating the “hiss” common to many Class D amplifiers.
.>
Caraudio class D amps with typical class B efficiency are exist too. However manufacturers do not employ the designer, but probably instead of him employ the worker for erasing/renaming standard chips (ie CD4060->F16, comparator->B52 etc. kind of phobia?). In the caraudiophiles forums there is stable opinion regarding class D is a dirty/uncontrolled bass, for the full range class D isn't considered even. I try to protect class D reputation by explanation that amplifier's class isn't matter, but designer's class is matter ;-) So "new kid of the block" need reabilitation already.

PS: BTW, J.P. could blow up this wild market segment by the UcD based subamp for starting.