UCD180 questions

[Jan-Peter]

FuriosD,

It seems you have some experience with amplifiers and Class-D amplifiers.

Just curious, can you share us with some of your experience?

Regards,

Jan-Peter


www.hypex.nl

[Sheriff]

In response to some of Bruno's comments, I find it very difficult to pigeon hole the audio magazines in this way.

Magazines perception of technology can be broken down to the reviewers individual experience.

The amount of times that you would have to point out that 'class D' is not 'digital' makes me smile.

Sure everyone has their underlying preferences, but a good journalist will put those asside, and listen. You would think that Valve amplifier should be considered passe - most are not.

I would also guess that this perception changes from country to country.

On measurements vs sound quality..

If the amplifier sounds good and i want to continue listening to it after 30 mins, then it must be doing something right, and measurements generally back this up.

In the main, first rate technical performance equals first rate sound quality - as long as you know what to measure, I hope that we can all find agreement in that.

For me, if its class A, AB, D, H or a hamster in a wheel it matters not - as long as it performs.

As for JohnW's observation of the SACD vs Redbook - all i have to say is that Bruno must have a very good CD player!

Best Regards

Sheriff

[phase_accurate]

The amount of times that you would have to point out that 'class D' is not 'digital' makes me smile.

The fact that those who had Bruno on-site for a demo still use the word digital amp when they write about any type of switching amp - is even funnier. They even mentioned that NOT all switching amps could be called digital back then, but sometimes memory is short-lived.

Regards

Charles

[FuriousD]

Bruno,

Glad we got all that cleared up then.

My own experience with the hifi mags (rags) is quite the opposite. I continue to be amazed at how far reviewers are willing to push back their performance standards in order to be able to endorse S-Master, or at least not to break it down to the last morsel. Good analogue class D's get the boot because they're analogue and therefore passé.

The trouble with the review field is that reviewers want to "discover" new technologies or brands. So they end up with their own pet projects. Once a new brand or technology comes along, then it's bashing time for the old one. It's sensationalism tabloid style, but thats what the readers like!

In this case, a mere cursory glance at the THD+N graph would have told you not to expect <-80dB harmonics at 100W. It would certainly not have required a fascination for it.

It's not so much the THD level that interests me, more any miscellaneous spurae that exists on or around the noise floor and the relationship between the harmonics as they rise in freqeuncy. These facts tell me far more information about the way the amplifier might sound.

Interestingly, a pseudo 3-D FFT plot of "FFT of THD" vs Frequency vs "Output power" would be very useful to see. Does anyone know of any software that could compile this from AP or R&S data? It's pretty easy for me to write some VB code to increment the output power and then sweep the FFT of THD and store the date to file. Matlab would do it obviously, but thats a bit extreme.

[Bruno Putzeys]

Originally posted by Sheriff
The amount of times that you would have to point out that 'class D' is not 'digital' makes me smile.

I wish I had your moral stamina. It makes me dispair, not smile...

Originally posted by Sheriff
I would also guess that this perception changes from country to country.

I admit I've somewhat "shorn them all over the same comb", and it can't be taken as a rule. My sneer was inspired largely by a few German magazines.

Originally posted by Sheriff
As for JohnW's observation of the SACD vs Redbook - all i have to say is that Bruno must have a very good CD player!

I use an SACD player with illegal DSD outputs feeding into a homegrown discrete DAC. The DAC always processes a 1-bit, 2.8224MHz signal. In SACD mode it's the bits from the disc, in PCM mode, a digital filter/noise shaping chain is used to obtain a 1-bit signal. To the actual DAC circuit therefore there's no difference between DSD and PCM (other players invariably operate the DAC at different clock rates or even use different DACs altogether).

[FuriousD]

For me, if its class A, AB, D, H or a hamster in a wheel it matters not - as long as it performs.

Sheriff,

I'm interested in patenting your hamster in a wheel technology, it would certainly give a product a unique selling point, although I'm not sure how you would maintain consitency of operation from one unit to another. Perhaps you could elaborate on your ideas?

F.

[Sheriff]

Dear Furious,

I think that this technology is already subject to a patent by Sir Clive Sinclair, although i am sure that this would have expired by now.

Either way i am covered, as my hamster is for my own private use............

There are a couple of flaws with this technique. One is to make sure that the rodent does not suffer from exhaustion when driving difficult loads, another being supplying energy to it and lastly, it is the removal of waste products - a simple heatsink just will not do.

When developing new technologies you must consider the pitfalls. All in all i would not recomend this approach for a commercial design.

BR

Sheriff

[Bruno Putzeys]

Originally posted by FuriousD
It's not so much the THD level that interests me, more any miscellaneous spurae that exists on or around the noise floor and the relationship between the harmonics as they rise in freqeuncy. These facts tell me far more information about the way the amplifier might sound.

True. It's an issue that needs to be considered with equal care as the "constant thd vs frequency" criterion.

Originally posted by FuriousD
Does anyone know of any software that could compile this from AP or R&S data?

I found AP has some new software plug-ins available on its web site, specifically for making more complicated plots. Maybe it can do that sort of plot too.

[phase_accurate]

I'm not sure how you would maintain consitency of operation from one unit to another

We live in the 21st century, hey !! Never heard of cloning ?

Regards

Charles

[koldby]

Hi Bruno

Is it possible for you to share your experience with the SACD scheme you use?
Evt. in a differnet thread?
I find the promise of SACD sadly missing in all the commercial offerings.(haven´t heard the Meithner stuff though)

Best
Koldby