UCD180 questions

[Bruno Putzeys]

Originally posted by classd4sure
I was also under the impression that a full bridge has less EMI.

At the carrier frequency and its first few harmonics, the FB amp will a have lower common mode output, provided it's a two level amp. This advantage is not very important unless hundreds of meters of speaker cable are attached.

Originally posted by classd4sure

All that aside, which one should sound better?

There's no difference in principle. I did a listening test once where one channel was a HB, the other a FB UcD. No problem...

[Bruno Putzeys]

Originally posted by phase_accurate
And much worse most audio engineers lack the lateral thinking needed for the development of class-d amps. But this one is solved also nowadays.

Such optimism. How many good class D desigers are there? I mean - people who can design a class D amp worthy of being called an amplifier (not smps'es that happen to respond to audio-bandwidth signals and further double as an involuntary FM transmitter).
I dare you to name 10 people worldwide.

In my view, the problem lies in the difficulty of following the diversification in audio technology in educational institutions. I'm not sure I've posted my vision on this before. If I have, sorry for repeating myself.

In the 50's and 60's, audio amplification counted for a sizable chunk of "electronics" as a whole. Therefore schools could devote a reasonable amount of time to the subject. The result is that still now, the number of people capable of designing a good valve amp is large (thoustands?).

In the 70's and 80's, when solid-state technology largely supplanted valves, the field of electronics grew so much that analog electronics started getting cornered. With a bit of luck, the average engineering student knew how to analyse a Miller amp, but was happy further to treat it as a triangle with 3 leads on it. Luckily, building a class AB power amp was considered an acceptable thesis subject, and quite some people graduated on it.
Now, designing a good solid-state linear amplifier from scratch is decidely more complicated than a valve amp. The result is that engineers able to design really good linear amps number only in the hundreds at most.

In the 90's, the new kid on the block became class D. At the same time, schools hardly mentioned the existence of something like an audio power amplifier. Understandably - audio is only a fringe activity compared with the rest of electronics. It's beginning hard to find decent audio engineers, let alone ones that understand a technology that's yet more complicated than the previous one?

Really Charles, this problem isn't going to go away anytime soon.

[paradigm]

Originally posted by Jan-Peter
Hi Guys,

I have been a way for a few days , sorry for the late reply!

Roland (Paradigm),

Nice to hear about your experience!

Many thanks for your congratulation. We are manufacturing for almost 10 year audio power amplifers (besides my 15 years of personal hobby experience), and during this time I have seen a lot of Class-D amplifiers. When I test an amp on the workbench I always first put a dummy load on the amp and a sinewave generator together with an oscilloscope. To see how much power we can get out of this amp and if everything looks ok. By testing the Class-D amplifiers I was always very disappointed with the outputsignal of this kind of amps, a lot of HF-switching noise and an awful clipping behavour.

Till I get the opportunity for a demonstrating by the Philips Labs in Belgium of the Universal Class D amplifier. On that moment I saw for the fist time a Class-D amplifier with a very clean outputsignal, who runs in clipping very nice, and showed a very good 10KHz rectangular wave at the output.

After a listening test and a comparing with our own analog amplifier I was convinced and decided to use this technique!

Roland, can you show us your pictures on this forum? I am quit curious....

....
Regards,

Jan-Peter

www.hypex.nl

Hi Jan-Peter!

You're very welcome to my praise. You sure deserve it!

I also played it safe as I tested them for the first time.
I played them for a few hours on a pair of old Pioneer speakers, which I never had any high thoughts of before, but the way they sang right from the start, really shocked me, although there was a bit of harshness around the edges initially.
I simply couldn't believe the realism these cheapo speakers presented. So when I was convinced everything was OK I immediately switched to the JBL 2445's and 075.

I'm not kidding, the experience overwhelmed me to the point, where I had to swallow a few times, trying to get rid of the lump in my throat. I just sat there for a while, totally flabbergasted, stammering the word Jesus over and over. How many times I really don't know.

BTW, what about my other questions/suggestions?

Pictures, well I'll try it once again. The first time the entire post just disappeared into cyberspace somewhere, just as I was almost done writing it.

Is this BTW a common problem? Should I write my postings in word or something and then paste them here, just before posting them?

/Roland

[classd4sure]

Hi,

What kind of caps have you got there? They almost look like stiffening caps for car audio. Nice setup you have there, well done. Just going by your reaction to it, I'd say it looks like mid fi has come a long way, woulnd't you agree?

Regarding your question about composing in word, I wouldn't think so. I think the same thing has happened to me all of about two times, maybe they reboot the server once a month or something.. Usually things work very well here!

Thanks for those pics,
Chris

[paradigm]

Hi again!

Please don't mind the finish on the amp.

This one was purely experimental and I have done absolutely nothing about the finish.

I hope you can appreciate my hurry to LISTEN to what they were capable of.

In future UcD projects I'll try to add a bit of finish and design improvements as well.

However it's quite compact though. 22cm*12cm*21cm.

/Roland

[classd4sure]

heh, don't worry, that went without saying. Really if you cared I guess you could take a belt sander to the front panel or something.

I like the way it's assembled, only I'd probably solder everything out of habbit, looks like you cut no corners where it matters. Dual full bridge rectifier, nice stuff. That's about what I'd like to have. Aifa caps? From what I've found they make remote controls..

Anyway once again, nice work. I'm sure someone else will tackle your other questions.

[paradigm]

Hi Chris!

The caps are Swedish high quality caps RIFA 6800uF/100V.

What do you mean by mid-Fi???

Perhaps I haven't had the opportunity to listen to the most expensive gear out there, but I'd say I have listened to some quite highly regarded stuff, like Tac-T Millennium and Classé, some esoteric OTL tube amps, big B&W's, Dali's and so on and I don't mind stating that these UcD180 modules don't come in second to any of the stuff I've listened to before.

If you wan't to call this mid-Fi, then that's fine with me. I can only congratulate you to the standards you're obviously used to and the gear you surely must have.

/Roland

[classd4sure]

Originally posted by paradigm
Hi Chris!

The caps are Swedish high quality caps RIFA 6800uF/100V.

What do you mean by mid-Fi???

Perhaps I haven't had the opportunity to listen to the most expensive gear out there, but I'd say I have listened to some quite highly regarded stuff, like Tac-T Millennium and Classé, some esoteric OTL tube amps, big B&W's, Dali's and so on and I don't mind stating that these UcD180 modules don't come in second to any of the stuff I've listened to before.

If you wan't to call this mid-Fi, then that's fine with me. I can only congratulate you to the standards you're obviously used to and the gear you surely must have.

/Roland

Hi,

Rifa! Looked like Aifa from the pics, thanks for the info I'll have to dig up some info on them. They look, robust, to say the least.

What I meant by mid fi, just a joke to an earlier post.

Regards,
Chris

[paradigm]

Here you can find the info:
http://www.elfa.se/en/

Just type in: "RIFA PEH" in the search box.

/Roland

[Jan-Peter]

Paradigm,

Thanks for the idee of swapping pin#2 with pin#3. In future we will also supply cable kits, to make it easier to connect the amp to an input cich or something else. But please when you don't want to use the symmetrical input, solder the -input line to ground/screen at the source side and NOT at the side of the amplifier connector. This will improve the quality of the signal.

Nice pictures!

Peranders;
In don't think a full bridge will have less EMC, because you have now two "hot outputs". An half bridge has only one "hot output" and a reference ground. In this case it is much easier t remove the HF-dirt.
It has no sense to use a N-FET and P-FET, becuase they are used as pure switches. Thereby a N-FET is much better as a P-FET, so with both N-FET you have it more symmetrical

Why does the UcD sound so good? I guess Bruno can explain this much better, but I will give it a try.

With a Class-D amplifier, the gain comes from a comparator and not from liniear components. In the original UcD amplifier the gain of the amp is 4.5x without any liniear components! So in a way there is no active analog amplification, just a comparator who creates the gain.

The less active components in the signal chain the better the sound...........

This gain without liniear components is valid for more Class-D amplifiers, but there are very less who use the feedback behind the outputcoil! A further improvement in the sound

Regards,

Jan-Peter

www.hypex.nl