Class D Amplifiers: The present SOTA

mac · « **Reply #20 on:** 22 Feb 2005, 10:26 pm »

Quote from: AKSA

Mac, you are welcome here! You certainly know how to provoke discussion! Should we invite Occam to comment?? ...

Thanks Hugh.

WEEZ · « **Reply #21 on:** 22 Feb 2005, 10:28 pm »

I'm old enough

to remember when solid state would make vacuum tubes "obsolete".

And we all remember when digital cd's would make analog "obsolete".

The new class 'D' ; 'T'; etc. amplifiers will not likely make anything "obsolete"- they will add another option to people for in-home amplification.

Who knows what will happen- but my guess is that it will add competition to the marketplace- and stimulate engineering activity for all makers of amplifiers.

Unfortunately, it will likely push more and more manufacturing to third-world countries- which is, IMHO, sad.

WEEZ

doug s. · « **Reply #22 on:** 22 Feb 2005, 11:05 pm »

Quote from: AKSA

...I had been concerned that PWM amps might now be surpassing good analog designs. However, after extensive listening I've come to the conclusion that they cannot match good Class AB or A analog designs at present until they increase their resolution; this probably means they must increase their operating frequency to beyond 1MHz. I'm informed that only at 2.7MHz operating frequency can they give true 20 bit resolution; this is probably more resolution than is required, but it indicates a clear evolutionary path. ...

am i missing something here? sharps "old" product states 2.8mhz sampling speed; its latest stuff is 5.6mhz sampling speed...

doug s.

AKSA · « **Reply #23 on:** 23 Feb 2005, 12:01 am »

Doug,

Haven't heard the Sharp offering. Can you tell us what it sounds like?

Cheers,

Hugh

doug s. · « **Reply #24 on:** 23 Feb 2005, 12:07 am »

Quote from: AKSA

Doug,

Haven't heard the Sharp offering. Can you tell us what it sounds like?

Cheers,

Hugh

hi hugh,

nope, i am still on the fence w/these: which one should i try???

but i am sure others will chime in - there's a *HUGE* thread about one of the sharp amps on this forum...

doug s.

Occam · « **Reply #25 on:** 23 Feb 2005, 03:58 am »

Quote from: mac

Quote from: AKSA
Mac, you are welcome here! You certainly know how to provoke discussion! Should we invite Occam to comment?? ...

Thanks Hugh.

Well...... OK.
mac - I was astounded by Hugh's frank praise for class D technology. Here we have a designer who I greatly respect for his work on classic design telling us that simply taking another AB amp's powersupply and a bog standard switching amp, lashing them together, results in an amp that performs very impressively.

Now, I do understand you've made your own diy UCD amp; you've told everyone many, many, many times.The pictures are very nice and you should be justifiably proud. Also, you can build amplifiers for far less than folks who expect to profit by providing other than a parts list and a dream.
Regardless of your obvious expertise, I would think you'd ask some obvious questions. Given both Hugh's high praise for a 'lashup' and his reputation in conventional amplification, I'd expected you to ask -

Hugh, given your initial findings, what do you see as potential areas where you can add value?
Specifically, are you considering enhancing that inevitable analog front end and powersupply optimization, to address some of your concerns?

Dunno about you, but I find that I learn the most about technology (as well as the poster), by asking specific questions and digesting the response. Trying to engage another in a 'mine is bigger' discussion is rather pointless, unless solely for entertainment purposes.

mac · « **Reply #26 on:** 23 Feb 2005, 04:23 am »

Quote from: Occam

Dunno about you, but I find that I learn the most about technology (as well as the poster), by asking specific questions and digesting the response.

Paul, you're sure one tough act to follow. Your suggestion beats the heck out of constantly ridiculing people.

AKSA · « **Reply #27 on:** 23 Feb 2005, 06:32 am »

Hey, you two jes' git along, you there........

Cheers

Hugh

tg3 · « **Reply #28 on:** 23 Feb 2005, 10:14 pm »

Quote from: AKSA

Folks,
I was captivated by this very efficient concept in my youth from a UK entrepreneur called Clive Sinclair, and was interested to see how it had progressed in forty years.

Same Sinclair who did the computer stuff?

AKSA · « **Reply #29 on:** 24 Feb 2005, 06:57 am »

Yup, he's the guy..... Was it called the Z80?

Hugh

RonR · « **Reply #30 on:** 24 Feb 2005, 09:47 am »

Strangely enough, Sir Clive Sinclair started out designing and building Amplifier kits!
My first 'HiFi' Amp was a modular Sinclair job, built in the early '70s.

He then went on to make one of the first 'affordable' digital watches, working his way up to the Sinclair ZX80, one of the first 'mass market' home computers (for which he was knighted). Always an innovator/entrepreneur, he came an absolute cropper in the '80s with the Sinclair C5, a one-person electric 'city car'. Because so few were sold, these are now collector's items!

So Hugh, the moral is:

Don't deviate too far from you 'core' business, or if you do, get some market research done!

Ron.

Rocket · « **Reply #31 on:** 24 Feb 2005, 09:55 am »

Hi Guys,

Okay i have a confession to make

. I have gone over to the dark side and purchased a ps audio hca - 2 amplifier. I bought it from the states as it was a bargain and from what i had read review wise it is an outstanding amplifier.

Anyway i have auditioned and compared this amplifier many times to my aksa 100 nirvana plus. Unfortunately it just doesn't have the same emotional impact of the aksa amplifier. It has a slightly wider soundstage compared to the aksa however it doesn't have the same depth. The top end is slightly better, the midrange is quite transparent but i think it has a slightly hard sound (fatiguing

). The bass is poor and just doesn't get anywhere near as low as the aksa amplifier, i had read reviews which indicated the bass was excellent.

Apart from those impressions the amplifier has almost no emotion and fails to keep me interested. It sounds reasonable but it doesn't get my foot tapping.

I have ordered some blackgate caps to try and improve the sound quality.

At this stage the aksa is the winner and is in my system.

Regards

Rod

AKSA · « **Reply #32 on:** 24 Feb 2005, 10:26 am »

Ron,

Many thanks for jogging my memory..... it's sad how the mighty fall, and I have no plans to build the successor to the Segway, though electric cars do fascinate me - I'll leave it to Honda and Toyota!!

Another to study was Tucker, who built a technically interesting family sedan in the US in the fifties. He used a flat six of aero engine roots - shades of the Subaru, and the Corsair? Of course, he went broke too....

To stay in business, you must not be too far advanced technically. You can't make the bleeding edge pay - the key to profitability is very careful use of inexpensive components. The market fixes the price for the finished product; the essential ingredient is to build it cheaper while offering the same or slightly better performance. And much of the marketing success relies on that enigmatic word - 'branding'.

Now here's an interesting one to look at: http://deltahawkengines.com/

I sincerely hope these guys make a practical and commercially successful product; the light plane industry desperately needs diesel power. It's very important in my view; the present crop of gasoline engines is about forty years old and a technological disgrace.

Rod,

Thank you for your comments. You said it much better than I could have.....

Cheers,

Hugh

mac · « **Reply #33 on:** 28 Feb 2005, 12:10 am »

http://www.diyaudio.com/forums/showthread.php?postid=578830#post578830

http://www.diyaudio.com/forums/showthread.php?s=&postid=581767#post581767

Hugh, I just upgraded the NE5532 diff input buffers on my UcD180 modules to AD8620's. Even with the stock coupling caps still in the signal path the sound is very noticeably improved.

Cheers, mac.

AKSA · « **Reply #34 on:** 28 Feb 2005, 12:31 am »

Thanks Mac,

Interesting information. Feeding the modulator requires Zout on the non-inverting side of less than 200R, and less than 1K on the inverting side. This is a tough call, particularly as level at this injection point needs to be 13dB above line. There aren't too many ways to do this other than an IC (or discrete, linear SS), and it would seem that this is the weak link in the chain.

Did you fit the new IC yourself, Mac? Difficult? Presume it's SMD......

Can you now get the emotions of music through your upgraded amp? Another way of saying this is, 'Does it make you weep', or 'Does your foot break into spontaneous tapping'??

Cheers,

Hugh

mac · « **Reply #35 on:** 28 Feb 2005, 12:46 am »

Hugh, The latest crop of high performance audio operational amplifiers are really quite good. I'm adding the 8620 to my list. Some have talked about transformer coupling the input but I really don't see the need.

The chips are SMD and I replaced them myself. (This isn't the first time I've done SMD soldering).

I felt like the amps were quite "emotional" prior to upgrading the opamps.

Now, they just sound more refined and detailed (in a good kind of way). I considered removing the coupling caps but I'm probably going to use some BG's in place of the stock ones.

Cheers, mac.