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Old 27th December 2003, 11:35 AM   #101
Pan is offline Pan  Sweden
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Quote:
Originally posted by km
hi.

pan i think you should hear some of the better pwm amps

im sure feedback after the output filter is way to go for all pwm amps , perhaps in some it doesnt give much improvement but i think this is due to other factors.

sorry if im repeating myself but i think that usable opinions about class-d ctr. class a or a/b is only valid from those who has a reasonable background to talk from , meaning those who have actually heard some of the better types from both camps , right?

my personal feeling is that this is perhaps 1-2 guys here at most

im gettting a little bored with the usual hear-say and the usual talk about good static thd specs, i have heard and compared boards with good (published) specs and the good specs didnt help much re. sound quality.

happy new year to all.

karsten madsen - www.cadaudio.dk

ps. the easiest way to get low thd numbers is simply to lie and imho this is also used quite often.....
Karsten,
Iīd love to hear the better PWM amps . So far I have only heard the ice modules in the B&O speaker but that didnīt tell me much at all.

Are you saying my opinion is not worth much because I lack experience or becasue I have not heard PWM amps? Do you know what equipment I have used/listened at?

I donīt care much for hear-say but do read reviews, whatch specs and no1 listen very criticall on various equipment.

Would love to listen to your designs.

Regards,

/Peter
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Old 27th December 2003, 11:39 AM   #102
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Quote:
according to Peter at TacT they do not use feedback.
You are of course correct. I should have reread more carefully before posting
My statement is true only for the Sharp amp.

Regards

Charles
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Old 27th December 2003, 12:02 PM   #103
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Default Only 1 or 2 guys???

Surely, you jest.

Yeah, I know........somedays it seems that way.

"And don't call me 'Shirley'."

Jocko
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Old 27th December 2003, 12:25 PM   #104
km is offline km
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hi.

>pan wrote ; Are you saying my opinion is not worth much because I lack experience or becasue I have not heard PWM amps? Do you know what equipment I have used/listened at?>

im saying that imho listening experience comparing several good pwm amplifier designs preferably to one or more good class-a and a/b designs has a lot more value than posting reviews from magazines or posting hear-say from others who hasnt heard much either.

to give valuable opinions about the subject of this thread (class-d vs. class a and a/b) i think at least you should have listened to the better of each type.

i think that some of the beolabs use class a/b amps for the hf so please check this if you want to compare , imho again its a lot better to listen to different amps using same speakers and the rest of the setup , if you hear one set of amp + speakers and next week another set , hmm. i dont think it adds very much to the issue.....

rgds karsten madsen - www.cadaudio.dk
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Old 27th December 2003, 01:11 PM   #105
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Karsten Madsen: I agree with your views completely! I never heard your PWM amp, but i would be very interested to switch sets with you for a week for a mutual comparison.

Last friday i went with a couple of friends to visit AV-Reality (Who are located at the local bowling alley, one kilometer (not to confuse with km from my office), and then later to a B&O shop in downtown Holstebro 2 floors below my appartment.
Before this day i had only heard Beolab 5 through the building and floor, the bass vibrations, of the Beolab 5's are really impressive even 2 floors up.

I must say it was an interesting experience. These two systems sound completely different to each other, even if they probably use more or less the same Icepower modules. The placement in the rooms were also very different, which may be a contributing factor.
I think the Icepower modules are good enough not to be the limiting factor in either system, but other things would more probably be the source of the system's 'own sound'. Only my own private guess.

A very interesting couple of hours
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Old 27th December 2003, 04:21 PM   #106
Pan is offline Pan  Sweden
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km,

I have listnened to a lot of gear thru same speaker in same room. Several times at different locations.

I have also listened to some of the really good amps you talk about but as I mentioned no PWM amps.

So, I have very good experience with top notch class A and A/B in very high standard setups. Never have I tried to judge PWM amps from what I read in papers. As I say, I read graphs and I do own listening tests in carefully treated room.

Of course I canīt compare PWM amps to A and A/B since Iīve never heard a PWM amp. (except from the B&O speaker).
Maybe you did react on my verdict on the B&O speaker... I believe the driverunits and the room was the casue of the less than impressing sound I heard. I did not in any way mean that it had someting to do with the amps.

I do agree with the message in your post.

What "bother" me with PWM amps is that they have a rising THD at the high range. Most A A/B electronics I have heard that have such characteristics have been affected of it IMO.

/Peter
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Old 27th December 2003, 04:36 PM   #107
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Quote:
im saying that imho listening experience comparing several good pwm amplifier designs preferably to one or more good class-a and a/b designs has a lot more value than posting reviews from magazines or posting hear-say from others who hasnt heard much either.
This is of course true. But while it is quite easy to get a chance to listen to a lot of the good equipment, it is much harder to get a chance to COMPARE the stuff at the same place/time, at least for Joe Average.

Quote:
i think that some of the beolabs use class a/b amps for the hf .....
That's what I also once read.

Quote:
Before this day i had only heard Beolab 5 through the building and floor, the bass vibrations, of the Beolab 5's are really impressive even 2 floors up.
The way the sub-bass driver with it's heavy cone is mounted it is a suitable candidate for generating a lot of structure-borne sound.

Quote:
These two systems sound completely different to each other, even if they probably use more or less the same Icepower modules.
Do you want to say that you got a chance to listen to AV's active speaker system ? (Does it also use class-d for the tweeter ? How did it sound ?)


Regards

Charles
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Old 27th December 2003, 04:40 PM   #108
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Quote:
What "bother" me with PWM amps is that they have a rising THD at the high range. Most A A/B electronics I have heard that have such characteristics have been affected of it IMO.
I think this could be dealt with at the expense of the THD figures at lower frequencies.


Regards

Charles
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Old 27th December 2003, 06:58 PM   #109
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Having done 3 PWM amps myself, I guess I have some
basis for an opinion. One of these even got a good comment
from Gordon Holt, but I think he was being polite.

So far, I've not heard one which takes on the better Class A
or AB types except in the bottom end, and I have to lay the
blame at inadequate switching speeds and inadequate input
comparators.

No doubt these issues will be resolved over time, but the best
engineering talent does not seem to be working on the
problem from the high-end audiophile viewpoint - they are
still letting their meters tell them what's good and what's not.
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Old 27th December 2003, 08:38 PM   #110
subwo1 is offline subwo1  United States
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Thanks for the comments, Mr. Pass. Maybe my idea of using differential input and feedback transistors helps because a packaged comparator is not used.
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