Interesting 
We discuss at http://www.hififorum.nu/topic.asp?TOPIC_ID=17198 about LC Audios ZAPulse which knocks out radio and TV.
Was this product CE-marked?
My point of view regarding ZAPulse is about shielding and how much is said about this? A switched amp must have a good metallic case.
We discuss at http://www.hififorum.nu/topic.asp?TOPIC_ID=17198 about LC Audios ZAPulse which knocks out radio and TV.Was this product CE-marked?
My point of view regarding ZAPulse is about shielding and how much is said about this? A switched amp must have a good metallic case.
In earlier days of PWM amps it was believed that the output filter should remove ALL switching residuals for high audio quality. I never believed this and newer statements seem to confirm that.
This is of course only valid if you look at the amp-speaker interface alone.
All the unwanted stuff might interfere with other equipment as others seemed to have lerned the hard way.
With a notch filter you could suppress the carrier frequency (and it's 3rd and fifth as well if you add more "notches").
Since you need quite a large antenna to get 250 kHz into the air it is the higher harmonics of the switching signal that seem to interfere with most other equipment.
So it should be possible to attenuate these by the use of a 2nd or 4th order filter whose f3 is significantly higher than the amp's f3 (as suggested by Tripath for example).
Some older versions of the ZAP Pulse use a air-cored coil in the output filter. These are superior in terms of hysteresis distortion, but may produce a large stray-field, even at the switching frequency fundamental.
Regards
Charles
This is of course only valid if you look at the amp-speaker interface alone.
All the unwanted stuff might interfere with other equipment as others seemed to have lerned the hard way.
With a notch filter you could suppress the carrier frequency (and it's 3rd and fifth as well if you add more "notches").
Since you need quite a large antenna to get 250 kHz into the air it is the higher harmonics of the switching signal that seem to interfere with most other equipment.
So it should be possible to attenuate these by the use of a 2nd or 4th order filter whose f3 is significantly higher than the amp's f3 (as suggested by Tripath for example).
Some older versions of the ZAP Pulse use a air-cored coil in the output filter. These are superior in terms of hysteresis distortion, but may produce a large stray-field, even at the switching frequency fundamental.
Regards
Charles
Hi Peranders,
These prototype amps have conventional torroidal/bridge/caps supply, in a fully enclosed earthed case, and have electronic balanced line input.
I am sure that the radiation is from the speaker leads - very strong, and a friend and I could feel it too.
I have heard some hints that an additional output filter tuned differently improves inteference problems, and improves distortion performance.
Any info on this ?.
Your Danish is better than mine - can you give a summary of what was said in the link you give ?.
Eric.
These prototype amps have conventional torroidal/bridge/caps supply, in a fully enclosed earthed case, and have electronic balanced line input.
I am sure that the radiation is from the speaker leads - very strong, and a friend and I could feel it too.
I have heard some hints that an additional output filter tuned differently improves inteference problems, and improves distortion performance.
Any info on this ?.
Your Danish is better than mine - can you give a summary of what was said in the link you give ?.
Eric.
Hi Eric
I think I once read that the fullrange versions run at 250 kHz approx. According to the patent and functional description the switching frequency should be quite stable (opposed to delta-sigma amps like Tripath and Sharp).
You should be able to determine the switching frequency from the residual at the output if you don't apply any signal at the input.
AFAIK they are using a full-bridge with carriers in qadrature (i.e. with a relative phase of 90 deg).
Regards
Charles
I think I once read that the fullrange versions run at 250 kHz approx. According to the patent and functional description the switching frequency should be quite stable (opposed to delta-sigma amps like Tripath and Sharp).
You should be able to determine the switching frequency from the residual at the output if you don't apply any signal at the input.
AFAIK they are using a full-bridge with carriers in qadrature (i.e. with a relative phase of 90 deg).
Regards
Charles
Indeed, becuase it's in swedishmrfeedback said:
The main content is the ZAPulse is rather nasty towards TV and radio (FM band) if care not is taken.
250 kHz and ns risetimes create lot's of stuff up to 500 MHz I'll guess, maybe even higher.
If a normal radio dies in the same room is not so good. The thread also is about good shielding.
I'm surprised that commercially sold products have som high RF- emission
I know about a commercial product, danish (not unexpected) which is stand-alone
http://www.icepower.bang-olufsen.com/sw1330.asp
The amp got good reviews, but on the other hand the hifi magazine High-Fidelty is like everybody else, nice to the advertizers.
Very cool design, triangular! This amp must pass normal CE approval I suppose.
http://www.acoustic-reality.com/
http://www.icepower.bang-olufsen.com/sw1330.asp
The amp got good reviews, but on the other hand the hifi magazine High-Fidelty is like everybody else, nice to the advertizers.
Very cool design, triangular! This amp must pass normal CE approval I suppose.
http://www.acoustic-reality.com/
The Ice Power Amplifiers Mr Feedback seems overly concerned about are experimental prototypes
They were designed as bolt on amplifiers, to fit on the back of speaker boxes to give very short speaker cables, not 3 meter antennas
No attempt has been made to reduce RF Radiation at this point
Moreover, they have been lent to several people to experiment with, and one of these people seems to have damaged one of the amplifiers so the output is no longer symmetrical from it
This will naturally produce an excessive amount of RF Radiation
I will investigate what has happened, but suspect one leg of the output filter has been "Cooked" due to one of the speaker leads has been accidentally grounded
An absolute No-No with that type of amplifier
Suggest to be Scientific and Analytical, before throwing theories about
They were designed as bolt on amplifiers, to fit on the back of speaker boxes to give very short speaker cables, not 3 meter antennas
No attempt has been made to reduce RF Radiation at this point
Moreover, they have been lent to several people to experiment with, and one of these people seems to have damaged one of the amplifiers so the output is no longer symmetrical from it
This will naturally produce an excessive amount of RF Radiation
I will investigate what has happened, but suspect one leg of the output filter has been "Cooked" due to one of the speaker leads has been accidentally grounded
An absolute No-No with that type of amplifier
Suggest to be Scientific and Analytical, before throwing theories about
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