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Old 21st October 2004, 02:23 PM   #71
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Lars, A thought occurs. I find the Zappulse really gets harsh in the treble when there is a lot of other "music" playing. When it's only a few voices, they sound OK. Bring on the backing guitars and the voices get quite "harsh"

Since I have gone multi-amp and moved some of the bass to a sub amp, it's a *little* better.

Thought is, could my 400va power supply running at 62V rectified, be just underspecified for the job?

Power supply was a single LCaudio PS with 10,000 caps if you remember
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Old 22nd October 2004, 10:47 AM   #72
Dibley is offline Dibley  Wales
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Are youre output inductors saturating, this will add distortion also perhaps you could wind some air core's and try them.
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Old 22nd October 2004, 12:38 PM   #73
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The Zap coils are very comfortably rated. There's little chance of ever seeing them getting near saturation. Any sonic colouration is not to be looked for in the coil.

An air coil in a class D amp (or in any other step-down converter) is an EMI hazard, as well as a logistical problem. The proximity of a circuit board simply shorts out the coil, requiring it to be mounted in "free space". Air coils and class D amplifiers are uneasy bedfellows.

The Zap coils have something of an external field problem as well. Presumably due to a chronic difficulty in obtaining of core halves with the air-gap ground into the center leg, two unmodified RM core halves are used with a spacer inserted. The result is an external air gap, which causes a strong stray field nearby. I would not be surprised if two of these modules mounted close together would eventually suffer from whistle noises due to the stray field of one module's coil interfering with the modulation circuit of the other.
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Old 22nd October 2004, 01:18 PM   #74
ghemink is offline ghemink  Netherlands
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Quote:
Originally posted by ewildgoose
Lars, A thought occurs. I find the Zappulse really gets harsh in the treble when there is a lot of other "music" playing. When it's only a few voices, they sound OK. Bring on the backing guitars and the voices get quite "harsh"

Since I have gone multi-amp and moved some of the bass to a sub amp, it's a *little* better.

Thought is, could my 400va power supply running at 62V rectified, be just underspecified for the job?

Power supply was a single LCaudio PS with 10,000 caps if you remember

This sounds like intermodulation distortion to me.

Gertjan
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Old 22nd October 2004, 01:58 PM   #75
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Thanks for the thoughts Bruno. Yes, these things do have some whistle noise quite easily if for example I use my mains conditioner nearby. There is a little static type noise as well on idle.

Thanks Gertjan, yes, I think it probably is intermodulation. Basically, the amps have fantastic stereo imaging and great bass, but ultimately, compared with my Meridian 557 commercial job, I just can't listen to these things with any kind of volume. It's just as though someone has turned up the treble and it sounds a lot louder than it really is...

Now, bear in mind that I have just been to the Queen musical (which is basically a rock concert in a theatre, and I can assure you that the PA rig there putting out probably 120dB+ was a lot nicer to listen to than my zappulse....

Basically anything that has a treble component *sounds* a LOT louder than it should do. I'm fairly sure this is the text book description of IM distortion?

The question is how to fix it though...?

Now I have another pair of Zappulse here, (and 4x UCD400s in transit.) I was going to build the other Zappulse pair with a single 1000va transformer, ditch the DC filter, and put each module on the opposite side of the case and bonded to the alu sides for cooling. We will see if this improves things at all. If so, then I may try to re-engineer this current one for better performance

Thanks all
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Old 22nd October 2004, 06:36 PM   #76
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Quote:
The Zap coils have something of an external field problem as well. Presumably due to a chronic difficulty in obtaining of core halves with the air-gap ground into the center leg, two unmodified RM core halves are used with a spacer inserted. The result is an external air gap, which causes a strong stray field nearby. I would not be surprised if two of these modules mounted close together would eventually suffer from whistle noises due to the stray field of one module's coil interfering with the modulation circuit of the other.
Hello ... I'm Guessing now but what help my modules from ever saying a single piiiiiip or noise at all ... shortcircuiting the to ferrites in the coils with a testwire ..

i dont know why it would help but it most certainly did ...
allthough this was on version 1.20 haven't tried my new 2.2's yet ..... i hope it would have the same effekt

besides i would consider the windings on the coils to be EXTREMELY loose .... given that most talk about how firm coils for high frequencies ( SMPS ) have to be made.

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Old 23rd October 2004, 08:45 PM   #77
mattjk is offline mattjk  United States
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Interesting situation here.

In the begining of this thread, I noted that my amp was very clean sounding -- no noise. This was on a test bench with only the single ended input hooked up with cheap coaxial style cable.

Now that I have it installed in a case, I am getting noise when music is playing... Especially through high frequencies, it sounds like there is sand in my speakers.

One of the things I did was connect a set of balanced inputs, which I am not using. I cut the "-" connection and the noise went away.

Matt
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