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Old 5th February 2007, 06:44 PM   #1
icebear is offline icebear  Norway
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Thumbs up Shielding the Charlize

I have earlier tried to shield the coils in the charlize. Aluminumtape wrapped around the coils and the tripath-chip. It was a quick test, and did not bother to earth the shield (to bad it doesn't work then )

This weekend I stumbeld accross the modifications on the Trends Audio TA-10 by Michael Mardis (Thanks Michael )
The modifications looked a lot better than my pitty test, so I gave it another go. I cut the copper plate in the correct height and rolled it in 12mm diameter sylinders (which is the diameter of the coils). A wire is attached to run the shields to ground. I also shielded the chip with aluminumtape.

Click the image to open in full size.

Click the image to open in full size.

I did not have high hopes for this mod. I was thinking it should at least make the circuit healtier, and it would not harm applying the tweak. But I was in for a suprise. The sound has improved quite a lot. (I need at least 15% change for my brain to respond ). The whole preformance has got clearer. Sondstage improved in all directions. Expecialy at higher levels. Makes sense since the radiation is greater. For me a successfull tweak.

Are there others who have tried this?


Cheers
Bjorn
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Old 5th February 2007, 06:58 PM   #2
icebear is offline icebear  Norway
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The spot I earthed the shield is inside the red ring. Scratch the laquer away an make an arrangement to attache the wires.

Click the image to open in full size.

The aluminumtape looks a bit untidy, but I guess it's important to not touch the metal on the tripath chip?

Cheers

Bjorn
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Old 5th February 2007, 07:00 PM   #3
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No did not try it on my Amp6 yet, but it looks interesting.
However, I am a bit concerned about your way of shielding the TA2020. The alu foil seems to come awfully close to the pins. Aren't you afraid of shorting it? Besides that, don't you need a little more heatsinking for your chip to stay healthy? Just some concerns for the sake of your music pleasure of course.
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Old 5th February 2007, 07:02 PM   #4
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Ah, you just took the words right out of my mouth...
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Old 5th February 2007, 07:08 PM   #5
icebear is offline icebear  Norway
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Hi DocLorren

The tape is far from any pins. I'm planning to switch it with a piece of copper
It's clearly stated that there is no need for cooling the chip. I have tougth about it, but it does not get warm.


For those who is curious on the caps: The input caps on the right is 2,2 uF Obbligato's. The caps on the left is just bunch of different small caps for the railsupply. I run it by SMPS and a battery.

Bjorn
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Old 5th February 2007, 07:25 PM   #6
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Hi Bjorn,

I agree you do not need heatsinking under low-power conditions; for medium or higher power/low impedance loads though it does not hurt to add a little metal there. You will probably do OK if it does not get warm to the touch in your application. Just be careful when stressing the amp and putting it in a poorly ventilated case.
Btw, what is your source and speakers and did you DIY the Charlize?
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Old 5th February 2007, 08:03 PM   #7
icebear is offline icebear  Norway
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Thanks DocLorren

No probs to put on a little coolingfin. Next time I open it up I migth just attach one. There is no ventilation in the box as it is. It's DIY yes.

Click the image to open in full size.

The Charlize is powering a set of Bastani Prometheus MK2. I run a Cambrige CD to a modified Behringer DCX 2496 (digital input). Trough a 4 channel pot and tube/ss pre. The charlize is filtered from 60 hz and up.


Cheers
Bjorn
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Old 5th February 2007, 09:46 PM   #8
Pano is offline Pano  United States
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Hi Icebear. Glad you tried the shielding and liked it. The aircore inductors do sound nice, but they are also wonderful little radio transmitters!

And big caps, like the Obbligato and others make wonderful radio receiving antennae. (50/60Hz too). Some caps have metal cases that can be grounded.

My measurements showed that most of the radiation comes from the sides of the coils. When two coils are close together, they really radiate!

What we need to remember with Tripath and other switching amps is that we are not only working with audio signals, but radio frequency signals too. Keeping the signal path and power as clean and free of this RF as possible is good for the overall sound. That's why shielding and good quality power caps can make a difference.

Enjoy your new, better Charlize.
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Old 5th February 2007, 10:20 PM   #9
infinia is offline infinia  United States
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Default Shield connections

Hi
Best place to tie the inductor shields is the reservoir caps near the power switches. The residual noise currents in the shield want to return to whence they came, eventually. If you tie them to chassis the currents can cause offsets in the signal ground. The inductor shields as shown in the image should be somewhat effective because they are acting as a shorted turn.
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Old 5th February 2007, 10:32 PM   #10
icebear is offline icebear  Norway
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Thanks Pan and Infinia

Do you recomend shielding the input caps as well?


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