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Class D Switching Power Amplifiers and Power D/A conversion

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Old 5th July 2005, 05:16 AM   #11
starn02 is offline starn02  Italy
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I actually use it with a Marantz CD 17 and a pair of Triangle Titus.
I tried with other combinations too, and I can say that the sound is easy to "trim" ... do you want more highs? Use a different CD player ... do you want more softness ? Well, switch to speakers with a silk dome tweeter ...
My suggestion is that the sound of the amp is a bit on the "warm" side (just like a tube amp ... ) so inserting it in a pre-existing setup should normally be easy and rewarding .... a good upgrade, in other words (an a cheap one too ).

Bye.
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Old 5th July 2005, 02:45 PM   #12
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Quote:
Originally posted by starn02
I actually use it with a Marantz CD 17 and a pair of Triangle Titus.
I tried with other combinations too, and I can say that the sound is easy to "trim" ... do you want more highs? Use a different CD player ... do you want more softness ? Well, switch to speakers with a silk dome tweeter ...
My suggestion is that the sound of the amp is a bit on the "warm" side (just like a tube amp ... ) so inserting it in a pre-existing setup should normally be easy and rewarding .... a good upgrade, in other words (an a cheap one too ).

Bye.
Thanks for the information !

I plane to use the amp in my main system. I have a KT-88 based tubes amp, but I like to have an amp that I can use for short listening session. I curently us Brian GT NIGC as second amp and as mush as I think it's a good amp, I know that the T-AMP kit will do better. I had a stock SI in my system a few days and it already showed how superior a T-amp design can be (I killed it when trying to modify it ).

My speakers are big DIY 3-way and they use a soft dome tweeter (OWI). I think that the kit will be a good match.

It's just a question of time....I'll soon order a first kit & who know, maybe a second one for the living room

Thanks again !
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Old 5th July 2005, 07:42 PM   #13
dillo is offline dillo  Italy
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Default autocostruire kit

Hello to everybody,
I have not bought the kit, but one year ago I bought another one from them and it was great! Its name is Ella and it is an hybrid power amp; 12AX7 driver directly coupled to a class A transistor followed by an output transformer for an overall 6 watts.
It was a very strange design and I was dubious about it, but now it is my favorite amp: few watts but great watts!
The designer of their projects is a fanatic of air cored inductors and transformers.
I saw this new kit and I was wondering if those filter inductors would cause EMI, because they are supposed to block high frequency switching noise.
IMHO donut cored inductors (= 41Hz) should be better for this task, because of the closed magnetic circuit, while open inductors like those in the kit should spread a lot of EMI.
Thank you starn02 for solving this doubt for us!
On the other side, it is sure that air cored inductors don't saturate and this is very nice if you have to run the amp close to the max output power (=undistorted sound until heavy clipping)
Starn, did you use a grounded steel box for the electronics?

Bye
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Old 6th July 2005, 07:26 AM   #14
solar2 is offline solar2  United Kingdom
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I too am concerned about the EMI radiation from the air-cored inductors in the Audiodigit design. However, the Amp3 uses “low permeability iron powder” cored toroids which are supposedly better than standard iron/ferrite and causes less radiation that air-cored. What is the mechanism for EMI to cause actual sound problems does anyone know? Presumably the idea is that some other component is affected and causes some sort of adverse feedback.

Here is an article on inductors which answers some questions:
http://ldsg.snippets.org/appdx-el.php3
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Old 6th July 2005, 10:37 PM   #15
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I wonder if using a second board for the inductors & taking care of their relative position from each other could be a good thing ?

It will be easy to wire the inductors to the amp. board using good silver plated wire (shielded) and the distance should not matter to much.


What do you think ?
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Old 7th July 2005, 07:26 AM   #16
starn02 is offline starn02  Italy
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My small contribution ....
I have never performed measurements or tests on the EMI of the 2020 kit (and neither for the original t-amp), but I had them for a lot of time on my desk without an enclosure between computers and audio equipment .... with NO PROBLEM at all: no noises, no interferences, no stange ripples on the computer screen ...

And all that without an enclosure. They did not show any influence even when sitting one beside the other for comparisons ... so my opinion is that the EMI problem is not so much a problem.
If you use a metallic enclosure then ...
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Old 7th July 2005, 07:26 AM   #17
starn02 is offline starn02  Italy
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Ah, I forgot one thing.
I don't think it's wise to set the inductors far from the circuit. The board is small (about 80 x 50 mm) and the circuit is optimized for creating very small current loops.
If you take a look at the Tripath web site and read the data sheets you'll see that they underline the imporance of maintaining the components close to che chip, inductors too.... so in my opinion
the kit already comes with a very good solution.

Experimenting is allowed, of course ....

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Old 7th July 2005, 12:42 PM   #18
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Quote:
Originally posted by starn02
Ah, I forgot one thing.
I don't think it's wise to set the inductors far from the circuit. The board is small (about 80 x 50 mm) and the circuit is optimized for creating very small current loops.

Thanks for the information !

the reason why I mentionned the second board is that when building speakers x-over, it's important to make sure that the big inductors are perpendicular to each other (to prevent interaction). The inductors on the kit are very close and // to each other. When looking at the picture on their web site, we can see that they give a light angle to each inductors. I wonder if they do that to make them a little bit les //

Another thing that could be done is to solder two inductors on the top and two on the bottom of the board (T, B, T, B). This would not change the small current loop and prevent the possible interraction.


Regards,
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Old 7th July 2005, 02:04 PM   #19
dillo is offline dillo  Italy
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Yes, Itotally agree with starn02: all pcb traces + wiring should be kept to the minimum in order to reduce inductive loops.
output capacitors are the most sensitive components in this respect, chokes are less critical, but I wouldn't put them too far from the chip.
Starn02's experience is interesting, since the chip is supposed to output a lot of noise above 30kHz, and this is to be filtered by the LC couple.
IMHO the reason why there is no interference (also with other equipment) could be one of the following:
- the energy radiated is very spread in spectrum so it doesn't tune strongly with other equipment
- the caps do a great job attenuating the most of the unwanted frequencies
- since the amp is bridged some of the radiated noise cancels out in some way.
I think that this new technology is full of good nice surprises.

bye
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Old 7th July 2005, 03:04 PM   #20
mourip is offline mourip  United States
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Hi,

This is an encouraging thread. I have a 41mz kit in my drawer. The smd components are the size of fly speck. I am excited that someone made a kit with through hole components.

One problem. I tried to email them via the link on their site but have received no response. I wanted to ask a couple of questions before making a purchase.

Does anyone know if they have a direct email address or if they speak English?

Thanks a lot,

Paul
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