SI with AMP3 toroid output inductors - diyAudio
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Old 3rd July 2005, 04:26 AM   #1
BWRX is offline BWRX  United States
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Default SI with AMP3 toroid output inductors

I got an AMP3 kit and have all the components soldered but the chip, which proved to be rather hard to do properly. i made one attempt, but my soldering iron wasn't fine enough (and my hand shakes more than I'd like it to ) to do each pin so I'm waiting for a finer tip that's on order. In the interim I decided to see what a stock SI would sound like with the AMP3's output filter inductors.

In the short amount of time (a few hours) that I've had to listen to it, you can tell that there is a bit of an improvement. The most noticeable change is the imaging. The location of voices and certain instruments are more precise compared to just the stock SI. Also, I first thought the high frequency response was lowered a bit. Rather, it seems that the bass response was increased. It's hard to say by how much but there's definitely more substance in the low end. I'll post some photos tomorrow when I find my camera.
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Old 3rd July 2005, 07:13 PM   #2
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Default Otput inductors

I am glad someone finally did this and reported their findings. Thank you. It is a bit out of context though. What other mods have you done to the SI? What are you powering it with? I would think that the more stock the unit, the less the differences would be heard. We maybe finding that the PC board it's self is a major limitation for the SI design. I do know that the amp3 is far better sounding than an extensively upgraded SI. I have both and have done direct A/B with every thing the same including the power supply.
The only reasonable remaining mod left on the SI would be the inductors so I am appreciative of this information.
Roger
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Old 3rd July 2005, 08:26 PM   #3
BWRX is offline BWRX  United States
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The date on the PCB is 2003.07.03 and it's one of the first revision PCB's without any protection diodes before the output filter. I've been listening to the completely stock SI with an unregulated 9V 2A wall wart power supply originally used for powering a portable TV. When connected to the SI the output voltage of the supply is anywhere between 12 and 12.5VDC - my speakers are 8ohm 90dB 1W/1m in a small room so I don't need the volume very high to get a lot of output.

It's encouraging to know that the AMP3 sounds better than the SI. I can't wait to get it up and running!

Here are some photos.
Click the image to open in full size.
http://www.personal.psu.edu/users/b/...p/DSC01276.jpg
http://www.personal.psu.edu/users/b/...p/DSC01274.jpg
http://www.personal.psu.edu/users/b/...p/DSC01273.jpg
http://www.personal.psu.edu/users/b/...p/DSC01277.jpg
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Old 4th July 2005, 10:04 AM   #4
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Default Pictures

Thanks for the pictures. Wondered how you did it.
Roger
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Old 4th July 2005, 07:57 PM   #5
BWRX is offline BWRX  United States
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I was just playing some acoustic guitar music fairly loud and my brother walked in my room and said "I thought you were playing your guitar in here, but I knew you weren't that good so I had to see for myself..." Sadly, he's right but that does show how good the SI sounds with better output inductors.
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Old 5th July 2005, 06:16 AM   #6
starn02 is offline starn02  Italy
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If the new toroids helped with the sound ... you could also try the real jump forward: air core inductors. They are on sale on www.autocostruire.com.
I think they are the real secret of my kit with the ta2020 that i bought on them. I tried to assemble it also with normal ferrite core inductors (10 uH), and the difference is really shocking .... eek:

You can read more on this thread: Class t-amp-2020 Kit - Check it!

Bye.
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Old 5th July 2005, 06:56 AM   #7
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Default Inductors

It seems the knowledgeable people worry about radiated field with air core inductors. A possible solution would be to wind them on a toroid shaped core made from some inert substance, possibly Teflon. This would not contain the field as a magnetic core would but would be of some help I would think. Of course it would be a lot larger than if it had a core and would have much higher copper losses. It would still probably be worth a try. If I have the time I will look into it.
Roger
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Old 7th July 2005, 10:53 AM   #8
Mick_F is offline Mick_F  Germany
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Default Re: SI with AMP3 toroid output inductors

Quote:
Originally posted by BWRX
In the interim I decided to see what a stock SI would sound like with the AMP3's output filter inductors.

These inductors should be rather easy to make yourself. Could you let us know some more details? What kind of core is in there, what are the dimensions of the core, what is the wire diameter, how many turns to you do and how are the wire ends wound?

This may be another fruitful tweak for the SI.

Mick
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Old 7th July 2005, 06:51 PM   #9
BWRX is offline BWRX  United States
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Default Re: Re: SI with AMP3 toroid output inductors

Quote:
Originally posted by Mick_F

These inductors should be rather easy to make yourself. Could you let us know some more details? What kind of core is in there, what are the dimensions of the core, what is the wire diameter, how many turns to you do and how are the wire ends wound?

This may be another fruitful tweak for the SI.

Mick
The 41Hz kit is supplied with 0.5mm wire to wind the inductors. It takes about 70cm of wire for 39 turns around the core of one inductor (10uH). I don't know exactly what the supplied T60 toroid cores are made of. Searching the 41Hz forum may come up with an answer to that question.
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Old 8th July 2005, 08:07 AM   #10
Mick_F is offline Mick_F  Germany
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Thanks for your reply. Can you also give the (approximate) dimensions of the core?

Mick
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