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Old 7th July 2010, 01:25 AM   #411
fb is offline fb  Australia
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Location: Brisbane, Aus
Where's the heatsink go?

Nick122147, will you be able to sell a suitable SMPS for the T3 board?
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Old 7th July 2010, 04:50 AM   #412
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Quote:
Originally Posted by cOz View Post
Where can we find more information about the T3 board?

Thanks,
Robert
It's TC2000+STA517B mono board, parallel circuit, 30~50V DC supply, about 300W power output(at 50V,4ohm). PCB size is 56*80mm.
I post before for advice, and more description will come out in about a week when we public it formally, and I will post a new picture with heat-sink then.
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Old 7th July 2010, 06:10 AM   #413
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Location: Shanghai
Quote:
Right, it's not good "engineering practice". In the real world, you never know what people will connect to your design, so you have to be careful. The most important thing is that is works. And with a wide range of equipment. You don't have that restriction, you know what you are using.

I've tried the cap only and like it. But to my ear the transformer output sounds better. A matter of taste, really. Scott likes the cap coupling better.
Can you say more, in what circumstances would it not work very good?
I would guess that cap out or transformer out doesn't make that big difference, compared to the direct out vs through filters and opamps.. thats very the big difference is.

I got a PM asking for pictures on how i connected the dac for direct out, so here it is. I was luck that this dac was mounted on a bigger connector plate, so it was quite easy to solder in my case.

I'm thinking about if I could talk hifimediy into making this type of direct out DAC . I know at least it works very good with this amp !


Click the image to open in full size.

Click the image to open in full size.
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Old 7th July 2010, 10:25 AM   #414
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Quote:
Originally Posted by ArjenShenzhen View Post
for Don,

The 2.2uF or 3.3uF will not make a difference at that impedance, but if you make the size smaller than 2.2uF the cap starts acting as a high pass , and it will reduce the bass that comes thru. so if you need less bass, 1uF is just fine, i know from my amps that 2.2uF is also perfect, larger is not needed.
I think that I will go with 2.2uF K73-16 PETP capacitors:
http://www.diyaudio.com/forums/parts...-one-best.html

I think that comparing the frequency response of a 2.2uF setup vs 3.3uF setup there should be no appreciable difference in the audible range (20-20.000Hz).
My 2 cents and thanks for your info.
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Old 7th July 2010, 11:24 AM   #415
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Received my 2 boards a couple of days ago.
had a couple of 12v batteries laying and it came sound

Click the image to open in full size.

Last edited by bambadoo; 7th July 2010 at 11:30 AM.
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Old 7th July 2010, 11:30 AM   #416
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Hi Hifimediy and Nick (great initiative of you making this board accessibe via ebay)!

I recieved my board for a couple of days and I have let it run day and night to burn it in.

Ive made some listing comparison to my moderate modded 2x100 sureboard (valab MKP2000 4.7uF input caps, passive cooling, T106-2
coils, stock ouput and tank caps) driven by a 27v 350w meanwell SMPS turned up to 29v.

I think your card performs very well, hard to say which I like best, my modded sureboard have some more depth/3D-sound and
"loudness", your board on the other hand I find more neutral sounding (and perhaps more correct).
Anyway, your card is far better than a stock sureboard and would be the obvious choice for someone deciding between them.

Some other observerations:

* the heat dissipation are similiar (I use a Zalman ZM-NB47J sink), perhaps your board is slightly warmer.
* The gain are close to the surebords lower gain setting (I think the sureboard have 16 v/v gain and yours 15 v/v)

Now to my question: I don't need the volumepot so I'm think of removing it and solder the line in cables direct to the output
holes of the removed pot. Do I instead need resistors (lets say 20k) parallell between signal lines and signal ground to give my
source some load or can I skip that? According to Tripath's application/test diagrams it doesn't seems necessary.

Last edited by Kpax; 7th July 2010 at 11:38 AM.
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Old 7th July 2010, 11:46 AM   #417
sendler is offline sendler  United States
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Default Input termination

Quote:
Originally Posted by Kpax View Post
Now to my question: I don't need the volumepot so I'm think of removing it and solder the line in cables direct to the output

holes of the removed pot. Do I instead need resistors (lets say 20k) parallell between signal lines and signal ground to give my

source some load or can I skip that? According to Tripath's application/test diagrams it doesn't seems necessary.
You can try it with and with out an additional input termination resistor in place of the pot or even just connect the input cables to the output pins of the pot instead of going through the pot to hear what that sounds like and use the pot setting toward the quiet end of it's adjustment to give the termination load. The input gain setting resistors of the amp will form a virtual 20K load with the pot removed but my dac sounded a little better with a 20K resistor to ground right before the amp's input cap.
__________________
Scott
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Old 7th July 2010, 11:48 AM   #418
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Location: Rome, Italy
Quote:
Originally Posted by hifimediy View Post
Hi, refer to high pass filter formula.
fc=1/ (2*π*Ri*Ci ), π=3.14. Ri=20k
if you use Ci=2.2uF, fc=1/(2*3.14*20000*0.0000022=3.6Hz
means your amplifier will allow down to 3.6Hz siglal input.
we use Ci=3.3uF now, and will get better bass.
But don't try to use larger caps, which will lead to power off pop noise( will not happen on our boards, but we still not suggest use unnecessary large caps).
thanks.
You're right, because larger caps are slower in filtering:
Ft is 2.4Hz or 3.6Hz
if Ft = 1 / (2*pi*Tau), then Tau = 1 / (2*pi*Ft) = 66ms (or 44ms)

So the caps charging time will be = 3.5 * Tau = 230ms (or 150ms)
So larger caps are not the preferable choice for filtering DC.
Bye!
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Old 7th July 2010, 11:48 AM   #419
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After 10 minutes use the initial sound quality of the board in "stock" form is not good. A slight "ringing" in the upper treble and weak bass. At the same time it feels like "loudness" in the mid. The voice of Rickie Lee Jones feels even more intence. Hopefully it will become better after a while of break in.

I will make a SS psu later for the boards also.
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Old 7th July 2010, 12:59 PM   #420
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Quote:
Originally Posted by sendler View Post
You can try it with and with out an additional input termination resistor in place of the pot or even just connect the input cables to the output pins of the pot instead of going through the pot to hear what that sounds like and use the pot setting toward the quiet end of it's adjustment to give the termination load. The input gain setting resistors of the amp will form a virtual 20K load with the pot removed but my dac sounded a little better with a 20K resistor to ground right before the amp's input cap.
Thanks for your "input" Scott! I will try around with your suggestions.
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