BUILD THREAD - A New Take on the Classic Pass Labs D1 with an ESS Dac - Page 44 - diyAudio
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Old 22nd April 2012, 07:42 PM   #431
NicMac is offline NicMac  Italy
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Do,

I may have a board for you.....

PSU section stuffed (except for regulators), components from original opc kit, mosfets (matched by qusp), power resistors and even a custom made toroid.
Basically everything except for heat sinks and chassis - the most difficult part of the build.

Selling because I have two many projects and now realize that I will never be able to make something as nice as salomon.....
I will post later over at the swap meet.

Ciao,

Nic
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Old 22nd April 2012, 08:27 PM   #432
Salomon is offline Salomon  Germany
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Hello,

thank you all for the praise!
Owen it is no problem to mount the Buffalo III Board to the first version of mainboard.
You only have to be sure that the side with the ribbon cable shows to the power supply side.
To turn the ribbon side to the input side of the mainboard is not possible, because the screw holes of the Buffalo are not symmetric. There is not much space between the ribbon cable and the capacitors of the mainboard. But it is ok.
In December I got a Buffalo III board and there was no other option than to integrate it to the mainboard, that I got from you.
With the Buffalo III board now it it easy to integrate a high quality digital volume control and you get it free with the Buffalo III.
The temperature:
Normally nobody is so crazy to squeeze such a “hot DAC” into such a little case.
But the problem is, I haven’t more space in my Hifi Rack (see the photo).
So I tried to modify the case. It is only 230 x 280mm and there is no more space between the parts.
But now it is ready and the case is good for 4 hours music.
I will test it the next weeks and maybe make one more little changes to get a longer time before the temperature gets high. But for the next time I wanna enjoy the sound.
Owen it is a good idea to take the next bigger size of this case series and additionally install bigger heat sinks on the left and the right side of the case.
But be sure to integrate four L-formed heat sinks (look at my sketch) to get enough of the heat coupled to the left and right side and to the top of the case.
Owen it would be nice to get a little bit more gain in the output stage. Have you an idea how I should to it. Change the source and the drain resistors? Which values?
My Aleph-X is not very sensitive. I use the DAC between my Trinnov Optimizer ST2 Hifi and the Aleph-X amplifier. The sound comes from my BigCDPro transport.
I only use the digital signal path of the Trinnov.
It would be nice to get 3dB more, better 6 dB more gain.
If it is not possible or difficult, then I have to change the value of the input resistors of my Aleph-X. Can you simulate possible changes to get more output gain in the DAC?

Regards
Horst
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Last edited by Salomon; 22nd April 2012 at 08:32 PM.
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Old 29th April 2012, 02:19 PM   #433
Salomon is offline Salomon  Germany
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Quote:
Originally Posted by NicMac View Post
Do,


........ heat sinks and chassis - the most difficult part of the build .....


Ciao,

Nic
Yes this is correct.
To dissipate the heat of this DAC design is the biggest problem.
Owen, should we think about less rail voltage?
Does it really sound bad with lower rail voltage?
If you wanna use this DAC with +- 45V for a longer time, you need a big case with big heat sinks. Also the regulaters get very hot in a closed case.

Owen, because I get no answer from you based on my inquiry about modify the output stage to get more gain, I think it is not possible. Is this correct?

Where are all the other DAC builds?
The first group buy was including 37 boards.
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Old 29th April 2012, 03:11 PM   #434
opc is offline opc  Canada
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Hi Salomon,

It's certainly possible to get far more gain by simply increasing the resistor values for the four power resistors. Doubling the value will double the output voltage swing.

It will also halve the current through each leg, which will halve the power dissipation.

So, in short, you get twice the gain, half the power dissipation, and less performance in terms of distortion.

As for the absolute impact on sound, you'll really have to try it and decide for yourself. The results are easily measurable, but may not be audible.

Regards,
Owen
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Old 29th April 2012, 03:27 PM   #435
Salomon is offline Salomon  Germany
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Hi Owen,

thank you for your quick response.
I think I will test it and then tell you about the sound.
Maybe this will also be a option for other builders.
67 watts are too much for me for a DAC in my little case. I hope that it is still possible to get a good performance and additional more gain changing the resistors to a higher value.

Regards,
Horst
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Old 29th April 2012, 04:31 PM   #436
qusp is offline qusp  Australia
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well tbh when I saw your case I thought you were being quite optimistic, hopefully you can sort it out without too much impact on the sound, but for me the sound is good enough that I dont mind having a dac that needs this much heatsink. your case is too small for any optioned up modern dac (particularly ess) regardless of IV stage IMO (just look at what is required for the SEN jfet IV). Me i'm building 4 channel dac and its a 2 box build. in my experience it does sound slightly more constricted at lower voltages, and in my testing for matched fets the behavior of the fets at lower voltage was easy to see. YOU are free to lower the voltage, ME, not a chance.

Last edited by qusp; 29th April 2012 at 04:34 PM.
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Old 30th April 2012, 03:26 PM   #437
Salomon is offline Salomon  Germany
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Hi Qusp,

I do not wanna decrease the rail voltage, because I know that it is not good for the sound. Maybe because the FETs then are running with a very low Drain-Source voltage (only about 10V).
+- 45V is my choice too. Then the Drain-Source voltage will be about 20V - 1,7V = 18,3V
I only have to order four caddock MP930-750 Ohm. That´s all.
And then will change the drain resistor to 400 Ohm and the source resistor to 750 Ohm. So I can use the Source resistor as the Drain resistor and must not order both values.
This modification is doubling the output level and decrease the power consumption nearly to the half. The drain-source voltage stay nearly the same (only about 1V difference) as before the modification, but the current is nearly the half. Also the Gate-Source-Voltage is nearly the same (from 4,20V to 4,15V)
Because my Input resistor of the power amp is about 20 KOhm and the XLR-Cables are very short, I think it will sound good.

Owen maybe you can simulate the difference between the two versions, especially THD+N
That would be very fine. Thank you for all.

Regards,
Horst
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Old 18th May 2012, 08:06 AM   #438
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I am ordering components from RS, can someone advise me for SMD, especially for capacitors, must I use the same package/case as specified in the BOM? For example: 1uF 100V must be 1210? Since RS has MOQ of 100 for some components. Thanks
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Old 18th May 2012, 08:33 AM   #439
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Yes you will need same size smt package.

Is there any reason to order from rs? For us in Australia we find they have obscene markup and shipping costs and is normally better to order from mouser or digikey and pay for their international shipping.
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Old 18th May 2012, 09:47 AM   #440
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Quote:
Originally Posted by hochopeper View Post
Yes you will need same size smt package.

Is there any reason to order from rs? For us in Australia we find they have obscene markup and shipping costs and is normally better to order from mouser or digikey and pay for their international shipping.
I take your advice and ordered most of the parts from digikey although it is more expensive than Australia but still cheaper than RS Hong Kong. Thanks. But I have another problem, I can't source the Pulse Transformer in Hong Kong

It is only for balance input, may be I will try other brand.

Last edited by bigpandahk; 18th May 2012 at 09:50 AM.
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