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A NOS 192/24 DAC with the PCM1794 (and WaveIO USB input)
A NOS 192/24 DAC with the PCM1794 (and WaveIO USB input)
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Old 27th September 2018, 11:44 AM   #6681
Bfpca is offline Bfpca  Canada
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Join Date: Feb 2007
Location: Nova Scotia
A NOS 192/24 DAC with the PCM1794 (and WaveIO USB input)
I have considered the Broskie Unbalancer as well. My problem is that I would like to keep the balanced outputs. It should work just fine with 1 board. You have an output Z of 134 ohms so no trouble driving a tube input. With more boards you do not get more output voltage, only more current. The existing voltage level is much higher than typical current drive on most DACs. With a gain of 10 in the tube output stage you will end up with maybe 6 volts rms output IIRC, which is plenty. Right now I am running SE into a 12au7/6DJ8 Aikido preamp. Transformers are a great solution for letting you use the balanced outputs and also be able to drive SE or balanced input stages. They also act as a LPFilter, block DC, have excellent CMMR and are simple to implement. Problems are expense and the need for more output boards or a buffer.
There are lots of output options baked into the DDDac recipe by Doede and we can all pick what we like best. It’s nice to hear what everyone is discovering about this versatile and great sounding DAC
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Old 30th September 2018, 05:34 PM   #6682
Almeg69 is offline Almeg69  United Kingdom
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Join Date: Mar 2009
I am still optimising my 16 Dac boards DDDAC. I am running a 300VA transformer with 25 + 25 V secondaries which allows me to use a 2R2 resistor in the R1 position for extra smoothing.

I still want to run 16 Tent boards in the future so I am making sure I will have enough power to run them.

As the voltage and current is a lot higher than standard, I have made some PCB`s with wider tracks, hole centres for the MBR20200 changed to fit a DSA70C200 rectifier and changed the TIP122 holes for TIP142 which mounts underneath the PCB and onto the heatsink.

The R1, R2 and R6 holes moved and increased in size to take 1.4 mm wire for remote mounting.

C1 and C3 have centres for Mundorf 10000uF 63V capacitors. So now plenty of power available when I convince Doede to make me a main board with more buffers to supply the I2s to 16 Tent boards :-)
Attached Images
File Type: jpg 300Va PCB 1.jpg (805.8 KB, 195 views)
File Type: jpg 300Va PCB 3.jpg (937.2 KB, 188 views)
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Thanks, Alex.
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Old 2nd October 2018, 10:21 AM   #6683
edwtsui is offline edwtsui  Hong Kong
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Join Date: Oct 2017
Quote:
Originally Posted by Almeg69 View Post
I am still optimising my 16 Dac boards DDDAC. I am running a 300VA transformer with 25 + 25 V secondaries which allows me to use a 2R2 resistor in the R1 position for extra smoothing.

I still want to run 16 Tent boards in the future so I am making sure I will have enough power to run them.

As the voltage and current is a lot higher than standard, I have made some PCB`s with wider tracks, hole centres for the MBR20200 changed to fit a DSA70C200 rectifier and changed the TIP122 holes for TIP142 which mounts underneath the PCB and onto the heatsink.

The R1, R2 and R6 holes moved and increased in size to take 1.4 mm wire for remote mounting.

C1 and C3 have centres for Mundorf 10000uF 63V capacitors. So now plenty of power available when I convince Doede to make me a main board with more buffers to supply the I2s to 16 Tent boards :-)
How's the sound of 16 x DAC boards compared with 8x and 4x???
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Old 3rd October 2018, 02:49 AM   #6684
johno210 is offline johno210  Australia
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Join Date: Jun 2012
Impressive Alex,
You could perhaps also convert R2 to a choke ?
Perhaps a Hammond, Model 159ZG, 15mH,4 A,0.25 ohm,2.75lb
Model effects in Duncan PSU

Cheers Johno
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Old 3rd October 2018, 03:09 AM   #6685
johno210 is offline johno210  Australia
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Join Date: Jun 2012
Default 12V PSU heatsink for Darlington pair TIP 122

Hi there,

This may be helpful to those building 12V - PSU supplied by Audio Creative.

The heatsink that comes with the kit for TIP 122 is 50mm high there is a alternative heatsink that fits perfectly in PCB and is 63.5mm high, Model SK 129 63.5 (refer attachment)

Running 3-4 DAC boards with this larger heatsink makes TIP 122 run noticeably cooler.

The only disadvantage I can see to using this 63mm heatsink is the additional height as it may cause clearance issues with some enclosures.


Cheers Johno
Attached Files
File Type: pdf POWER SUPPLY HEATSINK DDDAC.pdf (266.3 KB, 35 views)
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Old 6th October 2018, 11:22 AM   #6686
Almeg69 is offline Almeg69  United Kingdom
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Join Date: Mar 2009
Quote:
Originally Posted by edwtsui View Post
How's the sound of 16 x DAC boards compared with 8x and 4x???
I have found that the more Dac boards used, the separation, depth and transient attack gets better.

Another mod to do on the main board, is to change the LF50 to a Micrel MIC29500 which has a 5A capacity and attach a small heatsink to it especially if you are using the Wave IO board.

It seems to cut down the bedding in time. I am used to waiting about 4 weeks for everything to settle down after doing any mods before its full potential is realised but I just tried it with the Micrel regulator and I had instant depth with the speakers disappearing as when fully bedded in.

If it improves even further, I will be very pleased with the results :-)
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Old 7th October 2018, 03:52 PM   #6687
Almeg69 is offline Almeg69  United Kingdom
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Join Date: Mar 2009
Quote:
Originally Posted by johno210 View Post
Impressive Alex,
You could perhaps also convert R2 to a choke ?
Perhaps a Hammond, Model 159ZG, 15mH,4 A,0.25 ohm,2.75lb
Model effects in Duncan PSU

Cheers Johno
Hi Johno,

Yes it could be a choke instead of the resistor. I am going to make a separate power supply so I can take the power supply out from the Dac case. I will have more room to try different value resistors and chokes without having to disable the Dac while I change things.

I will have the resistor/choke wiring points changed over to a plug/socket arrangement which will make swapping components a lot easier.
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Old 7th October 2018, 05:59 PM   #6688
juancho is offline juancho  United Kingdom
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Location: London, England
Does anyone know the current draw of 1 Tent Board? They consume a lot more than the old boards.
Thanks
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Old 7th October 2018, 06:55 PM   #6689
MagicBus is offline MagicBus  Greece
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Read post #6630
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Old 7th October 2018, 07:00 PM   #6690
juancho is offline juancho  United Kingdom
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Thanks. They consume a hell of a lot!
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