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Old 14th March 2003, 04:31 PM   #1
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Default I started my new Tube DAC

I started my new hi quality DAC using this very good desing:

http://members.brabant.chello.nl/~m....tml/dactop.htm

I got all the parts and just completed the Low Voltage Power Supply.
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Old 14th March 2003, 07:53 PM   #2
wazzup is offline wazzup  Netherlands
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That looks really good!

I was looking into that DAC myself too. I wonder how it sounds, keep the info about your project comming!

Good luck! (by looking at your board I think you won`t let the outcome depent on luck )
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Old 15th March 2003, 04:58 AM   #3
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Default I will keep you posted

I would be great to share with someone else on this project. But don't expect to fast a result. I'm doing this part time with the familly, 3 boys, ouf...

I will start to assemble the main DAC PCB that I got from Guido Tent (Great guy). You can buy from him with confidence. I also bought two XO low jitter clock modules for my two CD Players. I didn't have the time to install them either...

Bye.

SB
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Old 7th April 2003, 03:05 AM   #4
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Default DAC PCB almost finished

Here the DAC Main PCB amost finished. You can see the Jensen caps stacked together. I had to use 0.01 and 0.022 uf caps in parallel to get the needed 0.033uf cap. I needed to install the two 4.7uf MKT4 (big blue caps installed up side down) in a peculiar way. They were bigger than the one used for the desing of the pcb, probably 160V instead of the 250V that I got.

I hope that the Jensen are worth the money that I spent. They are really expensive...
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Old 7th April 2003, 03:11 AM   #5
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Default HV Tube output amp

Here the High Voltage Tube Amplifier PCB almost completed. The power supply choke will be connected externally using the molex connector. The big orange connector will connect the input 120V and the custom HV and filament transfo. Check the big Jensen Cap, copper foil and silver leads. I'm also using Riken, all copper, resistors in the signal path. Circuit is using Svotek 6922 tube dual triode and 6X4 Rectifier Tube.

Bye.
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Old 17th April 2003, 02:47 AM   #6
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Default Here the Tube output completed

Here my new tube voltage gain stage for my new DIY DAC. It is using a HV 6X4 Tube rectifier and a double triode Svotek 6922. The 6922 is using DC filement voltage using schottky rectifer and LM317T regulator. The HV is filtered using a CLC filter with two 47uF cap. an a Hammond 9H, 40ma choke.

And I just forgot. I'm also using in the signal path all copper Riken resistors and the very good Jensen copper foil and silver lead.

I will listen to this beauty soon...

Comments are welcome. Any suggestion on my tube choice will also be appreciated.

Don't be too hard on me, it is my first tube circuit. Better late than never.


Since the DAC is not completed, here a few measurements to test everything:

Bandwidth (0.767V, 1Khz reference): 20Hz-300Khz in 50 Kohms

Voltage Gain (in 50Kohms)
0.5Vin = 22.5
31.6mVin (Vout=0dB) = 24.2

Distorsion (in 50Kohms, Vout 0.767V)
100Hz: 0.5%
1Khz: 1.2%
10Khz: 1.4%
20Khz: 1.5%

Are these values of distorsion typical or an other tube brand can give me better values?
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Old 17th April 2003, 02:49 AM   #7
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Default And the DAC PCB back view

Here you can see that most resistors are SMD and are mounted under this nice 4 layers PCB.
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Old 17th April 2003, 02:52 AM   #8
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Default Here where I took the measurments

Here where I took the measurments. You can see my custom HV tranfo made by Victoria Magnetics. Incredible service, good communication and good guys. Call them for any custom needs.

Thanks again...
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Old 17th April 2003, 05:09 PM   #9
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Default Re: Here the Tube output completed

Quote:
Originally posted by Algar_emi

Distorsion (in 50Kohms, Vout 0.767V)
100Hz: 0.5%
1Khz: 1.2%
10Khz: 1.4%
20Khz: 1.5%

Are these values of distorsion typical or an other tube brand can give me better values? [/B]
Hi there

neat work !

Distortion looks higher than normal, we meaured -51 dB at 1 kHz

http://members.chello.nl/~m.heijlige...asurements.htm

(scroll down)

which equals about 0,3%

which tube (brand) did you use ?

How does the residue of distortion look like ? (I hope you can monitor that) Is it harmonics or maybe 50 / 100 Hz ?

Guido
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Old 17th April 2003, 05:12 PM   #10
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Default Re: DAC PCB almost finished

Quote:
Originally posted by Algar_emi
Here the DAC Main PCB amost finished. You can see the Jensen caps stacked together. I had to use 0.01 and 0.022 uf caps in parallel to get the needed 0.033uf cap. I needed to install the two 4.7uf MKT4 (big blue caps installed up side down) in a peculiar way. They were bigger than the one used for the desing of the pcb, probably 160V instead of the 250V that I got.


Hi all

I now have limitted stock on the original 4.7 uF caps intended for the PLL loop filter. These will fit the PCB, I admit, these are quite hard to get.
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