DIY dac ver.3 and cd-rom controller kit - diyAudio
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Old 15th August 2006, 05:38 PM   #1
Kip is offline Kip  United States
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Join Date: Jul 2003
Location: Sellersville, Pa
Default DIY dac ver.3 and cd-rom controller kit

This thread is for Thomas' dac ver.3 and cd-rom controller kit. I purchased the fully assembled dac ver.3 with transformer and the cd-rom controller. Once I figured out the wiring for the transformer for the USA, the dac powered up and worked. I purchased the upgraded caps (which are not installed) and a TDA1541AS2. I also have BB 627 opamps I would like to try also.

My first attemp with the cd-rom controller was not so good. I used an old 4x Creative Labs cd-rom drive. I purchased and briefly tried an ASUS CD-S520/A5 52X cd-rom drive. This drive seems to work well so far. It has not been hooked up to the dac ver.3 kit yet, but the cd-rom controller seems to control it.

I still need to supply a chassis, fix the U4 heat issue, connect the drive to the dac ver.3 and install all upgrades and test.
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Old 15th August 2006, 06:13 PM   #2
Kip is offline Kip  United States
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I hooked-up the Asus cd-rom drive using its 2 pin digital out to the dac. I used the TTL input on the dac and set S1 jumper to posision 2. All works well.
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Old 16th August 2006, 07:19 AM   #3
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yup mine works well on a LG CDROM. The play push button doesn't seem to work, but i can use the remote. Pray hard the remote doesn't spoil.

other than that, if i press the other buttons too much, my unit will hang and will need a 'reboot'.

however, i have a concern. I was told the digital out of the CDROM has a high current/voltage (5v) than normal digital output from CDP (<2v). Is the non profit DAC design to take that input at that voltage ?

Well, i did use it b4 with no problem. was thinking of using this on a long term, any problem ?

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Old 16th August 2006, 08:34 AM   #4
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hi kip


I will prepare a linear power supply 5V for the CD-rom, If U had interest, U an consderate to get one the estimate power supply will be a kit only. include the power transformers will less than USD50.( estimate value).

thx

thomas
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Old 16th August 2006, 11:20 AM   #5
Kip is offline Kip  United States
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Hi Thomas, I might be interested, but I would also like to run the cd-rom too so I assume a +12 would be needed too.

InfinityPWS, I think the TTL input is for the higher voltage digital input. I am not positive, so it would be at your own risk. I chanced mine and it works fine. I don't know the output voltage of the Asus rom, but assume it is the same as other rom drives.
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Old 16th August 2006, 06:42 PM   #6
Kip is offline Kip  United States
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Quote:
Originally by stefanobilliani
Thank you Jean-Charles for putting at the surface the noise problem ... I confirmed myself your findings immediately . Anyway the cure for it is also very easy to implement .

1) look at the Clock little board : Disconnect the GND from J1 to J85(main board )
This immediately eliminate the noise pollution.

2) now look at the SAA7220 dig. filter board :
disconnect GND form J1 to J75 ( main board).
Disconnect GND form J5 to J24 (main board) .

Probably was a ground loop . It would be nice if you measure again the noise at the chips after this trategy.
I tried this today and find it helps. I still get some hum when I turn the volume all the way up with no music playing. For normal listening levels the noise is now low. I need to separate my ground at the output which could help more.
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Old 16th August 2006, 11:52 PM   #7
Kip is offline Kip  United States
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I feel like I am writing to my self, but anyway.

I sat down for a listen to the dac and found that the Asus cd rom drive is causing some sort of a distortion issue with the dac. I put in old Genesis cd and heard tizziness in the voice and on some instruments. I then tried another cd and heard the same thing. It was like a high rattle in the sound. I then used my Eastsound E5 as a transport and the problem went away.

I am using the digital out on the Asus drive connected via TTL on the dac. Any comments?
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Old 17th August 2006, 07:51 AM   #8
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Quote:
Originally posted by Kip


I tried this today and find it helps. I still get some hum when I turn the volume all the way up with no music playing. For normal listening levels the noise is now low. I need to separate my ground at the output which could help more.
I received the dac just yesterday so I need to look at it carefully before finding more solutions .
Yes there is still some noise ...but :
a) I do not think it is coming form a ground loop anymore
b) I think the PS need more filtering capacitance just before the diodes
c) consider that the output level of the dac is exceptionally high and no muting circuit involved .

By the way Thomas ( tubelover) ... what type of diodes there are in this ver.3 ? thanks .
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Old 17th August 2006, 11:23 AM   #9
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Quote:
Originally posted by stefanobilliani


b) I think the PS need more filtering capacitance just before the diodes

Ehm I mean *after* the diodes .
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Old 18th August 2006, 03:33 PM   #10
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Need to specfy one thing : Tubelover dac V3 has and inverted phase analog output . I noticed in schematics that the 1541A output is loaded by 50 ohms before entering ( via 2k ohm) the Op Amp .
Elsewhere is explained that loading the output that way produces more distorsion ( and I believe noise ) .
Tonight I will try my JFET Pass -Cascode- Buffered output stage and will let you know how it goes, since it is a very quiet output stage .

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