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Old 16th April 2012, 08:54 PM   #2371
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Quote:
Originally Posted by dixter View Post
Quick question... I noticed there are now pre-orders taking place for the ODAC boards...

Will a new forum be started or will we use the O2 forum for questions on the ODAC ??

right now I have three questions on the ODAC...

1) what is the part number for the output jack
2) what enclosure will be suitable for the ODAC, stand alone
3) anyone have a front/back panel design yet....for stand alone enclosure
Take a look at JDS Labs blog entry about the ODAC and options, one of which will be a fully cased standalone unit. At the moment they only have the assembled PCB available for pre-order. I imagine the other options will become active once the units arrive. I pre-ordered one on Sunday

I'd expect the Digital Line Level area would be the best place to start a specific ODAC thread ... But iirc the smallest of the BoxEnclosure cases is the correct size, not sure on the output jack or panel design...

Paul
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Last edited by BuildMeSomething; 16th April 2012 at 09:09 PM.
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Old 16th April 2012, 09:02 PM   #2372
Turbon is offline Turbon  Sweden
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OML - Digital Line Level - diyAudio , what a mess. Hopefully the thread stays on top fo a while...
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Old 17th April 2012, 03:39 AM   #2373
nezbleu is offline nezbleu  Canada
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Quote:
Originally Posted by ethanolson View Post
I know that the caps after the pot perform the same function, but I'm under the impression that the gain-stage OpAmp can be stressed a bit by DC so I'd like to stop it. If that's not actually the case, then I'd like some correction.
Ethan I feel you have had a lack of good advice here. You are absolutely correct that putting DC offset into the gain stage is a Bad Thing. Of course, it depends on how much DC we are talking about; a few milliVolts is no big deal, a Volt is way too much, I would definitely say 100mV is too much. It will produce early and asymmetric clipping in the gain stage opamps, increase power dissipation in the opamps, reduce battery life, increase distortion, etc.

I applaud your selection of polystyrene dielectric capacitors, but I fear that 100nF is far too low a value. Getting a capacitor of the value you need (more like 1uF) in a good dielectric material, even at a low working voltage, is going to mean a rather bulky cap. You might try evaluating something like stacked film caps, or PPS. But your best option might be to try to fit the blocking cap on the output of the sound card rather than the input of the amp; or just get a better sound card with negligible DC offset on the output!
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Old 17th April 2012, 05:16 AM   #2374
swalter is offline swalter  Switzerland
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Quote:
Originally Posted by dixter View Post
Quick question... I noticed there are now pre-orders taking place for the ODAC boards...

Will a new forum be started or will we use the O2 forum for questions on the ODAC ??

right now I have three questions on the ODAC...

1) what is the part number for the output jack
2) what enclosure will be suitable for the ODAC, stand alone
3) anyone have a front/back panel design yet....for stand alone enclosure
Hi, to answer your questions:

1) the part is 3.5mm Digikey CP-3523SJCT-ND
2) it will fit in the smallest B1 enclosure from boxenclosures, PCB size is 49 x 58 mm
3) JDS Labs has some pics in their blog how the panels might come out.
I will wait till I have the boards in hand for precise measurements of the cut outs that need to be made. Panels for the O2 upgrade and the stand alone version including an enclosure should then be available by mid of June in my shop (see footer for the link). For now I take pre-orders for the boards only.

Stefan
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Old 17th April 2012, 05:52 AM   #2375
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Quote:
Originally Posted by nezbleu View Post
Ethan I feel you have had a lack of good advice here. You are absolutely correct that putting DC offset into the gain stage is a Bad Thing. Of course, it depends on how much DC we are talking about; a few milliVolts is no big deal, a Volt is way too much, I would definitely say 100mV is too much. It will produce early and asymmetric clipping in the gain stage opamps, increase power dissipation in the opamps, reduce battery life, increase distortion, etc.

I applaud your selection of polystyrene dielectric capacitors, but I fear that 100nF is far too low a value. Getting a capacitor of the value you need (more like 1uF) in a good dielectric material, even at a low working voltage, is going to mean a rather bulky cap. You might try evaluating something like stacked film caps, or PPS. But your best option might be to try to fit the blocking cap on the output of the sound card rather than the input of the amp; or just get a better sound card with negligible DC offset on the output!
Hey, thanks. That's the kind of answer I was looking for.
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Old 17th April 2012, 11:45 AM   #2376
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You should really measure the offset though. The kind of asymmetrical clipping you mentioned can also be created in front of an output coupling cap. There still wouldn't be any DC offset on the output as long as the signal is kept out of clipping.

I would really be surprised if there were any soundcard shipping with DC offsets exceeding a few 10 mV.
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Old 18th April 2012, 05:16 AM   #2377
Mull3t is offline Mull3t  United States
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Having an issue with my newly built O2. All tests passed. When I fire the amp up and touch VR1 my left channel keeps on going out. I can get two channels to play if I wiggle the pot. This happens no matter if I have the amp cased up. It could either be one of two things - some hasty soldering or could my pot be bad? Otherwise, the amp sounds great. Tomorrow I'll try reflowing the pins to see if that solves the issue. I'd hate to have to pluck VR1 out.
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Old 18th April 2012, 02:03 PM   #2378
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Default Amazing album!

If you're looking for some music to give your O2 and headphones a good workout, check out the new 'Orbital' album, 'Wonky' - amazing stuff!
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Old 18th April 2012, 04:50 PM   #2379
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I have created a thread under 'Digital Line Level' for the ODAC. It will keep the O2 thread from losing focus.
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Old 18th April 2012, 07:19 PM   #2380
Mull3t is offline Mull3t  United States
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False alarm. Reflowing the solder on the VR1 pins did the trick.
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