Measurable probably yes when the Ic´s are pushed to their limits, audible difference I do not thinks so....for standard use It seems to me very hard to hit those limits and hear a palpable difference.
Maybe some guys here with very demanding cans can gives us some insight on the matter.
It's important to me as I wish to do sustained, high power sine wave testing. It's how I make my headphones sound wonderful. As it happens I also have a modded Fostex T50rp's and the mod I chose, while cheap, results in a large bump in the low mids that results in a painful shoutiness. That, and other artifacts, need equalising out.
I've got a question for everyone. My soundcard has some DC offset that I want to combat with DC blocking caps on the O2's input. What do I need to know in terms of ideal placement, cap size, and cap type?
I thought I'd just place one of these in front of R3 and another in front of R7. Am I OK here?
I thought I'd just place one of these in front of R3 and another in front of R7. Am I OK here?
Now ethanolson et al. Is there really any room in a sence of bettering this design? Remember that this was put toghether by a rocketscientist. Horray, he showed his outstanding qualities. Actually I mean it.
We are as I see it put in the corner. OK, by me - dull, but ok in the sence of that I can't better the really good SQ it gives. I can only go horray again.
Brgds
We are as I see it put in the corner. OK, by me - dull, but ok in the sence of that I can't better the really good SQ it gives. I can only go horray again.
Brgds
I don't think I'll be bettering the measurements... if anything, taking a slight hit. I think it's a good move since my PC soundcard is putting out some DC. I haven't measured it with a meter, but when I have it feeding my DAW, the baseline hovers noticably high and I have to employ DC offset correction in the software to correct the waveform. It also causes clipping at and near 0dBfs which is something I want to correct passively.
FYI, the clipping, of course, only occurs when I have it being recorded at levels without any margin. Audio output from the line out is just a bit higher in voltage on one side than the other, so I'm not hearing any clipping with my ears just for listening purposes. So this is mainly to preserve the gain OpAmp and to keep the audio as balanced as possible.
FYI, the clipping, of course, only occurs when I have it being recorded at levels without any margin. Audio output from the line out is just a bit higher in voltage on one side than the other, so I'm not hearing any clipping with my ears just for listening purposes. So this is mainly to preserve the gain OpAmp and to keep the audio as balanced as possible.
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Then again your PC problems are quite OT here. Lower the output from your soundcard would be the natural answer unless you consider it to be the rule...
2V input doesn't seem to be 2V to everyone. If you want 1.4V - loose some energy at the input stage.
Brgds
2V input doesn't seem to be 2V to everyone. If you want 1.4V - loose some energy at the input stage.
Brgds
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.
So your looking for a solution to something that's not to known being a problem in this universe?
Brgds
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
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
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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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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!
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
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.
I would really be surprised if there were any soundcard shipping with DC offsets exceeding a few 10 mV.
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.
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!
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!
I have created a thread under 'Digital Line Level' for the ODAC. It will keep the O2 thread from losing focus.