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Old 21st December 2011, 11:05 PM   #1601
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Soldering Question:
I once read somewhere that cutting the lead first and flat to the pcb before soldering gives better performance. Because there are no sharp edges (from the cut) on the finished solder that can act as an antenna, if i remember correctly. Or is soldering first and cut the leads afterwards better. Option C is neither of the above. So what do the pro's think around here?
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Old 21st December 2011, 11:25 PM   #1602
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I think it's an urban myth :-)
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Old 22nd December 2011, 01:14 AM   #1603
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Little antennas? You'd be up in the buh-jillion Herz range or so fractional of any terrestrial frequency that it's not worth fussing over.

Anyway, if you want them gone (and there's one on the O2 you really need to have flush with the PCB), I'd much rather do whatever it takes to not have to file it down after it's soldered. My dikes have a little ramp to it so I could take some, but not all of the pile. Maybe that's good enough for you too.
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Old 22nd December 2011, 03:22 AM   #1604
nezbleu is offline nezbleu  Canada
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Quote:
Originally Posted by Jelle Schrijver View Post
Soldering Question:
I once read somewhere that cutting the lead first and flat to the pcb before soldering gives better performance. Because there are no sharp edges (from the cut) on the finished solder that can act as an antenna, if i remember correctly. Or is soldering first and cut the leads afterwards better. Option C is neither of the above. So what do the pro's think around here?
I don't know about the "antenna" business. In earlier times it was considered good practice to "clinch" leads, that is, to bend them flush to the PCB before soldering, but I think it was just thought to provide a more solid, secure joint. I don't think anyone would have seriously argued that it produced measurably better performance. But, in the days before wave soldering when everything was hand soldered, I think properly clinched leads were taken as a sign of "professionalism". Of course they also made everything harder to repair.
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Old 22nd December 2011, 09:57 AM   #1605
qusp is offline qusp  Australia
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Alexium, whatever opamp you choose for SE conversion, make sure it can slew really fast, not ridiculously fast unless you know how to tame such things as ADSL drivers, but fast enough to cope with the edges of a very fast waveform without distortion or ringing. i see no benefit whatsoever in using such a low output level, what is the point if you have to add it back in gain of the next stage and in the meantime have a much more susceptible low voltage, low current output? the idea of minimalism is to use enough to do the job properly and nothing more
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Old 22nd December 2011, 10:05 AM   #1606
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Quote:
properly clinched leads were taken as a sign of "professionalism"
There's even a special tool that bends the lead over and chops it off very short - http://hillscomponents.com/product.a...*&BrNavLink=No

I have one, but rarely use it, I generally prefer to cut the lead with sharp side cutters after soldering, looks just as neat.

Last edited by greenalien; 22nd December 2011 at 10:09 AM.
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Old 22nd December 2011, 10:55 AM   #1607
Alexium is offline Alexium  Ukraine
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Quote:
Originally Posted by qusp View Post
Alexium, whatever opamp you choose for SE conversion, make sure it can slew really fast, not ridiculously fast
Could you please make a guess on appropriate slew rate range?
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Originally Posted by qusp View Post
i see no benefit whatsoever in using such a low output level, what is the point if you have to add it back in gain of the next stage
No benefit, except, like I said, I'm using passive I/U converter, and it's resistance should be as low as possible, resulting in low output voltage (about 150mV).
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Old 22nd December 2011, 01:34 PM   #1608
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Quote:
Originally Posted by FREDtheDOG View Post
I think it's an urban myth :-)
LOTS of things in the audiophile world are myth. They usually start from a grain of truth, get convoluted by audiophiles, and are repeated often enough to create a widespread myth. The other posts are correct. At gigahertz frequencies little sharp bits to nowhere can matter--but not even remotely at audio frequencies.

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Originally Posted by ethanolson View Post
The PCM179x chips are great. Isn't it interesting how most all of the modern DACs aren't as good as the ones created 6-12 years ago?

This makes me wonder how the ODAC is coming along. I'm itching for details.
I need to do more research, but I'm not sure I buy most of "NOS DAC" arguments. It seems you're merely trading one minor set of issues for another. If modern DACs can be entirely transparent in listening tests (nobody can tell when they're added to the signal path), and measure extremely well, I'm not sure what further benefit ancient DAC chips have? Does anyone have any <i>objective</i> evidence supporting 10 year old DAC chips? See "urban myths" above.

As for the your ODAC question, I just posted an update on my blog. I'm still a few more weeks out before the next ODAC article.

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Originally Posted by Limp View Post
I just wanted to say a big thank you to everyone who have posted tips and tricks on how to make a face plate, with only the minimum of tools. I do not think I could have come up with eve half of this on my own.

This is the first time I've tried drilling into aluminum, and I think it proves that as long as you do not expect boutique quality looks and perfect alignment, there's nothing stopping you doing it on your own.
Thanks for posting the pictures. Your panel turned out well. I especially like that you showed it screwed down to the scrap wood. There have been lots of great suggestions in this (now massive) thread.


Quote:
Originally Posted by Alexium View Post
Could you please make a guess on appropriate slew rate range?
I would suggest following the reference design for whatever DAC chip you choose including using the same op amp. Slew rate really depends on the filtering in the DAC chip, what sample rates it will run at, and if you want to have enough slew rate to cover signals that only exist in test tracks (versus commercial recordings of music). Many DIY, and some "boutique" commercial designs, use op amps that are too fast.

Most really fast op amps are compromised in other ways (higher noise, distortion and/or power consumption with lower stability). Without the test equipment to measure your design, you really won't know what you end up with. You might hear a difference but it could be ultrasonic oscillation. You could mistakenly conclude it's because one V-I converter sounds different than another but it's really that one of your designs is completely unstable.

As others have suggested, trying to use a passive I-V stage is self-defeating as you just have to make up the gain later. It's safe to assume the best performance will be achieved with the manufacture's reference design. They're all trying to out perform their competitors DACs and the reference designs are the ruler by which they're evaluated and measured. If something improved the performance significantly, you can be reasonably sure they would incorporate it in the design.
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Old 22nd December 2011, 01:44 PM   #1609
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OK RS, so what are your thoughts as to using the ODA/ODAC as a preamp stage? I'm thinking of (eventually) using that for "critical listening" by hooking it directly to an amplifier (with no volume control). Or would the ODAC line out with a passive volume control be better? Let's assume the amp has a fairly high (~20KOhm) input impedance. Because the ODA is so transparent, would there be any harm in having it in the chain? Any benefit?
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Old 22nd December 2011, 01:57 PM   #1610
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@FloridaBear, I would very much suggest using the ODA (or some other high quality active preamp) after the ODAC rather than a passive volume control. Passive volume controls seem like a nice idea, and they're sometimes OK for non-critical applications, but they have some significant issues. The most notable problem is they dramatically increase the output impedance at typical volume settings of whatever is connected to them. That can create several problems and usually degraded performance over a decent active preamp. And their performance will vary depending on the components, and sometimes even cables, involved.
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