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Post by Deleted on Sept 24, 2012 20:19:20 GMT
Go for the LME 49720HA`s Dawson, i like those, just thought i would try the 49990`s, nothing ventured nothing gained was my thinking, and i am more than happy with the resulting SQ, even if longevity does become an issue.
Mick.
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Post by Deleted on Sept 24, 2012 20:20:07 GMT
About the same time Mick got his I also got some LME49990s from the same guy to use in the voltage gain of my CHAmp.
When I installed them to replace the original LM4562s in a matter of seconds they got incredibly hot to the point of burning one of my finger tips, they smelled burnt too. I removed them inmediately and went to the part box for a while.
Later on I decided to try them in the I/V stage of the Xonar ST of my usic PC replacing the metal can LME49720HAs Mick had installed in lieu of the stock JRC2114s. The LME49990s don't even get warm there and there are seems to be no nasties, at least not any I can hear.
Funnily enough those metal cans, which are supposed to be exactly the same opamp as the LM4562, also get very hot in the CHAmp, probably due to they long "spider" legs that had to be added to the extra length of the socket pins compared to soldering directly to the PCN.
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Post by Deleted on Sept 24, 2012 20:56:34 GMT
\Hi Javier I put that down to better thermal management with the LM4562HA/LME49720HA as they have the same power dissipation. Perhaps that is why they sound better too ? In the SC (Jaycar) H.A. we fitted them with push on TO5 heatsinks. Usually the copper traces of a PCB are fairly fine for I.C.s so I doubt that a DIP8 version would get much additional heat dissipation from a typical PCB. I once remarked that the DIP8 versions must get hot inside their overcoats. Regards Alex
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Post by Deleted on Sept 24, 2012 21:15:53 GMT
I meant the the metal cans got hotter then the plastic LM4562 and couldn't be used for long, I think the reason has to do with too long a path to decoupling caps (DIP socket + long metal can legs) or at least that is what I think Frans said, maybe soldering them on the PCB will make them stable?. I gave up on trying anything else and been using the trusty ol' 4562s since then.
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Post by Deleted on Sept 24, 2012 21:26:35 GMT
I meant the the metal cans got hotter then the plastic LM4562 and couldn't be used for long, I think the reason has to do with too long a path to decoupling caps (DIP socket + long metal can legs) or at least that is what I think Frans said, maybe soldering them on the PCB will make them stable?. I gave up on trying anything else and been using the trusty ol' 4562s since then. Javier That's different if you are plugging them into DIP8 sockets. All of my LM4562HAs and LME497 10HA are soldered directly into the PCBs. If an I.C. that is used in these types of circuits becomes too hot for you to keep your finger on it for more than several seconds, then it has a problem, which is most likely due to it oscillating. Most will feel just a little warmer than ambient temperature. Regards Alex
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Post by daws0n on Sept 25, 2012 14:32:26 GMT
Thanks everyone, all this advice is a big help - I posted the same questions on headfi and asus' BBS and have had nothing but silence, so I really appreciate the food for thought. I think I will play it safe and go for the LME9720HAs metal cans... FWIW, the LME9990s appears to be a common replacement for the NE5532s but as mentioned power supply bypassing is important... The Essence One has some WIMA caps for this, but perhaps they are not up to spec? Funny you should mention the ST soundcard Javier - I actually have 3 LME9720HAs on order already for my Asus STX That upgrade was a bit of a no brainer since asus' released their own "upgrade kit" to replace the JRC2114s with LME9720NAs. It seemed logical to buy the slightly better metal capped versions instead. Do they fit OK under the metal shield? Your mention of the excessive heat is a bit worrying (they're on DIP-8 adaptors too), so maybe I should of gone for the cheaper plastic ones. Any road I can keep them by for the Essence One instead if they don't work out.
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Post by daws0n on Oct 9, 2012 13:06:50 GMT
Well that was a scary half hour! First off... Can someone recommend a decent IC puller? I was feeling frugal and got a chinese one for 99p off eBay - and it's total rubbish.. The teeth on it are so thin that it's hard to maintain a central grip on the chips - the first one I pulled only came out on one end! It was the output stage chip, and I thought I'd shafted my beloved DAC into RMA land in record time! I kept a cool head, but no matter what I tried the other half of the chip would not budge and I couldn't reseat it either due to the awkard angle... None of my precision screw drivers are small enough to prize it out, so after a bit of head scratching I had an idea. The saviour of the day being.... Dental floss This took some serious force to prize out of the DIP-8 socket, and the chip is proper mangled: I moved onto the LPF chips regardless and *almost* had the same trouble, but they were a bit easier. I ended up resorting to pin nose pliers as this "IC puller" was more trouble that it was worth. Thankfully all is working fine now it's back together - but I'll need to open her up again to do the I/V stage when the rest of the chips arrive. Sound wise I couldn't give a monkeys atm, I'm just glad it's still working Lesson of the day - don't use a £1 tool on a £400 DAC!!!
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Post by daws0n on Oct 11, 2012 11:33:55 GMT
Had a chance to listen properly last night - even with just 3 chips replaced the change is not subtle! The "edgy" treble/brightness has gone and the DAC's sound signature has more midrange weight/presence. Above all, there's a noticeable increase in bass output too. I found myself listening at lower volumes than usual on the preamp dial as the sound is much fuller. So far I'm liking it - and am hoping that replacing the I/V stage with LME9720HAs too will yield further improvement. It's surprising what swapping a few tiny chips can do
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Post by daws0n on Oct 16, 2012 17:49:12 GMT
Hmm interesting development... Asus are releasing a special "MUSE" edition using 6 x NJRC MUSE 01 opamps for the I/V and LPF stages: www.6moons.com/audioreviews/asus/1.htmlIt's considerably more expensive, so I checked out these chips are they're $50 each on digikey?! Wow, I sure hope they're worth the money - strange how Asus have gone for this seemingly little known estoric chip and not something reputable from Texas Instruments, Burr Brown et al.
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Post by daws0n on Oct 17, 2012 17:31:05 GMT
New chips have arrived and upgrade completed - all went far more smoothly this time If anyone else to thinking of attempting this, I would advice the following: 1. DON'T use an IC Chip puller, they're more trouble than they're worth 2. Rather than use a small pin nose pliers, try a set with a squarer/wider end. I found that the bigger teeth and larger surface grip on the chip made it much easier to extract them and they came out evenly every time (rather than pulling out on one side only).
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XTRProf
Fully Modded
Pssst ! Got any spare capacitors ?
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Post by XTRProf on Oct 20, 2012 1:39:33 GMT
That's interesting. Metal can type and how much? How is the sound in your Asus?
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Post by daws0n on Oct 20, 2012 14:41:52 GMT
They're standard DIP-8 plastic type, but very expensive - $50 per chip!
Asus are using 6 in the "MUSE" edition, and the mark up compared to the stock version is $200 extra... So, at least they're offering a reasonable saving.
The Xonar sounds much better after the upgrade - it's tamed the hot/splashy treble and has increased the bass output and midrange presence. Altogether it has a smoother and "bigger" sound. I was considering sell it and getting an M-DAC instead, but after replacing the NE5532Ps it sounds like a different source altogether.
Interestingly, swapping the LPF and output chip made the biggest difference, I've replaced the I/V stage since I've not noticed that much of a change.
heliharris - if you use the XLR or RCA ouputs, try swapping out the stock LM4562NA(s) for the metal can LME49720HA. It's worth the small cost IMO.
It's nice Asus have provided swappable sockets to allow tweaking like this, more manufacturers should do the same.
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