If you want to do a budget version then why not use the Buf634P as that's about half the price of the identical(?) 49600.
Otherwise, my own findings using my ears, are that the plastic chips are grossly inferior to the TO99 version of the 49720 which is very inferior to two single TO99 49710HA.
So unless someone really does not care about quality and needs bargain basement, why sink the ship for a few $ of tar?
Otherwise, my own findings using my ears, are that the plastic chips are grossly inferior to the TO99 version of the 49720 which is very inferior to two single TO99 49710HA.
So unless someone really does not care about quality and needs bargain basement, why sink the ship for a few $ of tar?
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The BUF634F is $1 or $2 cheaper than the LME49600 in a similar TO263 package. The P (DIP) version would likely have thermal issues in this application. It might be worth looking into the BUF634F if it really does perform the same but it would only save a couple bucks.
I've heard the TO99 "sounds better" thing a few times before but I've never experimented with those versions myself. I met one of the National audio guys at a trade show and he said something like it was "audiophile myth" and had no basis in fact. I can't say for sure either way. I can say the plastic LME4xxxx packages I've used measure, and sound, great.
I'm one of those practical engineer types. If there's objective evidence why something more expensive might be better, I'm happy to consider it. But, in this case, I'm not aware why the TO99 version is worth the nearly $40 higher cost ($6 for two LM4562NA's vs $44 with the LME49710HA).
I don't think I'm proposing anything that even comes close to "sinking the ship" unless someone has a balanced source and wants a balanced input. The OCP design in this thread also uses the plastic SOIC packages and National's performance data, as well as OPC's own excellent measurements, are hard to argue with.
I'm aiming more for "hard-to-beat measured performance at any price" sort of amp rather than a cost-no-object design.
Here's an ex-National guy who says they do.
http://www.diyaudio.com/forums/solid-state/132471-national-opamp-inflation.html#post1707305
I'm both scientific and pragmatic about the 'sound' of components. I ran in the various versions for weeks before comparing them. They often sound dreadfull at first and really needed three weeks at least.
Can your instruments demonstrate that change by measurement?
The OP, Owen, said he felt the smt chips he used were the best sounding beating his previous and possibly my favourite, the AD797 which I've not yet compared with the now very run in 47910HA.
I could buy the 5 pin BUF634 for about half the cheapest price I could find the 49600 for. I forget just now if that figure was skewed by the fact I'm in the UK and so have to pay 20% tax plus £10 duty on imported items.
On a trawl yesterday I started to find comments by DIY constructors over on HeadFi referring to 'stacked' 634's. I've not had time to look into those threads.
http://www.diyaudio.com/forums/solid-state/132471-national-opamp-inflation.html#post1707305
I'm both scientific and pragmatic about the 'sound' of components. I ran in the various versions for weeks before comparing them. They often sound dreadfull at first and really needed three weeks at least.
Can your instruments demonstrate that change by measurement?
The OP, Owen, said he felt the smt chips he used were the best sounding beating his previous and possibly my favourite, the AD797 which I've not yet compared with the now very run in 47910HA.
I could buy the 5 pin BUF634 for about half the cheapest price I could find the 49600 for. I forget just now if that figure was skewed by the fact I'm in the UK and so have to pay 20% tax plus £10 duty on imported items.
On a trawl yesterday I started to find comments by DIY constructors over on HeadFi referring to 'stacked' 634's. I've not had time to look into those threads.
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Thanks for the added info. You also helped solve the mystery of the "National guy" here on diyaudio. I corresponded with him here a few years back but couldn't remember his member name. But he's not the same one I met at a trade show.
Anyone who's read much on my blog knows I'm with Sean Olive on sighted listening tests. I believe it's really hard to filter out all the subjective bias when you know what you're listening to and there's lots of evidence to back me up on that.
I know National did some blind tests when they developed the LME4xxxx series of audio parts and had a respectable listening room to do it in. I don't know if they ever did a blind test of the TO99 vs plastic packages. It would certainly be an interesting thing to try sometime.
I'm going to start my comparison adventure on a more "macro" level. I hope to compare the cheap cmoy, to a respected Class-A discrete design, to an ultra-low distortion "analytical" design (this one). The testing will include measurements, blind listening by several people, and audio differencing (subtracting the input from the output and analyzing what's left over playing real music into real headphones).
Once I get past the broad brush strokes of comparing the above, I can see if it's justified to start worrying about some of the smaller details--like IC packages. The plan is to ultimately go as far as required until no further improvements are found using the above methods.
Anyone who's read much on my blog knows I'm with Sean Olive on sighted listening tests. I believe it's really hard to filter out all the subjective bias when you know what you're listening to and there's lots of evidence to back me up on that.
I know National did some blind tests when they developed the LME4xxxx series of audio parts and had a respectable listening room to do it in. I don't know if they ever did a blind test of the TO99 vs plastic packages. It would certainly be an interesting thing to try sometime.
I'm going to start my comparison adventure on a more "macro" level. I hope to compare the cheap cmoy, to a respected Class-A discrete design, to an ultra-low distortion "analytical" design (this one). The testing will include measurements, blind listening by several people, and audio differencing (subtracting the input from the output and analyzing what's left over playing real music into real headphones).
Once I get past the broad brush strokes of comparing the above, I can see if it's justified to start worrying about some of the smaller details--like IC packages. The plan is to ultimately go as far as required until no further improvements are found using the above methods.
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Back to "The Wire" I wanted to report that the oscillation problem I had was only due to the temporary (bad) wiring I did for testing. With proper cables and shielding, it is ultra silent. No stopper resistors needed.
Thanks,
Davide
Thanks,
Davide
Hi Davide,
That's great news! I was pretty sure it was just a wiring/layout/chassis/grounding thing, but I'm glad you were able to confirm that it works well with proper wires.
It is important to keep in mind that it's an extremely wide bandwidth design, as as such, it does require a fair bit of care in connecting it up and using it.
Where are other people at with this build? I know 37 of these went out the door, but I certainly haven't heard back from 37 people! I've since built a second one for work which I use daily running straight out of an Analog Devices reference DAC and powering a pair of AKG 240 MK II headphones. I don't like the AKGs anywhere near as much as the Denon phones I use at home, but they're still pretty decent and definitely benefit from the better amp.
RocketScientist:
That was a pretty blatant thread hijack, but what's done is done. Next time it would be best to start your own thread and generate interest that way.
Regarding your proposal, I would really suggest steering clear of the DC servo circuit used on the reference national design. It's a poor implementation, and it actually has significantly higher DC offset at the output than a properly implemented DC coupled circuit. As far as BW limiting goes, it certainly would be the easier way to go, and would make layout and implementation much less critical. As with all things though, BW limiting always comes with some drawbacks.
As for the cheaper dual op-amps, you might want to look closely at the limitations of dual pack op-amps, and also at the implications in terms of layout. The best op-amps out there generally only come in single pack variants, and at best you stand to save a few dollars. If you're going to put all that work in, then $15 worth of op-amps should be the least of your worries.
If you did an SE variant, then all you would need is 1 op-amp per channel, one LME49600, and you'd be all set. At that point using a dual op-amp to save money would only net you about $2 in savings, and wouldn't be worth it.
The argument with PTH vs. SMD parts is a moot point in my book as well. If you can solder one properly, then you can solder the other. SMD nearly always makes for better layout, and it's quicker to solder once you get the hang of it. It's honestly no harder to do than PTH parts.
Cheers,
Owen
That's great news! I was pretty sure it was just a wiring/layout/chassis/grounding thing, but I'm glad you were able to confirm that it works well with proper wires.
It is important to keep in mind that it's an extremely wide bandwidth design, as as such, it does require a fair bit of care in connecting it up and using it.
Where are other people at with this build? I know 37 of these went out the door, but I certainly haven't heard back from 37 people! I've since built a second one for work which I use daily running straight out of an Analog Devices reference DAC and powering a pair of AKG 240 MK II headphones. I don't like the AKGs anywhere near as much as the Denon phones I use at home, but they're still pretty decent and definitely benefit from the better amp.
RocketScientist:
That was a pretty blatant thread hijack, but what's done is done. Next time it would be best to start your own thread and generate interest that way.
Regarding your proposal, I would really suggest steering clear of the DC servo circuit used on the reference national design. It's a poor implementation, and it actually has significantly higher DC offset at the output than a properly implemented DC coupled circuit. As far as BW limiting goes, it certainly would be the easier way to go, and would make layout and implementation much less critical. As with all things though, BW limiting always comes with some drawbacks.
As for the cheaper dual op-amps, you might want to look closely at the limitations of dual pack op-amps, and also at the implications in terms of layout. The best op-amps out there generally only come in single pack variants, and at best you stand to save a few dollars. If you're going to put all that work in, then $15 worth of op-amps should be the least of your worries.
If you did an SE variant, then all you would need is 1 op-amp per channel, one LME49600, and you'd be all set. At that point using a dual op-amp to save money would only net you about $2 in savings, and wouldn't be worth it.
The argument with PTH vs. SMD parts is a moot point in my book as well. If you can solder one properly, then you can solder the other. SMD nearly always makes for better layout, and it's quicker to solder once you get the hang of it. It's honestly no harder to do than PTH parts.
Cheers,
Owen
Nice Job!
Regarding the high frequency concerns...Was the measurement source derived from a computer or stand-alone test set? Computers have quite a lot of RF energy...if it measured well at close proximity and/or was driven by a computer, I think I would see how it does without the inductors ad filtering....
Regarding the high frequency concerns...Was the measurement source derived from a computer or stand-alone test set? Computers have quite a lot of RF energy...if it measured well at close proximity and/or was driven by a computer, I think I would see how it does without the inductors ad filtering....
Sorry about that. I, like some others here, missed getting in on your buy. I didn't get the impression you were planning a "2nd round" but I probably should have asked? I did start another thread, and interestingly, it largely turned into a debate of the LME49600 vs BUF632 vs TPE6120. I personally think the LME49600 is a better choice than the BUF632, but the TPE6120 seems to warrant further investigation--including if the TI recommended 10 ohm series output resistor can be eliminated. So the "National Reference Design" is on hold pending that evaluation.
As for the rest, thanks for your suggestions. I'll look into the servo issue. And everyone has their preferences, priorities, etc. I agree SMT has some layout advantages. And with a really wide bandwidth design, those could be significant in some circumstances. But I've encountered lots of people who either don't like, or don't want to even try, surface mount work. I've done lots of both and certainly prefer through hole.
As for costs, I normally wouldn't cost optimize a "one of" DIY design for myself. But if dozens of people, or more, are going to build one, then I believe it makes sense to consider providing lower cost options to those who are more cost conscious, or otherwise look at ways to reduce the cost with no change in performance.
@AUDIODH, the finest audio measuring instrument in the world is the Audio Precision SYS-2722. It can measure noise down below the inherent Johnson Noise in a single 4.7K resistor and costs more than a nice German luxury car. And it's entirely run from a computer. It's proof having a computer nearby doesn't mean inferior measurements. In this case it's better than any stand-alone audio instrument I know of.
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Thanks, I've used the Portable One and System One & Two in production...indeed the industry standards!
opc:
Any chance you would do another run of PCBs if there is sufficient interest?
Best regards,
mike-sp
Any chance you would do another run of PCBs if there is sufficient interest?
Best regards,
mike-sp
I am very happy with this circuit, but i did not figure out a nice way to enclose it.
From one side i don't like the idea of the separate psu, but on the other side it will have a funny shape if you put everything in one box, using the onboard connectors.
Could you post some pictures of your build, I need some inspiration.
Thanks,
Davide
From one side i don't like the idea of the separate psu, but on the other side it will have a funny shape if you put everything in one box, using the onboard connectors.
Could you post some pictures of your build, I need some inspiration.
Thanks,
Davide
not quite sure what you mean there, 'the wire' uses lme49600/10 buffers from national. if its the buf634T you used its similar, but not the same, the national chip is higher performance as well
sorry Davide, i havent cased mine up yet either. btw finally making good and consistent progress with the matching and getting results on par with opc. it took a couple more steps to fully get rid of the dc, but all good now will have it all done by this time next week
I contacted OPC months ago about sharing his PCB files and he was positive so a second run is possible but he haven't answered me since 6th March. Any news of him?
not to me they arent (actually the lme49610 i used edges the ti chip out ever so slightly), i used buf634 for years and while a nice buffer, its not nearly as dynamic as the national chip. illogical i know, but in actual tests against another of my amps with lme49990 and 3 stacked buf634 the wire wins in dynamic performance. perhaps its down to owens layout, but i have always preferred the lme buffer. the national chip allows larger swing +/-22v and swings closer to the rails. in fact a mod i considered for the wire was a separate supply for the buffers of higher voltage
opc is around, but i dont know that pushing for him to share the cad files is all that kosher. he may do it, but it should not be expected. (not saying you are)
opc is around, but i dont know that pushing for him to share the cad files is all that kosher. he may do it, but it should not be expected. (not saying you are)
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Thanks. Good to know he is alright.
I asked him nicely and he offered some help . He is a nice guy. I just lost contact after that.