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dacboy

LME49990/LME49600 headphone amp

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Hi all,

Just saw this yesterday and thought you might like something new to do

for 2011. :)) Well this is just a standard hookup of an instrumentation amp ( 3 opamps-LME49990) and

a high current buffer LME49600.Now these are National Semiconductors new line of high performane

opamps designed for audio as most opamps are for industrial uses.

 

The thread in diyaudio -

http://www.diyaudio.com/forums/headphone/1...ifier-pcbs.html

 

He is offering 2 channel amp pcb + power supply at US or CAN $20 combo only and partial kit at $98 but may

go down as more people join in.But I think you can save a little if you source locally but if you don't want

the hassle he says he's not doing at cost as last group buy he made a loss .

Anyway I checked Farnell singapore ( they now renamed their site- 14 elements sg)

PS. The pcb is smt (surface mount technology) so may be tricky for some people.

 

LME49990 - $7.21 you need 3/channel total= 6

LME49600 - $13.70 at 1/channel total=2 subtotal = $70.66 before GST.

 

Edit- Sorry,mistake in calculation ,now show correct amount.

Looks like you may really save if you add $20 pcb + smt resistors + caps. :think:

 

You can do the math and it's not a cheap project.If I had my way I'll not use instrumentaion style circuit

but modify the 3 opamps and connect them in parallel by doing so you lower the noise level like Nelson

Pass' Pearl2 phono amp.He parallels 4 jfets so that will get 6db reduction of noise level theoreticallly.

But bear in mind if you modify the amp it may not be stable so there's the catch. :helpsmilie:

 

I will not use the supplied generic power supply but make a Walter Jung super regulator instead and that will

move this amp in the real very high performance level also theoretical. :))

 

Super regulator links: the most recent is the 2000 version.Be careful with the part selection ,use the recommended

ones like PN2907 and not 2N2907 and LM329 voltage reference.If you can't get LM329 then use

a 6.8 zener(noisy) or series other voltage ref. but costly,then of course there are cheaper alternatives.

 

Edit- wrong part number X 2709 X previous. :blush:

Super regulator is a challenge to construct from what I've read,if you are not up to it then stay with conventional type.Which is based on the same principle except with regards the refinements and complexity.

 

http://waltjung.org/Regs.html

 

There's one easy to read page titled opamp regulators ,see if you can search it.

 

So just see the pics and test results made with a Audio Precision test setup.Quite impressive.

But then again despite the claims I cannot vouch for the sound quality as it varies with individual's

taste and experience.

Welcome 2011. Cheers. :thumbup:

Edited by dacboy

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I'm interested to know on real life test, how much improvement on the sound quality, using Walter Jung super regulator compares to common regulator such as LM317.

 

Have you ever test them?

 

Thanks for the nice article!

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I'm interested to know on real life test, how much improvement on the sound quality, using Walter Jung super regulator compares to common regulator such as LM317.

 

Have you ever test them?

 

Thanks for the nice article!

 

Hi bribadi,

I have not built the jung super regulator as you know the people who help

to implement it at diyaudio is very protective of it's IP ( interlectual property) of the circuit

but as you know one cannot copyright a circuit so it is in public domain so to speak.Nonetheless jung

had some clever tricks done.On paper the design is easy but when you want to make it there are a number

of obstacles such as the components used like LM329 which by now could be obsolete or NS only makes it

as a 6.8v voltage reference is not commonly used nowadays though you can still find it in electronic catalogs.

The last revision was in 2000.Looks like it's largely "forgotten" and the following paragraph may reveal the "difficulty".

 

If you try to substitute the original components or change values you may get an unstable circuit.

so this is a major hurdle as I see it.I am trying to find a less complicated solution of course with not as good

performance as jung super regulator but still serve a purpose in high end audio like a MC phono stage.The Lm49990

can be a part of the solution.By the way the jung super reg does use a LM317 as preregulator to inprove performance in a floating arrangement.

 

Regards.

 

 

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