National opamp inflation

[audioman54]

Hi Jack,

Remember that the LME49810 is a totally different animal than the LME49811 and LM4702. The 810 must have a heatsink to run at the higher currents (up to 50ma) the 811 and 4702 can only do 5ma or so and I run mine without heatsinks when running +/-50VDC rails. For 75VDC rails then I have to use heatsinks on those two parts. I found they sounded better in the 50 VDC units without heatsinks but in the 75VDC rail units they are required (anything above +/-50VDC use the heatsinks).

Ken,

I did my attenuation in the D/A preamp I designed so I did not worry about an attenuation pot in the power amp. Also we reduced the input gain resistor not because of bandwidth but because of resistor noise. I used a 390 ohm input resistor with a 10K feedback resistor on my inverting LME49811 amplifier.

Best Regards Everyone from a Still Out Of Work after 6 months (anyone have a job for me?) Audio Engineer,

Mark / audioman54

[mlloyd1]

mark:
hang in there; took me about 9 mos.

best of luck and thanks for your contributions here,
mlloyd1

Originally posted by audioman54
...
Best Regards Everyone from a Still Out Of Work after 6 months (anyone have a job for me?) Audio Engineer,

Mark / audioman54

[klewis]

Mark,

Thanks again for the help, I've made up the board, but got busy with other things, so I haven't stuffed the board yet. I'm looking forward to hearing the sound...

Sorry you haven't had luck on the job market yet, you had mentioned a few interviews a month ago, and I was hoping you would be successful. Continued best wishes in your job hunt.

Regards,

Ken

[panson_hk]

Originally posted by jackinnj
Do you have a heat-sink on the LME device ? Heat degrades their performance.

I did not see any difference for using or not using heat sink during tests.

[audioman54]

Hi Ken,

Did you stick with the non-inverting configuration for the LME49713's?

I am going to play with my new "AKM4399" demo board tomorrow. (I will just be using the digital front end.) I am told that with the 32-bit DAC the internal digital volume control is as good as a pot!? Need to test that out the next couple of weeks. Has anyone else done that already? Sure would make part of the analog design simpler...but then you need a micro to run the darn thing! AND it might not sound right at lower levels (less bits).

"That Corp" actually flew me out to Boston and I had a 12-hour interview that I thought went great! Later in the week the owner of the company talked to the group that interviewed me over the phone on a conference call (he was at NAB). After that conference he called me to let me know they would not be making me an offer because the team "ALL" said I did not have enough "professional audio experience". Very, very disappointing for me. They appeared to me (during my 1 day visit) to be a great group of engineers. I would have really enjoyed working with them.

Oh well, more free time to work on my new AKM4399 D/A board with my LME based power supplies. Hopefully I can get a job in the next 6 months so I don't loose my sound room, i.e. house!

Best "High End Audio" Regards Everyone,

Mark / audioman54

P.S. If have to leave the Bay Area where is the best "Audio" community to move to?

[jackinnj]

Originally posted by panson_hk


I did not see any difference for using or not using heat sink during tests.

See Mark's comments above. We're using the same AP test equipment I would suspect.

[jackinnj]

Originally posted by audioman54
P.S. If have to leave the Bay Area where is the best "Audio" community to move to?

I would not recommend New Jersey. The State's budget is off by another $1.2bn and the drivers have seized the laurel wreath from Massachusetts for their bad behavior.

Youtube New Jersey.

[klewis]

Mark,

No, I inverted it. I don't have the schematic with me at work, but will post it in the next few days.

I am using the 48600 for the power supply regulator, I built one and it seems to run great. I'm not very sophisticated with testing, but, the noise/ripple on my scope vs a 317 regulator was considerably less.

Ken

[scott wurcer]

Originally posted by jackinnj


and the drivers have seized the laurel wreath from Massachusetts for their bad behavior.

Youtube New Jersey.

[panson_hk]

Originally posted by jackinnj


See Mark's comments above. We're using the same AP test equipment I would suspect.

Hi jack,

Thank you for your advice. I run the test again with a better heat sink (a small home-made was used). I can see the difference this time. The loaded THD performance is better than before.