Hi Ken,
The circuit looks great except I prefer inverting circuits where ever possible. Most audio people I respect agree with me that inverting circuits sound better...and sometimes measure better also. In my D/A preamp I designed the two gain stages were inverting circuits that used the LME49713's. That does mean you have to take a little care with the input gain resistor after the pot. I used a 1k Alps pot in my simple design. I used a rather unusual impedance matched, relay / computer controlled 63dB attenuator network in my more expensive designs. The one you have will work great though but again I usually inverting opamp ckts when ever I can.
Best Regards,
Mark / audioman54
The circuit looks great except I prefer inverting circuits where ever possible. Most audio people I respect agree with me that inverting circuits sound better...and sometimes measure better also. In my D/A preamp I designed the two gain stages were inverting circuits that used the LME49713's. That does mean you have to take a little care with the input gain resistor after the pot. I used a 1k Alps pot in my simple design. I used a rather unusual impedance matched, relay / computer controlled 63dB attenuator network in my more expensive designs. The one you have will work great though but again I usually inverting opamp ckts when ever I can.
Best Regards,
Mark / audioman54
Hi audioman54,
I did some measurement for 49810. 49830 and 49811. Spec says 49810 can output 50+ mA. However, its performance degrades when the current is higher than ~2.8 mA. Do you have any comment?
My test results: http://www.diyaudio.com/forums/showthread.php?postid=1817069#post1817069
I did some measurement for 49810. 49830 and 49811. Spec says 49810 can output 50+ mA. However, its performance degrades when the current is higher than ~2.8 mA. Do you have any comment?
My test results: http://www.diyaudio.com/forums/showthread.php?postid=1817069#post1817069
panson_hk said:
Do you have a heat-sink on the LME device ? Heat degrades their performance.
The thermal impedance is going to be a function of the absolute rail voltage --
The device might not operate in Class-A at higher currents as well -- Nelson Pass wrote a comment that some of his clients heard a "thump" when one of his amplifiers transitioned from Class-A to Class AB -- those clients were obviously suffering from audiophilia nervosa.
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
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
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
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
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?
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?
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
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
Hi Panson,
Nice graph! Looks like a heatsink for the 810 is the way to go...but we already knew it needed one because of the extra Class A/B output stage that was put into that part for 3KW guitar amplifiers for Fender. You should be using the 811 if your rails are only 50VDC and you don't need more than 5ma to drive your darlington output stage (around a 120w into 8 ohms with 50VDC rails) The 811 sounds better than the 810!!!
Mark / Audioman54
Nice graph! Looks like a heatsink for the 810 is the way to go...but we already knew it needed one because of the extra Class A/B output stage that was put into that part for 3KW guitar amplifiers for Fender. You should be using the 811 if your rails are only 50VDC and you don't need more than 5ma to drive your darlington output stage (around a 120w into 8 ohms with 50VDC rails) The 811 sounds better than the 810!!!
Mark / Audioman54
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