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Chip Amps Amplifiers based on integrated circuits

Composite amplifier: LM3886 + LME49710
Composite amplifier: LM3886 + LME49710
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Old 11th July 2019, 04:50 AM   #101
kokoriantz is offline kokoriantz  Lebanon
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I don't have any experience with 24 bit , but with 16 . To get lowest closed loop distortion you must output the sine wave with the highest level to be described by 24 bit , then attenuate by resistors to get -3db FS . May be there is a minimum to search for .
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Old 11th July 2019, 10:49 AM   #102
zarandok is offline zarandok  Austria
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The Xonar D2X is a relative good card (I've it too) with PCM1796 dacs. But: the analog on-board regulator is a 7805 (!!!), and there are some lower quality ceramic caps in the signal path wher they shouldn't be... I've updated them to Elna Silmic and TPA7S4700...
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Old 11th July 2019, 10:56 AM   #103
zarandok is offline zarandok  Austria
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Just let me please one queston what I do not understand:
The R23, R25... resistors with 1k (parallel with + input of LM3886) seems to be very low value for me!!! With simulations I got the best parameters with ca. 10k by this position!
Anyway, in the case of 1k you have a huge signal voltage drop..
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Old 11th July 2019, 04:19 PM   #104
jeanlemotan is offline jeanlemotan
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Quote:
Originally Posted by tomchr View Post
For measuring a bridged amp, you need a differential input.

Tom
After the 2nd round of resistor smoke, I figured this out
I'll build a differential probe with a LME49710, 9V batteries and hand picked resistors and that's it.
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Old 11th July 2019, 04:22 PM   #105
jeanlemotan is offline jeanlemotan
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Quote:
Originally Posted by zarandok View Post
Just let me please one queston what I do not understand:
The R23, R25... resistors with 1k (parallel with + input of LM3886) seems to be very low value for me!!! With simulations I got the best parameters with ca. 10k by this position!
Anyway, in the case of 1k you have a huge signal voltage drop..
Those resistors together with R6 and R31 form 2 voltage dividers (R6+R25 and R31+R23) that is meant to allow the LME49720 to clip before the 3886. Like this I get much better clipping behavior than if the 3886 would clip.
There was some discussion about in earlier posts (Composite amplifier: LM3886 + LME49710)
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Old 11th July 2019, 06:43 PM   #106
zarandok is offline zarandok  Austria
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Thanks. What is the simulated THD+N of the whole cicruit? Could you show me a step response with about 500ns/div resolution?


Tom is using by this positions 1k-330R. Pretty low...
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Last edited by zarandok; 11th July 2019 at 07:00 PM.
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Old Yesterday, 09:24 AM   #107
jeanlemotan is offline jeanlemotan
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Quote:
Originally Posted by zarandok View Post
Thanks. What is the simulated THD+N of the whole cicruit? Could you show me a step response with about 500ns/div resolution?


Tom is using by this positions 1k-330R. Pretty low...

The first post has the simulated step response and THD+N. Note that the TINA model doesn't include the LM3886 THD so the simulation for that is not relevant.
I got a good sound card to measure this but I'm still learning about how to calibrate the whole thing in REW...
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Old Yesterday, 09:25 AM   #108
jeanlemotan is offline jeanlemotan
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Just finished analyzing some NE5532 opamps that I got in a preamp. They seem to be fake, LM358 in disguise...
Here's the thread here: Fake NE5532
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