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dac I/V convertion with very low distortion
dac I/V convertion with very low distortion
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Old 16th March 2019, 03:23 AM   #871
smms73 is offline smms73
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This was the circuit I used back in 2012 to test the distortion of the circuit
5% carbon resistors and random transistors .
this test was made with 8ma at the input and 4volts output, two times more current that a pcm1794 could provide at the output, as you can see the distortion is immeasurable.
The distortion was measure with a emu1212 using the Arta program.
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Old 16th March 2019, 07:30 AM   #872
samoloko is offline samoloko  Bulgaria
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because It Is user friendly and with lowest jitter <50 psec
please take a look AK4118 Digital Receiver Board Coaxial Optical AES to I2S Sampling Rate Display | eBay

you got select from 3 spdif and I2S Input, display
you can think to do a modular type pcb - separate pcb for pcm1794 with I2S Input, separate pcb for analogue I/V, separate power supply pcbs

BTW would anyone please confirm connecting of DC servo schematic that Sergio proposed dac I/V convertion with very low distortion to last Tagus differential dac I/V convertion with very low distortion and Tagus X dac I/V convertion with very low distortion schematics

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Originally Posted by rsavas View Post
why? experience? it does look like it is a good part to use, 0.5mm pitch soldering can be an issue for some.

Last edited by samoloko; 16th March 2019 at 07:33 AM.
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Old 16th March 2019, 01:28 PM   #873
dreamth is online now dreamth  United Kingdom
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Quote:
Originally Posted by smms73 View Post
This was the circuit I used back in 2012 to test the distortion of the circuit
5% carbon resistors and random transistors .
this test was made with 8ma at the input and 4volts output, two times more current that a pcm1794 could provide at the output, as you can see the distortion is immeasurable.
The distortion was measure with a emu1212 using the Arta program.
Thank you! I never tried to use a sound card for measuring distortions as i had some doubts upon the truth it can provide.I saw once a 1000w /2 ohms audio amplifier measured under ARTA and the results were smth like 0.00006% at 150w/8ohm which automatically triggered an alarm for me.I think that it's absolutely impossible to get those results in real life and i don't believe anyone in the world that they can get you such results with a high power amplifier .To be absolutely honest i appreciate more a simple sine-square signal measurement on a scope . It would be nice if the audio manufacturers would provide ultralow distortion equipment and a separate distortion" eq" box to give you the option of making the music sound "worse".
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Old 16th March 2019, 04:22 PM   #874
bimo is offline bimo  Indonesia
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Quote:
Originally Posted by dreamth View Post
I saw once a 1000w /2 ohms audio amplifier measured under ARTA and the results were smth like 0.00006% at 150w/8ohm which automatically triggered an alarm for me.
What kind sound card to measure? There is any sound card that can loop back with 0.00006% THD?
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Old Yesterday, 05:09 AM   #875
dreamth is online now dreamth  United Kingdom
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Quote:
Originally Posted by bimo View Post
What kind sound card to measure? There is any sound card that can loop back with 0.00006% THD?
You got the point Unfortunately not many are aware of the fact that it is physically impossible to get those measurements with just a sound card...you don't pay 6000-20000 dollars for just a "20 kilos empty box"called THD analyzer...Some say that you can do it with a fairly good soundcard if you attach a distortion lens magnifier and a high quality notch filter though...I never tried.I might try it soon because i don't have 6000 dollars to spend for anything in this world

Last edited by dreamth; Yesterday at 05:17 AM.
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Old Yesterday, 10:11 AM   #876
bimo is offline bimo  Indonesia
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Quote:
Originally Posted by dreamth View Post
You got the point Unfortunately not many are aware of the fact that it is physically impossible to get those measurements with just a sound card...you don't pay 6000-20000 dollars for just a "20 kilos empty box"called THD analyzer...Some say that you can do it with a fairly good soundcard if you attach a distortion lens magnifier and a high quality notch filter though...I never tried.I might try it soon because i don't have 6000 dollars to spend for anything in this world
BS.

Bob Cordell distortion magnifier can do magnify 40dB Linear Audio | your tech audio resource

To get amplifier 0.00006% THD is very difficult.
I used Distortion Analyzer in my previous work, long time ago.
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Old Today, 01:14 PM   #877
samoloko is offline samoloko  Bulgaria
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Hi Serjio,

Would you please confirm, when we want to use schematic with dac chips without offset, like pcm1704, we don't use Q7.
If we like to go without coupling caps dc servo dac I/V convertion with very low distortion can be added to the output, but would you please explain how to connect It.

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Originally Posted by smms73 View Post
A forum member asked me to make a functional circuit for the pcm1794a, and this weekend I was in ltspice and did this, the idea was to have a more stable circuit. The resistance R3 can be a resistance of 180ohm in series with a potentiometer of 100 ohms, this will serve to cancel the DC offset at output, (R11,12,16,17) can have a lower value , with 10 Ohms value the input impedance is 7 ohms. Vcc is 15V and Vdd is -15V.
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