DAC AD1862: Almost THT, I2S input, NOS, R-2R

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miro1360

Member
Joined 2010
mllum said:
Often times, past wisdom is forgotten due to the passage of time. You guys might want to try out this discrete i/v circuit refined by Rudolf Broertjes. I used to play with this circuit when modding cd payers based on TDA 1541 and PCM63, AD1860, and PCM58 dacs about 20 years ago; and all with very good results. From memory, the sound of the "simple i/v" whilst typically having a BJT signature, unlike FETs or tubes, is engaging and is very good. I recall that op amp based i/v's typically used in cd players when compared against it in shootouts, could not hold a candle to the "simple i/v".
I also recall, that the circuit was initially developed and posted by the late "jocko homo", who had a dry sense of humour and wit, bordering on being irascible. There was much discussion on this and developments therefrom in those early days of diyaudio.

The schematic and instructions for the "simple i/v/" may be found here;
https://www.diyaudio.com/community/threads/simple-i-v-for-tda1541.9226/
Click to expand...

Interesting I/V where the conversion depends on the R4 resistor. Anyway, the output wave quality heavily depends on the R6 potentiometer position (my simulation said :unsure:), therefore always check the output on the oscilloscope. The music will be slightly colored by the output capacitor C3 (y)
 
EUVL

EUVL

Member
Joined 2003
xen-audio.com
mllum said:
....... I am surprised that apart from me and one other forum member, nobody else seems to have tried out the PCM56 dacs.
Click to expand...

We did.
And I am not too bothered now to try the same with AD1862, even though a compatible board is ready.

The measurement was done with PCM56K (no trimming) and a DF1704, but we have adaptor boards for PMD100 as well as a NOS Shifter with 2x 74AHCT164.
All of them functional. Still need a bit of work on the source (QA550 like) and to case up properly.


Cheers, Patrick
 

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grunf

grunf

Member
Joined 2006
EUVL said:
We did.
And I am not too bothered now to try the same with AD1862, even though a compatible board is ready.

The measurement was done with PCM56K (no trimming) and a DF1704, but we have adaptor boards for PMD100 as well as a NOS Shifter with 2x 74AHCT164.
All of them functional. Still need a bit of work on the source (QA550 like) and to case up properly.


Cheers, Patrick
Click to expand...
Interesting, I have a pair of PCM56s somewhere in the drawers, maybe they’ll go out one day too.
Why is no one pushing PCM1702? Looks like I'm the only one addicted to them. I recently bought five more so I can put them together in parallel.
 

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grunf

grunf

Member
Joined 2006
EUVL said:
Next step for us is PCM1704.
PCM56 is meant for 16/44, with or withoout OS.
So either 16 bit with 8x OS, or 24 bit with 4x OS.
20 bit offers no advantage.

Incidentally, we were told that the I2SoverUSB can be configured to drive the PMD100.
So it is not limited to SD card as source.


Patrick
Click to expand...
The PCM1704 is also my weak point, they should also have a PMD200 filter, which is difficult to obtain today, although the PMD100 can also be used. The prices of the PCM1704 have literally skyrocketed, and they are no better for the PMD100 either. PMD100 is a great filter although some do not have a good opinion of it .
I am currently having fun with SM5842-SAA3750-TDA1547.

Igor
 
M

miro1360

Member
Joined 2010
AD1862 sounds nicer for me in comparison with the PCM1704 on the same setup (NOS, the same PSU, I/V and USB-I2S, same components). It's hard to say at first glance why, it is noticeable with longer listening :unsure:
With AD1862 I can listen for hours and hours without fatigue.
With PCM1704 I had to take a break after a few hours.
I have made this comparison several times randomly.
PCM1704 is not bad at all, it is perfect but not for that price.
Very much can change with digital filter. Long-term listening without fatigue is crucial for me and I have not yet found a digital filter that I would be happy with in this regard 😁 I think less disruptive (although not as effective) will be a post filter on the output :)
 
grunf

grunf

Member
Joined 2006
miro1360 said:
AD1862 sounds nicer for me in comparison with the PCM1704 on the same setup (NOS, the same PSU, I/V and USB-I2S, same components). It's hard to say at first glance why, it is noticeable with longer listening :unsure:
With AD1862 I can listen for hours and hours without fatigue.
With PCM1704 I had to take a break after a few hours.
I have made this comparison several times randomly.
PCM1704 is not bad at all, it is perfect but not for that price.
Very much can change with digital filter. Long-term listening without fatigue is crucial for me and I have not yet found a digital filter that I would be happy with in this regard 😁 I think less disruptive (although not as effective) will be a post filter on the output :)
Click to expand...
The PCM1704 can certainly sound good, and it should be better than the AD1862, only other things need to be matched. A DAC is not an amplifier or preamp but a set of multiple components where each has an impact on the sound. One mistake can lead to disappointment and bad sound. Regulators suitable for the AD1862 don't have to be good for the PCM1704, just as it doesn't matter how the power supply for the PMD100 filter is made, not to mention the effect of I / V on sound.
I am currently overjoyed with the sound of the PMD100 and PCM1702, but a lot of time (and money) was spent until that level was reached.

Igor
 
M

miro1360

Member
Joined 2010
That is Patrick, my conclusion based on my specific and very simple setup which somehow resulted in a nice thread :worship: I put these R-2R chips in the same environment to make it fair.
Many people do the comparison by buying 2 different DAC devices - different DAC devices with different I/V and the final conclusion can't be fair (a good DAC chip with a bad I/V will not sound good, we know this). If one make a perfect environment for the PCM1704, testing the AD1862 on this environment should not harm the AD1862, options are open ;)
My only hope is that the increased interest in obsolete AD1862 will not push its price as high as it was with the PCM1704 :ROFLMAO: ebay responded quite quickly and increased the price from 10 per used chip (polida seller) over 67 ... wtf AD1862 is biting TDA1541's *** :ROFLMAO::ROFLMAO:
 
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