The original discrete R2Rs, Accuphase DC81 and DC81L

morricab

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Anyone heard/own these DACs and how do they work for PCM (obviously pre-DSD machines) compared to contemporary IC R2Rs (BBPCM63, AD1865 etc.) and modern discrete R2Rs. What I found interesting is that they have optically decoupled the whole digital circuitry.

Just curious because they are such nicely made machines and I can imagine from an engineering POV that Accuphase did this implementation quite well.
 

Legolas

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Anyone heard/own these DACs and how do they work for PCM (obviously pre-DSD machines) compared to contemporary IC R2Rs (BBPCM63, AD1865 etc.) and modern discrete R2Rs. What I found interesting is that they have optically decoupled the whole digital circuitry.

Just curious because they are such nicely made machines and I can imagine from an engineering POV that Accuphase did this implementation quite well.

I think the DC81L is an oversampling DAC, not R-2R? Can you confirm. In most cases DACs of 1989 vintage sound fairly poor next to the later advances, but not always. Interesting to know about this DAC.
 

morricab

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I think the DC81L is an oversampling DAC, not R-2R? Can you confirm. In most cases DACs of 1989 vintage sound fairly poor next to the later advances, but not always. Interesting to know about this DAC.

Oversampling has to do with digital filtering and not the DAC architecture. The DC-81L is a 20 bit discrete R2R dac. Most DACs from the past used an oversampling digital filter. For example my Monarchy M24 DAC uses the BB PCM63K R2R dac chip and is using the BB DF1704 digital filter. This oversamples to 352.8Khz before feeding the DAC chip. The new R2Rs are different by being discrete rather than an IC. However, Accuphase, before going to Multi-Multibit, was making fully discrete designs...first a 16 bit (DC-81) and later 20bit (DC-81L).

BTW, I disagree with you that the older IC R2R DAC chips sound obsolete.
 

DasguteOhr

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Hi Morricab,

i had an old Sonic Frontiers with Ultraanalog 20Bit Ladder Dac and a modern Soekris R2R Dac.
http://cdn.head-fi.org/b/b6/635x323px-b6d60e51_sfd1_2.jpg
http://soekris.com/products/audio-products/dam1021.html
With 16Bit/44.1khz the Winner is Sonic Frontiers,with the Same Music"Muddy Waters Folk Singer in
24Bit/96khz Quboz Rip the Soekris sounds in same league not better more transparent open offers more details.
I like the Old Machine sounds like a good Turntable realistic and more energy...
 

microstrip

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(...) What I found interesting is that they have optically decoupled the whole digital circuitry.

Just curious because they are such nicely made machines and I can imagine from an engineering POV that Accuphase did this implementation quite well.

In the late 80's optically decoupling the DACs was even fashionable - it would clean digital signals from their impurities :) - I remember cannibalizing a Sony X7ESD to insert a few 100 MHz optocouplers with TTL output in the clock, data and word input lines of the DAC chips. They were not easy to source at that time. The X7ESD really was built like a tank - my old unit is still working as new in the neighborhood.
 

DasguteOhr

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Hi Microstrip,

the best from X7ESD is the Transformer XLR Output is good Way to sound good.
With High current Dac Chip goes direct to transformer output no Opamp in the
Signal Path...great.
 

microstrip

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Hi Microstrip,

the best from X7ESD is the Transformer XLR Output is good Way to sound good.
With High current Dac Chip goes direct to transformer output no Opamp in the
Signal Path...great.

Do you remember them? They are still being used mainly to test balanced equipment is a fast way using my USB EMU soundcard based spectral analyzer (only SE line inputs) . The transformers have however some harmonic distortion in the low bass.
 

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DasguteOhr

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Hi,

yes i had a X7 many Years ago,for me sounds the Transformer output better.
I had a modified dac with sowther transformer for I/V Dac output sounds good
for two Years.
http://www.sowter.co.uk/dacs.php
 
Last edited:

morricab

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Apr 25, 2014
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Hi Morricab,

i had an old Sonic Frontiers with Ultraanalog 20Bit Ladder Dac and a modern Soekris R2R Dac.
http://cdn.head-fi.org/b/b6/635x323px-b6d60e51_sfd1_2.jpg
http://soekris.com/products/audio-products/dam1021.html
With 16Bit/44.1khz the Winner is Sonic Frontiers,with the Same Music"Muddy Waters Folk Singer in
24Bit/96khz Quboz Rip the Soekris sounds in same league not better more transparent open offers more details.
I like the Old Machine sounds like a good Turntable realistic and more energy...

I wonder if you mated the Soekris to a good tube output stage like the SF if you get some of that energy and realism but maintain the resolution advantage of the Soekris?

I have a couple of DACs that use the Ultraanalog, a PS Audio Ultralink II and a Kinergetics Research KCD-55 Ultra that has had the output stage Lampizated with an Amber output board. The PS Audio is good but my Monarchy Audio M24 with BBPCM63K chips and a tube output stage (no transistors) is better. The Lampizated Kinergetics sounds awesome but the gain is too high and I am still working on a solution.
 

DasguteOhr

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Sep 26, 2013
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Hi Morricab,

i hear the Soekris Dac without a Outputstage direct from Ressistor ladder (1,4V/625Ohm)
sounds really good so.
Go higher with UA 20bit with Stax x1t,Sonic Frontiers or Spectral sdr 2000 you want leave BB63K trust me...
 

morricab

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Apr 25, 2014
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Hi Morricab,

i hear the Soekris Dac without a Outputstage direct from Ressistor ladder (1,4V/625Ohm)
sounds really good so.
Go higher with UA 20bit with Stax x1t,Sonic Frontiers or Spectral sdr 2000 you want leave BB63K trust me...

I have two DACs with the UA chipset, PS Audio Ultralink II and Kinergetics Research KCD-55 Ultra that has had the output Lampizated. Both are good (the Lampizated Kinergetics more so) but I have always wanted to get a STAX DAC.
 

morricab

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Apr 25, 2014
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Does the DC-81 use the same ladder dac as L version?

DC-81 is a 16 bit implementation and the DC-81L uses a 20 bit implementation but the design is the same I think.
 

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