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A NOS 192/24 DAC with the PCM1794 (and WaveIO USB input)
A NOS 192/24 DAC with the PCM1794 (and WaveIO USB input)
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Old 12th November 2018, 11:27 AM   #6711
Terry Demol is offline Terry Demol  Australia
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Quote:
Originally Posted by abraxalito View Post
I feel fairly sure that an I/V using a CFP for an input stage (as the Legato does) should easily be able to get down to 1ohm, perhaps even lower. Using a common-base stage though does have practical limits though in terms of voltage transformation, I've found somewhere in the realm of 200X is a practical maximum - meaning if the input impedance is 1ohm, the output can't be more than 200ohm.
The 1794 is ideal for open loop I-V as you describe. Because it has such high
OP Z and is tolerant to OP swing, the distortion can be made very low.

I have simulated open loop I-V's for 1794, even without any local CFP type
FB that get a lot better than -120dB distortion. Obviously the sim is ideal and
usually optimistic but it does give some indication of the potential.

T
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Old 12th November 2018, 12:13 PM   #6712
abraxalito is offline abraxalito  United Kingdom
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Thanks Terry, very interesting info in that link.
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Old 13th November 2018, 03:32 AM   #6713
Terry Demol is offline Terry Demol  Australia
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Quote:
Originally Posted by abraxalito View Post
Thanks Terry, very interesting info in that link.
The amazing thing is, he achieved such good results with everything hanging
off a breadboard LoL.
I'm quite sure the high Z current source OP really helps here.... read - don't
try this with a Sabre
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Old 13th November 2018, 05:22 AM   #6714
abraxalito is offline abraxalito  United Kingdom
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Ha well I'm also a fan of DACs with hiZ current source outputs. I just recently very crudely measured my TDA1387 and found its most likely over 1Mohm and also I get great results on a breadboard
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Old 13th November 2018, 01:15 PM   #6715
NIXIE62 is offline NIXIE62  Serbia
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This is my version of dddac 1794 (4 boards) with Nixie frequency display made about 6 months ago. Motherboard and supply are modified so that everything fits horizontally and the height is just 65mm. I do not think anyone has a Nixie display on a DAC, maybe I'm wrong. It looks much more beautiful in nature than on photos. I will probably replace the front panel in the future for something nicer, this one is only plasticized and printed with an UV printer. I do not care much for the look and the sound is phenomenal. Done with a little help from my friends.
Attached Images
File Type: jpg DAC1.jpg (91.4 KB, 92 views)
File Type: jpg DAC2.jpg (77.5 KB, 93 views)
File Type: jpg DAC3.jpg (52.8 KB, 90 views)
File Type: jpg DAC4.jpg (110.3 KB, 90 views)
File Type: jpg DAC5.jpg (38.7 KB, 91 views)
File Type: jpg DAC6.jpg (18.1 KB, 40 views)

Last edited by NIXIE62; 13th November 2018 at 01:37 PM.
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Old 14th November 2018, 01:44 PM   #6716
juancho is offline juancho  United Kingdom
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Here's mine. Seven power supplies, three chokes, valve output stage, reclocker and four boards.its been tidied up since the pic! Sounds phenomenal and has seen some very heavyweight competition!IMG_20181009_112942.jpeg
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