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Old 15th June 2010, 03:54 PM   #11
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Quote:
Originally Posted by SoNic_real_one View Post
Sure, if the PS is so bad that will induce noise in the outputs, the PS is the point of improvement. I see here people that complain about hum, ground loops and such. Yes, OpAmps won't make a difference there.
Well I've moved a little way beyond having hum as a problem in my DAC designs

Quote:
But if we are talking about TDH+N below -60dB, the cheap, "bargain" OpAmps are the weak point. In all my mods that involved swaping OpAmps in existing DAC's, the results where noticeable - from 'wow' to just a slight change.
Not having bought or built myself a THD analyser, I couldn't be sure that that's the change I'm seeing. I have had rather strange audible effects with NE5532s in my current DAC exploration though, to be mentioned in my blog in due course. Never had a 'wow' change from swapping an opamp in an I/V conversion job, but they're the most sensitive ones IME.
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Old 15th June 2010, 05:27 PM   #12
kevinkr is offline kevinkr  United States
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I recommend you consider a TI differential amplifier like the THS4131 which sounds amazingly good with both the PCM1798 and the PCM1794A. This is what I used in my dac, and then a line to line (600:600) transformer to convert the differential output to unbalanced. This is the best sounding combination I have yet heard.

Operational Amplifier (Op Amp) - Fully Differential Amplifier - THS4131 - TI.com
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Old 15th June 2010, 06:25 PM   #13
Alexium is offline Alexium  Ukraine
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I've heard about this opamp, but it's extremely hard to find where I live (not to mention it's quite expensive).

Last edited by Alexium; 15th June 2010 at 06:48 PM.
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Old 15th June 2010, 08:18 PM   #14
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Quote:
Originally Posted by Alexium View Post
I've heard about this opamp, but it's extremely hard to find where I live (not to mention it's quite expensive).
Sign up for TI's excellent sample program. It's very easy and the THS4131 is avaliable as samples now. You can also get PCM1798 and OPA1632.
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Old 15th June 2010, 08:25 PM   #15
Alexium is offline Alexium  Ukraine
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From what I've heard, they're not sending free samples to my country anymore.

Last edited by Alexium; 15th June 2010 at 08:34 PM.
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Old 15th June 2010, 09:05 PM   #16
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нема ніякої проблеми дістати 4131, я їх юзаю в одному з моїх цапів і регулярно купую, як треба то звертайся.
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Old 16th June 2010, 03:48 AM   #17
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Quote:
Originally Posted by kevinkr View Post
I recommend you consider a TI differential amplifier like the THS4131 which sounds amazingly good with both the PCM1798 and the PCM1794A.
What values of input and feedback resistor are you using? It looks a little bit limited in the choice of Rfb.
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Old 16th June 2010, 03:51 AM   #18
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I've heard about this opamp, but it's extremely hard to find where I live (not to mention it's quite expensive).
For audio it would be a bit daft to use the 4131 As far as I'm aware, the OPA1632 is the same part but targetted at audio rather than instrumentation so probably tested a little differently. And around half the price
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Old 17th June 2010, 09:28 AM   #19
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1632 is lower quality parts of 4131
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What values of input and feedback resistor are you using? It looks a little bit limited in the choice of Rfb.
I use 390 with 1794A. But simple put 4131 as I\U converter for DS DAC is really not good, dac glitch and HF noise terribly reduces sound quality)
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Old 19th October 2010, 09:41 PM   #20
Klim is offline Klim  Ukraine
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Quote:
Originally Posted by Nazar_lv View Post
But simple put 4131 as I\U converter for DS DAC is really not good, dac glitch and HF noise terribly reduces sound quality)
What do you mean?
What measures are needed to filter glitch similar to those used in Picardian Chord?

Or that the application THS4131 in conjunction with the DS DACs, in particular the PCM1794, does not sound good at all?

Last edited by Klim; 19th October 2010 at 10:08 PM.
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