PCM1798 - looking for advice on cheap and simple I/U - diyAudio
Go Back   Home > Forums > Source & Line > Digital Line Level

Digital Line Level DACs, Digital Crossovers, Equalizers, etc.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 27th May 2010, 04:47 PM   #1
Alexium is offline Alexium  Ukraine
diyAudio Member
 
Join Date: May 2010
Default PCM1798 - looking for advice on cheap and simple I/U

I'm building my first DAC based on PCM1798. I'm new to this, and I'm not very good with electronics (though I'm trying to learn). That's why I ask for your help.
I am about to assemble the I/U and adder according to datasheet using NE5532. Are there possible improvements to be made in this schematics, or is it good enough as it is? Advices or references to other good outputs for 1798 would be much appreciated.
Thanks in advance.

PCM1798 datasheet. Subject schematics is on page 19.
  Reply With Quote
Old 28th May 2010, 10:20 AM   #2
Alexium is offline Alexium  Ukraine
diyAudio Member
 
Join Date: May 2010
This is the schematic:
Click the image to open in full size.
  Reply With Quote
Old 28th May 2010, 02:00 PM   #3
diyAudio Member
 
Join Date: Jan 2008
Location: Virginia
Replace the 5532 with another decent OpAmp
LM4562 are not that expensive and sound great. Others might be slightly better, but way more expensive...

Last edited by SoNic_real_one; 28th May 2010 at 02:03 PM.
  Reply With Quote
Old 28th May 2010, 04:43 PM   #4
Alexium is offline Alexium  Ukraine
diyAudio Member
 
Join Date: May 2010
I know 5532/34 are not much appreciated, but some other people say they can sound good enough when applyed correctly. They are so cheap that I want to experiment with them.
And I have a problem with price/availability of some opamps in my region. LM4562 are avaliable, but they are more expensive than AD811/826 etc., OPA2132, OPA627 and such. It's $7, to be specific, which is not cheap here.
I can get very cheap LM2904; OPA1632 and OPA2134 are also available for a reasonable price.
And I still hve to resolve the problem of obtaining the "right" schematics - most suitable for the particular opamp, I mean. They say datasheet schematic has its issues, and I'm not good enough to understand it...

There's a problem with the picture above, and I can't edit messages, so this is the right one:
Click the image to open in full size.

P.S. Sorry for my English, I'm doing my best to be clear, but sometimes I fail...
  Reply With Quote
Old 28th May 2010, 07:37 PM   #5
diyAudio Member
 
Join Date: Jan 2008
Location: Virginia
I have tried the OPA 2134 and was OK.
I have tried also OPA 1642 and that is better than the 2134... You should try it. The 22pF compensation it is not necessary for it, it is unity gain stable.
  Reply With Quote
Old 29th May 2010, 04:38 AM   #6
Alexium is offline Alexium  Ukraine
diyAudio Member
 
Join Date: May 2010
Thanks! I'll try OPA1642 then.
  Reply With Quote
Old 29th May 2010, 05:33 AM   #7
diyAudio Member
 
abraxalito's Avatar
 
Join Date: Sep 2007
Location: Hangzhou - Marco Polo's 'most beautiful city'. 700yrs is a long time though...
Blog Entries: 98
Send a message via MSN to abraxalito Send a message via Yahoo to abraxalito Send a message via Skype™ to abraxalito
Quote:
Originally Posted by Alexium View Post
I know 5532/34 are not much appreciated, but some other people say they can sound good enough when applyed correctly. They are so cheap that I want to experiment with them.
My sentiments entirely - the 5534 is amazing bang for the buck, so experiment away and let us know how it goes. In my experience (I'll get around to putting it on my blog soon) layout and power supplies (noise control in general) are more than 90% of the sound of a DAC. Changing opamps once the layout is exemplary seems to make almost no difference.

Quote:
And I still hve to resolve the problem of obtaining the "right" schematics - most suitable for the particular opamp, I mean. They say datasheet schematic has its issues, and I'm not good enough to understand it...
I don't consider the datasheet recommended schematic that you posted up to be ideal. My guess is this one that gives the best numbers for the datasheet but it doesn't give me the best sound. The 2700pF feedback cap is way too big, I've experimented with less than a tenth of this value and such a reduction seems to open up the sound considerably. I'd also take issue with the first stage passive filtering - the 220R/27nF is too low a load, even for a 5534. I'd scale up the resistors to at least 680R here, with a proportional reduction in the capacitor size. Be very careful in regards to the grounding of the decoupling capacitors if you want the highest transparency. Beyond that, see what sounds good.
__________________
It doesn't have to take the form of a conspiracy, rather a consensus... James H Kunstler
  Reply With Quote
Old 29th May 2010, 04:52 PM   #8
Alexium is offline Alexium  Ukraine
diyAudio Member
 
Join Date: May 2010
abraxalito, thanks a lot for your input on improving the circuit. I'll start building the DAC soon, and I sure will experiment a lot
  Reply With Quote
Old 15th June 2010, 02:24 PM   #9
diyAudio Member
 
Nazar_lv's Avatar
 
Join Date: Oct 2009
Location: Banderstadt
Blog Entries: 4
Send a message via ICQ to Nazar_lv
Quote:
In my experience (I'll get around to putting it on my blog soon) layout and power supplies (noise control in general) are more than 90% of the sound of a DAC. Changing opamps once the layout is exemplary seems to make almost no difference.
+1
__________________
"In developing audio devices we can always find creative non standart solutions that will ensure the best sound" (с) S-Audio.Systems
  Reply With Quote
Old 15th June 2010, 02:42 PM   #10
diyAudio Member
 
Join Date: Jan 2008
Location: Virginia
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.

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.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
What do you use for a simple cheap load? digital desire Solid State 30 30th December 2006 10:04 AM
The cheap simple ClassD TroelsM Class D 30 25th October 2005 09:24 AM
Simple and cheap sparkle Solid State 33 14th May 2004 05:19 PM


New To Site? Need Help?

All times are GMT. The time now is 10:09 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2