Zen -> Cen -> Sen, evolution of a minimalistic IV Converter - Page 79 - diyAudio
Go Back   Home > Forums > Source & Line > Digital Source

Digital Source Digital Players and Recorders: CD , SACD , Tape, Memory Card, 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 10th May 2012, 11:28 PM   #781
diyAudio Member
 
Join Date: Jul 2006
Location: Edinburgh
Hi everyone,

I've built quite a few DACs with the usual opamp methods.

My best DAC so far is based on PCM1792 and LME49710, it does have a respectable sound

Just recently i found out about the Zen V/I method and it looks quite interesting.

Is there an implementation compatible with PCM1792?

I'm sure that the answer to this is covered somewhere of these 78 pages or the other 100 pages related so i apologise is advance but don't have the time to go through them.

My concern with the PCM1792 is that it only sinks current and is idling on -6.2mA, also how about using the diff output to cancel distortion?

I'm very interested to listen to this method... that's why i'm looking for an implementation that has already been tested...

Also i noticed a lot of discussion on batteries... Considering that my job for 3 years used to be designing battery management systems i might be able to help you with something...

Thanks.
Attached Images
File Type: jpg dac-shot.jpg (274.5 KB, 564 views)
  Reply With Quote
Old 11th May 2012, 03:27 AM   #782
heb1001 is offline heb1001  China
diyAudio Member
 
Join Date: Sep 2011
Quote:
Originally Posted by otherside View Post
Is there an implementation compatible with PCM1792?

Thanks.
I've been using PCM1794 which is similar I think.

SEN is very simple and there are simple explanations about how to deal with the bias current without using servos in the thread above.
You should probably try those first for the best sound.

My room temperature varies by about 25C throughout the year and my jfets are not matched perfectly so I have been trying to come up with a circuit with servos to deal with the bias current and unmatched jfets.

I posted a circuit in #674 which works for the bias current but the servo in that circuit introduces some high order distortion and the jfets need to be well matched.

I posted a later circuit in #749 which DOES NOT WORK (the filter is noisy and the two servos are unstable) but I have a 2 servo circuit similar to #749 working at home which is stable and quiet with measured 2nd and 3rd harmonic about -95dB for an unbalanced half.

This latest circuit is currently on a breadboard and is picking up some RFI. I want to do a soldered balanced version this weekend.

If it sounds good, I'll post the schematic soon.
  Reply With Quote
Old 11th May 2012, 04:38 AM   #783
EUVL is offline EUVL  Europe
diyAudio Member
 
Join Date: Oct 2003
Here is an example of CEN used with a current sinking DAC.

Zen -> Cen -> Sen, evolution of a minimalistic IV Converter

You just need to add a current source upfront of the standard CEN.
But as Calvin said before, I would start with a single JFET CCS first.

As to distortion cancellation, simply use balanced output.
If you have to add a balanced to SE converter (opamp) or otherwise, you add both complexity and distortion.
I would then just use the +ve phase and leave pin 3 of the XLR open.


Patrick
__________________
xen-audio.com
  Reply With Quote
Old 11th May 2012, 10:18 AM   #784
EUVL is offline EUVL  Europe
diyAudio Member
 
Join Date: Oct 2003
Here is an example of a current source based on a TL431 which I have used before.


Patrick
Attached Images
File Type: png TL431 CCS.png (6.2 KB, 511 views)
__________________
xen-audio.com
  Reply With Quote
Old 11th May 2012, 01:59 PM   #785
diyAudio Member
 
Join Date: Jul 2006
Location: Edinburgh
Thanks guys i'll look into these and try them out,

Just as an indication, how much difference (compared to Op-amps) do you hear with these circuits?

Cheers,

Panagiotis
  Reply With Quote
Old 11th May 2012, 02:17 PM   #786
heb1001 is offline heb1001  China
diyAudio Member
 
Join Date: Sep 2011
Quote:
Originally Posted by otherside View Post
Thanks guys i'll look into these and try them out,

Just as an indication, how much difference (compared to Op-amps) do you hear with these circuits?

Cheers,

Panagiotis
Enough ;-)
  Reply With Quote
Old 11th May 2012, 03:52 PM   #787
diyAudio Member
 
Join Date: Jul 2006
Location: Edinburgh
Couple of questions,

Quote:
I posted a circuit in #674 which works for the bias current but the servo in that circuit introduces some high order distortion and the jfets need to be well matched.

I posted a later circuit in #749 which DOES NOT WORK (the filter is noisy and the two servos are unstable) but I have a 2 servo circuit similar to #749 working at home which is stable and quiet with measured 2nd and 3rd harmonic about -95dB for an unbalanced half.
Why so many parallel JFETs?

What caps are you guys using for the output? polyprop @ 200uF it's not easy to find
I've used the AMPOHM caps for ac coupling in other amps before but 30uF is about the max value you get. There are some Vishay MKPs at 200u but are 50quid a pop...
  Reply With Quote
Old 11th May 2012, 05:02 PM   #788
EUVL is offline EUVL  Europe
diyAudio Member
 
Join Date: Oct 2003
Go to Linear Audio Magazine website and download the article there for free.
It will give you a lot of information that allows you to build a very good sounding system.

Of course I shall not stop you from experimenting with exotic parts.
But that would be the last 2% at most.
And before that you should figure out how the other 98% appeal to you.


Patrick
__________________
xen-audio.com
  Reply With Quote
Old 11th May 2012, 05:12 PM   #789
heb1001 is offline heb1001  China
diyAudio Member
 
Join Date: Sep 2011
Quote:
Originally Posted by otherside View Post
Couple of questions,
Why so many parallel JFETs?

What caps are you guys using for the output? polyprop @ 200uF it's not easy to find
The PCM1794 likes to drive a virtual ground. If you parallel them up you get a lower input impedence and so closer to a virtual ground.

I'm using Rubycon electrolytics. They are very cheap.
  Reply With Quote
Old 11th May 2012, 09:33 PM   #790
diyAudio Member
 
Join Date: Jul 2006
Location: Edinburgh
Patrick thanks very much for the tip.

I read your article and i understand much more of this now.

It made me even more curious to try it out.

Also now that i got a change to study this a bit better i see your point about the current source to bias the output of the DAC.

I'll try a couple of things on simulation first

You mention quite a few times about the spice sims you did, what jfet sim model did you use? do you have a model for the 2sk170/2sj74?

Cheers,

Panagiotis
  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
FOR REGA Turntable>>> The heavy weight + Vta adjuster+ceramic ball prooptiki Swap Meet 1 22nd May 2010 05:57 PM
Multi-DAC: Lynx AES16 -> DIR9001/SRC4392 (-> SRC4192) -> PCM1794A novec Digital Line Level 11 11th May 2010 11:57 AM
> Audio <> music <> quick <> synergy <> angst>? rick57 Everything Else 0 4th May 2007 04:03 PM
&gt;&gt;&gt; cheap 50,000uF 60V capacitors here &gt;&gt;&gt; Lubomir Swap Meet 0 1st February 2007 03:36 PM


New To Site? Need Help?

All times are GMT. The time now is 11:10 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