Reference DAC Module - Discrete R-2R Sign Magnitude 24 bit 384 Khz Reference DAC Module - Discrete R-2R Sign Magnitude 24 bit 384 Khz - Page 311 - diyAudio
Go Back   Home > Forums > > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Vendor's Bazaar Commercial Vendors large & small hawking their wares

Reference DAC Module - Discrete R-2R Sign Magnitude 24 bit 384 Khz
Reference DAC Module - Discrete R-2R Sign Magnitude 24 bit 384 Khz
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 16th July 2015, 12:00 PM   #3101
spikestabber is offline spikestabber  Canada
diyAudio Member
 
Join Date: Feb 2015
Quote:
Originally Posted by zfe View Post
An other approach to keep Vref stable, would be to keep the load stable. This could e.g. be done by using one DAM per cannel, feeding the second ladder with the complementary signal (in sense of current load) and use a common Vref for both ladders. This is an a bit "wasteful" approach, but should, in theory, give an a much cleaner Vref.
It would be less wasteful if you could use the second ladder for the inverted signal.
__________________
Soekris dam1021-12v2 dual-mono balanced: https://imgur.com/a/fD68M
Hypex nc400: https://imgur.com/iORCyna | Overkill TT2USB: https://imgur.com/a/p6OiS
  Reply With Quote
Old 16th July 2015, 01:35 PM   #3102
zfe is offline zfe
diyAudio Member
 
Join Date: Dec 2014
Quote:
Originally Posted by spikestabber View Post
It would be less wasteful if you could use the second ladder for the inverted signal.
If using the second lader for stable Vref load, you need an other sort of inversion than for ballanced mono. Loosely speaking the second ladder needs to play "something" high volume when the "listening-ladder" plays low and vice versa.
More precisely, the bits of the second signal should have all but the sign bit flipped (0->1, 1->0).
  Reply With Quote
Old 17th July 2015, 11:08 AM   #3103
DIYBras is offline DIYBras  Brazil
diyAudio Member
 
DIYBras's Avatar
 
Join Date: May 2015
Location: Parana
Default Original 4V great upgrade!

Dear Friends of DAM,
I have good news to those who will not be able or want to do very deep upgrades in DAM supplies.
Reading the page of our DAM-master friend Paul, and measuring various parts of the source of 4V, I realized a lot of noise in the opamp output, this noise that was being filtered by output capacitor and the 10R series resistor. This noise was being generated by some signal difference between inverting and non-inverting inputs of opamp. Clearly we have some trouble here! I tinking the ceramic capacitor used here was not doing its job, since we have approximately 0V on the same, and high-K ceramic capacitors sometimes dramatically reduce the capacitance value when used with no DC bias. But when I bypass this capacitor with an 47F electrolytic, the noise reached 100mV at opamp output, worsening the noise on the 4V out capacitor. Instabilities, is it? Or potential/noise difference between reference and feedback line?
Anyway, I decided to grab this electro capacitor and direct connect in the output. In theory, we now have a single gain unity stage and without using the stabilization feature, but I got a VERY good result, and now is totally impossible for me to see some noise from the 4V source on my oscilloscope! It's very clean! If I ground the signal oscilloscope probe (or disable the oscilosc input) results in same trace!
So there is the tip, and if someone wants to prove it in practice are welcome.
Soon I make one illustration to show the cap position.
  Reply With Quote
Old 17th July 2015, 12:43 PM   #3104
DIYBras is offline DIYBras  Brazil
diyAudio Member
 
DIYBras's Avatar
 
Join Date: May 2015
Location: Parana
Illustration here...

This worked very well in practice, without instabilities!
I'm are using the Nichicon FP series I talked in some earlier post, and I confirm their efficacy: I have measured a little less interference than alecm before making this "strange"-upgrade. Definitive recommended!
Attached Images
File Type: png DAM exp3.png (134.5 KB, 2030 views)
  Reply With Quote
Old 17th July 2015, 12:56 PM   #3105
danny_66 is offline danny_66  Belgium
diyAudio Member
 
danny_66's Avatar
 
Join Date: Jun 2005
Location: Lierde
Nice find DIYBras !

What's the recommended uF for the 4 capacitors?

Can you make an illustration with the cap polarity on this picture ?

Regards,
Danny
__________________
My RefSpeaker
  Reply With Quote
Old 17th July 2015, 01:01 PM   #3106
DIYBras is offline DIYBras  Brazil
diyAudio Member
 
DIYBras's Avatar
 
Join Date: May 2015
Location: Parana
Quote:
Originally Posted by danny_66 View Post
Nice find DIYbras !

What's the recommended uF for the 4 capacitors?

Can you make an illustration with the cap polarity on this picture ?

Regards,
Danny
I tested with 47F.
Since this cap operates without biasing, I recommend using bipolar electro or at least an ceramic with guaranteed value with 0V bias. If you use an polar electro, you not need to worry about polarity due to 0V bias.
Ops, your photo differs in some parts positions in 4V reg circuit. This is an different model/prototype?
Since the 4 regulators use the same component positions, you can copy the positions to other 3 regs based on my illustration, but make sure if your PCB is same from my illustration.

Last edited by DIYBras; 17th July 2015 at 01:10 PM. Reason: Different photo
  Reply With Quote
Old 17th July 2015, 01:13 PM   #3107
danny_66 is offline danny_66  Belgium
diyAudio Member
 
danny_66's Avatar
 
Join Date: Jun 2005
Location: Lierde
Or 2 polar caps back to back to make a bipolar?

I took the picture from the Soekris website, I didn't notice any difference.
__________________
My RefSpeaker

Last edited by danny_66; 17th July 2015 at 01:18 PM.
  Reply With Quote
Old 17th July 2015, 01:27 PM   #3108
soekris is offline soekris  Denmark
diyAudio Member
 
Join Date: Jun 2009
Reference DAC Module - Discrete R-2R Sign Magnitude 24 bit 384 Khz
Okay, here is the official recommendation for vref buffer circuit, after I spend some time simulating and real hardware testing. The original circuit was ok, I didn't spend that much time on it originally as things seems to work fine. But yes, there is room for improvements there...

The output capacitors, marked with red, can be paralleled as much as wanted, but a single 47uF X5R 0603 capacitor is really enough and will fit nicely.

The output series resistors need to be much lower, I recommend to parallel the existing one, marked with blue, with a 0.1 ohm 0603 resistor.

The feedback need to be moved to before the output resistor, by paralleling the feedback capacitor, marked with orange, with a low ohm resistors, t.ex. 0.1 ohm 0603.

I strongly recommend to parallel additional parts instead of removing parts as there then is much less chance of damaging anything.

These modification will result in less than 1 mV p-p ripple, at all frequencies, with no peaking or changes in voltage precision. It's also what the next production series will look like.
Attached Images
File Type: jpg dam1021_top2_vref_caps.JPG (305.4 KB, 2207 views)
__________________
Sren

Last edited by soekris; 17th July 2015 at 01:29 PM.
  Reply With Quote
Old 17th July 2015, 01:56 PM   #3109
DIYBras is offline DIYBras  Brazil
diyAudio Member
 
DIYBras's Avatar
 
Join Date: May 2015
Location: Parana
Quote:
Originally Posted by danny_66 View Post
Or 2 polar caps back to back to make a bipolar?

I took the picture from the Soekris website, I didn't notice any difference.
You can use back-to-back, but I don't see real need for this (back-to-back is for 2H HD cancelling, in audio signals).
The "feedback" cap and the 10R res are inverted in your photo.
The Soekris PCB photo showing factory upgrades is equal to mine PCB, but not the upgrade; my upgrade change the buffer behavior.
Ironically, my upgrade also results in very low noise and zero peaking in 4V line, so I will make other channel with Soekris propositions to compare.

Last edited by DIYBras; 17th July 2015 at 02:00 PM. Reason: Need to test the Soekris proposition first
  Reply With Quote
Old 17th July 2015, 02:01 PM   #3110
hop.sing is offline hop.sing  Germany
diyAudio Member
 
Join Date: Feb 2009
Would be bridging those resistors an option? Or do we need those little 0.1 ohm resistances?
  Reply With Quote

Reply


Reference DAC Module - Discrete R-2R Sign Magnitude 24 bit 384 KhzHide 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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
e18 DAC - 8 channels at 32bit /384 kHz exa065 exaDevices 30 29th June 2012 05:11 PM
384 Khz DAC? SunRa Digital Source 8 1st October 2009 11:14 PM
24 bit/192 kHz via USB? gentlevoice Everything Else 3 22nd December 2008 06:24 AM
sign magnitude DAC Bernhard Digital Source 0 30th January 2007 01:40 PM
24 bit / 192 kHz Tube DAC questions Overlord Digital Source 4 29th April 2003 05:14 PM


New To Site? Need Help?

All times are GMT. The time now is 05:00 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright ©1999-2017 diyAudio
Wiki