Opening the new DacMagic???? - Page 38 - 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 10th December 2011, 02:19 PM   #371
diyAudio Member
 
Join Date: Feb 2011
Quote:
Originally Posted by gvelim View Post
The more I study the digital supply the more I infer the effect of noise to clock jitter is significant hence by removing the digital noise you improve jitter performance... I presume ripple/noise affects raise/fall times hence adding to jitter.

If this is valid, in the context of DacMagic is best to tackle jitter performance by using an Ultra low noise Clock PSU + ultra low phase noise Clock + ultra low noise HEX inverter (clock buffer)... this change would give best possible results comparing to the "new power supply" path.

I have found the combo of Flea PSU + Crystek CCHD-957 + PO74G04A to give outstanding sound results.
Cool!

I have experience in soldering SMD, so that should be an easy trick. But it took me some time to find the PO74G04A. But it seems that I found it on a german homepage, since I need to buy inside EU, to avoid extra taxes and so on.
But that is, definitely a mod that I will do
I allready did the clock. I used this one.
NewClassD Audio Clocks

Only difference is, that mine does not have the output transformer. But then again, I got it for 1/4 of the original price
  Reply With Quote
Old 10th December 2011, 05:36 PM   #372
diyAudio Member
 
Join Date: Feb 2011
Damn! It seems that I cant find a single local dealer for that PO74G04A here in Denmark

So now I have written to Potatosemi.com and asked them for advice.
I want a top notch Hex inverter to
  Reply With Quote
Old 10th December 2011, 05:48 PM   #373
gvelim is offline gvelim  United Kingdom
diyAudio Member
 
Join Date: Jun 2007
Quote:
Originally Posted by Tordenguden View Post
Damn! It seems that I cant find a single local dealer for that PO74G04A here in Denmark
bought from ebay here, and it was sent directly from US, total cost $5USD :
eBay - The UK's Online Marketplace

no need to purchase through a local dealer

Last edited by gvelim; 10th December 2011 at 05:50 PM.
  Reply With Quote
Old 10th December 2011, 06:13 PM   #374
diyAudio Member
 
Join Date: Feb 2011
Quote:
Originally Posted by gvelim View Post
bought from ebay here, and it was sent directly from US, total cost $5USD :
eBay - The UK's Online Marketplace

no need to purchase through a local dealer
Thank you.

I just bought it. Even though I saw that this one i a PO74G14A and not PO74G04A. But they are very close to each other, so I took a chance
  Reply With Quote
Old 12th December 2011, 08:39 PM   #375
diyAudio Member
 
Join Date: Feb 2011
Looked closer at the datasheet. And it seems that the difference lies in the following:
Propagation delay = 5,5ns http://www.fairchildsemi.com/ds/74/74VHC14.pdf

Propagation delay = 1,8ns : http://www.potatosemi.com/datasheet/PO74G14A.pdf

Propagation delay = 1,4ns http://www.potatosemi.com/datasheet/PO74G04A.pdf

gonna be exciting to hear the difference - if any
  Reply With Quote
Old 13th December 2011, 10:53 AM   #376
gvelim is offline gvelim  United Kingdom
diyAudio Member
 
Join Date: Jun 2007
It is also the special noise cancellation technology those hex inverters are equipped with. The clock clock quality that feeds the hexinv is also an important factor.

The theory is that limiting noise you reduce jitter.
  Reply With Quote
Old 14th December 2011, 03:41 PM   #377
diyAudio Member
 
Join Date: Feb 2011
Quote:
Originally Posted by gvelim View Post
It is also the special noise cancellation technology those hex inverters are equipped with. The clock clock quality that feeds the hexinv is also an important factor.

The theory is that limiting noise you reduce jitter.
Oh yes. forgot about that feature. waiting patiently on the mail from ebay
  Reply With Quote
Old 23rd December 2011, 02:49 AM   #378
gvelim is offline gvelim  United Kingdom
diyAudio Member
 
Join Date: Jun 2007
With the clock improvements I have started noticing the sound of LME49720 so I am looking around for something more suitable and musical.

I have just looked at the AD8672 specs to replace the LME49720 that poses as a Differential multipolar bessel filter at the DAC's output - Wolfson DAC is operating in dual differential mode per channel, that is, 2 x dual opamps per DAC.

Considering the filter's goal is removal of common ground noise from the signal should this be a more suitable opamp (recommended for use in precision active filters) ? Open to suggestions.

The RCA stage is also running on LME49720 which I am looking to replace with OPA1612. Would there be any issue with AD8672 driving OPA1612 ?

Considering I have already removed the stage/signal coupling NP caps, could this upgrade introduce a DC offset in the outputs ?

PS: A-Class biasing mod has been postponed for the time being.

Last edited by gvelim; 23rd December 2011 at 02:53 AM.
  Reply With Quote
Old 23rd December 2011, 12:15 PM   #379
diyAudio Member
 
Join Date: Feb 2011
Im unsure if it is the LME4972 is such a goo choise. Or maybe its just because you now can hear the true nature of the wolfson dac. I dont know. But I was just afraid that the 1612, would be to "closed" in the sound. Because I do not want less detail than what the 5532 gives me.
  Reply With Quote
Old 29th December 2011, 04:41 PM   #380
gvelim is offline gvelim  United Kingdom
diyAudio Member
 
Join Date: Jun 2007
following upon earlier discussions on post-DAC stages and
1) since I am using XLR->RCA using only (R+,GND) & (L+,GND)
2) all 6 x LME49720 were getting too hot
3) had already bypassed the output coupling caps

... I decided to "disconnect" the RCA stage which was implied that increases the Diff filters' output load and subsequently influence THD distortion. Hence I removed U61/U57 and C6/C48. C293 & C299 were already removed.

I played the system with the remaining 49720s on. The sound was felt with increased detail in highs and micro-dynamics, but not a day night/difference.

Then I moved on to replace the 49720 with OPA2211. All well with the SMD job however the sound was coming out distorted on the highs. This revealed that one of the 4 opamps was baking hot. Removed and resoldered and the it was absolute fine. I played some sample tones via USB tones and I did not notice any oscillations on the output, which was quite reassuring. The opamps are running also much cooler.

The sound & stage appears to be on par to 49720 however fatter on base notes... at least it is not worse to my ears, so I'll let it burn for awhile.

A big PLUS of the opamp change is that box temperature has dropped to a point that I can keep my finger on the opamps and regulators' aluminium alloy for more than 15'' without any discomfort... comparing to 5'' before that was already a painfull experience.
Attached Images
File Type: jpg IMG_20111229_142519.jpg (580.7 KB, 341 views)

Last edited by gvelim; 29th December 2011 at 04:48 PM.
  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
Dacmagic Mods Blue_Max Digital Line Level 54 9th June 2013 12:12 PM
Sony CD-X33ES CD Tray not opening-help? eldarvanyar Digital Source 7 14th January 2008 05:12 PM
Help! Cracks opening in my veneer suzyj Multi-Way 7 28th December 2006 04:42 AM
Cambridge Dacmagic 1 ManUtd Digital Source 1 6th October 2003 10:17 AM


New To Site? Need Help?

All times are GMT. The time now is 10:41 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