Opening the new DacMagic???? - Page 46 - 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 June 2012, 01:09 AM   #451
diyAudio Member
 
Join Date: Jul 2011
Up to you. I spent less then $100, and kept the DEXA to the DAC where it made the most sense. Check with Morgan Jones' book on what components are good and bad and why. This research is backed up other places as well. It will also supply proven mathematical formulas for changing out components. You should also use an oscilloscope and current meter to make sure you changes are making improvements. Improvements without measurements are hard to recommend. Understandable that not everything can be measured but power can, unlike cables that have to be heard.
  Reply With Quote
Old 27th June 2012, 05:12 AM   #452
diyAudio Member
 
ClefChef's Avatar
 
Join Date: Sep 2011
Super reg on DAC makes the most sense, I agree. Changes such as decoupling caps in DAC circuits are somewhat scientific too, easy to see with digital oscilloscope. However, analog stage coupling and power decoupling caps are more ear/taste matter.
78xx, 79xx regs have datasheets too...

Most of the "improvements" in the analog domain are subjective, throwing money on more expensive opamps or "fairy-wings-in-virgin-blood" gold caps might make you feel good...Discerning ear is the ultimate judge.

Dacmagic in stock form is quite excellent given its price/quality ratio. I would add no more than $50 worth of quality parts.

On a separate note I would like to share my dealings with L1 induction coil - it was too noisy and the chirping was really loud with Dacmagic cover off.
Short version: removed it from the board, cut around the base to remove ferrite shield, put some shrink tubing on the coil, packed the housing with epoxy, put it back together. Now it's silent as a church mouse...

Last edited by ClefChef; 27th June 2012 at 05:25 AM.
  Reply With Quote
Old 27th June 2012, 05:47 AM   #453
diyAudio Member
 
ClefChef's Avatar
 
Join Date: Sep 2011
And here's the list of my mods:
DAC Section:
C419 - Panasonic FC 1000uf 16v
C275, C303 Oscon 10uf 25v
The rest are bi-polar Nichicon Muse
Waiting for dexa reg.

All digital section caps changed to Oscons
Removed C17 and C18 from digital inputs 1 and 2 (we absolutely don't need capacitance there)
bypassed C126 and C127

Analog output:
removed C269 and C264, those are HF filtering caps - snip snip.
opamp supply rail caps bypassed with small wimas

The rest is usual cap upgrade to quality Nichicons, Panasonics, and Elnas.

I have a pair of ASC LL/88 transformers, might experiment with output stage a bit since they do fit on the pcb with coupling caps removed...
  Reply With Quote
Old 27th June 2012, 06:51 PM   #454
diyAudio Member
 
ClefChef's Avatar
 
Join Date: Sep 2011
Quote:
Originally Posted by Ajcrock View Post
C414 and 415 I would not go more then 22uf
OP275G datasheet shows recommended 0.1uf + 10uf decoupling caps on both power pins, I assume similar recommendations for the rest of opamps. Dacmagic has only 10uf per rail feeding all 6 opamps, not enough I suspect. I would recommend at least 47-100uf for C414 C415, since it would be difficult to put decoupling caps for each opamp separately.
  Reply With Quote
Old 2nd July 2012, 08:01 PM   #455
gvelim is offline gvelim  United Kingdom
diyAudio Member
 
Join Date: Jun 2007
Quote:
Originally Posted by Ajcrock View Post
Try updating to better opamps. I replaced the NE5532s with LME 49720 and the OP275Gs with OPA1612. But this requires that one can surface mount solder
Yesterday replaced AD797 on the +XLR stage with AD823. AD823 run less hot (45-50C), sounds close to the AD797 and sounds less distorting with more detailed than LME49720.

Experimenting with AD797 I infer it runs stable on the XLR topology however due to current draw of 10-12mA per Opamp across 30Vdc I installed them only on the XLR+ stage, they run hot around 65-70C. The sound is the best I've heard across a range of opamps however I am skeptic to go full way on XLR stage with 8 x AD797 on browndogs
  Reply With Quote
Old 3rd July 2012, 02:40 AM   #456
diyAudio Member
 
ClefChef's Avatar
 
Join Date: Sep 2011
Today I tried running ASC LL/88 transformers on Dacmagic output. LL/88 is BBC transformer 1:1 600ohm primary and secondary, with primary centertapped. I believe they were used to convert unbalanced signals to balanced and vice versa, and believed to be made by Sowter.

Primary was connected to to balanced signal running from U55-U56 and U59-U60 and output was fed to right side of the rca coupling cap (removed). The primary centertap is left unused, although I think it could be grounded...

The sound is GORGEOUS.

I think I am going to remove all coupling caps and disable XLR outputs - a pair of RCA will suffice for now. I had previously removed summing opamps that feed RCA outputs and ran one-sided XLR - hardly an optimum setup. The most important thing - those trafos fit within the box and could be mounted on the pcb.

Click the image to open in full size.

Last edited by ClefChef; 3rd July 2012 at 02:48 AM.
  Reply With Quote
Old 3rd July 2012, 06:04 AM   #457
diyAudio Member
 
ClefChef's Avatar
 
Join Date: Sep 2011
Click the image to open in full size.

Last edited by ClefChef; 3rd July 2012 at 06:11 AM.
  Reply With Quote
Old 3rd July 2012, 09:56 AM   #458
gvelim is offline gvelim  United Kingdom
diyAudio Member
 
Join Date: Jun 2007
this sounds quite promising...

Mihaylov also mentioned this here, but it was overshadowed by the OpAmp discussions
Opening the new DacMagic????

Could you share a schematic on how the xformers are connected in ?
  Reply With Quote
Old 3rd July 2012, 06:51 PM   #459
diyAudio Member
 
ClefChef's Avatar
 
Join Date: Sep 2011
Quote:
Originally Posted by gvelim View Post
this sounds quite promising...

Mihaylov also mentioned this here, but it was overshadowed by the OpAmp discussions
Opening the new DacMagic????

Could you share a schematic on how the xformers are connected in ?
Mihailov went extreme and bypassed all the opamps, coupling DAC Vout to outputs directly via transformers. I connected my transformers after the first cascade of opamps.

As we all know in audio Less is More. WM Dac chips already have Vout with filtering that are sufficient do drive the output, all the other opamps add distortion and coloring.

I really like tube output stages, and in this case something like Broskie CF would probably work well. Smallish Dacmagic box makes me explore other options and my current transformer mod seems to be OK.
Attached Images
File Type: jpg DacmagicTrafout.jpg (25.0 KB, 142 views)

Last edited by ClefChef; 3rd July 2012 at 07:09 PM.
  Reply With Quote
Old 3rd July 2012, 09:59 PM   #460
gvelim is offline gvelim  United Kingdom
diyAudio Member
 
Join Date: Jun 2007
Quote:
I had previously removed summing opamps that feed RCA outputs and ran one-sided XLR - hardly an optimum setup
As I also take the output from XLR+ I am keen to try out the mod.

Led by your mod I found this while looking for xformer parts: Phono Preamplifier with Line Output Transformers

Is the sound improvement because the xformer does the summing up of the XLR+ and XLR- signals ? When you say sound improvement in what way ?
  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 01:12 PM
Sony CD-X33ES CD Tray not opening-help? eldarvanyar Digital Source 7 14th January 2008 06:12 PM
Help! Cracks opening in my veneer suzyj Multi-Way 7 28th December 2006 05:42 AM
Cambridge Dacmagic 1 ManUtd Digital Source 1 6th October 2003 11:17 AM


New To Site? Need Help?

All times are GMT. The time now is 06:36 AM.


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