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 14th September 2011, 03:14 PM   #3831
diyAudio Member
 
Join Date: Sep 2008
Quote:
Originally Posted by -ecdesigns- View Post
Hi Krokotam_,



My mistake, I use 470uF Oscon caps here (attached picture). The DC bias circuit contains of a 1K (bulk metal foil) multiturn trimmer, a 470uF / 16V Oscon decoupling cap and a Honeycomb Mobius loop for each channel.


The 1uF SMD film caps are used on the wipers of the DC-offset pot on the MK7 board that is used for achieving 0V DC on the DAC chip output pins.
Looks great ! Excelent work
  Reply With Quote
Old 17th September 2011, 09:10 AM   #3832
diyAudio Member
 
Join Date: Oct 2009
Location: Brunei
John, why have you chosen not to decouple the power supply for each individual flipflop?

Also you have removed the ferrite beads in the latest mk7. What has been your experience in using/removing them?

Thanks
__________________
--------
TDA1541a-S2 / 6072a / MediaplayerDac -- Michell Gyrodec -- Aikido Preamp -- Pass F5 -- Audio Physic Tempo 2SE -- Yamamura Cabling
  Reply With Quote
Old 17th September 2011, 04:18 PM   #3833
qusp is offline qusp  Australia
diyAudio Member
 
qusp's Avatar
 
Join Date: Oct 2009
Location: Brisbane, Australia
hey John, just wondering, on the discrete regulators, do you recommend a particular hfe part for bcv61/62? i have all the other parts in my bin already and i thought i'de give these a whirl as they can potentially take up so little space
  Reply With Quote
Old 18th September 2011, 08:33 AM   #3834
diyAudio Member
 
-ecdesigns-'s Avatar
 
Join Date: May 2006
Hi studiostevus,

Quote:
John, why have you chosen not to decouple the power supply for each individual flipflop?
I left out local decoupling for U5 (WS synchronous reclocker) and U6 (DATA synchronous reclocker) only. These signals are being sampled by BCK so transient rise time is not very important as long reliable sampling is still possible. The transients however do introduce interference, the faster the transients, the more interference. This is especially problematic with the DATA signal that can easily swamp the connected DAC chip with interference.

CMOS logic draws maximum (surge) current at signal transients. With effective local decoupling these surge currents are boosted. This in turn increases interference and risk of triggering resonance circuits (ringing). So decoupling isn't always a guarantee for less interference, in some cases it can make matters worse.

One way of reducing transient surge current is reducing available current for the circuit (current limiter). I used 1K5 resistors in series with the flip-flop power supply rail to achieve this. Using a local decoupling cap would create a reservoir that enables surge currents again, so I had to leave it out.

The 1K5 series resistor also places a high impedance between reclocker flip flop and 5V power supply. The resistor value was chosen to get around 2.4V power supply on the flip flop when processing I2S DATA / WS signals.

The flip-flops are required to attenuate source jitter (synchronous reclocking) and driving the I2S attenuators that require a balanced drive signal.


Quote:
Also you have removed the ferrite beads in the latest mk7. What has been your experience in using/removing them?
Ferrite beads only operate in a specific frequency range. So they basically filter only part of the interference spectrum. This leads to unwanted coloration of the sound. I experienced distortion / coloration in the upper audio frequency range as result of using ferrite beads.

In the MK7 I use RC filters and extremely clean power supplies instead. In order to maintain some degree of control over feedback loops, I started using fast local feedback loops, also in the voltage regulators.

The latest development in the MK7 power supply is a common mode ripple filter followed by a common mode filtered buffered zener reference. The voltage regulators on the MK7 board were removed / bypassed for this experiment.

I still have to perform direct comparison with common-mode ripple filter plus MK7 discrete voltage regulators. First impressions are increased sound stage, very natural sound (timbres) and the impression of attending a true live performance.
  Reply With Quote
Old 18th September 2011, 08:45 AM   #3835
diyAudio Member
 
-ecdesigns-'s Avatar
 
Join Date: May 2006
hi qusp,

Quote:
hey John, just wondering, on the discrete regulators, do you recommend a particular hfe part for bcv61/62? i have all the other parts in my bin already and i thought i'de give these a whirl as they can potentially take up so little space
I use these:

NXP|BCM61B|TRANSISTOR,NPN/NPN MATCHED,SOT143B | Farnell Nederland
NXP|BCM62B|TRANSISTOR,PNP/PNP MATCHED,SOT143B | Farnell Nederland

They have higher Vce breakdown voltage and are matched.

For LED voltage reference I use these:

KINGBRIGHT|KPTD-3216SEC|LED, SMD, 1206, LENS, ORANGE | Farnell Nederland
  Reply With Quote
Old 18th September 2011, 09:00 AM   #3836
EUVL is offline EUVL  Europe
diyAudio Member
 
Join Date: Oct 2003
BCM61B / 62B seems to provide a better match ?


Patrick
  Reply With Quote
Old 18th September 2011, 02:14 PM   #3837
galeb is offline galeb  Spain
diyAudio Member
 
Join Date: Apr 2008
Default No regulation or at least, simple regulation.

I agree with you John. I've been using since 3 months, common mode ripple filters and "simple" discrete zener+bjt regulators, and this, at least for me in my system, and for now, is the best and most natural sound obtained. I still have to try mosfet instead bjt, but for now it sounds....

Kind regards.
__________________
galeb saleh
Sarte Audio Elite´s technical audio department

Last edited by galeb; 18th September 2011 at 02:15 PM. Reason: error
  Reply With Quote
Old 18th September 2011, 03:02 PM   #3838
qusp is offline qusp  Australia
diyAudio Member
 
qusp's Avatar
 
Join Date: Oct 2009
Location: Brisbane, Australia
thanks John and Patrick, I actually had loaded the B of the nxp in my cart at digikey, farnell pricing is rude here in australia, i also probably have the orange kingbright 1206 LED already, i know i used their red, yellow and green in another build and had plenty spare, think i got a range of colours at the time, 'just in case'.
  Reply With Quote
Old 18th September 2011, 03:30 PM   #3839
spurlte is offline spurlte  United States
diyAudio Member
 
Join Date: Aug 2011
Hello ECDESIGN, I too am a new member and would like to start by building an amplifier. My sister gave me a pair of high current speakers (I am in Arizona at the moment-I am from Chicago visiting my parents), and used a Sansui A2000 that only had outputs of 65wpc I believe and did not do any justice my sister's speakers. What diyaudio amplifier would you suggest today? I have built my own oscillator, power supply and other stuff while at DeVry so I know how to respect electricity, solder, and some electricity theory. I did purchase a chinese Krell KSA-100 MKII Clone because I saw the thread for it, but should have consulted first as I am now. I know this thread is old, but I hope you reply. Spurlte
  Reply With Quote
Old 19th September 2011, 08:03 AM   #3840
diyAudio Member
 
-ecdesigns-'s Avatar
 
Join Date: May 2006
Hi EUVL,

Quote:
BCM61B / 62B seems to provide a better match ?
Quote from NXP datasheet:

"Matched version of BCV61" / "Matched version of BCV62".
  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



New To Site? Need Help?

All times are GMT. The time now is 05:25 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