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 14th January 2007, 08:00 AM   #1
diyAudio Member
 
hollowman's Avatar
 
Join Date: Jan 2007
Default Borbely ALL-FET DAC I/V stage

I'm new to this forum so the answer to this query may be in its archives. Apologies in advance for any redundancy in this message.

In these articles (<http://www.borbelyaudio.com/adobe/borb502.pdf>, <http://www.borbelyaudio.com/pics/305borbely-new.pdf>), Borbely describes an ALL-JFET line stage, provides schematics and part values.

I'm interested in building the ALL-FET Dac audio board <http://www.borbelyaudio.com/allfetdac.asp>. Some schematics are provided on this page, but no part values are given. Can anyone hypothesize what the values may be? (Even the Starter Kit version of Borbely I/V may work for me: <http://www.borbelyaudio.com/eb604417.asp>, but again, no component values are given.)

In any case, is/are there an equivalent or better I/V design(s) in the diyaudio.com archives that may work like (or better than) the ones at borbelyaudio.com?

Please note my criteria for DAC I/V:

- No vacuum-tube-based projects, as I prefer smaller, more-portable solutions.
- Should work for a variety of DAC chips (e.g. TDA1541, TDA1543, TDA1545; and PCM1704, PCM1794)

Thx in advance for any help you can provide.
  Reply With Quote
Old 16th January 2007, 07:27 AM   #2
spencer is offline spencer  Hong Kong
diyAudio Member
 
Join Date: Jun 2004
Location: Hong Kong
Send a message via MSN to spencer Send a message via Skype™ to spencer
This is a balance version Jfet IV modified from NP D1.

R9/10 adjust output stage gate/source at 10V.

R11/12 adjust input offset at 0V or desire value.

Adjust R3/4 for different DAC out current. 1.5k is good for PCM63 and TDA1541.

Use half will be Single ended verrsion.

I have good result with that.

Spencer
Attached Files
File Type: pdf jfet iv 2.pdf (16.4 KB, 1994 views)
  Reply With Quote
Old 16th January 2007, 08:13 AM   #3
diyAudio Member
 
hollowman's Avatar
 
Join Date: Jan 2007
Quote:
Originally posted by spencer
This is a balance version Jfet IV modified from NP D1.

R9/10 adjust output stage gate/source at 10V.

R11/12 adjust input offset at 0V or desire value.

Adjust R3/4 for different DAC out current. 1.5k is good for PCM63 and TDA1541.

Use half will be Single ended verrsion.

I have good result with that.

Thx for posting that.

Do you have a standard (unbalanced) schematic?
  Reply With Quote
Old 16th January 2007, 08:30 AM   #4
spencer is offline spencer  Hong Kong
diyAudio Member
 
Join Date: Jun 2004
Location: Hong Kong
Send a message via MSN to spencer Send a message via Skype™ to spencer
Use left half for left channel, use right half for right channel.

Spencer
  Reply With Quote
Old 16th January 2007, 08:33 AM   #5
diyAudio Member
 
Join Date: Oct 2004
Hi hollowman,

I'd like to build a similar I/V stage for my Philips cd723 (tda1545a).
I've found an interesting article on Borbely's site, look:

http://www.borbelyaudio.com/adobe/xover.pdf

Regarding this page:

http://www.borbelyaudio.com/eb604417.asp

the input discrete opamp is the same that he describes here (604/410)

http://www.borbelyaudio.com/pics/305borbely-new.pdf

I don't know what kind of fet and values he used in filter buffer, sorry.
I'm not referring to the filter values but to the cascade buffer.
Probably 2sk/2sj series are a really good choice.

I hope someone knows and share it here ;-)

Mark
  Reply With Quote
Old 16th January 2007, 08:47 AM   #6
spencer is offline spencer  Hong Kong
diyAudio Member
 
Join Date: Jun 2004
Location: Hong Kong
Send a message via MSN to spencer Send a message via Skype™ to spencer
This is my estimation:
Q9 = 2SK246BL
Q10=2SK170BL
Q11=2SJ74BL
Q12=2SJ103BL

It must be the jfet that he is selling in his website!

Also take not on the below stated by Borbeley:
The 3rd order Bessel filter is built around a complementary JFET follower Q10-Q11. These are cascoded with Q9-Q10 to reduce input capacitance and distortion caused by capacitance modulation at high source impedance. Q10-Q11 is selected for Idss=8-10mA. Idss of Q9-Q12 has to be higher than that of Q10/Q11 to avoid forward biasing.
  Reply With Quote
Old 17th January 2007, 08:00 AM   #7
diyAudio Member
 
hollowman's Avatar
 
Join Date: Jan 2007
Quote:
Originally posted by spencer
This is a balance version Jfet IV modified from NP D1.
Was the orig. Nelson Pass D1 a single-ended class-A preamp (not sure if your schematic is SE class-A...sorry, I'm a novice, here)? How feasable (accurate-sounding) are solid-state single-ended class-A I/V's for DAC's? I can't recall having encountered any in the past, so I'm not sure if the lack-of-popularity is based on over-technicality-of-design, availability of needed components, etc.
  Reply With Quote
Old 17th January 2007, 08:18 AM   #8
spencer is offline spencer  Hong Kong
diyAudio Member
 
Join Date: Jun 2004
Location: Hong Kong
Send a message via MSN to spencer Send a message via Skype™ to spencer
Study this thread.

D1 I/V Stage Finished.
  Reply With Quote
Old 17th January 2007, 08:32 AM   #9
diyAudio Member
 
Join Date: Oct 2001
Location: .
Quote:
Originally posted by hollowman


Was the orig. Nelson Pass D1 a single-ended class-A preamp (not sure if your schematic is SE class-A...sorry, I'm a novice, here)? How feasable (accurate-sounding) are solid-state single-ended class-A I/V's for DAC's? I can't recall having encountered any in the past, so I'm not sure if the lack-of-popularity is based on over-technicality-of-design, availability of needed components, etc.
You can't throw a stone in this place without hitting a ss/se i/v of some sort from the 2 mosfet original Pass D1 through Jocko's simple i/v and its variants, rbroer's i/v, Elso Kwak's i/v to Pedja's AD844 based i/v , an OP660 based i/v, the Hawksford i/v and the Wadsworth/Wadia/PA630 i/v and on and on.......
  Reply With Quote
Old 17th January 2007, 11:48 AM   #10
diyAudio Member
 
hollowman's Avatar
 
Join Date: Jan 2007
Quote:
Originally posted by spencer
Study this thread.

D1 I/V Stage Finished.
Thx. It looks like a very do'able project but rfbrw mentions a bunch of other "ss/se i/v's" so I'm tossed as to which one to build first.

Quote:
Originally posted by rfbrw


You can't throw a stone in this place without hitting a ss/se i/v of some sort from the 2 mosfet original Pass D1 through Jocko's simple i/v and its variants, rbroer's i/v, Elso Kwak's i/v to Pedja's AD844 based i/v , an OP660 based i/v, the Hawksford i/v and the Wadsworth/Wadia/PA630 i/v and on and on.......
As I said in the last thread: "sorry, I'm a novice, here".

IAC, I appreciate the keywords you provided above. They will help me use diyaudio.com's search engine to find topical threads.

BTW, is there a "consensus" amongst DIYers as to which is the better design to build -- SE or Diff (both SS) -- if $/effort are equal but sound quality was the ultimate deciding factor?

Thx again!
  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
Borbely DAC board Prune Digital Source 22 17th September 2011 08:51 AM
Borbely Discrete Analog stage for DAC or CDP regal Swap Meet 6 18th July 2008 12:25 PM
Borbely Audio phono stage biovizier Swap Meet 12 9th February 2007 07:09 AM
Borbely audio 420 phono stage biovizier Solid State 0 16th May 2006 09:45 AM


New To Site? Need Help?

All times are GMT. The time now is 07:54 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