Salas DCG3 preamp (line & headphone) - diyAudio
Go Back   Home > Forums > Source & Line > Analog Line Level
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, 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 7th September 2016, 12:48 PM   #1
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Default Salas DCG3 preamp (line & headphone)

Hi all, this thread is about a JFET & MOSFET preamp I am cooking for sometime now. Its two stage single ended Class A circuit.
It was developed on the bench involving much experimentation with topology and a range of active parts. Simulations came second.

Some speakers are insensitive, some amps also, or a source is relatively low output like a phono stage. So a line preamp with gain is good to have.

Its named DCG3 because it has DC servo and three MOSFETS. Its standard gain setting is also times three.

The main schematic is attached* Click for circuit description

Some THD plots when driving 1.5kOhm line input and various headphones are also attached.

*(12 Oct 2016 updated and build guide/bom pdf added)

erratum: C6,C7 should read 4x in the BOM. J3 in preamp's schematic is named Q5 on the actual board.

About J3/Q5 possible tolerances read post#452
Attached Images
File Type: png Line100mA400mV.png (19.3 KB, 5507 views)
File Type: png LineFFT.png (14.1 KB, 5293 views)
File Type: png Sen100mA400mV.png (19.3 KB, 5186 views)
File Type: png AKG100mA400mV.png (20.4 KB, 5012 views)
File Type: png Fostex100mA400mV.png (17.9 KB, 4123 views)
File Type: png Grado100mA400mV.png (17.0 KB, 674 views)
File Type: png Grado150mA400mV.png (17.5 KB, 673 views)
File Type: png DCG-3_Sch.png (26.7 KB, 2780 views)
Attached Files
File Type: pdf BOM-SCH-GUIDE_DCG3-DCSTB.pdf (785.3 KB, 743 views)
  Reply With Quote
Old 7th September 2016, 02:26 PM   #2
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Some pictures

There is also a simple series DC stabilizer I designed for it
Attached Images
File Type: jpg Brbrd.jpg (382.0 KB, 2770 views)
File Type: jpg 1DCG3detail.jpg (387.7 KB, 2295 views)
File Type: jpg DSCF4623.JPG (575.1 KB, 2431 views)
File Type: png DCSTB_Sch.png (12.4 KB, 1852 views)
File Type: png DCSTB_Raw_Sch.png (5.7 KB, 1557 views)
  Reply With Quote
Old 7th September 2016, 02:34 PM   #3
diyAudio Member
 
merlin el mago's Avatar
 
Join Date: Sep 2009
Location: Catalonia - Europe
Subscribed!!!!!!
  Reply With Quote
Old 7th September 2016, 02:39 PM   #4
diyAudio Member
 
merlin el mago's Avatar
 
Join Date: Sep 2009
Location: Catalonia - Europe
Is suitable for high impedance headphones?
What are the rail voltages?
Power consumption?
Etc....
  Reply With Quote
Old 7th September 2016, 02:45 PM   #5
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Beta build samples by friends. Thanks for the good early feedback to Michael V and Tham C especially.

And clips by Tea tampering away in his basement following no particular order of instructions
https://www.youtube.com/watch?v=QSQSrmGxBAY https://www.youtube.com/watch?v=URX2...ature=youtu.be
Attached Images
File Type: jpg Michael_V.JPG (462.5 KB, 2296 views)
File Type: jpg Tham_C.jpg (310.4 KB, 2079 views)
  Reply With Quote
Old 7th September 2016, 02:49 PM   #6
diyAudio Member
 
merlin el mago's Avatar
 
Join Date: Sep 2009
Location: Catalonia - Europe
What are these lights at the psu?
  Reply With Quote
Old 7th September 2016, 03:00 PM   #7
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Quote:
Originally Posted by merlin el mago View Post
Is suitable for high impedance headphones?
What are the rail voltages?
Power consumption?
Etc....
Of course. Sennheiser HD40 you see measurement for is 600 Ohm for instance. Its an old insensitive for SPL headphone I got. Those measurements were done like in the O2 tests to can have perspective. It was loud enough with gain 3X but you can go 4X. 1.5K R6 will do that. With AKG K612 PRO 120 Ohm its very loud at 3X and hiss is absent.

Rail is +/- 17.3V. Power consumption about 7W for two channels (when with 100mA output stage bias)
Attached Images
File Type: jpg DCG_HP_FOOBAR.jpg (493.3 KB, 1867 views)
  Reply With Quote
Old 7th September 2016, 03:05 PM   #8
diyAudio Member
 
merlin el mago's Avatar
 
Join Date: Sep 2009
Location: Catalonia - Europe
What about the SQ?
  Reply With Quote
Old 7th September 2016, 03:09 PM   #9
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Quote:
Originally Posted by merlin el mago View Post
What are these lights at the psu?
Bargraph Leds. No need to match Vref Leds for DCG3 because it does not care about exact same +/- rails. Bar Led packs are compact, straightforward to solder, looking great.
Attached Images
File Type: jpeg DCSTB (2).jpeg (129.3 KB, 1549 views)
  Reply With Quote
Old 7th September 2016, 03:10 PM   #10
diyAudio Member
 
merlin el mago's Avatar
 
Join Date: Sep 2009
Location: Catalonia - Europe
Quote:
Originally Posted by Salas View Post
Bargraph Leds. No need to match Vref Leds for DCG3 because it does not care about exact same +/- rails. Bar Led packs are compact, straightforward to solder, looking great.
Thanks.
  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
Using a line preamp to drive headphone ginetto61 Solid State 25 6th May 2015 06:19 PM
Correct way to split line level inside dual headphone amp Seggelke Analog Line Level 6 7th September 2014 02:25 PM
Glassware Janus Shunt or regulated B+ (like Salas) for tube headphone amp? dludingt Power Supplies 0 21st April 2014 12:28 PM
FS: Crown Straight Line 2 Preamp, Power Line 4 Amp, FM 3 Tuner (SL-2, PL-4, FM-3) spitz Swap Meet 1 24th August 2013 11:01 PM
line stage + headphone amp then_dude Headphone Systems 0 2nd July 2006 09:17 PM


New To Site? Need Help?

All times are GMT. The time now is 11:26 AM.


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

Content Relevant URLs by vBSEO 3.3.2
Wiki