Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

Salas DCG3 preamp (line & headphone)
Salas DCG3 preamp (line & headphone)
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
Salas DCG3 preamp (line & headphone)
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 IDSS tolerances and a matching R3 value read post#452
Attached Images
File Type: png Line100mA400mV.png (19.3 KB, 10779 views)
File Type: png LineFFT.png (14.1 KB, 10446 views)
File Type: png Sen100mA400mV.png (19.3 KB, 10275 views)
File Type: png AKG100mA400mV.png (20.4 KB, 9988 views)
File Type: png Fostex100mA400mV.png (17.9 KB, 8990 views)
File Type: png Grado100mA400mV.png (17.0 KB, 1113 views)
File Type: png Grado150mA400mV.png (17.5 KB, 1094 views)
File Type: png DCG-3_Sch.png (26.7 KB, 5457 views)
Attached Files
File Type: pdf BOM-SCH-GUIDE_DCG3-DCSTB.pdf (785.3 KB, 1510 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
Salas DCG3 preamp (line & headphone)
Some pictures

There is also a simple series DC stabilizer I designed for it
Attached Images
File Type: jpg Brbrd.jpg (382.0 KB, 5342 views)
File Type: jpg 1DCG3detail.jpg (387.7 KB, 4076 views)
File Type: jpg DSCF4623.JPG (575.1 KB, 4315 views)
File Type: png DCSTB_Sch.png (12.4 KB, 3689 views)
File Type: png DCSTB_Raw_Sch.png (5.7 KB, 3069 views)
  Reply With Quote
Old 7th September 2016, 02:34 PM   #3
merlin el mago is offline merlin el mago
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
merlin el mago is offline merlin el mago
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
Salas DCG3 preamp (line & headphone)
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, 3993 views)
File Type: jpg Tham_C.jpg (310.4 KB, 3665 views)
  Reply With Quote
Old 7th September 2016, 02:49 PM   #6
merlin el mago is offline merlin el mago
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
Salas DCG3 preamp (line & headphone)
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. DC 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, 3217 views)
  Reply With Quote
Old 7th September 2016, 03:05 PM   #8
merlin el mago is offline merlin el mago
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
Salas DCG3 preamp (line & headphone)
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, 2615 views)
  Reply With Quote
Old 7th September 2016, 03:10 PM   #10
merlin el mago is offline merlin el mago
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


Salas DCG3 preamp (line & headphone)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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
FS: Pass VFET 2 essential+supplemental kit and Salas DCG3 kit 32y0 Swap Meet 3 16th April 2018 05:22 AM
FS : Salas DCG3 pinnocchio Swap Meet 2 9th January 2018 10:32 PM
FS: 2x Salas DCG3 and DCSTB complete kits bvtrinh Swap Meet 5 26th October 2017 11:29 PM
WTB Salas DCG3 pcb or kit savvas Swap Meet 0 8th February 2017 10:50 AM
Using a line preamp to drive headphone ginetto61 Solid State 25 6th May 2015 06:19 PM


New To Site? Need Help?

All times are GMT. The time now is 04:30 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki