The Objective2 (O2) Headphone Amp DIY Project - Page 248 - diyAudio
Go Back   Home > Forums > Amplifiers > Headphone Systems

Headphone Systems Everything to do with Headphones

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 21st May 2012, 01:23 AM   #2471
diyAudio Member
 
Join Date: Mar 2010
Quote:
Originally Posted by agdr View Post
Hey that is pretty slick! You found a way to use the (bigger than ceramic) film caps for the boost mod by sticking them on the bottom. I like the contrast there, the tiny SMD resistors and the huge 0.1uF film cap. That is what is needed electrically though. Looks like you are not going to use a switch on the boost mod (on all the time)? Another fellow has tried the boost mod and discovered the switch really doesn't fit anywhere in a B2-080 chasis. Have to go to B3. I just wired it all up to make sure it worked electrically, but hadn't tried to mount the switch in the box and got caught flat footed on that one.
Yup, it is on all the tim,. I need more bass all the time . and I also don't know where to mount the switch in my B2 case.
  Reply With Quote
Old 21st May 2012, 08:48 AM   #2472
PATPP2 is offline PATPP2  France
diyAudio Member
 
Join Date: May 2012
Hi AGDR,many thanks for you reply,
By searching on the forum,i found a post of nwavguy who used 20V vgs mosfet with succes and one can add 15V zener in //to G/S
You understand i cannot order a 1,50 mosfet and pay 20 of shipping so i must find the part locally
In the meantime,i found the culprit it was not the mosfet but the comparator 2903!!,i replace it with an LM2903 and all works fine now for many hours
I'll post asap a photo of my box in... walnut
patrice

e

Quote:
Originally Posted by agdr View Post
Vgs(max) of 20Vdc for the mosfets won't work (for very long, anyway). The power supply rails when running on AC are +/-12Vdc, so there is 24Vdc rail to rail, or more like 23Vdc after voltage drops across the schottky diodes and comparator chip output. The " 9v" NiMH batteries charge up to around 10.5Vdc, as I recall. That results in 21Vdc rail to rail when running on batteires, or right at 20Vdc after the various voltage drops.

So... you should get a mosfet with a Vgs(max) of at least 25Vdc. All the alternate mosfets RocketScientist lists in the BOM have Vgs(max) = 25Vdc.

Good luck!
  Reply With Quote
Old 21st May 2012, 06:16 PM   #2473
agdr is offline agdr  United States
diyAudio Member
 
agdr's Avatar
 
Join Date: Sep 2010
Quote:
Originally Posted by PATPP2 View Post
By searching on the forum,i found a post of nwavguy who used 20V vgs mosfet with succes and one can add 15V zener in //to G/S
Yep, a zener, or resistive divider, added on the gate circuit to reduce the voltage would also work.

That is good news you got it working!
  Reply With Quote
Old 26th May 2012, 07:37 PM   #2474
T2T is offline T2T  United States
diyAudio Member
 
Join Date: Sep 2005
Quote:
Originally Posted by jschristian44 View Post
Can anyone point me towards a Front Plate stencil so I can make my custom desktop version O2 amp? I want to have the RCA red/white plugs as well as the 1/4" adapter. Does the 1/4" adapter go on the front and the RCA plugs in the back? Also how do the RCA plugs attach as well as the 1/4" adapter. Thank you!
Be careful of JSChristian44. So far, he has taken members on Head-Fi.Org for $1,000+ in money and merchandise. Normally, he resides in Pennsylvania, but is apparently in Alaska for the summer.
__________________
Nothing beats the smell of solder vapors in the morning.
  Reply With Quote
Old 26th May 2012, 09:02 PM   #2475
Zigis is offline Zigis  Latvia
diyAudio Member
 
Join Date: May 2005
Location: Riga, Latvia
Quote:
Originally Posted by coolhead View Post
Here is the picture, the picture is not so good as I am using mobile phone to capture it. All old resistors are removed and new SMD resistors are mount underside of the board as it is easier to work with. Attachment 283268
Nice work, coolhead! Inspired by your work, I make bass boost too, few days ago. With ordinary resistors. Now in my O2 gain switch work as bass boost switch too. Since I use gain 2 and unity, Gain 2 is with bass boost and in unity gain position bass boost practically does not work.

I have 3K in feedback and 3K+100nf in parallel.

b.t.w., coolhead, since you use SMD resistors, you can make physically shortest possible feedback loop. Just solder feedback resistor direct between opamp's pin 1 and 2, and between 6 and 7. Leave in old place only bass boost RC.
  Reply With Quote
Old 27th May 2012, 10:10 AM   #2476
PATPP2 is offline PATPP2  France
diyAudio Member
 
Join Date: May 2012
Quote:
Originally Posted by PATPP2 View Post
Hi AGDR,many thanks for you reply,
By searching on the forum,i found a post of nwavguy who used 20V vgs mosfet with succes and one can add 15V zener in //to G/S
You understand i cannot order a 1,50 mosfet and pay 20 of shipping so i must find the part locally
In the meantime,i found the culprit it was not the mosfet but the comparator 2903!!,i replace it with an LM2903 and all works fine now for many hours
I'll post asap a photo of my box in... walnut
patrice

e
and voila!
Attached Images
File Type: jpg o2.JPG (640.6 KB, 465 views)
File Type: jpg o21.JPG (636.5 KB, 442 views)
File Type: jpg o22.JPG (551.5 KB, 435 views)
  Reply With Quote
Old 28th May 2012, 10:54 AM   #2477
diyAudio Member
 
Join Date: Oct 2011
Location: North West, UK
Blog Entries: 7
Smile ODAC wiring...

Hi everyone, two quick reference pic's for those looking to wire their ODAC to the O2.

1. Odac lineout connects to P1 on the O2 board. P1.1 [square] = left, P1.2 = Gnd, P1.3 = right.

2. IIRC, with the input jack fitted you need to cut two traces on the reverse of the board.

Paul.
Attached Images
File Type: jpg odac_wire.JPG (133.1 KB, 407 views)
File Type: jpg o2_cut_trace.JPG (97.1 KB, 387 views)
__________________
Listening with Gusto!
  Reply With Quote
Old 29th May 2012, 04:28 AM   #2478
diyAudio Member
 
Join Date: Aug 2009
If you wire to P1 holes, the ODAC will always be connected to the amp input.

If you want the jack switch to function to select between external source (jack in),
or internal ODAC (no jack in), you cut the traces and then ODAC L & R connection
are pins 3 & 4 of the input jack socket on the underside of the O2 PCB.

In order to route the wires for L & R, I squeezed some 24g teflon insulated wire through
the PCB lead holes at P1 and under the board to solder to pins 3 & 4.

Last edited by bada bing; 29th May 2012 at 04:34 AM.
  Reply With Quote
Old 31st May 2012, 08:02 AM   #2479
diyAudio Member
 
Join Date: Jan 2009
Hi Guys,
Sorry to be a little of topic but I'm running a charity raffle to win JDS gear including the O2 Headphone Amplifier and ODAC to help build schools in Kenya and Tanzania, details can be found on the raffle page:

Charity Giving - JDS LABS CHARITY RAFFLE PAGE

There's an article on JDS Labs:
JDS Labs

We're hoping to generate a little more interest because we don't have many entries at the moment so your participation would be gladly appreciated, also the odds of winning are good
  Reply With Quote
Old 1st June 2012, 10:27 PM   #2480
JZatopa is offline JZatopa  United States
diyAudio Member
 
Join Date: May 2003
Location: Chicago
Is there any reason I couldn't short C13 and C14 to remove all caps from the signal path? I know that I would have to be concerned with DC offset but is there any other reason I couldn't do this? Has anyone else tried this and noticed any difference in anything.
  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
Headphone amp project grahamfocal Headphone Systems 7 21st June 2011 05:28 PM
My latest project - DAC + headphone amp gmarsh Digital Line Level 105 13th December 2010 02:31 PM
My headphone amp project trifidmaster Headphone Systems 2 22nd December 2008 03:52 PM
Mini Ipod headphone amp DIY project Nordic Headphone Systems 14 11th March 2007 02:35 PM
Need help for a battery headphone amp project dismalonyx Headphone Systems 1 15th April 2004 11:22 PM


New To Site? Need Help?

All times are GMT. The time now is 06:16 PM.


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