The Objective2 (O2) Headphone Amp DIY Project - Page 290 - 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 12th November 2012, 03:47 PM   #2891
jneong is offline jneong  United States
diyAudio Member
 
Join Date: Nov 2012
Exclamation Need Some Pro Help!

So I have completed my O2 build and while it looks great, only the left channel is working as intended.

I have completed all documented troubleshooting steps and now need some pro advice! Details below:
Since the left channel works perfectly, and there is no sound at all from right channel (no noise either) I can attest the power circuit is functioning properly, so its neither the FETs or regulators. I have reflowed every joint on the board to ensure there are no cold solder joints. All voltage and resistance tests are within range.

I have swapped U3 and U4 and still the problem persists in the right channel so both op-amps are functioning properly and the issue must be with the right channel output circuit? I discovered the 2068D was getting hot quickly when turned on. This is only happening when the 2068D right channel is being connected to its output channel circuit (I have a ALPS pot with a built in switch, and the 2068D does not get hot when powered on but the volme pot is turned off.) Thinking it might be a problem with one half of the 2068D op-amp, I put the DIP8 package on a protoboard and was able to use the "right" channel of the 2068D to drive the left channel of the O2 properly, yet the known working "left" side op-amp on the 2068D will not drive the right output channel in the same fashion.

Someone who knows more than me please help!

Thanks in advanced to such an awesome community and project!
  Reply With Quote
Old 12th November 2012, 05:19 PM   #2892
agdr is offline agdr  United States
diyAudio Member
 
agdr's Avatar
 
Join Date: Sep 2010
Quote:
Originally Posted by jneong View Post
(I have a ALPS pot with a built in switch, and the 2068D does not get hot when powered on but the volme pot is turned off.)
I'll take a guess that you didn't cut the switch leads off the pot+switch before you soldered it in, and that your pot+switch might be the ALPS RK0971221Z05? If so then when you turn on the switch on the pot it is shorting pin 1 of your NJM2608 to ground, which will short out the right channel (ring on the output TRS connector) and cause the chip to heat up (probably damaged).

As luck would have it, those two rear switch leads on the pot just fit right into the holes for the back gang of the 20mm version of the pot, which are pin 1 on one side and ground on the other. Unsoldering the pot may be difficult though.

If this is what happened, try to unsolder the pot and cut those switch leads off, then solder it back in, making sure the switch leads don't touch any pads.

Last edited by agdr; 12th November 2012 at 05:23 PM.
  Reply With Quote
Old 12th November 2012, 07:02 PM   #2893
jneong is offline jneong  United States
diyAudio Member
 
Join Date: Nov 2012
Lightbulb 15mm ALPS pot with switch warning

Quote:
Originally Posted by agdr View Post
I'll take a guess that you didn't cut the switch leads off the pot+switch before you soldered it in, and that your pot+switch might be the ALPS RK0971221Z05?
Agdr, that is the exact ALPS part I have and precisely what has occurred! I will have to wait until I get home this evening to unsolder and trim the rear pot switch pins, but looking at the pinout (which I previously assumed was the same) pin 1 is grounding out the right channel. Since the "right" channel of the 2068D is working to drive the "left" output channel in my testing, I am hoping the 2068D is not damaged.

Thank you so much for your quick response! I cant tell you how frustrating the weekend was while troubleshooting and every published test was coming out as expected.

That 15mm ALPS pot with switch does fit almost perfectly in the 20mm footprint and should be noted for others in the future since I ordered RK0971221Z05 because the official BOM part was unavilable.
  Reply With Quote
Old 12th November 2012, 07:15 PM   #2894
agdr is offline agdr  United States
diyAudio Member
 
agdr's Avatar
 
Join Date: Sep 2010
Quote:
Originally Posted by jneong View Post
Agdr, that is the exact ALPS part I have and precisely what has occurred!
Well here is some good news, in the attachment below. You can just cut the two PCB traces on the bottom of the board going to one of the switch contacts, in that red circle below, with an xacto knife. Then jumper around the cut with an insulated wire following the green connection. That will disconnect the switch part of the pot and allow the signals to get where they are going without having to unsolder anything. That bottom connection on the green path is a via hole with no wire through it. That is OK, just put a little solder on it and solder the end of the wire right to the via.

The NJM2068 may seem to work OK after the fix, but the data sheet doesn't show any on-chip current limiting. The chip is probably damaged to some extent. Probably will be noiser, more distortion, etc. in that channel. Would be worth changing it next time you have a chance to order stuff.

Yes, you are probably the first one to discover this O2 layout hiccup! I hadn't noticed that the 15mm pot + switch would just happen to fit into the hole pattern until your post. I'll bet RocketScientist didn't notice it either, lol. Originally there were just two rows of pot holes in the back section for the 20mm alps pot. But then Mouser ran out of them early on forcing RocketScientist to do a board re-work and add the two rows of holes in front for the 15mm pot. But in the process he apparently accidentally laid out the perfect hole pattern for a 15mm pot + switch.
Attached Images
File Type: png O2 1.png (15.8 KB, 272 views)

Last edited by agdr; 12th November 2012 at 07:28 PM.
  Reply With Quote
Old 12th November 2012, 10:15 PM   #2895
jneong is offline jneong  United States
diyAudio Member
 
Join Date: Nov 2012
Smile Thanks Agdr!

Quote:
Originally Posted by agdr View Post
Well here is some good news, in the attachment below. You can just cut the two PCB traces on the bottom of the board going to one of the switch contacts, in that red circle below, with an xacto knife. Then jumper around the cut with an insulated wire following the green connection.
I feel so lucky being the first one to find a new way to fail! But thanks so much for your help Agdr! The re-route sounds much easier than trying to desolder the pot pins with the package being completely flush on top. I will attempt the fix you mentioned tonight and cross my fingers that the 2068D is not damaged, but since its a relatively cheap component like the rest of this board, no worries if it is!

I have to say, I have read most of this ~3000 post thread and the level of support on this forum and site (especially for an open-source project) is amazing and please keep it up!
  Reply With Quote
Old 13th November 2012, 08:46 PM   #2896
jneong is offline jneong  United States
diyAudio Member
 
Join Date: Nov 2012
Talking Fixed!

Quote:
Originally Posted by agdr View Post
You can just cut the two PCB traces on the bottom of the board going to one of the switch contacts, in that red circle below, with an xacto knife. Then jumper around the cut with an insulated wire following the green connection.
I just wanted to update and say the reroute fix worked perfectly. I have attached a pic just in case it can help someone in the future. Also the 2068D is not noticeably damaged (no noise etc) perhaps because I never stay on for more than a few seconds or let it breach 200F when testing the short.

Thanks again Agdr!
Attached Images
File Type: jpg O2_Repair.JPG (129.4 KB, 245 views)
  Reply With Quote
Old 14th November 2012, 11:14 AM   #2897
agdr is offline agdr  United States
diyAudio Member
 
agdr's Avatar
 
Join Date: Sep 2010
Quote:
Originally Posted by jneong View Post
I just wanted to update and say the reroute fix worked perfectly.
I'm glad that worked out!
  Reply With Quote
Old 14th November 2012, 05:12 PM   #2898
diyAudio Member
 
mrnothing's Avatar
 
Join Date: Oct 2012
hey guys
first,thanks RocketScientist,
this is my O2 Black Cube version
just finish this little thing about 1 hour ago
it's a desktop only version,the black case come from a 110mm*110mm*100mm transformer cover, perfectly fit!
Attached Images
File Type: jpg IMG_0055.jpg (519.0 KB, 228 views)
File Type: jpg IMG_0061.jpg (567.2 KB, 212 views)
File Type: jpg IMG_0064.jpg (962.5 KB, 205 views)
File Type: jpg IMG_0069.jpg (807.7 KB, 116 views)
File Type: jpg IMG_0072.jpg (504.9 KB, 96 views)
File Type: jpg IMG_0085.jpg (487.9 KB, 66 views)
File Type: jpg IMG_0090.jpg (546.2 KB, 73 views)
File Type: jpg IMG_0068.jpg (674.6 KB, 84 views)

Last edited by mrnothing; 14th November 2012 at 05:27 PM.
  Reply With Quote
Old 15th November 2012, 04:17 AM   #2899
Nevod is offline Nevod  Russian Federation
diyAudio Member
 
Join Date: Nov 2007
Send a message via ICQ to Nevod
Hello!

I have an somewhat off-topic question.
Has anyone tried to conduct a memory distortion measurement for O2 amp, using Gerard Pierrot's method?
  Reply With Quote
Old 15th November 2012, 06:49 AM   #2900
jcx is offline jcx  United States
diyAudio Member
 
Join Date: Feb 2003
Location: ..
link??

thermal distortion was recognized, minimized by design, layout in op amp chips long ago

you can often see some evidence of the residual of this type of distortion in comprehensive THD, IMD plots

it can be further (meaninglessly for audible perception) be reduced by using composite multiloop circuits with the output op amp in the global loop of a input op amp which can be operated from subregulated, reduced power supply – the input device power only varies by uW
  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 05:42 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