The Objective2 (O2) Headphone Amp DIY Project - Page 324 - 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 20th April 2013, 03:22 PM   #3231
agdr is offline agdr  United States
diyAudio Member
 
agdr's Avatar
 
Join Date: Sep 2010
Quote:
Originally Posted by ybz90 View Post
I don't know if anyone else has observed this, but I have channel imbalance problems with my O2 at low levels.
Yep, the problem is the pot, that issue has come up a lot. Any of the analog 9mm pots are only accurate to 20% or so between channels. It shows up most at low volume levels. The Bourns pot will work - I've built a few O2's with that pot - but will have the same channel imbalance issue. The Bourns pot solves another problem though. There is a problem with the left channel getting scratchy which seems to be a design problem with the Alps 9mm units.

To solve the channel imbalance problem you would have to go with an electronic pot, like JDS Labs did with their new C5:

JDS Labs - C5 Headphone Amplifier

You also may be able to adjust the gain up or down on one channel on the O2, using the gain setting resistors, to get the two channels to match up a little better.
  Reply With Quote
Old 20th April 2013, 04:51 PM   #3232
diyAudio Member
 
Join Date: Apr 2013
Great, thanks for the information. Are there any electronic pots you can recommend for use with the O2?
  Reply With Quote
Old 20th April 2013, 05:00 PM   #3233
diyAudio Member
 
Join Date: Jun 2004
Location: Champaign, Illinois
Default No wonder Rocket Sciensist disappeared.

Hello everyone,

I'm surprised that this discussion lasted as long as it did without Rocket Scientist blowing on the flames. Why did RS disappear if this design delivers such wonderful cost vs. performance value? I really appreciated RS time to document his/her design so dutifully. I wish more of us would do that. But is O2 as impressive as the following would indicate?

I dutifully built my O2, and liked it initially. But I have no other testing instruments than my ears. My "instruments" tell me that O2 is a good performer for $30 naked, but once wrapped up in a $120 package it is rather average for DIY.

Are you really hearing something I don't?
  Reply With Quote
Old 20th April 2013, 05:05 PM   #3234
Davey is offline Davey  United States
diyAudio Member
 
Join Date: Dec 2001
Location: Bremerton, WA.
Quote:
Originally Posted by ybz90 View Post
I don't know if anyone else has observed this, but I have channel imbalance problems with my O2 at low levels. It's fine at higher volumes, but I don't like to listen too high especially with IEMs, and at listening volumes, it actually is an issue at times.

I've narrowed the issue down from testing and logic to the potentiometer... it seems the Alps RK097 pot might just not be that great. Can someone tell me if it would be okay to swap in this pot to test if this solves the issue: PTD902-2015F-A103 Bourns | Mouser

In theory it should fit, but in theory and in practice are often to different issues. Thanks!
It's been mentioned earlier in the thread......clip out R19 and R23. This will turn the high-gain position into a unity gain position and yield a better (higher and better balanced) position on the volume control.

Cheers,

Dave.
  Reply With Quote
Old 20th April 2013, 05:08 PM   #3235
diyAudio Member
 
Join Date: Apr 2013
Quote:
Originally Posted by Francois G View Post
Hello everyone,

I'm surprised that this discussion lasted as long as it did without Rocket Scientist blowing on the flames. Why did RS disappear if this design delivers such wonderful cost vs. performance value? I really appreciated RS time to document his/her design so dutifully. I wish more of us would do that. But is O2 as impressive as the following would indicate?

I dutifully built my O2, and liked it initially. But I have no other testing instruments than my ears. My "instruments" tell me that O2 is a good performer for $30 naked, but once wrapped up in a $120 package it is rather average for DIY.

Are you really hearing something I don't?
That you have assigned a monetary value to it betrays your inherent expectation bias. I'm not afraid to say it here since people here seem intelligent rather than fanatical like certain other forums, but do listen blind for a while between this and your other amp (truly blind, that is) and see how you like it. Unless your other amp is very colored (ie tube) or way less accurate, I'll be impressed if you can tell a meaningful difference.

Many people dislike the O2, that's for sure. But what they're failing to realize isn't that the amp is bad -- rather, it's as *accurate* and in that sense, close to as perfect as can be -- but instead they just do not like or are not accustomed to the sound it produces. You often hear in subjective, and therefore, mostly meaningless reviews, how the O2 is "not warm enough" or "lacks bass punch". They're forgetting to affix the phrase, "compared to what I'm used to." In other words, they amps they like or routinely use are in fact, probably less accurate, less neutral, and more colored. They just happen to enjoy the coloration.

I'm one of those folks actually. I love the buttery smooth and warm tube sound. But I'm not fooled by one moment that my tube amp is actually more accurate or features less distortion. That's what it really is, but that's beautiful distortion to my ears.
  Reply With Quote
Old 23rd April 2013, 06:12 AM   #3236
diyAudio Member
 
availlyrics's Avatar
 
Join Date: May 2011
Quote:
Originally Posted by ybz90 View Post
Great, thanks for the information. Are there any electronic pots you can recommend for use with the O2?
IMHO it would be difficult (& expensive) for a novice to implement digital vol. pot in O2. Detailed discussions of analog v/s digital pot can be found here:-

JDS Labs Blog | Premium Headphone Amplifiers

agdr's method of reducing gain using voltage divider (if 1X is too much) is preferable. If space permits(bigger non standard enclosure) stepped attenuator can solve this issue for parts costing no more than 5$.
__________________
Thanks,
availlyrics

Last edited by availlyrics; 23rd April 2013 at 06:15 AM.
  Reply With Quote
Old 27th April 2013, 11:28 AM   #3237
LuisMCP is offline LuisMCP  Spain
diyAudio Member
 
LuisMCP's Avatar
 
Join Date: Jun 2001
Location: Madrid, Spain
Default "pop" noise when ON

I get a huge "pop" noise when switch ON the amp.

Stefan sugest me that likely Q2 was bad.
I replaced Q2 but pop noise remains the same.

Some idea?

Regards,
Luis.
  Reply With Quote
Old 27th April 2013, 01:53 PM   #3238
agdr is offline agdr  United States
diyAudio Member
 
agdr's Avatar
 
Join Date: Sep 2010
Quote:
Originally Posted by LuisMCP View Post
I get a huge "pop" noise when switch ON the amp..
Connecting a 10K resistor between the "+" of C8 and "-" of C9 helps to eliminate the turn-off thump. There is a chance it would help with turn-on thump too, although I haven't tested it. If you want to experiment just connect a 1/8W or larger 10K resistor between the two points in the diagram below. Please post the results if you try it!

The resistor helps with turn-off thump because the only load after the mosfets that RocketScientist / NwAvGuy had connected is the ICs U1, U3, and U4. The ICs are not exactly a linear load and are unrated as to what happens below 2V. The resistor gives the mosfets a direct linear load which may improve switching time and help the power rails come up and go down in syncronization. The "thump" happens when one mosfet switches a fraction of a second before or after the other rather than at exactly the same time, and/or when one power supply rail comes up or drops faster than the other.
Attached Images
File Type: png thump.png (18.2 KB, 164 views)

Last edited by agdr; 27th April 2013 at 01:59 PM.
  Reply With Quote
Old 27th April 2013, 05:23 PM   #3239
diyAudio Member
 
Join Date: Apr 2013
Hi all! Long time lurker here, decided to post my success story here. My implementation of the O2+ODAC has RCA outs for the ODAC, in the B3-080 chassis. The best thing is, all the inputs, RCA, buttons and AC jack are at the back. The front has a very clean minimalist design with only the volume, LED and 1/4 jack. This means everything except the LED is remote mounted. Can't wait to show u guys the pics!
  Reply With Quote
Old 27th April 2013, 05:43 PM   #3240
diyAudio Member
 
Join Date: Apr 2013
In my moment of noobness I had mistaken U5,U6 for a pair, which means I swapped their places and soldered them in. The voltage across the battery terminals measured only ~20V. Luckily the opamps and ICs were undamaged. LOL. They were a nightmare to desolder and remove, I ended up having to destroy them.
  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 06:28 PM
My latest project - DAC + headphone amp gmarsh Digital Line Level 105 13th December 2010 03:31 PM
My headphone amp project trifidmaster Headphone Systems 2 22nd December 2008 04:52 PM
Mini Ipod headphone amp DIY project Nordic Headphone Systems 14 11th March 2007 03:35 PM
Need help for a battery headphone amp project dismalonyx Headphone Systems 1 16th April 2004 12:22 AM


New To Site? Need Help?

All times are GMT. The time now is 12:40 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