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

Headphone Systems Everything to do with Headphones

The Objective2 (O2) Headphone Amp DIY Project
The Objective2 (O2) Headphone Amp DIY Project
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 24th August 2017, 05:09 AM   #5001
ammel68 is offline ammel68  United States
Banned
 
Join Date: Sep 2009
Location: Southeast, U.S.
The Objective2 (O2) Headphone Amp DIY Project
Quote:
Originally Posted by mt490 View Post
Both Digikey and Mouser have them in stock.
All I see are ROHM op-amps for that part number at Mouser:
LM4565F-GE2 ROHM Semiconductor | Mouser

I typically associate a op-amp with a "LM" prefix with being made National Semiconductor, not ROHM(whoever that is).
So where is the National or TI equivalent and what's so special about it other than it's relatively high output current?
It's less-than-stellar slew rate of 5V/us certainly isn't nothing special, but at a price of only $.45 ea. it's cheap enough to try.

Last edited by ammel68; 24th August 2017 at 05:12 AM.
  Reply With Quote
Old 7th September 2017, 07:35 PM   #5002
marioneta is offline marioneta
diyAudio Member
 
Join Date: Sep 2017
Default d4 measurement not ok

Hello all, i hope you can help me out.

I bought a kit from head'n'hifi, soldered everything and now i'm testing.
the voltage measurement (with ac power and only u2 installed) of the banded end of d4 should be 13.5-22.5 but it's 0. the source is 17V. the banded end of d3 is 23.7.
the non-banded end of d4 seems ok: -23.5.
the resistor measurement (in circiut) seems ok but some of the values with (*) are at their max values r4, r24=270k or greater: r2=236, r1=238.

thank you!
  Reply With Quote
Old 7th September 2017, 08:52 PM   #5003
marioneta is offline marioneta
diyAudio Member
 
Join Date: Sep 2017
Quote:
Originally Posted by marioneta View Post
Hello all, i hope you can help me out.

I bought a kit from head'n'hifi, soldered everything and now i'm testing.
the voltage measurement (with ac power and only u2 installed) of the banded end of d4 should be 13.5-22.5 but it's 0. the source is 17V. the banded end of d3 is 23.7.
the non-banded end of d4 seems ok: -23.5.
the resistor measurement (in circiut) seems ok but some of the values with (*) are at their max values r4, r24=270k or greater: r2=236, r1=238.

thank you!
never mind me. i was not measuring vac. total noob here.
everything works fine - me happy.
  Reply With Quote
Old 8th September 2017, 07:09 AM   #5004
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
The Objective2 (O2) Headphone Amp DIY Project
No problem. Pleased it all works.
  Reply With Quote
Old 14th October 2017, 01:36 PM   #5005
PixelWizzard is offline PixelWizzard  Germany
diyAudio Member
 
Join Date: Oct 2017
Hello,
I have a problem with my Objective2 + ODAC combo I need some help with.
My objective 2 iteself works fine. The same goes for the ODAC.
My ODAC output pins are soldered to the Objective2 input pins as they are supposed to.
When I listen to the ODAC via the headphone input of the Objective2, everything is completely fine. But when I power on the Objective2 and listen to the headphone output (ODAC still being the source), there are several problems;
- I have to turn up the volume knob all the way up to hear at a somewhat decent volume.
- There is a significant channel imbalance
- With the volume know turned down all the way, I can still hear the lower frequencies (equally loud on both channels)

I really hope anyone can help me, I'm really running out of ideas...
  Reply With Quote
Old 14th October 2017, 01:48 PM   #5006
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
The Objective2 (O2) Headphone Amp DIY Project
Welcome to diyAudio

I'm a bit confused as to what is happening tbh.

You say the 02 is OK and also the ODAC.

I'm assuming that when you mention I listen to the ODAC via the headphone input of the Objective2, everything is completely fine I am taking that to mean you have headphones plugged into the 3.5mm input jack of the O2.

This is really where an oscilloscope comes into its own for faultfinding.....

Lets work with this bit first With the volume know turned down all the way, I can still hear the lower frequencies (equally loud on both channels)


If you look at the 02 circuit then you can see that the wiper (middle pin) of the volume control goes to ground when the pot is rotated to minimum. That should kill all audio.

Can you confirm that that is not happening when you listen to the 02 headphone output ?
  Reply With Quote
Old 14th October 2017, 02:39 PM   #5007
PixelWizzard is offline PixelWizzard  Germany
diyAudio Member
 
Join Date: Oct 2017
Thanks for the fast reply.
Quote:
I'm assuming that when you mention I listen to the ODAC via the headphone input of the Objective2, everything is completely fine I am taking that to mean you have headphones plugged into the 3.5mm input jack of the O2.
That's what I was trying to say, yes.

Quote:
If you look at the 02 circuit then you can see that the wiper (middle pin) of the volume control goes to ground when the pot is rotated to minimum. That should kill all audio.
Can you confirm that that is not happening when you listen to the 02 headphone output ?
That is correct. And also the reason why I'm so confused myself.
  Reply With Quote
Old 14th October 2017, 05:50 PM   #5008
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
The Objective2 (O2) Headphone Amp DIY Project
Hmmm... its an interesting problem then

You need to look first of all at why the volume control isn't fully muting the audio.

First thing to check is:

That with the control fully anticlockwise and the O2 powered down (OFF) that there is no more than one or two ohms between the middle leg of the volume control and the ground leg next to it. It should theoretically be zero but it never is on most pots. Also confirm that the ground leg of the control has virtually zero resistance to the audio input grounds and power supply ground. It should be fractions of an ohm at most.

Any problem there will almost certainly be something physical that is wrong.

Even if the readings seem OK we still have to go one step further and now add a quick shorting link from the middle pin of the volume control (both channels) to the ground pin next to them. There has to be zero audio present now.
  Reply With Quote
Old 14th October 2017, 08:30 PM   #5009
PixelWizzard is offline PixelWizzard  Germany
diyAudio Member
 
Join Date: Oct 2017
Measuring the resistance between the middle leg and the ground pin of the volume control resulted in 6.5 ohms and 11.2 ohms.
There's exactly 0 ohms between the volume control grounds and input ground. I wasn't exactly sure what you mean by power supply ground, but I suppose it's one of the battery-pin grounds (which would measure 0 ohms as well).
Now to the interesting part. After soldering the center and ground pins of the volume control together, I could still hear some slight signal coming out of the output.
This still only happens with the ODAC as my input source and not when connecting a source to the input jack of the O2...
  Reply With Quote
Old 15th October 2017, 07:08 AM   #5010
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
The Objective2 (O2) Headphone Amp DIY Project
Not sure what to make of that.

It looks like the pot resistance readings are probably normal for the pots used.

With the pot deliberately shorted and you still hearing audio... that is weird. And it only does that with the ODAC and not a normal line level input.

The only things I could suggest would be to look at how the ODAC grounds are connected and how the power supplies interact.

Are you running the O2 on battery for test purposes ?

Headphones are super sensitive and will give detectable audio with only a millivolt or two of signal. With the volume control pins shorted out the only thing I can think of is that some circulating audio related current is being developed across the essentially 'zero resistance' of the ground traces. That would only be possible if there were a loop and also if the ODAC had considerable 'drive ability' (which it may well have).
  Reply With Quote

Reply


The Objective2 (O2) Headphone Amp DIY ProjectHide 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
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 10:01 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