The Objective2 (O2) Headphone Amp DIY Project

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If you have a remote volume control in front of the O2 then you really need the 02's volume on maximum and then just see how it all sounds and feels. If it is all much to loud then you need to attenuate the O2 input rather than just turn its manual volume down.

If it is not loud enough then increase the O2 gain.

A DVR input is no good. You need an audio output that is under control of the Yamaha's preamp section if you want to use the Yamaha's volume control.
 
A DVR input is no good. You need an audio output that is under control of the Yamaha's preamp section if you want to use the Yamaha's volume control.

In a normally built receiver, the only outputs that are volume controlled are the speakers and the headphones outputs. Since in most receivers and amplifiers nowadays the headphones output is just the speakers output attenuated by resistors, I would go with that.

Another way would be to use a tape output (or video output), that would in theory give you better sound quality, since the signal doesn't go through the power amp section. But you will have to use the O2's volume control.
 
In a normally built receiver, the only outputs that are volume controlled are the speakers and the headphones outputs. Since in most receivers and amplifiers nowadays the headphones output is just the speakers output attenuated by resistors, I would go with that.

Another way would be to use a tape output (or video output), that would in theory give you better sound quality, since the signal doesn't go through the power amp section. But you will have to use the O2's volume control.

Thank you! I will check this out as well.

True enough :)

The person asking the question never returned though...

I am here, don't worry, you will hear/read from me.

So far I haven't started, somehow I'm "afraid" that I would damage something or do something wrong. I measured the resistors though, so I could theoretically start.
 
Damn, here I come back again :D

I finished soldering the resistors and diodes, so far I think I did good, except I accidentially soldered "any" of the gain resistors in...whoops. We'll see how it turns out.

Unfortunately I am stuck now with the ceramic caps because I think that my multilmeter isn't able to measure them and therefore I can't tell which are which :(

Any idea how I could this find out with this multimeter? Imgur: The magic of the Internet
 
Hello everyone! I am registered here for a long time but never posted anything so maybe a newbie here :).


I already have built O2 years before, but not, I want to use spare pcb and some parts (some will be upgraded by agdr modern parts upgrade list). Also I want to move everything except volume control and jack to headphones to back of the case. And I thought it would be nice to turn off O2 with volume pot - there are some with switch inside like Bourns PTR902-1015K-A103. Problem is, it is only single pole switch (SPST).


I was thinking about connecting relay to pot switch using pin 2 of original power switch which will then switch 2 to 3 ping and 5 to 6 as original power switch does.
Is it a good idea? Can it be done better way? I know that the pot is not compatible with switch to pcb but I would mount it on panel and not on pcb either way - I want big knob and have case with higher height. Also, I am thinking about agdr booster board, if this makes it easier to make power switch with pot - pluses to make booster board.
Thanks!
 
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DC is the worst for switches because any arc produced is maintained as the contacts open... until there is enough space for it to stop.

AC is much kinder as the voltage passes through zero each cycle.

Same applies to relays. Just look at any data sheet and you will see something like 250v ac at say 8A and perhaps as little as 28v dc at just 1amp as a maximum.
 
That meter doesn't seem to have a cap range on it, however there should be markings on the parts related to the value.

Unfortunately not :( I have:

  • 1xyellow one with 223 on it
  • 4x yellow ones with BC(?) 221 (could be the 220pF Stecked C0G Cap?)
  • 1x yellow with BC(?)105(?)Z
  • 2x blue with 105 (could be the 0.022uF Ceramic?)


Any idea on how I could figure that out? I'm still stuck here
 
Unfortunately not :( I have:

  • 2x yellow one with 223 on it -i.e. 22nf or 0.022uF
  • 4x yellow ones with BC(?) 221 (could be the 220pF Stecked C0G Cap?)
  • 1x yellow with BC(?)105(?)Z - Probably the 1.0uF?
  • 2x blue with 105 - 1000 nF 1.0 uF - Those aren't on my BOM?:confused::confused:

Any idea on how I could figure that out? I'm still stuck here

Seems I'm blind or is it not possible to edit answer? Anyways, I could confirm via a calculator / overview website, that the

  • 4x yellow ones with BC(?) 221 (could be the 220pF Stecked C0G Cap?)

were the 220pf ones :)

I edited the list, the two blue ones are confusing me...Did head and hifi send me the wrong ones or am I worng?
 
Again I am a bit insecure: I am stuck now with the 0.22uF MKT/MKS Film Cap. On the BOM it says there should be 6 in total for C6, C7, C10, C15, C17, C18 - But first of all I only have 4 out of the 6 blue film caps and on the build log of the user @6L6 are also only 4 but he has placed the other, yellowish ceramic caps on C6 and C7 which are empty in my case?

I've no idea :)

I only help out in this thread by working from the 02 circuit, I've never seen one, heard one or know anything about the kits :)

1uF instead of 2.2uF will reduce the low frequency response but it's still below 5Hz so no problem.

Allright :D Thank you for helping me out! :)
 
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Again I am a bit insecure: I am stuck now with the 0.22uF MKT/MKS Film Cap. On the BOM it says there should be 6 in total for C6, C7, C10, C15, C17, C18 - But first of all I only have 4 out of the 6 blue film caps and on the build log of the user @6L6 are also only 4 but he has placed the other, yellowish ceramic caps on C6 and C7 which are empty in my case?



Allright :D Thank you for helping me out! :)


Sorry...Sometimes my Edit button just disappears? :confused:

Surprise, the DIP Sockets are also causing confusion...All 4 of them U1, U2,(U3, U4) look the same to me? DUal Channel, Dual Low Noise and Dual High Current? All 4 of them have the number 8 (for the pins I suppose?) on it but one has "y" one has "v", "E" and an "o" on it? How do I know which is which?
 
Hi ktre,
it seems you are looking at an outdated BoM, NwAvGuy revised it in 2011 and C6 and C7 have been changed to 1uF.
You can find the updated BoM here: NwAvGuy O2 V11 BOM 2 Dec 2011.xls - Google Drive

Unfortunately the documentation pack has never been updated and still shows the old values in the schematics and BoM.
Hope this helps and happy soldering


Again I am a bit insecure: I am stuck now with the 0.22uF MKT/MKS Film Cap. On the BOM it says there should be 6 in total for C6, C7, C10, C15, C17, C18 - But first of all I only have 4 out of the 6 blue film caps and on the build log of the user @6L6 are also only 4 but he has placed the other, yellowish ceramic caps on C6 and C7 which are empty in my case?



Allright :D Thank you for helping me out! :)