[Detectit]

Got the O2 for a month now. It's a good amp.

Yes it's quiet
Yes it's reference with no change to the sound.
And i came to the conclusion for myself an amp must have some coloration.

Almost sold the O2. But gave it a second change with opamp rolling.

OPA2228PA and the OPA2134. And the amp came alive....

Bass is deeper more present and the cimbles highs are clearer.

Thats the way I like it. An upgrade of a few dollars but a good one.

 

[raoultrifan]

So, you replaced the original NJM/JRC2068 with OPA2228PA or with OPA2134?

 

[Detectit]

So, you replaced the original NJM/JRC2068 with OPA2228PA or with OPA2134?

Only the U11 slot with OPA2228PA
And U3/4 with OPA2134

 

[raoultrifan]

[...]
And U3/4 with OPA2134

I wouldn't do that, honestly. You're cutting in half the output power and you're also not in line with designer's recommendations (please read his blog before replacing the output opamps). However, OPA2134 is just not designed to work as headphones output buffer, so I strongly suggest you to remove it. You might find more answers from this entire forum, but also from diyaudio (lot of EE info in there too).

 

[Detectit]

I wouldn't do that, honestly. You're cutting in half the output power and you're also not in line with designer's recommendations (please read his blog before replacing the output opamps). However, OPA2134 is just not designed to work as headphones output buffer, so I strongly suggest you to remove it. You might find more answers from this entire forum, but also from diyaudio (lot of EE info in there too).

But if it sound right It's okay i guess? I don't have the idea it sucks a lot of power down? Maybe a little but not much.

And yes the designer didn't meant it that way. But i think reference equals lifeless to me.

BTW I have searched the forum yesterday and there weren't any results. Thought I post it.
But now there are.... Guess the search function was broken.
I will read up.

 

[439598]

My o2 is measuring different DC voltages on the negative and positive rail, with a 12V AC supply it reads -15V and +12V DC, is this a problem?

 

[raoultrifan]

Yes. Please measure again.

 

[439598]

still getting that, there is also 24V AC on positive rail, 0V AC on negative rail.

there isnt any op amps in or extra caps

 

[439598]

measuring directly from the voltage regulator's outputs shows +12V DC and +24V AC on U5 but +0.6V DC and 0V AC on U6... is this totally wrong?

 

[raoultrifan]

Just measure between GND and opams V-/+ both rails, also between GND and batteries + & -.

 

[raoultrifan]

Here's an already uploaded picture on Head-Fi:

Try measuring the voltage on C8, C9 or C17 and C18, reference with GND, of course.
Though, what is the issue, actually?

 

[439598]

I noticed strange problems after adding additional caps, some occasional fluttering and booming in the bass. on MC7912 negative regulator output there is just 0.6v but it should be -12V, this faulty regulator has probably been the cause of the sound quality issues all along. the extra caps must have caused the unregulated negative rail to increase in voltage even more, probably past the op amp max -18V. edit: or the caps will only increase voltage without a load so maybe not

 

[raoultrifan]

Are you referring to https://www.head-fi.org/threads/obj...mpressions-thread.704804/page-5#post-14078842? Please triple-check of short circuit. I got 2 x 4.700uF/50V huge Nichicon caps in parallel to existing 470uF/35V caps and AC ripple remains constant, hence I left the original caps only. AGDR had a comprehensive post, most likely on diyaudio forum about that and he also proved that adding more caps will not improve the ripple in no way; instead, cutting the PCB traces between the 2 caps (not the GND, just the rails) and adding 2x1 ohms resistors will decrease the already very low ripple (however, first 2 caps need to get changed from 35V to 50V).

Usually, when adding more and more caps to a power rail or to bypass opamp rails you might expect to pre and/or post ringing. This may also cause oscillations to some power regulator. In this case, also the 2 FETs might get into issues, so please revert what you've done and see if O2 works fine after that.

You need to measure the voltages around C6 and C7 (reference to GND), but also around C8, C9 or C17 and C18. Also, measure the voltage across C10.

Usually, if a rail fail, then all DC goes to the headphones, so I doubt you're having an entire rail defective.

P.S.: If you really-really want to add more caps, get some WIMA MKP100-200nF) and add then on the bottom of the PCB between V+GND and V-/GND to bypass each opamp (at least the 4556 ones). Additionally, you could add tantalums too, because they can handle the ripple very well and can also fit between the PCB and the O2's aluminium case.

 

[JakeJack_2008]

We've only shipped 15VAC, 500mA transformers since at least 2014, if not longer:
https://www.jdslabs.com/products/147/15vac-power-adapter/

Triad P/N WAU12-200 was a 12VAC, 200mA adapter originally recommended by NwAvGuy in 2011. It was acceptable under light loads. Voltage dips into unacceptable territory from 100-110VAC outlets. We've long since abandoned this part.

Hi, I have bought both the Triad P/N WAU12-200 - 12VAC, 200mA and the current one 15VAC, 500mA from you for using in the USA.
Not having golden ears, I do not hear any difference in sound quality while using either of them with my Beyerdynamic DT 880 (250 Ohm; 2005 Edition) headphones.
Are my ears missing something here?

 

[jseaber]

Hi, I have bought both the Triad P/N WAU12-200 - 12VAC, 200mA and the current one 15VAC, 500mA from you for using in the USA.
Not having golden ears, I do not hear any difference in sound quality while using either of them with my Beyerdynamic DT 880 (250 Ohm; 2005 Edition) headphones.
Are my ears missing something here?

No, the difference is unlikely to be noticed except under extreme conditions.