OPA 627 Sounded very dull

[golf_bht]

I am not too sure weather this is the correct place to post this or not.
I mod my D/A but it doesn't sound as I expected. The original chip was OPA2134. I replace it with BD adaptor to place 2x 627 SMD on the DAC.

It sound like Low Pass filter activated somehow. What could be a problem?

[jcx]

it couldn't hurt to have (free) RMAA tests before and after just to make sure something did't happen during the swap

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but detailed memory for sound is usually considered one of our poorer human abilities - usually only gross features get transfered to long term memory and a suprizing amount of our "memory" is is reconstructed on the fly with the new input only having to hit a few key points

for reliable aural comparision few seconds of switching time and careful level matching is necessary to begin to make valid distinctions of small differences - blind testing also helps increase reliability by reducing expectation effects

[golf_bht]

I tested that by swapping out the 2134 to 627 and back. Could it be the lower than optimum supply voltage? What would be a minimal burn-in time for 627? it now has about 30 hours.

[analog_sa]

In some systems the 627 does indeed sound dull. Local PS bypassing with suitable caps like ERO 1837 may help some.

[FAA]

if you bought the 627 in ebay, they are probably fakes/remarked opamps..

[Andrea:]

Originally Posted by golf_bht

I am not too sure weather this is the correct place to post this or not.
I mod my D/A but it doesn't sound as I expected. The original chip was OPA2134. I replace it with BD adaptor to place 2x 627 SMD on the DAC.

It sound like Low Pass filter activated somehow. What could be a problem?

That's well known. The OPA2134 is designed for audio and it hears. The OPA627 is not designed for audio and it hears too. Even the OPA827 is not mainly designed for audio, and it still hears.

Go with the OPA132UA, if you want a real good FET opamp. It's a definite upgrade over the dual (and lower grade) OPA2134, trust me.

[Andrea:]

Originally Posted by analog_sa

In some systems the 627 does indeed sound dull. Local PS bypassing with suitable caps like ERO 1837 may help some.

i.e. you need to color the sound through some peculiar sort of power supply bypassing... I know. I have used this trick with the (less dull than an OPA627) LME49710NA, and it works well.

[golf_bht]

I brought my 627 from a dealer in Bangkok "hifimod" What is the effect of having a bit low voltage anyway? I thought 627 will sounded more open than 2134 but instead sounded more dull.

[FAA]

I've used both 2134 and 627 in my cd player, defenitely 627 doesnt sounds dull compared to 2134.

You can check the resistance between pins 1 & 5 of the 627's to
check its legitimacy, it should read around 50k ohms.

please see attached photo. Meter set to x1K.

[Andrea:]

If you don't perceive sonic color(s), then certainly you won't perceive the OPA627 as duller than the OPA(2)134. But for all those who do perceive it...