Well, Analog Devices beat Texas Instruments in getting the samples to me.
While TI's Burr-Brown division has already shipped the samples (4 OPA2604 and 4
OPA2134) via UPS Ground and aren't expected to arrive until the 27th, Analog
Devices responded to my sample request by shipping 4 AD826AN opamps via UPS
Next Day Air! They got here today and I just installed them.
I hope it's not the placebo effect, but I think I can hear a lot of details in
the sound much better than now than ever before with 4 of those Japan Radio
4560D opamps. The high frequencies are smooth while the rest of the ranges
remain well controlled, the sound quality is more "airy" and dynamic with a
close 3D quality to it, and certain details, like fingers plucking on a harp or
bass strings, are more perceptible. Well, I hope a friend of mine who doesn't
know what I've done will tell me for sure if it sounds smooth and good.
I know that, on paper, the AD826 has five times the bandwidth and several times
the slew rate of the 4560. I just hope that the 4 AD826 chips that were
installed doesn't have problems oscillating, but so far the Onkyo DX-C106,
which has the chips and slight power supply upgrades installed, has been
playing great.
AD826
Bandwidth: 50 MHz
Slew rate: 350 V/(micron)s
(Because of these specs, I think the AD826 was never meant for audio, although
they could be used for it, hence my concern about oscillation with these ICs
when used in a CD player. The fact that audio applications were never
mentioned in the AD826 techsheet seems to support this. Although, so far, I've
not encountered any problems.)
OPA2604
Bandwidth: 20 MHz
Slew rate: 25 V/(micron)s
OPA2134
Bandwidth: 8 MHz
Slew rate: 20 V/(micron)s
NJM/JRC 4560
Bandwidth: 10 MHz
Slew rate: 4 V/(micron)s
I know there's much more info than this, but all I've got at the moment are the
first pages of the datasheets.
As for the Burr-Brown chips, I'm thinking of buying two used CD players with
4560 or 4558 opamps and use the Burr-Browns in them to see how they sound. Of
course, this will be after I beef up their power supplies. - Reinhart