[Iron_Dreamer]

Quote:

Originally posted by Jasper994 or you could just get a second RME and use two different chips...

That's Ed's strategy

Glassman, what value resistor would I need to bias the LT1122 to class A?

 

[Edwood]

OPA627 as well, please.

We'll have another pair to play with soon, hopefully.

-Ed

 

[Glassman]

like I said, 2mA per channel is ok, for any opamp.. see - you need to prevent opamp from swithing between current sinking and sourcing.. when you put the resistor from it's output to the most negative supply you can find (here -12V) so that around 2mA is constantly flowing from the opamp, the opamp will stay as curent source, never more current sink.. this equation presumes that you are conecting your card to some kind of preamplifier/headamp, which has usually between 10k and 100k of input impedance.. if the output voltage from the card is 2Vrms as usuall, it's 4V in peaks, which translates to 4V/10k which is 0.4mA, hence setting idle current to 2mA provides enough headroom and with 2mA the chips are warmer, but not even close to burning

so the value you need is around 6kOhm, that's all the magic

 

[Iron_Dreamer]

I just class-A'ed the LT1122's, and it definitely tightened up the sound, both in terms of impact (drums hit harder, notes seem better paced) and imaging. I will try the AD8065 in class A in a minute or two. BTW I used Ratshack 5K8 resistors, which should give ~2.14 mA of bias current. ED, don't worry I've got enough to do the two sets of OPA627 as well.

 

[Edwood]

Woohoo!

Still haven't gotten that last 627 yet.

-Ed

 

[Iron_Dreamer]

The AD8065 also benefitted by tightening up the sound a bit, but not as much as the LT1122, and it still retains its' less than exhilirating signature sound.

 

[Edwood]

Can't wait to find out how the OPA627s sound like in Class A. If I get that last one in on time, we could bias one and A/B between the two.

-Ed

 

[Iron_Dreamer]

Quote:

Originally posted by Edwood Can't wait to find out how the OPA627s sound like in Class A. If I get that last one in on time, we could bias one and listen for the difference. -Ed

Already though of that one

 

[Edwood]

Heheh, you're narrowing the gap between my lead in post counts?

Heheh, I finally caught up.

Don't worry I have more work coming up. Will keep me very busy this weekend.

-Ed

 

[Iron_Dreamer]

OK, I've changed all the opamps over to class A now, and after some listening, I've came to some conclusions about the opamps I have on hand:

LT1122:Wide soundstage, excellent imaging, sparkly yet not grainy, harsh or overemphasized treble, nice musical midrange and bass with plenty of impact.

AD8065: Ever so slightly wider soundstage, imaging about the same, no part of the frequency spectrum really sticks out (does that make this chip "neutral") however it is not the most musical chip and can get boring to listen to fairly fast, slightly less bass and treble than the LT.

AD8610: Soundstage is much less wide, imaging just a hair less tight, bass is less and less impactful than either before, treble is the most sparkly and emphasized of all, midrange is a bit unengaging, but not to the extent of the 8065.

AD797: Slightly wider soundstage than 8610, though still in a lower league than the other two, imaging is also tighter than 8610. Less treble than 8610, more bass and bass impact. The overall sound signature is quite like the LT, however the 797 is just not as slmmin' in the bass, musical in the mids. More treble sparkle than the LT or 8065, though.

The LT1122 is definitely my pick of this litter, however if the 8065 is reall "neutral" then I could see it appealing to people seeking that quality from their systems. The 797 is basically a less-refined 1122, so it has no place for me now. The 8610 doesn't really have an particular attraction for me either.

BTW the LT1360 oscillates badly, and as such is not reviewed, even though we mentioned buying it.

 

[Edwood]

We're in business. I just got the other OPA627's.

Zemo was kind enough to send a pair of them, so we don't have to try to desolder that pesky 637.

I read it carefully, looks like they're both 627AU's this time. Man, is it hard to read the text on the BurrBrown/TI chips.

-Ed

 

[Zemo]

Glad to hear you got 'em! I figured you'd want a couple extra's...especially if I screwed up again and misread those darn labels on 'em.

 

[Zemo]

OH, and I'm gonna be modding my Echo MiaMidi soundcard soon, so far, what's your reccomendation on opamps?

edit: I'll also need to know how to do that class A thing correctly....pics of the class-A setup?

 

[Iron_Dreamer]

Quote:

Originally posted by Zemo OH, and I'm gonna be modding my Echo MiaMidi soundcard soon, so far, what's your reccomendation on opamps? edit: I'll also need to know how to do that class A thing correctly....pics of the class-A setup?

We should have pics for you on Sunday. To do it you just connect one leg of the resistor to the leg on the far right, bottom (with the dot on the bottom left), and the other leg to the third leg from the left, on the top. Do this for both single-channel opamps.

From my testing, I would say that you'll want either the LT1122 or OPA627 (which I only heard for a little while, but it is more of a midrangy sound than the LT1122), or maybe the AD8065 if you are on of those people obsessed with "neutrality" (which meanings boringness to me).

 

[Zemo]

Keep in mind I need dual channel opamps....the LT1122 looks promising, but I'd need a browndog adapter....got a dual equivalent?